The Temporal Lobes: Language, Memory, Emotion,Auditory, Visual, Face Recognition, Aphasia, Epilepsy, & Psychosis



Rhawn Gabriel Joseph, Ph.D.











The temporal lobes are unique. These are the only regions of the brain that subserves personalized, subjective emotional and social experience and can store and recall this information from memory. The temporal lobes also contains the core structures of the limbic system involved in emotion and memory, the amygdala and hippocampus.





The temporal lobe/limbic allocortex is responsive to complex auditory and visual stimuli (Binder et al., 2014; Gross & Graziano 1995; Nakamura et al. 2014; Nelken et al., 2008; Nishimura et al., 2008; Price, 2011; Rolls 2002; Tovee et al. 2014), comprehending, in humans, complex speech, and contains the highest density and the greatest diversity of peptides and neurotransmitters as compared to all other brain regions (Niewenhujs, 2015).





Of all brain regions, only stimulation or activation of the temporal lobe or underlying limbic structures, gives rise to personalized, subjective, emotional, and sexual experiences (Gloor, 2011; Halgren, 2002). Although direct electrical stimulation of the frontal motor cortex can induce twitching of the lips, flexion or extension of a single finger joint, protrusion of the tongue or elevation of the palate, patients never claim to have willed these movements. That is, stimulation of the frontal lobes evokes behavior that seems outside the control of the patient (Penfield & Boldrey, 1937; Penfield & Jasper, 1954; Penfield & Rasmussen, 1950; Rothwell et al. 2007).





By contrast, electrode stimulation of the temporal lobes evokes experiences which become part of the subjective stream of consciousness, embedded into the very fabric of the personality, such that the personality, and even sexual orientation may be altered. Moreover, patients may experience profound visual and auditory hallucinations and even feel as if they have left their bodies and are floating in space or soaring across the heavens.





There is no subjective sensations with frontal or parietal or occipital stimulation. In fact, with stimulation to these other brain areas the patient only becomes aware of the stimulation when they attempt to speak or move, or if a finger begins to twitch or if they feel painful tingling or see flashes of light. Although damage to the frontal lobe can produce the "frontal lobe personality" it is the temporal lobe which subserves those aspects of experience which are experienced as personal and subjective, of pertaining to the self and one's personal and even spiritual identity. Indeed, stimulation of the temporal lobe can give rise to profound personal, emotional, sexual, and even religious feelings which are experienced as personally, spiritually and philosophically meaningful, including even sensations of having the "truth" revealed and of receiving knowledge regarding the meaning of life and death.





TEMPORAL TOPOGRAPHY

The temporal lobe is the most heterogenous of the four lobes of the human brain, as it consists of six layered neocortex, four to five layered mesocortex, and 3 layered allocortex, with the hippocampus and amygdala forming its limbic core.





As detailed in chapters, 5, 12, over the course of evolution the dorsally situated hippocampus became displaced and progressively assumed a ventral position, during the course of which it also contributed to the neocortical development of portions of the parietal, occipital and temporal lobe. Similarly, portions of the amygdala became increasingly cortical in structure, and together with the hippocampus, contributed to the evolution of the anterior, medial, superior, and lateral temporal lobes.

Because so much of the temporal lobe evolved from these limbic nuclei, unlike the other lobes, it consists of a mixture of allocortex, mesocortex, and neocortex, with allocortex and mesocortex being especially prominent in and around the medial-anterior inferiorally located uncus, beneath which and which abuts the amygdala and hippocampus.











Given the role of the amygdala and hippocampus in memory, emotion, attention, and the processing of complex auditory and visual stimuli, the temporal lobe became similarly organized (Gloor, 2011). Broadly considered, the neocortical surface of the temporal lobes can be subdivided into three main convolutions, the superior, middle, and inferior temporal gyri, which in turn are separated and distinguished by the sylvian fissure and the superior, middle, and inferior temporal sulci. Each of these subdivision performs different (albeit overlapping) functions, i.e. auditory, visual, and auditory-visual-affective perception including memory storage.





Specifically, the anterior and superior temporal lobes are concerned with complex auditory and linguistic functioning and the comprehension of language (Binder et al., 2014; Edeline et al. 1990; Geschwind 1965; Goodglass & Kaplan, 2008; Keser et al. 2011; Nelken et al., 2008; Nishimura et al., 2008; Price, 2011). The importance of the superior temporal lobe in auditory functioning, and (in the left hemisphere) language, is indicated by the fact that the superior temporal, including the primary auditory area, is larger in humans versus other primates and mammals. In addition, Heschl's gyri, a region of the brain directly implicated in auditory processing, are larger on the left, and the left planum temporal, also an auditory area, is 10 times larger (among the majority of the population) than its counterpart on the right (Geschwind & Levinsky, 1968).













The auditory areas, however, extend along the axis of the superior temporal lobe, extending in a anterior-inferior and posterior-superior arc, such that the connections of the primary auditory area extends outward in all directions throughout the brain, innervating, in a temporal sequences, the second and third order auditory association areas (Pandya & Yeterian, 2015). Thus, each area of the brain involved in auditory processing, from simple to complex analysis, are interlinked and these association areas in turn project back to the primary auditory area.









Vision and the Temporal Lobes

The temporal lobes perform complex analysis of visual stimuli, including the recognition of faces, animals, tools, houses, and other complex geometric forms.

The inferior and medial temporal lobe harbors the amygdala and hippocampus, performs complex visual integrative activities including visual closure, and contains neurons which respond selectively to faces and to the sight of complex objects (Gross & Graziano 1995; Nakamura et al. 2014; Rolls 2002; Tovee et al. 2014).















The inferior and middle temporal lobes, are the recipients of one two diverging (dorsal and ventral) streams of visual input arising from within the occipital lobe and thalamus (Ungerlieder & Mishkin, 1982); i.e. the pulvinar and dorsal medial nucleus of the thalamus. The dorsal stream is more concerned with the detection of motion and movement, orientation, binocular disparity, whereas the ventral stream is concerned with the discrimination of shapes, textures, objects and faces, including individual faces (Baylis et al., 2015; Perrett et al., 2004, 2002). This information flows from the primary visual to visual association areas and is received and processed in the temporal lobes and is then shunted to parietal lobe, and to the amygdala and entorhinal cortex (the gateway to the hippocampus) where it may then be learned and stored in memory.









The temporal lobes, however, also receive extensive projections from the somesthetic and visual association areas, and processes gustatory, visceral, and olfactory sensations (Jones & Powell, 1970; Previc 1990; Seltzer & Pandya, 1978) including the feeling of hunger (Fisher 2014). Hence, the temporal lobes perform an exceedingly complex array of divergent and interrelated functions.

FUNCTIONAL OVERVIEW

The right and left temporal lobe are functionally lateralized, with the left being more concerned with non-emotional language functions, including, via the inferior-medial and basal temporal lobes reading and verbal (as verbal-visual) memory. For example, as determined based on functional imaging, when reading and speaking the left posterior temporal lobe becomes highly active, due, presumably to its involvement in lexical processing (Binder et al., 2014; Howard et al., 199). The superior temporal lobe (and supramarginal gyrus) also becomes more active when reading aloud than when reading silently (Bookheimer, et al., 1995), and becomes active during semantic processing as does the left angular gyrus (Price, 2011).

These same temporal areas are activated during word generation (Shaywitz, et al., 1995; Warburton, et al., 1996), and sentence comprehension tasks (Bottini, et al., 2014; Fletcher et al., 1995). and (in conjunction with the angular gyrus) becomes highly active when retrieving the meaning of words during semantic processing and semantic decision tasks (Price, 2011). Likewise, single cell recordings from the auditory areas in the temporal lobe demonstrate that neurons become activated in response to speech, including the sound of the patient's own voice (Creutzfeldt, et al., 2008).





By contrast, the right is more concerned with perceiving emotional and melodic auditory signals (Evers et al., 2008; Parsons & Fox, 2011; Ross, 1993), and is dominant for storing and recalling emotional and visual memories (Abrams & Taylor, 1979; Cimino, et al. 2011; Cohen, Penick & Tarter, 1974; Deglin & Nikolaenko, 1975; Kimura, 1963; Shagass et al.,1979; Wexler, 1973). The right temporal lobe becomes highly active when engage in interpreting the figurative aspects of language (Bottini et al., 2014).

However, there is considerable functional overlap and these structures often become simultaneously activated when performing various tasks. For example, as based on functional imaging, when reading, the right posterior temporal cortex also becomes highly active (Bookheimer, et al., 1995; Bottini et al., 2014; Price, et al., 1996), and when making semantic decisions (involving reading words with similar meanings), there is increased activity bilaterally (Shaywitz, et al., 1995).

Presumably, in part, both temporal lobes become activated when speaking and reading, due to the left temporal lobe's specialization for extracting the semantic, temporal, sequential, and the syntactic elements of speech, thereby making language comprehension possible. By contrast, the right temporal lobe becomes active as it attempts to perceive, extract and comprehend the emotional (as well as the semantic) and gestalt aspects of speech and written language.

AUDITORY NEOCORTEX

Although the various cytoarchitectural functional regions are not well demarcated via the use of Brodmann's maps, it is possible to very loosely define the superior-temporal and anterior-inferior and anterior middle temporal lobes as auditory cortex (Pandya & Yeterian, 2015). These regions are linked together by local circuit (inter-) neurons and via a rich belt of projection fibers which include the arcuate and inferior fasciculus. The arcuate and inferior fasciculus project in a anterior-inferior and posterior-superior arc innervating (inferiorally) the amygdala and entorhinal cortex (Amaral et al., 1983) and posteriorally the inferior parietal lobule--as is evident based on brain dissection. That is, this rope of fibers links the auditory and language areas of the brain, from the amygdala, to the auditory neocortex, to the inferior parietal lobule and to Broca's speech area in the frontal lobes, and then back again.











It is also via the arcuate and inferior fasciculus that the inferior temporal lobe, entorhinal cortex (the "gateway to the hippocampus") as well as the amygdala (receive from) and transfer complex auditory information to the primary and secondary auditory cortex which simultaneously receives auditory input from the medial geniculate of the thalamus, the pulvinar, and (sparingly) the midbrain (Amaral et al., 1983; Pandya & Yeterian, 2015). As will be detailed below, it is within the primary and neocortical auditory association areas where linguistically complex auditory signals are analyzed and reorganized so as to give rise to complex, grammatically correct, human language.





It is noteworthy that immediately beneath the insula and approaching the auditory neocortex is a thick band of amygdala-cortex, the claustrum. Over the course of evolution the claustrum apparently split off from the amygdala due to the expansion of the temporal lobe and the passage of additional axons coursing throughout the white matter (Gilles et al., 1983) including the arcuate fasciculus. Nevertheless, the claustrum maintains rich interconnections with the amygdala, the insula, and to some extent, the auditory cortex (Gilles et al., 1983). This is evident from dissection of the human brain which reveals that the fibers of the arcuate fasciculus do not merely pass through this structure (breaking it up in the process) but sends and receives fibers from it.

CORTICAL ORGANIZATION

The functional neural-architecture of the auditory cortex is quite similar to the somesthetic and visual cortex (Peters & Jones, 2015). That is, neurons in the same vertical columns have the same functional properties and are activated by the same type or frequency of auditory stimulus. The auditory cortex, therefore, is basically subdivided into discrete columns which extend from the white matter (layers VII/6b) to the pial surface (layer I).









However, although most neurons in a single column receive excitatory input from the contralateral ear, some receive input from the ipsilateral ear which may exert excitatory or inhibitory influences so as to suppressed, within the same column, input from itself or from the contralateral ear (Imig & Brugge, 1978). These interactions have been referred to as summation interaction (excitatory/excitatory) and suppression interaction (inhibitory/inhibitory, inhibitory/excitatory).

Moreover, some columns tend to engage in excitatory summation, whereas others tend to engage in inhibitory suppression (Imig & Brugge, 1978)--a process that would contribute to the focusing of auditory attention and the elimination of neural noise thereby promoting the ability to selectively attend to motivationally significant environmental and animal sounds including human vocalizations (Nelken et al., 2008).















Among humans, the primary auditory neocortex is located on the two transverse gyri of Heschl, along the dorsal-medial surface of the superior temporal lobe. The center most portion of the anterior transverse gyri contains the primary auditory receiving area (Broadman's area 41) and neocortically resembles the primary visual (area 17) and somesthetic cortices (area 3). The posterior transverse gyri consists of both primary and association cortices (areas 41 and 42 respectively). The major source of auditory input is derived from the medial geniculate thalamic nucleus as well as the pulvinar (which also provides visual input).











Heschl's gyri is especially well developed and no other species has a Heschl's gyrus that as prominent as is the case with humans (Yousry et al., 1995). In fact, some individuals appear to posses multiple Heschl gyri--though the significance of this is not clear. However, it has been reported that this may be a reflection of genetic disorders, learning disabilities, and so on (see Leonard, 1996).





Heschl's gyrus is the blue area.

In over 80-90% of right handers and in over 50% to 80% of left handers, the left hemisphere is dominant for expressive and receptive speech (Frost et al., 2008; Pujol, et al., 2008). In humans, the auditory cortex including Wernicke's (i.e. the planum temporale) is generally larger on the left temporal lobe (Geschwind & Levitsky, 1968; Geschwind & Galaburda 2015; Habib et al. 1995; Wada et al., 1975; Witelson & Pallie, 1973). Specifically, as originally determined by Geschwind & Levitsky (1968), the planum temporal is larger in the left hemisphere in 65% of brains studied. By contrast, the planum temporal is larger on the right in 25%, whereas there is no difference in 10% of subjects studied. Geschwind, Galaburda and colleagues argue that the larger left planum temporale is a significant factor in the establishment of left hemisphere dominance for language.















AUDITORY TRANSMISSION FROM THE COCHLEA TO THE TEMPORAL LOBE

Within the cochlea of the inner ear are tiny hair cells which serve as sensory receptors. These cells give rise to axons which form the cochlear division of the 8th cranial nerve; i.e. the auditory nerve. This rope of fibers exits the inner ear and travels to and terminates in the cochlear nucleus which overlaps and is located immediately adjacent to the vestibular-nucleus from which it evolved within the brainstem (see chapter 5).





Among mammals once auditory stimuli are received in the cochlear nucleus there follows a series of transformations as this information is relayed to various nuclei, i.e., the superior olivary complex, the nucleus of the lateral lemniscus of the brainstem, the midbrain inferior colliculus and medial geniculate nucleus of the thalamus as well as the amygdala (which extracts those features which are emotionally or motivationally significant), and cingulate gyrus (Carpenter 2011; Devinksy et al. 1995; Edeline et al. 1990; Parent 1995). Auditory information is then relayed from the medial geniculate nucleus of the thalamus as well as via the amygdala (through the inferior fasciculus) to Heschl's gyrus, i.e. the primary auditory receiving area (Brodmann's areas 41 & 42) located within the superior temporal gyrus and buried within the depths of the Sylvian fissure.

Here auditory signals undergo extensive analysis and reanalysis and simple associations are established. However, by time they have reached the neocortex, auditory signals have undergone extensive analysis by the medial thalamus, amygdala, and the other ancient structures mentioned above.





As noted, unlike the primary visual and somesthetic areas located within the neocortex of the occipital and parietal lobes which receive signals from only one half of the body or visual space, the primary auditory region receives some input from both ears, and from both halves of auditory space (Imig & Adrian, 1977). This is a consequence of the considerable interconnections and cross-talk which occurs between different subcortical nuclei as information is relayed to and from various regions prior to transfer to the neocortex. Predominantly, however, the right ear transmits to the left cerebral neocortex and vice versa.

Hallucinations

Although the majority of auditory neurons respond to auditory stimuli, approximately 25% also respond to visual stimuli, particularly those in motion. In fact, Penfield and Perot (1963) were able to trigger visual responses from stimulation in the superior temporal lobe. In addition, these neurons are involved in short-term memory, as lesions to the superior temporal lobe can induce short-term memory deficits (Heffner & Heffner, 1986).

Conversely, electrical stimulation not only induces visual responses, but complex auditory responses. Penfield and Perot (1963) report that electrical stimulation can produce the sound of voices, and the hearing of music. These neurons will also respond, electrophysiologically, to the sound of human voices, including the patient's own speech (Creutzfeldt, et al., 2008). Conversely, injury to the left and right superior temporal lobe can result in an inability to correctly perceive or hear complex sounds; a condition referred to as pure word deafness, and if limited to the right ear, agnosia for environmental and musical sounds (see below). In fact, right temporal injuries can disrupt the ability to remember musical tunes or to create musical imagery (Zatorre & Halpen, 1993).

AUDITORY RECEIVING AREA NEUROANATOMICAL-FUNCTIONAL ORGANIZATION.

The primary auditory area is tonotopically organized (Edeline et al. 1990; Merzenich & Brugge, 1973; Pantev et al. 2008; Woolsey & Fairman, 1946), such that different auditory frequencies are progressively anatomically represented. In addition, there is evidence to suggest that the auditory cortex is also "cochleotopically" organized (Swarz & Tomlinson 1990). Specifically, high frequencies are received and analyzed in the anterior-medial portions and low frequencies in the posterior-lateral regions of the superior temporal lobe (Merzenich & Brugge, 1973). In addition, the primary auditory cortex processes and perceives pitch and intensity, as well as modulations in frequency. Primary auditory neurons are especially responsive to the temporal sequencing of acoustic stimuli (Wolberg & Newman, 1972).









Moreover, the auditory cortex appears to be organized so as to detect tones in noise, i.e. the non-random structure of natural sounds, which enables it to selectively attend to environmental and animal sounds including human vocalizations (Nelken et al., 2008). In fact, these same neural fields can be activated by sign language, that is, among the congenitally deaf (Nishimura et al., 2008).

Some neurons are also specialized to perceive specific-specific calls (Hauser, 2011) or the human voice (Crutzfeldt et al., 2008). This has been determined by single unit recording. Some neurons will react to the patient's voice, whereas yet others will selectively respond to a particular (familiar) voice or call, but not to others--which in regard to voices, indicates that these cells (or neural assemblies) have engaged in learning.

Auditory neurons in fact, display neurplasticity in response to learning as well as injury. For example, not only due auditory synapses display learning-induced changes, but auditory neurons can be classically conditioned so as to form associations between stimuli. For example, if a neutral sound is paired with a noxious stimulus, the neurons response properties will be greatly altered (Weinberger, 1993).





These neurons also display neuroplasticity in response to injury and loss of hearing. For example, due to cochlear or peripheral hearing loss, neurons that no longer receive high frequency auditory input, begin to respond instead to middle frequencies (Robertson & Irvine, 2008). In fact, in response to complete loss of hearing, such as congenital deafness, these neurons may cease to respond to auditory input and may instead respond to body language, such as the signing used by the deaf (Nishimura et al., 2008).

FILTERING, FEEDBACK & TEMPORAL-SEQUENTIAL REORGANIZATION

The old cortical centers located in the midbrain and brain stem evolved long before the appearance of neocortex and became specialized for performing a considerable degree of auditory analysis long before mammals evolved (Buchwald et al. 1966). This is evident from observing the behavior of reptiles and amphibians where auditory cortex is either absent or minimally developed.









Auditory information would be projected to the brainstem via two pathways; from the vestibular-cochlear nerve, also known as the 8th cranial nerve, and from the medial geniculate nucleus which is part of the thalamus. This information would then be sent to the inferior colliculus of the midbrain, and in mammals it would be transmitted to the auditory neocortex.









Moreover, many of these old cortical nuclei also project back to each other such that each subcortical structure might hear and analyze the same sound repeatedly (Brodal 2011; Pandya & Yeterian, 2015). In this manner the brain is able heighten or diminish the amplitude of various sounds via feedback adjustment (Joseph, 1993; Luria, 1980). In fact, not only is feedback provided, but the actual order of the sound elements perceived can be rearranged when they are played back.

















This same process continues at the level of the neocortex which has the advantage of being the recipient of signals that have already been highly processed and analyzed (Buchwald et al. 1966; Edeline et al. 1990; Scharz & Tomlinson 1990). Primary auditory neurons are especially responsive to the temporal sequencing of acoustic stimuli (Wolberg & Newman, 1972). It is in this manner, coupled with the capacity of auditory neurons to extract non-random sounds from noise, that language related sounds begin to be organized and recognized (e.g. Nelken et al., 2008; Scwazrz & Tomlinson 1990).

For example, neurons located in the primary auditory cortex can determine and recognize differences and similarities between harmonic complex tones and demonstrated auditory response patterns that vary in response to lower and higher frequency and to specific tones (Nelken et al. 2008; Scwarz & Tomlinson 1990). Some display "tuning bandwitdths" for pure tones, whereas others are able to identify up to seven components of harmonic complex tones. In this manner, pitch can also be discerned (e.g. Pantev et al. 2008).

Sustained Auditory Activity.

One of the main functions of the primary auditory neocortical receptive area appears to be the retention of sounds for brief time periods (up to a second) so that temporal and sequential features may be extracted and discrepancies in spatial location identified; i.e. so that we can determine from where a sound may have originated (see Mills & Rollman 1980). This prolonged activity, presumably also allows for additional processing and so that comparisons to be made with sounds that were just previously received and those which are just arriving. Hence, as based on functional imaging, the left temporal lobe becomes increasingly active as word length increases (Price, 2011), due presumably to the increased processing necessary.

Moreover, via their sustained activity, these neurons are able to prolong (perhaps via a perseverating feedback loop with the thalamus) the duration of certain sounds so that they are more amenable to analysis--which may explain why activity increases in response to unfamiliar words and as word length increases (Price, 2011). In this manner, even complex sounds can be broken down into components which are then separately analyzed. Hence, sounds can be perceived as sustained temporal sequences. It is perhaps due to this attribute that injuries to the superior temporal lobe result in short-term auditory memory deficits as well as disturbances in auditory discrimination (Hauser, 2011; Heffner & Heffner, 1986).

Although it is apparent that the auditory regions of both cerebral hemispheres are capable of discerning and extracting temporal-sequential rhythmic acoustics (Milner, 1962; Wolberg & Newman, 1972), the left temporal lobe contains a greater concentration of neurons specialized for this purpose as the left half of the brain is clearly superior in this capacity (Evers et al., 2008).











For example the left hemisphere has been repeatedly shown to be specialized for sorting, separating and extracting in a segmented fashion, the phonetic and temporal-sequential or linguistic-articulatory features of incoming auditory information so as to identify speech units. It is also more sensitive to rapidly changing acoustic cues be they verbal or non-verbal as compared to the right hemisphere (Shankweiler & Studdert-Kennedy, 1967; Studdert-Kennedy & Shankweiler, 1970). Moreover, via dichtoic listening tasks, the right ear (left temporal lobe) has been shown to be dominant for the perception of real words, word lists, numbers, backwards speech, morse code, consonants, consonant vowell syllables, nonsense syllables, the transitional elements of speech, single phonemes, and rhymes (Blumstein & Cooper, 1974; Bryden, 1967; Cutting, 1974; Kimura, 1961; Kimura & Folb, 1968; Levy, 1974; Mills & Rollman, 1979; Papcunm et al., 1974; Shankweiler & Studert-Kennedy, 1966, 1967; Studdert-Kennedy & Shankweiler, 1970). In addition, and as based on functional imaging, activity significantly increases in the left hemisphere during language tasks (Nelken et al., 2008; Nishimura et al., 2008), including reading (Binder et al., 2014; Price, 2011).

In part the association of the left hemisphere and left temporal lobe with performing complex temporal-sequential and linguistic analysis is due to its interconnections with the inferior parietal lobule (see chapters 6, 11)--a structure which also becomes highly active when reading and naming (Bookheimer, et al., 1995; Menard, et al., 1996; Price, 2011; Vandenberghe, et al., 1996) and which acts as a phonological storehouse that becomes activated during short-term memory and word retrieval (Demonet, et al., 2014; Paulesu, et al., 1993; Price, 2011).

As noted in chapters 6, 11, the inferior parietal lobule is in part an outgrowth of the superior temporal lobe but also consists of somesthetic and visual neocortical tissue. However, the inferior parietal lobule (the angular and supramarginal gyrus) also acts to impose temporal sequences on incoming auditory, as well as visual and somesthetic stimuli, and also serves to provide (via its extensive interconnections with surrounding brain tissue) and integrate related associations thus making complex and grammatically correct human language possible (chapters 5, 11).











However, the language capacities of the left temporal lobe are also made possible via feedback from "subcortical" auditory neurons, and via sustained (vs diminished) activity and analysis. That is, because of these "feedback" loops the importance and even order of the sounds perceived can be changed, filtered or heightened; an extremely important development in regard to the acquisition of human language (Joseph, 1993; Luria, 1980). In this manner sound elements composed of consonants, vowels, and phonemes and morphemes can be more readily identified, particularly within the auditory neocortex of the left half of the brain (Cutting 1974; Shakweiler & Studdert-Kennedy 1966, 1967; Studdert-Kennedy & Shankweiler, 1970).

For example, normally a single phoneme may be scattered over several neighboring units of sounds. A single sound segment may in turn carry several successive phonemes. Therefore a considerable amount of reanalysis, reordering, or filtering of these signals is required so that comprehension can occur (Joseph 1993). These processes, however, presumably occurs both at the neocortical and old cortical level. In this manner a phoneme can be identified, extracted and analyzed and placed in its proper category and temporal position (see edited volume by Mattingly & Studdert-Kennedy, 2011 for related discussion).

Take, for example, three sound units, "t-k-a," which are transmitted to the superior temporal auditory receiving area. Via a feedback loop the primary auditory area can send any one of these units back to the thalamus which again sends it back to the temporal lobe thus amplifying the signal and/or which allows for rearranging their order, "t-a-k," or "K-a-t." A multitude of such interactions are in fact possible so that whole strings of sounds can be arranged or rearranged in a certain order (Joseph 1993). Mutual feed back characterizes most other neocortical-thalamic interactions as well, be it touch, audition, or vision (Brodal 2011; Carpenter 2011; Parent 1995).









Via these interactions and feedback loops sounds can be repeated, their order can be rearranged, and the amplitude on specific auditory signals can be enhanced whereas others can be filtered out. It is in this manner, coupled with experience and learning (Edeline et al. 1990; Diamond & Weinberger 2008) that fine tuning of the nervous system occurs so that specific signals are attended to, perceived, processed, committed to memory and so on. Indeed, a significant degree of plasticity in response to experience as well as auditory filtering occurs throughout the brain not only in regard to sound, but visual and tactual information as well (Greenough et al. 2007; Hubel & Wiesel, 1970; Juliano et al. 2014). Moreover, the same process occurs when organizing words for expression.

This ability to perform so many operations on individual sound units has in turn greatly contributed to the development of human speech and language. For example, the ability to hear human speech requires that temporal resolutions occur at great speed so as to sort through the overlapping and intermixed signals being perceived. This requires that these sounds are processed in parallel, or stored briefly and then replayed in a different order so that discrepancies due to overlap in sounds can be adjusted for (see Mattingly & Studdert-Kennedy, 2011 for related discussion), and this is what occurs many times over via the interactions of the old cortex and the neocortex. Similarly, when speaking or thinking, sound units must also be arranged in a particular order so that what we say is comprehensible to others and so that we may understand our own verbal thoughts.

HEARING SOUNDS & LANGUAGE

Humans are capable of uttering thousands of different sounds all of which are easily detected by the human ear. And yet, although own vocabulary is immense, human speech actually consists of about 12-60 units of sound depending, for example, if one is speaking Hawaiian vs English. The English vocabulary consists of several hundred thousand words which are based on the combinations of just 45 different sounds.

Animals too, however, are capable of a vast number of utterances. In fact monkeys and apes employ between 20-25 units of sound, whereas a fox employs 36. However, these animals cannot string these sounds together so as to create a spoken language. Most animals tend to use only a few units of sound at one time which varies depending on their situation, e.g. lost, afraid, playing.

Humans combine these sounds to make a huge number of words. In fact, employing only 13 sound units, humans are able to combine them to form five million word sounds (see Fodor & Katz 1964; Slobin 1971)

PHONEMES

As noted, the auditory areas are specialized to perceive a variety of sounds including those involving temporal sequences and abrupt change sin acoustics--characteristics which also define phonemes, which are the smallest units of sound and which are considered the building blocks of human language. For example, p and b as in bet vs pet are phonemes. When phonemes are strung together as a unit they in turn comprise morphemes. Morphemes such as "cat" are composed of three phonemes, "k,a,t". Hence, phonemes must be arranged in a particular temporal order in order to form a morpheme, and phoneme perception is associated with the auditory area of the left temporal lobe (Ojemann, 2011).





Morphemes in turn make up the smallest unit of meaningful sounds such as those used to signal relationships such as "er" as in "he is older than she." All languages have rules that govern the number of phonemes, their relationships to morphemes and how morphemes may be combined so as to produce meaningful sounds (Fodor & Katz 1964; Slobin 1971).

Each phoneme is composed of multiple frequencies which are in turn processed in great detail once they are transmitted to the superior temporal lobe. As noted, the primary auditory area is tonotopically organized, such that related albeit differing auditory frequencies are analyzed by adjoining cell columns. As also noted, however, it is the left temporal lobe which has been shown to be dominant for the perception of real words, word lists, numbers, syllables, the transitional elements of speech, as well as single phonemes, consonants, and consonant-vowell syllables.

CONSONANTS AND VOWELS

In general, there are two large classes of speech sounds: consonants and vowels. Consonants by nature are brief and transitional and have identification boundaries which are sharply defined. These boundaries enable different consonants to be discerned accurately (Mattingly & Studdert-Kennedy, 2011). Vowels are more continuous in nature and in this regard, the right half of the brain plays an important role in their perception.

Consonants are more important in regard to left cerebral speech perception. This is because they are composed of segments of rapidly changing frequencies which includes the duration, direction and magnitude of sounds segments interspersed with periods of silence. These transitions occur in 50 msecs or less which in turn requires that the left half of the brain take responsibility for perceiving them. Moreover, many consonants are silent.





In contrast, vowels consist of a slowly changing or steady frequencies with transitions taking 350 or more msec. In this regard, vowels are more like natural environmental sounds which are more continuous in nature, even those which are brief such as a snap of a twig. They are also more likely to be processed and perceived by the right half of the brain, though the left cerebrum also plays a role in their perception (see chapter 11).

The differential involvement of the right and left hemisphere in processing consonants and vowels is a function of their neuroanatomical organization and the fact that the left cerebrum is specialized for dealing with sequential information. Moreover, the left temporal lobe is able to make fine temporal discriminations with intervals between sounds as small as 50 msec. However, the right hemisphere needs 8-10 times longer and has difficulty discriminating the order of sounds if they are separated by less than 350 msecs.

Hence, consonants are perceived in a wholly different manner from vowels. Vowels yield to nuclei involved in "continuous perception" and are processed by the right (as well as left) half of the brain. Consonants are more a function of "categorical perception" and are processed in the left half of cerebrum. In fact, the left temporal lobe acts on both vowels and consonants during the process of perception so as to sort these signals into distinct patterns of segments via which these sounds become classified and categorized (Joseph 1993).

Nevertheless, be they processed by the right or left brain, both vowels and consonants are significant in speech perception. Vowels are particularly important when we consider their significant role in communicating emotional status and intent.

GRAMMAR & AUDITORY CLOSURE

Despite claims regarding "universal grammars" and "deep structures," it is apparent that human beings speak in a decidedly non-grammatical manner with many pauses, repetitions, incomplete sentences, irrelevant words, and so on. However, this does not prevent comprehension since the structure of the nervous system enables H. sapiens sapiens to perceptually alter word orders so they make sense, and even fill in words which are left out.

For example, when subjects heard a taped sentence in which a single syllable (gis) from the word "legislatures," had been deleted and filled in with static (i.e. le...latures), the missing syllable was not noticed. Rather, all subjects heard "legislatures" (reviewed in Farb 1975)

Similarly, when the word "tress" was played on a loop of tape 120 times per minute (tresstresstress....") subjects reported hearing words such as dress, florists, purse, Joyce, and stress (Farb 1975). In other words they organized these into meaningful speech sounds which were then coded and perceived as words.

The ability to engage in gap filling, sequencing, and to impose temporal order on incoming (supposedly grammatical speech) is important because human speech is not always fluent as many words are spoken in fragmentary form and sentences are usually four words or less . Much of it also consists of pauses and hesitations, "uh" or "err" sounds, stutters, repetitions, and stereotyped utterances, "you know," "like".

Hence, a considerable amount of reorganization as well as filling in must occur prior to comprehension. Therefore, these signals must be rearranged in accordance with the temporal sequential rules imposed by the structure and interaction of Wernicke's area, the inferior parietal lobe and the nervous system -what Noam Chompsky (1957) referred to as "deep structure"- so that they may be understood.

Consciously, however, most people fail to realize that this filling in and reorganization has even occurred, unless directly confronted by someone who claims that she said something she believes she didn't. Nevertheless, this filling in and process of reorganization greatly enhances comprehension and communication.

UNIVERSAL GRAMMARS

Regardless of culture, race, environment, geographical location, parental verbal skills or attention, children the world over go through the same steps at the same age in learning language (Chompsky, 1972). Unlike reading and writing, the ability to talk and understand speech is innate and requires no formal training. One is born with the ability to talk, as well as the ability to see, hear, feel, and so on. However, one must receive training in reading, spelling and mathematics as these abilities are acquired only with some difficulty and much effort. On the other hand, just as one must be exposed to light or he will lose the ability to see complex forms, one must be exposed to language or he will lose the ability to talk or understand human speech.

In his book Syntactic Structures, Chompsky (1957) argues that all human beings are endowed with an innate ability to acquire language as they born able to speak in the same fashion, albeit according to the tongue of their culture, environment and parents. They possess all the rules which govern how language is spoken and they process and express language in accordance with these innate temporal-sequential motoric rules which we know as grammar.

Because they possess this structure, which in turn is imposed by the structure of our nervous system, children are able to learn language even when what they hear falls outside this structure and is filled with errors. That is, they tend to produce grammatically correct speech sequences, even when those around them fail to do so. They disregard errors because they are not processed by their nervous system which acts to either impose order even where there is none, or to alter or delete the message altogether. It is because humans possess these same Wernicke-inferior parietal lobe "deep structures" that speakers are also able to realize generally when a sentence is spoken in a grammatically incorrect fashion.

It is also because apes, monkeys, and dogs and cats do not possess these deep structures that they are unable to speak or produce grammatically complex sequences or gestures. Hence, their vocal production does not become punctuated by temporal-sequential gestures imposed upon auditory input or output by the Language Axis.

LANGUAGE ACQUISITION: FINE TUNING THE AUDITORY SYSTEM

The auditory cortex is organized so as to extract non-random sounds form noise, and in this manner in adaptive for perceiving and detecting animals sounds and human speech (Nelken et al., 2008). However, by time humans have reached adulthood, they have learned to attend to certain language-related sounds and to generally ignore those linguistic features that are not common to speakers native tongue. Some sounds are filtered and ignored as they are irrelevant or meaningless. Humans also lose the ability to hear various sounds because of actual physical changes, such as deterioration and deafness, which occur within the auditory system.

Initially, however, beginning at birth and continuing throughout life there is a much broader range of generalized auditory sensitivity. It is this generalized sensitivity that enables children to rapidly and more efficiently learn a foreign tongue, a capacity that decreases as they age (Janet et al. 2004). It is due, in part, to these same changes that generational conflicts regarding what constitutes "music" frequently arise.

Nevertheless, since much of what is heard is irrelevant and is not employed in the language the child is exposed to, the neurons involved in mediating their perception either drop out and die from disuse, which further restricts the range of sensitivity. This further aids the fine tuning process so that, for example, one's native tongue can be learned (Janet et al. 2004; Joseph 1993).









For example, no two languages have the same set of phonemes. It is because of this that to members of some cultures certain English words, such as pet and bet, sound exactly alike. Non-English speakers are unable to distinguish between or recognize these different sound units. Via this fine tuning process, only those phonemes essential to one's native tongue are attended to.

Language differs not only in regard to the number of phonemes, but the number which are devoted to vowels vs consonants and so on. Some Arabic dialects have 28 consonants and 6 vowels. By contrast, the English language consists of 45 phonemes which include 21 consonants, 9 vowels, 3 semivowels (y, w, r),4 stress, 4 pitches, 1 juncture (pauses between words) and 3 terminal contours which are used to end sentences (Fodor & Katz 1964; Slobin 1971).

It is from these 45 phonemes that all the sounds are derived which make up the infinity of utterances that comprise the English language. However, in learning to attend selectively to these 45 phonemes, as well as to specific consonants and vowels, required that the nervous system become fine tuned to perceiving them while ignoring others. In consequence, those cells which are unused, die (Joseph 1993).









Children are able to learn their own as well as foreign languages with much greater ease than adults because initially infants maintain a sensitivity to a universal set of phonetic categories (e.g. Janet et al. 2004). Because of this they are predisposed to hearing and perceiving speech and anything speech-like regardless of the language employed.

These sensitivities are either enhanced or diminished during the course of the first few years of life so that those speech sounds which the child most commonly hears becomes accentuated and more greatly attended to such that a sharpening of distinctions occurs (Janet et al. 2004). However, this generalized sensitivity in turn declines as a function of acquiring a particular language and presumably the loss of nerve cells not employed (see chapter 15 for related discussion). The nervous system becomes fine tuned so that familiar language-like sounds become processed and ordered in the manner dictated by the nervous system; i.e., the universal grammatical rules common to all languages.















Fine tuning is also a function of experience which in turn exerts tremendous influence on nervous system development and cell death. Hence, by the time most people reach adulthood they have long learned to categorize most of their new experiences into the categories and channels that have been relied upon for decades.

Nevertheless, in consequence of this filtering, sounds that arise naturally within one's environment can be altered, rearranged, suppressed, and thus erased. By fine tuning the auditory system so as to learn culturally significant sounds and so that language can be acquired occurs at a sacrifice. It occurs at the expense of one's natural awareness of their environment and its orchestra of symphonic sounds. In other words (at least from the perspective of the left hemisphere), the fundamental characteristics of reality are subject to language based alterations (Sapir 1966; Whorf 1956).

LANGUAGE AND REALITY

As detailed in chapters 2, 11, and elsewhere (Joseph 1982, 1988a, 2002b, 1993), language is a tool of consciousness, and the linguistic aspects of consciousness are dependent on the functional integrity of the left half of the brain. In that left cerebral conscious experience is, in large part, dependent on and organized in regard to linguistic and temporal-sequential modes of comprehension and expression, language, therefore can shape as well as determine the manner in which perceptual reality is conceived -at least by the left hemisphere.

According the Edward Sapir (1966) "Human beings are very much at the mercy of the particular language which has become the medium of their society...the real world is to a large extent built up on the language habits of the group. No two language are ever sufficiently similar to be considered as representing the same social reality."

According to Benjamin Whorf (1956) "language.... is not merely a reproducing instrument for voicing ideas but rather is itself the shaper of ideas... We dissect nature along lines laid down by language." However, Whorf believed that it was not just the words we used but grammar which has acted to shape human perceptions and thought. A grammatically imposed structure forces perceptions to conform to the mold which gives them not only shape, but direction and order.

Hence, distinctions imposed by temporal order and the employment of linguistically based categories and the labels and verbal associations which enable them to be described can therefore enrich as well as alter thoughts and perceptual reality. This is because language is intimately entwined with conscious experience.

For example, Eskimos possess an extensive and detailed vocabulary which enables them to make fine verbal distinctions between different types of snow, ice, and prey, such as seals. To a man born and raised in Kentucky, snow is snow and all seals may look the same. But if that same man from Kentucky had been raised around horses all his life he may in turn employ a rich and detailed vocabulary so as to describe them, e.g. appaloosa, paint, pony, stallion, and so on. However, to the Eskimo a horse may be just a horse and these other names may mean nothing to him. All horses look the same.









Moreover, both the Eskimo and the Kentuckian may be completely bewildered by the thousands of Arabic words associated with camels, the twenty or more terms for rice used by different Asiatic communities, or the seventeen words the Masai of Africa use to describe cattle.

Nevertheless, these are not just words and names, for each cultural group are also able to see, feel, taste, or smell these distinctions as well. An Eskimo sees a horse but a breeder may see a living work of art whose hair, coloring, markings, stature, tone, height, and so on speak volumes as to its character, future, and genetic endowment.

Through language one can teach others to attend to and to make the same distinctions and to create the same categories. In this way, those who share the same language and cultural group, learn to see and talk about the world in the same way, whereas those speaking a different dialect may in fact perceive a different reality. Thus, the linguistic foundations of conscious experience, and thus linguistic-perceptual consciousness can be shaped by language.

For example, when A.F. Chamberlain (1903), visited the Kootenay and Mohawk Indians of Brittish Columbia during the late 1800s, he noted that they even heard animal and bird sounds differently from him. For example, when listening to some owls hooting, he noted that to him it sounded like "tu-whit-tu-whit-tu-whit," whereas the Indians heard "Katskakitl." However, once he became accustomed to their language and began to speak it, he soon developed the ability to hear sounds differently once he began to listen with his "Indian ears." When listening to a whip poor will, he noted that instead of saying whip-poor-will, it was saying "kwa-kor-yeuh."

Observations such as these thus strongly suggest that if one were to change languages they might change their perceptions and even the expression of their conscious thoughts and attitudes. Consider for example, the results from an experiment reported by Farb (1975). Bilingual Japanese born women married to American Serviceman were asked to answer the same question in English and in Japanese. The following responses were typical.

"When my wishes conflict with my family's..."

"....it is a time of great unhappiness (Japanese)

....I do what I want. (English)

"Real friends should...."

"...help each other." (Japanese)

"...be very frank." (English)

Obviously, language does not shape all attitudes and perceptions. Moreover, language is often a consequence of these differential perceptions, which in turn requires the invention of new linguistic labels so as to describe these new experiences. Speech of course is also filtered through the personality of the speaker, whereas the listener is also influenced by their own attitudes, feelings, beliefs, prejudices and so on, all of which can affect what is said, how it is said, and how it is perceived and interpreted (Joseph 1993).

In fact, regardless of the nature of a particular experience, be it visual, olfactory or sexual, language not only influences perceptual and conscious experiences but even the ability to derive enjoyment from them, for example, by labeling them cool, hip, sexy, bad, or sinful, and by instilling guilt or pride. In this manner, language serves not only to label and filter reality, but affects one's ability to enjoy it.

SPATIAL LOCALIZATION, ATTENTION & ENVIRONMENTAL SOUNDS

In conjunction with the inferior colliculus and the frontal lobe (Graziano et al., 2008), and due to bilateral auditory input, the primary auditory area plays a significant role in orienting to and localizing the source of various sounds (Sanchez-Longo & Forster, 1958); for example, by comparing time and intensity differences in the neural input from each ear. A sound arising from one's right will reach and sound louder to the right ear as compared to the left.

Indeed, among mammals, a considerable number of auditory neurons respond or become highly excited only in response to sounds from a particular location (Evans & Whitfield, 1968). Moreover, some of these neurons become excited only when the subject looks at the source of the sound (Hubel et al., 1959). Hence, these neurons act so that location may be identified and fixated upon. In addition to the frontal lobe (Graziano et al., 2008) these complex interactions probably involve the parietal area (7), as well as the midbrain colliculi and limbic system. As based on lesions studies in humans, the right temporal lobe is more involved than the left in discerning location (Nunn et al., 2008; Penfield & Evans, 1934; Ploner et al., 199; Shankweiler, 1961).

There is also some indication that certain cells in the auditory area are highly specialized and will respond only to certain meaningful vocalizations (Wollberg & Newman, 1972). In this regard they seemed to be tuned to respond only to specific auditory parameters so as to identify and extract certain meaningful features, i.e. feature detector cells. For example, some cells will respond to cries of alarm and sounds suggestive of fear or indicating danger, whereas others will react only to specific sounds and vocalizations.

Nevertheless, although the left temporal lobe appears to be more involved in extracting certain linguistic features and differentiating between semantically related sounds (Schnider et al. 2014), the right temporal region is more adept at identifying and recognizing acoustically related sounds and non-verbal environmental acoustics (e.g. wind, rain, animal noises), prosodic-melodic nuances, sounds which convey emotional meaning, as well as most aspects of music including temp and meter (Heilman et al. 1975, 2004; Joseph, 1988a; Kester et al. 2011; Schnider et al. 2014; Spinnler & Vignolo 1966).

Indeed, the right temporal lobes spatial-localization sensitivity coupled with its ability to perceive and recognize environmental sounds no doubt provided great survival value to early primitive man and woman. That is, in response to a specific sound (e.g. a creeping predator), one is able to immediately identify, localize, locate, and fixate upon the source and thus take appropriate action. Of course, even modern humans relie upon the same mechanisms to avoid cars when walking across streets or riding bicycles, or to ascertain and identify approaching individuals, etc.

HALLUCINATIONS

Electrical stimulation of Heschyl's gyrus produces elementary hallucinations (Penfield & Jasper, 1954; Penfield & Perot, 1963). These include buzzing, clicking, ticking, humming, whispering, and ringing, most of which are localized as coming from opposite side of the room. Tumors involving this area also give rise to similar, albeit transient hallucinations, including tinnitus (Brodal, 2011). Patients may complain that sounds seem louder and/or softer than normal, closer and/or more distant, strange or even upleasent (Hecaen & Albert, 1978). There is often a repetitive quality which makes the experience even more disagreeable.

In some instances the hallucination may become meaningful. These include the sound of footsteps, clapping hands, or music, most of which seem (to the patient) to have an actual external source.





Penfield and Perot (1963) report that electrical stimulation of the superior temporal gyrus, the right temporal lobe in particular results in musical hallucinations. Patients with tumors and seizure disorders, particularly those involving the right temporal region, may also experience musical hallucinations. Frequently the same melody is heard over and over. In some instances patients have reported the sound of singing voices and individual instruments may be heard (Hecaen & Albert, 1978).

Conversely, it has been frequently reported that lesions or complete surgical destruction of the right temporal lobe significantly impaires the ability to name or recognize melodies and musical passages. It also disrupts time sense, the perception of timbre, loudness, and meter (Chase, 1967; Joseph, 1988a; Kester et al. 2011; Milner, 1962; Shankweiler, 1966).

Auditory verbal hallucinations seem to occur with right or left temporal destruction or stimulation (Hecaen & Albert, 1978; Penfield & Perot, 1963; Tarachow, 1941) --although left temporal involvement is predominant. The hallucination may involve single words, sentences, commands, advice, or distant conversations which can't quite be made out. According to Hecaen and Albert (1978), verbal hallucinations may precede the onset of an aphasic disorder, such as due to a developing tumor or other destructive process. Patients may complain of hearing "distorted sentences", "incromprehensible words" etc.





CORTICAL DEAFNESS

In some instances, such as due to middle cerebral artery stroke, the primary auditory receiving areas of the right or left cerebral hemisphere and/or the unerlying "white matter" fiber tracts may be destroyed. This results in a disconnection syndrome such that sounds relayed from the thalamus cannot be received or anlayzed by the temporal lobe. In some cases, however, the strokes may be bilateral. When both primary auditory receiving areas and their subcortical axonal connections have been destroyed the patient is said to be suffering from cortical deafness (Goodglass & Kaplan, 2008; Tanaka et al. 2011).

However, sounds continue to be processed subcortically --much like cortical blindness. Hence the ability to hear sounds per se, is retained. Nevertheless, since the sounds which are heard are not received neocortically and thus cannot be transmitted to the adjacent association areas, sounds become stripped of meaning. That is, meaning cannot be extracted or assigned and the patient becomes agnosic for auditory stimuli (Albert et al. 1972; Schnider et al. 2014; Spreen et al. 1965). Rather, only differences in intensity can be discerned --much like cortical blindness.











When lesions are bilateral, patients cannot respond to questions, do not show startle responses to loud sounds, lose the ability to discern the melody for music, cannot recognize speech or enviornmental sounds, and tend to experience the sounds they do hear as distorted and disagreeable, e.g. like the baning of tin cans, buzzing and roaring, etc. (Albert et al. 1972; Auerbach et al., 1982; Earnest et al. 1977; Kazui et al. 1990; Mendez & Geehan, 1988; Reinhold, 1950; Tanaka et al. 2011).

Commonly such patients also experience difficulty discriminating sequences of sound, detecting difference in temporal patterning, and determining sound duration wheareas intensity discriminations are better preserved. For example, when a 66 year old right handed male suffering from bitemporal subcortical lesions, "woke up in the morning and turned on the television, he found himself unable to hear anything but buzzing noises. He then tried to talk to himself, saying "This TV is broken." However, his voices sounded only as noise to him. Although the patient could hear his wife's voice, he could not interpret the meaning of her speech. He was also unable to identify many environmental sounds" (Kazui, et al. 1990; p. 477).

Nevertheless, individuals who are cortically deaf are not aphasic (e.g. Kazui et al. 1990. They can read, write, speak, comprehend pantomime, and are fully aware of their deficit. However, afflicted individuals may also display auditory inattention (Hecaen & Albert, 1978) and a failure to respond to loud sounds. Nevertheless, although not aphasic, per se, speech is sometimes noted to be hypophonic and contaminated by occasional literal paraphasias.

In some instances, rather than bilateral, a destructive lesion may be limited to the primary receving area of just the right or left cerebral hemisphere. These patient's are not considered cortically deaf. However, when the auditory receiving area of the left temporal lobe is destroyed the patient suffers from a condition referred to as pure word deafness. If the lesion is in the right temporal receiving area, the patient is more likely to suffer a non-verbal auditory agnosia (Schnider et al. 2014).

PURE WORD DEAFNESS

With a destructive lesion involving the left auditory receiving area, Wernicke's area becomes disconnected from almost all sources of acoustic input and patients are unable to recognize or perceive the sounds of language, be it sentences, single words, or even single letters (Hecaen & Albert, 1978). All other aspects of comprehension are preserved, including reading, writing, and expressive speech.

Moreover, if the right temporal region is spared, the ability to recognize musical and environmental sounds is preserved. However, the ability to name or verbally describe them is impaired --due to disconnection and the inability of the right hemisphere to talk.

Pure word deafness is most common with bilateral lesions in which case environmental sound recognition is also effected (e.g. Kazui et al. 1990). In these instances the patient is considered cortically deaf. Pure word deafness is more common with bilateral lesions simply because this prevents the any remaining intact auditory areas in the left hemisphere from receiving auditory input from the right temporal lobe via the corpus callosum.

Pure word deafness, when due to a unilateral lesion of the left temporal lobe, is partly a consequence of an inability to extract temporal-sequential features from incoming sounds. Hence, linguistic messages cannot be recognized. However, pure word deafness can sometimes be partly overcome if the patient is spoken to in an extremely slowed manner (Albert & Bear, 1974). The same is true of those with Wernicke's aphasia.

AUDITORY AGNOSIA

An individual with cortical deafness, due to bilateral lesions suffers from a generalized auditory agnosia involving words and non-linguistic sounds. However, in many instances an auditory agnosia, with preserved perception of language may occur with lesions restricted to the right temporal lobe (Fujii et al., 1990). In these instances, an individual loses the capability to correctly discern environmental (e.g. birds singing, doors closing, keys jangling) and acoustically related sounds, emotional-prosodic speech, as well as music (Nielsen, 1946; Ross, 1993; Samson & Zattore, 1988; Schnider et al. 2014; Spreen et al. 1965; Zatorre & Hapern, 1993).

These problems are less likely to come to the attention of a physician unless accompanied by secondary emotional difficulties. That is, most individuals with this disorder, being agnosic, would not know that they have a problem and thus would not complain. If they are their families notice (for example, if a patient does not respond to a knock on the door) the likelihood is that the problem will be attributed to faulty hearing or even forgetfulness.

However, because such individuals may also have difficulty discerning emotional- melodic nuances, it is likely that they will misperceive and fail to comprehend a variety of paralinguistic social-emotional messages; a condition referred to as social-emotional agnosia (Joseph, 1988a) and phonagnosia (van Lancker, et al., 1988). This includes difficulty correctly identifying the voices of loved ones or friends, or discerning what others may be implying, or in appreciating emotional and contextual cues, including variables such as sincerity or mirthful intonation. Hence, a host of behavioral difficulties may arise (see chapter 10).





For example, a patient may complain that his wife no longer loves him, and that he knows this from the sound of her voice. In fact, a patient may notice that the voices of friends and family sound in some manner different, which, when coupled with difficulty discerning nuances such as humor and friendliness may lead to the development of paranoia and what appears to be delusional thinking. Indeed, unless appropriately diagnoses it is likely that the patients problem will feed upon and reinforce itself and grow more severe.

It is important to note that rather than completely agnosic or word deaf, patients may suffer from only partial deficits. In these instances they may seem to be hard of hearing, frequently misinterpret what is said to them, and/or slowly develop related emotional difficulties.

THE AUDITORY ASSOCIATION AREAS

The auditory area although originating in the depths of the superior temporal lobe extends in a continuous belt-like fashion posteriorly from primary and association (e.g. Wernicke's) area toward the inferior parietal lobule, and via the arcuate fasciculus onward toward Broca's area. Indeed, in the left hemisphere, this massive rope of interconnections forms an Axis such that Wernickes Area, the inferior parietal lobule, and Broca's area. These areas often become activated in parallel or simultaneously during language tasks, and together, are able to mediate the perception and expression of most forms of language and speech (Joseph, 1982, Goodglass & Kaplan, 2000; Ojemann, 2011).

The rope-like arcuate and inferior and superior fasciculi are bidirectional fiber pathways, however, that run not only from Wernickes through to Broca's area but extends inferiorly deep into the temporal lobe where contact is established with the amygdala. Hence, via these connections auditory input comes to be assigned emotional-motivational significance, whereas verbal output becomes emotionally-melodically colored . Within the right hemisphere, these interconnections which include the amygdala appear to be more extensively developed.

















WERNICKE'S AREA

Following the analysis performed in the primary auditory receiving area, auditory information is transmitted to the immediately adjacent association cortex (Brodmanns area 22), where more complex forms of processing take place. In both hemispheres this region partly surrounds the primary area and then extends posteriorly merging with the inferior parietal lobule with which it maintains extensive interconnections. Within the left hemisphere the more posterior portion of area 22, and part of area 42 corresponds to Wernicke's area.

Wernickes area, and the corresponding region in the right hemisphere are not merely auditory association areas as they also receive a convergence of fibers from the somesthetic and visual association cortices (Jones & Powell, 1970; Zeki, 1978b). These interlinking pathways include the inferior and middle temporal lobes which are also multi-modal areas concerned with language, somesthesis, and complex visual functioning (Buchel et al., 1998; Luders et al., 1986; Nobre et al., 2014; Price, 2011), and the immediately adjacent inferior parietal lobule which becomes active when viewing words (Bookheimer, et al., 1995; Vandenberghe, et al., 1996; Menard, et al., 1996; Price, 2011) when performing syllable judgements (Price, 2011), and when reading ( Bookheimer, et al., 1995; Menard, et al., 1996; Price, et al., 1996).





The auditory association area (area 22) also receives fibers from the contralateral auditory association area via the corpus callosum and anterior commissure and projects to the frontal convexity and orbital region, the frontal eye fields, and cingulate gyrus (Jones & Powell, 1970). Hence, Wernicke's area receives input from a variety of convergence zones, and is involved in multimodal as well as auditory associational analysis and becomes highly active during a variety of language tasks (Buchel et al., 1998; Price, 2011).

Broadly considered, Wernicke's area encompasses a large expanse of tissue that extends from the posterior superior and middle temporal lobe to the IPL and up a over the parietal operculum, around the sylvian fissure, extending just beyond the supramarginal gyrus. Electrical stimulation, the surgical destruction, or lesions of this region results in significant language impairments (Kertesz, 1979; Penfield & Roberts, 1959; Ojemann, 2011). However, this vast expanse of cortex is actually made up of a mosaic of speech area, each concerned with different aspects of language, including comprehension, word retrieval, naming, verbal memory, and even expressive speech.

For example, only 36% of stimulation sites in the classically defined Wernicke's area (anterior to the IPL), interfere with naming, whereas phoneme identification is significantly impaired (Ojemann, 2011). By contrast, and as noted above, the IPL (which is an extension of Wernicke's area) becomes highly active when retrieving words or engaged in naming. In this regard, the IPL and Wernicke's area interact so as to comprehend and express the sounds and words of language--all of which is then transmitted via the arcuate fasiculus to Broca's area.

RECEPTIVE APHASIA

When the posterior portion of the left auditory association area is damaged there results severe receptive aphasia i.e. Wernicke's aphasia. Individuals with Wernicke's aphasia, in addition to severe comprehension deficits usually suffer abnormalities involving expressive speech, reading, writing, repeating, word finding, etc. Spontaneous speech, however, is often fluent, and sometimes hyperfluent such that they speak at an increased rate and seem unable to bring sentences to an end --as if the temporal-sequential separations between words have been extremely shortened or in some instances abolished. In addition, many of the words spoken are contaminated by neologistic and paraphasic distortions. As such, what they say is often incomprehensible (Chirstman 2014; Goodglass & Kaplan 2008; Hecaen & Albert, 1978). Hence, this disorder has also been referred to as fluent aphasia.





Individuals with Wernicke's aphasia, however, are still able to perceive the temporal-sequential pattern of incoming auditory stimuli to some degree (due to perseveration of the primary region). Nevertheless, they are unable to perceive spoken words in their correct order, cannot identify the pattern of presentation (e.g. two short and three long taps) and become easily overwhelmed (Hecaen & Albert, 1978; Luria, 1980).

Patients with Wernicke's aphasia, in addition to other impairments, are necessarily "word deaf". As these individuals recover from their aphasia, word deafness is often the last symptom to disappear (Hecaen & Albert, 1978).

THE MELODIC-INTONATIONAL AXIS

It has been consistently demonstrated among normals (such as in dichotic listening studies), that the right temporal lobe (left ear) predominates in the perception of timbre, chords, tone, pitch, loudness, melody, and intensity --the major components (in conjunction with harmony) of a musical stimulus (chapter 10). For example, when listening to Bach (the third movement of Bach's Italian concerto), the right temporal lobe becomes highly active, whereas when performing scales activity increases in the left temporal lobe (Parsons & Fox, 2011). Likewise, Evers and colleagues (2008) in evaluating cerebral blood velocity, found that a right hemisphere increase in blood flow when listening to harmony (but not rhythm), among non-musicians in general, and especially among females. Rhythm increased left hemisphere activity (Evers et al., 2008). Hence, the left hemisphere is clearly dominant in regard to the rhythmical and temporal sequential aspects of a musical stimulus (Evers et al., 2008; Parsons & Fox, 2011).

In part, it is due to its dominance for perceiving melodic information that the right temporal lobe becomes activated when engaged in a variety of language tasks. For example, the right temporal and parietal areas are activated when reading (Bottini et al., 2014; Price et al., 1996), and the right temporal lobe becomes highly active when engage in interpreting the figurative aspects of language (Bottini et al., 2014).

When the right temporal lobe is damaged (e.g. right temporal lobectomy, right amygdalectomy) there results a disrupts in time sense, rhythm, the ability to sing, carry a tune, perceive, recognize or recall tones, loudness, timbre, and melody. Similarly, the ability to recognize even familiar melodies and the capacity to obtain pleasure while listening to music is abolished or disrupted or significantly reduced; a condition referred to as amusia.

For example, a woman described by Takeda and colleagues (1990) and who was described as an expert singer of traditional Japanese songs, and who would accompany them on an instrument referred to as a samisen, lost this ability following a hemorrhagic stroke of the of the right superior gyrus including Heschl's gyrus. Although she was able to accurately produce the rhythmic aspects of music, melody and pitch were abolished.

In addition, lesions involving the right temporal-parietal area, have been reported to significantly impair the ability to perceive and identify environmental sounds, comprehend or produce appropriate verbal prosody, emotional speech, or to repeat emotional statements (Joseph, 1988a; Ross, 1993; van Lancker et al., 1988). Indeed, when presented with neutral sentences spoken in an emotional manner, right temporal-parietal damage has been reported to disrupt the perception and comprehension of emotional prosody regardless of its being positive or negative in content (see chapter 10).

Hence, the right temporal-parietal area is involved in the perception, identification, and comprehension of environmental and musical sounds and various forms of melodic and emotional auditory stimuli, and probably acts to prepare this information for expression via transfer to the right frontal convexity which is dominant regarding the expression of emotional-melodic and even environmental sounds. Indeed, it appears that an emotional-melodic-intonational Axis, somewhat similar to the Language Axis in anatomical design is maintained within the right hemisphere (Joseph 1982, 1988a; Gorelick & Ross, 2007; Ross, 1993).

When the posterior portion of the Melodic-Emotional Axis is damaged, the ability to comprehend or repeat melodic-emotional vocalizations in disrupted. Such patients are thus agnosic for non-linguistic sounds. With right frontal convexity damage speech becomes bland, atonal, and monotone.











THE AMYGDALA.

As detailed in chapters 13 and 15, the right cerebral hemisphere appears to maintain more extensive as well as bilateral interconnections with the limbic system. Indeed, the limbic system also appears to be lateralized in regard to certain aspects of emotional functioning such that the right amygdala, hippocampus and hypothalamus seem to exert dominant influences.

As noted, the arcuate fasciculus extends from the amygdala (which is buried within the anterior-inferior temporal lobe) through the auditory association area and inferior parietal region and into the frontal convexity. It is possibly through these interconnections that emotional colorization is added to neocortical acoustic perceptions as well as sounds being prepared for expression. In fact, the human amygdala can produce as well as perceive emotional vocalizations (Halgren, 2002; Heit, Smith, & Halgren, 1988). Moreover, when the right amygdala has been destroyed or surgically removed, the ability to sing as well as to properly intonate is altered (see Chapter 13). In this regard, the amygdala should be considered part of the melodic-intonational axis of the right hemisphere as it not only subcortically responds to and analyzes environmental sounds and emotional vocalizations but imparts emotional significance to auditory input and output processed and expressed at the level of the neocortex.

Nevertheless, it is possible that emotional-prosodic intonation is imparted directly to speech variables as they are being organized for expression within the left hemisphere. That is, although the right hemisphere is dominant in regard to melodic-emotional vocalizations, the two amygdalas are in direct communication via the anterior commissure. Hence, although originating predominantly within the right amygdala/hemisphere, these influences can be directly transmitted to the left half of the brain via the left amygdala and through anterior commissure and via the arcuate fasciculus which transmits this data into the linguistic stream of the Language Axis.

THE INFERIOR & MIDDLE TEMPORAL LOBE

The basal temporal region can be subdivided into a medial, inferior, middle, and anterior and posterior zones, harbors the amygdala and hippocampus in its depths. These tissues are extensively interconnected, and project to the auditory association area, frontal convexity, and orbital region (Jones & Powell, 1970; Pandya & Kuypers, 1969). The inferior arcuate fasciculus in it's journey from the amygdala to Wernickes areas also passes through this neocortical auditory territory. Hence, when considered a whole, the inferior and middle temporal lobe is a complex multifunctional tissue which is functionally lateralized and has extensive visual and auditory and linguistic capabilities.

In general, the anterior basal temporal lobe is more involved in auditory functioning, whereas the posterior basal temporal lobe is more intimately concerned with the processing of higher level visual information including form recognition and (in the left temporal lobe) the reading of the written language. Indeed, this generalized dichotomy, first proposed in the 1990 edition of this text, has since been born out by a variety of functional imaging studies and is supported by lesions and neurosurgical stimulation studies.

Specifically, the left inferior-middle posterior temporal lobe (Brodmann's area 37), is located between the visual cortex and the anterior temporal cortex and becomes activated during a variety of language tasks, including reading and object and letter naming (Price, 2011). This has been demonstrated not only by functional imaging (Buchel et al., 1998; Price, 2011), but direct cortical recoding (Nobre et al., 2014), and electrical stimulation (Luders et al., 1986). In fact, both normal, cognitally blind, and late-blind subject display activity in this area (Buchel et al., 1998). For example, reading of concrete and abstract words activates the left posterior basal temporal lobe and the left frontal operculum (Buchel et al., 1998).





Hence, because of its role in language, when the middle temporal lobe is stimulated there can result aphasic abnormalities (Penfield & Rasmussen, 1950). Lesions involving this area are also associated with subtle disturbances involving language, including word finding difficulty, confrontive naming deficits, abnormalities in the maintenance of temporal order and sequence, as well as verbal memory impairments (Luria, 1980). Patients may suffer from reading and naming deficits (Rapcsak, et al., 2007); a condition referred to as phonological alexia. Moreover, patients with developmental dyslexia have been found to have abnormalities in this area (Rumsey et al., 2011).

As noted, left temporal lobe activity increases as word length increases. Hence, with injuries in this area, including the basal temporal lobe, patients may have difficulty recalling word lists or order of word presentation, such that the longer the list, the greater the difficulty. Hence, if a list of four words were read, the patient cannot repeat the correct order even after repeated presentations, although individuals words may be recalled correctly (Luria, 1980).











However, the nature of the disturbances depends on the exact location of the lesion (Coltheart, 1998; Miozzo & Caramazza, 1998), for as noted, the anterior and posterior and inferior and middle temporal lobes perform interrelated but also divergent functions. In general, the more posterior aspect is concerned with the visual aspects of perception and language, including reading and object naming. Indeed, the left posterior basal temporal lobe is a convergence zone for visual, auditory, and tactile information. Hence, patients may suffer from alexia as well as visual and tactile anomia if this area is injured (Rapcsak, et al., 2007). In addition, these structures are lateralized, and although both the right and left temporal lobe become activated by various language and reading tasks (reviewed in Price, 2011), the right basal temporal lobe is much more concerned with non-verbal visual functioning.

THE 'VISUAL" MIDDLE INFERIOR TEMPORAL LOBE

The middle temporal lobe, (MTL) like other structures throughout the brain, appears to be functionaly lateralized such that the right temporal region is more involved in visual and non-verbal auditory functioning, whereas the left MTL is more concerned with auditory-linguistic capabilities. Hence, whereas the auditory-linguistic zones appear to be more extensive within the left temporal lobe (and include portions of the posterior temporal region), the right MTL seems to be more associated with visual responsiveness. In general, however, the middle temporal gyrus of both hemispheres appear to contain visually responsive neurons (Beckers & Zeki 1995; Felleman & Kaas, 1974; Heit et al. 1990; Maunsell & Van Essen 2004; Selemon et al. 2014). Nevertheless, since there have been relatively few published studies of the effects of lesions or the functional capabilities of the middle temporal lobes in humans, notions regarding the extensiveness of auditory vs. visual lateralized representation are admittedly speculative.

MIDDLE AND INFERIOR TEMPORAL LOBE VISUAL FUNCTIONING

Visual cells in the MTL receive direct projections from the striate cortex, area 17 and the association area 18 (Wall et al. 1982). This area in turns projects to the MTL of the opposite hemisphere via the corpus callosum, ipsilaterally to areas 17, 18, 19, the inferior temporal and the parietal-occipital cortex (Tigges et al., 2011; Wall et al., 1982), and maintains interconnections with the pulvinar, superior colliculus and pontine nuclei of the brainstem (Walls et al., 1982). Hence, this regions has connections with areas concerned with visual and visual attentional capabilities.















MTL neurons are sensitive to speed and direction of stimulus movement, motion, orientation, width, and disparity (Felleman & Kaas, 2004; Maunsell & Van Essen, 1983). However, most MTG neurons are not particular sensitive to the form of a stimulus--most preferring narrow stimuli (Albright et al. 2004; Maunsell & Van Essen, 1983). A large number of cells have binocular capabilities and respond to stimuli from either or both eyes. Hence, these cells are significantly involved in stereoscopic vision as well as determining distance.

Although not specialized for perception of form per se, via the combined analysis of width, orientation, speed and direction of movement these cells can process visual stimuli in a three-dimensional fashion, particularly in regard to trajectory, depth and position, i.e. if an object is near or far, approaching or withdrawing (Maunsell & Van essen, 1983).









Via its interconnections with the parietal-occipital lobe (an area involved in depth perception, visual fixation, and the visual-somesthetic guidance of movement) the MTL appears to provide visual guidance in regard to interactional object and body movement. That is, via the analysis of the flow of movement, local direction and speed, as well as the relative distances of objects, these neurons (in conjunction with area 7 cells) are important in guiding the movements of the body as well as the individuals limbs toward the object (Manunsell & Van Essen,1983).

The MTL maintains extensive interconnections with the inferior region and thus with limbic nuclei. It is probably via these connections that objects or conspecies of motivational significance can be discerned and attended to. That is, not only is the speed, movement, distance, etc. of a stimulus determined, but its emotional attributes (e.g. should it be feared, chased, eaten). Moreover, not just written words, but object recognition occurs in this area (in conjunction with the inferior temporal lobe), such that if injured, patients may suffer from agnosia, i.e. an inability to recognize visual images (Giannokapoulos et al., 2008).

HALLUCINATIONS.

Tumors involving the middle temporal lobe have been associated with the development of auditory and visual hallucinations, dreamy states, and alterations in emotional functioning--particularly as the lesion encroaches on the inferior regions (Luria, 1980). Electrical stimulation also initiates the development of complex hallucinations and alterations in consciousness (Penfield & Roberts, 1959).

INFERIOR TEMPORAL LOBE

As noted, it is possible to very loosely define the anterior-inferior temporal lobes as auditory cortex, although neurons in this vicinity receive visual as well as somesthetic input.. Hence, the inferior temporal lobes can respond to auditory as well as emotionally and visually significant stimuli (Gloor, 2011; Nakamura et al., 2014; Tovee et al., 2014).

That the inferior temporal lobe (ITL) processes complex auditory, visual and emotional stimuli is probably a function of it being a derivative of the amygdala (see chapter 14) as well as visual cortex (Diamond 1973; Gloor, 2011). Visual and auditory functions also reflect its reception of extensive (upper visual field) projections from the optic radiations, highly processed input from the visual association areas in the occipital lobes of both cerebral hemispheres (via the corpus callosum), and fibers from the superior colliculus by way of the pulvinar of the thalamus (Chow, 1950; Kaas & Krubitzer 2011; Kuypers et al., 1965; Previc 1990; Rocha-Miranda et al. 1975).















VISUAL CAPABILITIES & FORM RECOGNITION

Indeed, the neocortex of the ITL is specialized for receiving, analyzing, discriminating, recognizing and recalling complex visual information and is involved in attention and visually guided behavior (Gross & Graziano 1995; Gross et al. 1972; Tovee et al. 2014), including the recollection and learning of visual discriminations (Gross, 1972) and memory for objects and spatial locations (Nunn et al., 2008; Ploner et al., 2008). If the temporal lobe is injured, these functions become compromised.





For example, Kimura (1963) found that patients with right vs left temporal lobe injury were impaired when presented with overlapping nonsense shapes and then immediately tested for recognition. Likewise, Meier and French (1965), found that those with right vs left temporal lobe injuries were impaired when asked to make visual discriminations when presented with fragmented concentric circle patterns--skills which are also related to visual closure and gestalt formation. More recently, Nunn et al., (2008) found that right vs left temporal lobectomy patients were more impaired when required to remember and recognize toys and recall their location.





Cells in the ITL have very large, bilateral visual receptive fields which include the fovea, and many are sensitive to direction of stimulus movement, color, contrast, size, shape, orientation and are involved in the perception of three dimensional objects and the supramodal analysis of information already processed in the association areas (Eskander, et al. 2002; Gross & Graziano 1995; Gross, et al. 1972; Nakamura et al. 2014; Rolls, 2002; Sergent, et al.1990). Thus inferior temporal (IT) neurons appear to take part in the last stages of visual analysis for form recognition and receive terminal fibers from the primary and association visual areas (Gloor, 2011; Gross, et al. 1972; Ungerleider & Mishkin, 1982); that is, via the ventral visual stream. Indeed, a single neuron can respond to a combination of these features and many will fire selectively in response to particular shapes and faces (Eskander, et al. 2002; Gross, et al. 1972; Nakamura et al. 2014; Richmond, et al. 1983; Rolls, 2002; Sergent, et al.1990).

FORM & FACIAL RECOGNITION

Overall, the ITL appears to be involved in the highest level of visual integration containing highly developed neurons which seem to be the end station of a hierarchical system which mediates the perception and recognition of specific and particular shapes and forms (Desimone & Schein, 2007; Gross & Graziano 1995; Nakamura et al. 2014; Richmond, et al. 1983; Rolls, 2002.) Indeed, in addition to the optic radiations, there is a pathway (the ventral stream) beginning in the primary visual cortex which passes through areas 18 and 19 and terminates in the ITL (Kuypers et al., 1965; Previc 1990). As information is passed from the primary to these association areas various features important in the identification of specific objects become progressively and hiarchically analyzed and increasingly complex associations are formed.

In fact, based on single cell recordings, some of these ITL neurons have been found to become particularly excited when presented with two dimensional patterns or three dimensional objects such as hands, brushes, and in particular, faces (Deismone & Gross, 1979; Gross et al., 1972; Nakamura et al. 2014; Richmond et al., 1983; Richmond et al.2007). A variety of different feature detectors are found and the majority probably act collectively so as code and assemble a particular shape, including the formation of gestalts and thus the performance of visual closure, particularly the right temporal region (see chapter 10). Via closure an individual can detect a partial stimulus and recognize that it is a face vs a rabbit.





Some cells are responsive to particular facial orientations, such as a profile, some respond to only parts of the face, such as eyes or a mouth, whereas others respond only to the entire face; i.e. a correctly organized facial gestalt. Interestingly, the ITL also contains neurons which will fire even to a scrambled face, so long as all the features are present (Gross et al., 2004). Moreover, some cells respond preferentially to familiar faces, to the faces of certain individuals, to specific emotions conveyed via the face, and the direction of the face including the direction of gaze--especially cells within the amygdala. Specifically, the left amygdala acts to discriminate the direction of another person's gaze, whereas the right amygdala becomes activated while making eye-to-eye contact (Kawashima, et al., 2008). Hence, these cells can determine if someone is looking at them, or looking at someone else, if the facial expression conveys threat, and if there is a hand moving toward or away from the subject or another person.

Hence, these cells are especially equipped for determining social signals and to read the emotions conveyed facially between two people. Interestingly, these same capacities were originally mediated by the olfactory system which in turn gave rise to the amygdala and promoted its differentiation and thus the development of the temporal lobe. In this regard it is also noteworthy that with the bilateral removal of the anterior inferior temporal lobe (thus destroying the amygdala as well as parts of the hippocampus), patients (and non-human primates) develop so called "psychic blindness," and will pick up and smell and taste whatever object captures their attention. In other words, being deprived of an amygdala that can process, visually, social and emotional signals, the amygdalectomized patient/primate reverts back to those behaviors typical of creatures that rely on smell.





AGNOSIA AND TEMPORAL LOBE FUNCTIONAL LATERALITY

As noted, abnormalities affecting the middle temporal lobe (area 37) can result in agnosic disturbances (Giannokapoulos et al., 2008). There are however, to major forms of agnosia, and different subtypes as well, which can be produced by damage to tissues mediating complex visual perception or lesions disconnecting the IPL, for example, from visual, somesthetic, or auditory input.

For example, one type of agnosia, "apperceptive visual agnosia" refers to a disturbance in perceptual and visual-motor integration, such that patients have difficulty copying or matching various objects. This latter form of agnosia has been associated with lesions to the parietal occipital cortex (Mizuno, et al., 1996), as well as to bilateral damage to the inferior-occipital cortex (Shelton, et al., 2014).

By contrast, associative visual agnosia, which is a deficit in naming, such that auditory equivalents cannot be matched to a visual perception, is associated with left inferior and middle temporal (area 37) occipital abnormalities (Giannokapoulos et al., 2008), which may be accompanied with alexia (Feinberg et al., 2014), as well as to lesions to and atrophy of the parietal occipital cortex (Mizuno, et al., 1996).

It is noteworthy that depending on the laterality and location of the injury, e.g., right vs left inferior/medial vs superior temporal lobe, patients may display category specific agnosias. For example, a 27-year old man I examined who had sustained a massive right inferior-posterior temporal lobe injury that also involved surgical removal, was able to recognize pictures of tools (he had been a carpenter) but could not recognize or correctly name pictures of animals and he could not correctly remember facial stimuli that he had been shown five minutes earlier and could not differentiate them from faces he had not seen. By contrast, a 43 year old woman who had been a waitress, and had developed a left inferior temporal lobe glioma that required surgical removal (coupled with chemotherapy) was able to recognize and name pictures of animals and could remember different pictures of faces, but had considerable difficulty recognizing and naming common household objects.

In this regard a 47-year old woman I examined who was subsequently found to have a calcium cyst growing from the skull into the right superior temporal lobe, was able to name pictures of animals, tools and household objects. However, she was almost completely unable to recognize and correctly name animal and humans sounds (e.g. a baby crying, a crowd cheering, a lion roaring) which had been briefly presented, but was better able to recognize non-living sounds such as a creaking door, or a hammer hammering--though these abilities were also compromised.

These findings, which require independent confirmation, raises the possibility that the temporal lobes are not only able to distinguish between living and non-living things including tools and faces, but that the right temporal lobe is specialized for perceiving living creatures (and the sounds they make) whereas the left is specialized for perceiving and naming non-living things, such as tools and household objects.

VISUAL ATTENTION

Attention and visual fixation involves the activation of neurons in the superior parietal and frontal eye fields, the midbrain colliculi, and thalamic nuclei--regions with which the ITL maintains interconnections (Gloor, 2011; Gross & Graziano 1995; Previc 1990). Attention, however, generally requires that visual fixation be focused. Since many ITL neurons maintain large bilateral visual fields, when engaged in visual fixation ITL these cells appear to become partly suppressed. That is, the area of the visual field they respond to becomes restricted to the fovea (Pevic 1990; Richmond et al., 1983). In this manner, ITL neurons become less responsive to other objects such as those in the periphery as the receptive field contracts around the object attended to.

Hence, ITL neurons seems to scan the entire visual field so as to alert the organism to objects of interest or motivational importance (via interconnections with limbic nuclei). When detected, the frontal eye fields, the superior parietal lobe, and subcortical neurons are activated triggering visual fixation. Simultaneously, ITL visual form recognition neurons are activated whereas those with wide non-specific visual fields are inhibited. In this manner, objects of interest are detected and fixated upon (e.g. Previc 1990).

Of adjunctive importance is the middle temporal lobe which in turn can analyze the velocity and direction of the objects movement so that the individual may approach, and, via interaction with cells in area 7, grasp and manipulate the object.

THE INFERIOR AND MEDIAL TEMPORAL LOBE

PROSOPAGNOSIA & VISUAL DISCRIMINATION DEFICITS

As based on functional imaging (Sergent, et al., 2002), the medial temporal lobe, the right parahippocampal gyrus (in conjunction with areas 19, 37, 36), and the inferior and middle temporal lobe becomes highly active when viewing and categorizing faces and other complex stimuli. Likwise, electrical stimulation of these areas can produce hallucinations and memories of faces of complex visual stimuli (Gloor, 2011; Halgren, 2002).

Damage or removal of the inferior temporal lobe results in loss of the ability to recognize faces, as well as creating severe disturbances involving visual discrimination learning and retention (Braun et al. 2014; Gross & Mishkin, 1977; Mishkin, 1972), and difficulty performing visual closure and recognizing incomplete figural stimuli (Kimura, 1963; Lansdell, 1968,1970). For example, primates with lesions in this vicinity, have severe difficulty learning to discriminate between different shapes and patterns and objects which differ in regard to size or color, although visual acuity is normal.









With damage to the right temporal-occipital region, there can result a severe disturbance in the ability to recognize the faces of friends, loved ones, or pets (Braun et al. 2014; DeRenzi, 1986; DeRenzi et. al., 1968; DeRenzi & Spinnler, 1966; Hanley et al. 1990; Hecaen & Angelergues, 1962; Landis et al., 1986; Levine, 1978; Whitely & Warrington, 1977l ) or to discriminate and identify even facial affect (Braun et al. 2014); a condition referred to as prosopagnosia. In fact, with gradual deterioration and degeneration of the right inferior temporal lobe, patients may suffer a progressive prosopagnosia (Evans et al. 1995). Some patients may in fact be unable to recognize their own face in the mirror. For example, one patient was unable to even discriminate between people on the basis of sex but instead had to relie on the presence of details, su