1 Stein, B. E. & Meredith, M. A. The Merging of the Senses (MIT Press, 1993).

2 Alais, D. & Burr, D. The ventriloquist effect results from near-optimal bimodal integration. Curr. Biol. 14, 257–262 (2004).

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5 Lewkowicz, D. J. & Lickliter, R. (eds) The Development of Intersensory Perception: Comparative Perspectives (Lawrence Erlbaum Associates, 1994).

6 Stein, B. (ed.) The New Handbook of Multisensory Processing (MIT Press, 2012).

7 Stein, B. E., Stanford, T. R., Ramachandran, R., Perrault, T. J. Jr & Rowland, B. A. Challenges in quantifying multisensory integration: alternative criteria, models, and inverse effectiveness. Exp. Brain Res. 198, 113–126 (2009).

8 Binns, K. E. & Salt, T. E. Importance of NMDA receptors for multimodal integration in the deep layers of the cat superior colliculus. J. Neurophysiol. 75, 920–930 (1996).

9 Wallace, M. T., Meredith, M. A. & Stein, B. E. Multisensory integration in the superior colliculus of the alert cat. J. Neurophysiol. 80, 1006–1010 (1998).

10 Bolognini, N., Leo, F., Passamonti, C., Stein, B. E. & Làdavas, E. Multisensory-mediated auditory localization. Perception 36, 1477–1485 (2007).

11 Corneil, B. D. & Munoz, D. P. The influence of auditory and visual distractors on human orienting gaze shifts. J. Neurosci. 16, 8193–8207 (1996).

12 Diederich, A. & Colonius, H. Bimodal and trimodal multisensory enhancement: effects of stimulus onset and intensity on reaction time. Percept. Psychophys. 66, 1388–1404 (2004).

13 Fetsch, C. R., Pouget, A., DeAngelis, G. C. & Angelaki, D. E. Neural correlates of reliability-based cue weighting during multisensory integration. Nature Neurosci. 15, 146–154 (2012). This is a comprehensive review of the utility of Bayesian frameworks for studying multisensory integration.

14 Foxe, J. J. & Schroeder, C. E. The case for feedforward multisensory convergence during early cortical processing. Neuroreport 16, 419–423 (2005).

15 Frens, M. A. & Van Opstal, A. J. Visual-auditory interactions modulate saccade-related activity in monkey superior colliculus. Brain Res. Bull. 46, 211–224 (1998).

16 Hughes, H. C., Reuter-Lorenz, P. A., Nozawa, G. & Fendrich, R. Visual-auditory interactions in sensorimotor processing: saccades versus manual responses. J. Exp. Psychol. Hum. Percept. Perform. 20, 131–153 (1994). This early article helped to establish the relationship between multisensory integration and reaction speed.

17 Naumer, M. J. & Kaiser, J. (eds) Multisensory Object Perception in the Primate Brain (Springer, 2010).

18 Sánchez-García, C., Alsius, A., Enns, J. T. & Soto-Faraco, S. Cross-modal prediction in speech perception. PLoS ONE 6, e25198 (2011).

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20 Stein, B. E., Meredith, M. A., Huneycutt, W. S. & McDade, L. Behavioral indices of multisensory integration: orientation to visual cues is affected by auditory stimuli. J. Cogn. Neurosci. 1, 12–24 (1989). This paper showed that the physiological principles of multisensory integration that are evident in single superior colliculus neurons applies to overt orientation behaviour.

21 Talsma, D., Doty, T. J. & Woldorff, M. G. Selective attention and audiovisual integration: is attending to both modalities a prerequisite for early integration? Cereb. Cortex 17, 679–690 (2007).

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23 Zhang, M., Weisser, V. D., Stilla, R., Prather, S. C. & Sathian, K. Multisensory cortical processing of object shape and its relation to mental imagery. Cogn. Affect. Behav. Neurosci. 4, 251–259 (2004).

24 Goldring, J. E., Dorris, M. C., Corneil, B. D., Ballantyne, P. A. & Munoz, D. P. Combined eye-head gaze shifts to visual and auditory targets in humans. Exp. Brain Res. 111, 68–78 (1996).

25 Sperdin, H. F., Cappe, C., Foxe, J. J. & Murray, M. M. Early, low-level auditory-somatosensory multisensory interactions impact reaction time speed. Front. Integr. Neurosci. 3, 2 (2009).

26 Von Saldern, S. & Noppeney, U. Sensory and striatal areas integrate auditory and visual signals into behavioral benefits during motion discrimination. J. Neurosci. 33, 8841–8849 (2013).

27 Bremner, A. J., Lewkowicz, D. J. & Spence, C. (eds) Multisensory Development (Oxford Univ. Press, 2012).

28 Bizley, J. K. & King, A. J. Visual-auditory spatial processing in auditory cortical neurons. Brain Res. 1242, 24–36 (2008).

29 Brett-Green, B., Fifková, E., Larue, D. T., Winer, J. A. & Barth, D. S. A multisensory zone in rat parietotemporal cortex: intra- and extracellular physiology and thalamocortical connections. J. Comp. Neurol. 460, 223–237 (2003).

30 Driver, J. & Noesselt, T. Multisensory interplay reveals crossmodal influences on 'sensory-specific' brain regions, neural responses, and judgments. Neuron 57, 11–23 (2008).

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32 Graziano, M., Gross, C., Taylor, C. & Moore, T. in Crossmodal Space and Crossmodal Attention (eds Spence, C. & Driver, J.) 51–67 (Oxford Univ. Press, 2004).

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35 Schroeder, C. E. & Foxe, J. Multisensory contributions to low-level, 'unisensory' processing. Curr. Opin. Neurobiol. 15, 454–458 (2005). An examination of the impact of multisensory integration in cortical regions believed to be unisensory. The paper examines the evidence for multisensory information coding even within classically defined, modality-specific areas of that cortex.

36 Wallace, M., Ramachandran, R. & Stein, B. A revised view of sensory cortical parcellation. Proc. Natl Acad. Sci. USA 101, 2167–2172 (2004).

37 Winkowski, D. E. & Knudsen, E. I. Top-down control of multimodal sensitivity in the barn owl optic tectum. J. Neurosci. 27, 13279–13291 (2007).

38 Macaluso, E. & Driver, J. in The Handbook of Multisensory Processes (eds Calvert, G. A., Spence, C. & Stein, B. E.) 529–548 (MIT Press, 2004).

39 Cohen, Y. E. & Andersen, R. A. in The Handbook of Multisensory Processes (eds Calvert, G. A., Spence, C. & Stein, B. E.) 463–479 (MIT Press, 2004).

40 Burnett, L. R., Stein, B. E., Chaponis, D. & Wallace, M. T. Superior colliculus lesions preferentially disrupt multisensory orientation. Neuroscience 124, 535–547 (2004).

41 Burnett, L. R., Stein, B. E., Perrault, T. J. Jr & Wallace, M. T. Excitotoxic lesions of the superior colliculus preferentially impact multisensory neurons and multisensory integration. Exp. Brain Res. 179, 325–338 (2007).

42 Groh, J. M. & Sparks, D. L. Saccades to somatosensory targets. II. Motor convergence in primate superior colliculus. J. Neurophysiol. 75, 428–438 (1996).

43 Groh, J. M. & Sparks, D. L. Saccades to somatosensory targets. III. Eye-position-dependent somatosensory activity in primate superior colliculus. J. Neurophysiol. 75, 439–453 (1996).

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48 Munoz, D. P. & Wurtz, R. H. Saccade-related activity in monkey superior colliculus. II. Spread of activity during saccades. J. Neurophysiol. 73, 2334–2348 (1995).

49 Lomber, S. G., Payne, B. R. & Cornwell, P. Role of the superior colliculus in analyses of space: superficial and intermediate layer contributions to visual orienting, auditory orienting, and visuospatial discriminations during unilateral and bilateral deactivations. J. Comp. Neurol. 441, 44–57 (2001).

50 Levine, M. S., Hull, C. D. & Buchwald, N. A. Development of motor activity in kittens. Dev. Psychobiol. 13, 357–371 (1980).

51 Norton, T. T. Receptive-field properties of superior colliculus cells and development of visual behavior in kittens. J. Neurophysiol. 37, 674–690 (1974).

52 Meredith, M. A., Wallace, M. T. & Stein, B. E. Visual, auditory and somatosensory convergence in output neurons of the cat superior colliculus: multisensory properties of the tecto-reticulo-spinal projection. Exp. Brain Res. 88, 181–186 (1992).

53 Sparks, D. L. Translation of sensory signals into commands for control of saccadic eye movements: role of primate superior colliculus. Physiol. Rev. 66, 118–171 (1986).

54 Wurtz, R. H. & Goldberg, M. E. The role of the superior colliculus in visually-evoked eye movements. Bibl. Ophthalmol. 82, 149–158 (1972).

55 Moschovakis, A. K. et al. An anatomical substrate for the spatiotemporal transformation. J. Neurosci. 18, 10219–10229 (1998).

56 Knill, D. C. & Pouget, A. The Bayesian brain: the role of uncertainty in neural coding and computation. Trends Neurosci. 27, 712–719 (2004).

57 Patton, P. E. & Anastasio, T. J. Modeling cross-modal enhancement and modality-specific suppression in multisensory neurons. Neural Comput. 15, 783–810 (2003).

58 Rowland, B., Stanford, T. & Stein, B. A Bayesian model unifies multisensory spatial localization with the physiological properties of the superior colliculus. Exp. Brain Res. 180, 153–161 (2007).

59 Stein, B. E., Labos, E. & Kruger, L. Sequence of changes in properties of neurons of superior colliculus of the kitten during maturation. J. Neurophysiol. 36, 667–679 (1973). This was the first demonstration of the developmental chronology of sensory representations in the multisensory superior colliculus.

60 Stein, B. E., Labos, E. & Kruger, L. Determinants of response latency in neurons of superior colliculus in kittens. J. Neurophysiol. 36, 680–689 (1973).

61 Benedetti, F. Differential formation of topographic maps on the cerebral cortex and superior colliculus of the mouse by temporally correlated tactile- tactile and tactile-visual inputs. Eur. J. Neurosci. 7, 1942–1951 (1995).

62 Meredith, M. A., Clemo, H. R. & Stein, B. E. Somatotopic component of the multisensory map in the deep laminae of the cat superior colliculus. J. Comp. Neurol. 312, 353–370 (1991).

63 Meredith, M. A. & Stein, B. E. The visuotopic component of the multisensory map in the deep laminae of the cat superior colliculus. J. Neurosci. 10, 3727–3742 (1990).

64 Middlebrooks, J. C. & Knudsen, E. I. A neural code for auditory space in the cat's superior colliculus. J. Neurosci. 4, 2621–2634 (1984).

65 Stein, B. E., Magalhaes-Castro, B. & Kruger, L. Superior colliculus: visuotopic-somatotopic overlap. Science 189, 224–226 (1975).

66 Chalupa, L. M. & Rhoades, R. W. Responses of visual, somatosensory, and auditory neurones in the golden hamster's superior colliculus. J. Physiol. 270, 595–626 (1977).

67 Dräger, U. C. & Hubel, D. H. Physiology of visual cells in mouse superior colliculus and correlation with somatosensory and auditory input. Nature 253, 203–204 (1975).

68 Dräger, U. C. & Hubel, D. H. Topography of visual and somatosensory projections to mouse superior colliculus. J. Neurophysiol. 39, 91–101 (1976).

69 Gordon, B. Receptive fields in deep layers of cat superior colliculus. J. Neurophysiol. 36, 157–178 (1973).

70 Graham, J., Pearson, H. E., Berman, N. & Murphy, E. H. Laminar organization of superior colliculus in the rabbit: a study of receptive-field properties of single units. J. Neurophysiol. 45, 915–932 (1981).

71 King, A. J., Schnupp, J. W. & Thompson, I. D. Signals from the superficial layers of the superior colliculus enable the development of the auditory space map in the deeper layers. J. Neurosci. 18, 9394–9408 (1998).

72 Knudsen, E. I. Auditory and visual maps of space in the optic tectum of the owl. J. Neurosci. 2, 1177–1194 (1982).

73 Stein, B. E. & Dixon, J. P. Superior colliculus cells respond to noxious stimuli. Brain Res. 158, 65–73 (1978).

74 Stein, B. E., Magalhães-Castro, B. & Kruger, L. Relationship between visual and tactile representations in cat superior colliculus. J. Neurophysiol. 39, 401–419 (1976).

75 Alvarado, J. C., Vaughan, J. W., Stanford, T. R. & Stein, B. E. Multisensory versus unisensory integration: contrasting modes in the superior colliculus. J. Neurophysiol. 97, 3193–3205 (2007).

76 Jiang, W., Jiang, H. & Stein, B. E. Neonatal cortical ablation disrupts multisensory development in superior colliculus. J. Neurophysiol. 95, 1380–1396 (2006).

77 Wallace, M. T. & Stein, B. E. Development of multisensory neurons and multisensory integration in cat superior colliculus. J. Neurosci. 17, 2429–2444 (1997). This was the first study of the development of multisensory integration in superior colliculus neurons.

78 Wallace, M. T. & Stein, B. E. Onset of cross-modal synthesis in the neonatal superior colliculus is gated by the development of cortical influences. J. Neurophysiol. 83, 3578–3582 (2000).

79 Xu, J., Yu, L., Rowland, B. A., Stanford, T. R. & Stein, B. E. Incorporating cross-modal statistics in the development and maintenance of multisensory integration. J. Neurosci. 32, 2287–2298 (2012). This study demonstrates some of the experiential prerequisites for instantiating multisensory integration capabilities in superior colliculus neurons.

80 Meredith, M. A. & Stein, B. E. Interactions among converging sensory inputs in the superior colliculus. Science 221, 389–391 (1983). This was the first paper to demonstrate the multisensory integration capability of single superior colliculus neurons.

81 Kadunce, D. C., Vaughan, J. W., Wallace, M. T. & Stein, B. E. The influence of visual and auditory receptive field organization on multisensory integration in the superior colliculus. Exp. Brain Res. 139, 303–310 (2001).

82 Meredith, M. A., Nemitz, J. W. & Stein, B. E. Determinants of multisensory integration in superior colliculus neurons. I. Temporal factors. J. Neurosci. 7, 3215–3229 (1987).

83 Meredith, M. A. & Stein, B. E. Spatial factors determine the activity of multisensory neurons in cat superior colliculus. Brain Res. 365, 350–354 (1986).

84 Kadunce, D. C., Vaughan, J. W., Wallace, M. T., Benedek, G. & Stein, B. E. Mechanisms of within- and cross-modality suppression in the superior colliculus. J. Neurophysiol. 78, 2834–2847 (1997).

85 Pluta, S. R., Rowland, B. A., Stanford, T. R. & Stein, B. E. Alterations to multisensory and unisensory integration by stimulus competition. J. Neurophysiol. 106, 3091–3101 (2011).

86 Larson, M. A. & Stein, B. E. The use of tactile and olfactory cues in neonatal orientation and localization of the nipple. Dev. Psychobiol. 17, 423–436 (1984).

87 Kao, C. Q., McHaffie, J. G., Meredith, M. A. & Stein, B. E. Functional development of a central visual map in cat. J. Neurophysiol. 72, 266–272 (1994).

88 Hubel, D. H. & Wiesel, T. N. Receptive fields of cells in striate cortex of very young, visually inexperienced kittens. J. Neurophysiol. 26, 994–1002 (1963).

89 Horton, J. C. & Hocking, D. R. An adult-like pattern of ocular dominance columns in striate cortex of newborn monkeys prior to visual experience. J. Neurosci. 16, 1791–1807 (1996).

90 Hubel, D. H. & Wiesel, T. N. Receptive fields and functional architecture of monkey striate cortex. J. Physiol. 195, 215–243 (1968).

91 Rakic, P. Prenatal development of the visual system in rhesus monkey. Philos. Trans. R. Soc. Lond. B 278, 245–260 (1977).

92 Wallace, M. T., McHaffie, J. G. & Stein, B. E. Visual response properties and visuotopic representation in the newborn monkey superior colliculus. J. Neurophysiol. 78, 2732–2741 (1997).

93 Wallace, M. T. & Stein, B. E. Sensory organization of the superior colliculus in cat and monkey. Prog. Brain Res. 112, 301–311 (1996).

94 Edwards, S. B., Ginsburgh, C. L., Henkel, C. K. & Stein, B. E. Sources of subcortical projections to the superior colliculus in the cat. J. Comp. Neurol. 184, 309–329 (1979).

95 Huerta, M. F. & Harting, J. K. The projection from the nucleus of the posterior commissure to the superior colliculus of the cat: patch-like endings within the intermediate and deep grey layers. Brain Res. 238, 426–432 (1982).

96 Meredith, M. A. & Clemo, H. R. Auditory cortical projection from the anterior ectosylvian sulcus (Field AES) to the superior colliculus in the cat: an anatomical and electrophysiological study. J. Comp. Neurol. 289, 687–707 (1989).

97 Stein, B. E., Spencer, R. F. & Edwards, S. B. Corticotectal and corticothalamic efferent projections of SIV somatosensory cortex in cat. J. Neurophysiol. 50, 896–909 (1983).

98 Scannell, J. W. et al. Visual motion processing in the anterior ectosylvian sulcus of the cat. J. Neurophysiol. 76, 895–907 (1996).

99 Alvarado, J. C., Stanford, T. R., Rowland, B. A., Vaughan, J. W. & Stein, B. E. Multisensory integration in the superior colliculus requires synergy among corticocollicular inputs. J. Neurosci. 29, 6580–6592 (2009).

100 Alvarado, J. C., Stanford, T. R., Vaughan, J. W. & Stein, B. E. Cortex mediates multisensory but not unisensory integration in superior colliculus. J. Neurosci. 27, 12775–12786 (2007).

101 Jiang, W., Wallace, M. T., Jiang, H., Vaughan, J. W. & Stein, B. E. Two cortical areas mediate multisensory integration in superior colliculus neurons. J. Neurophysiol. 85, 506–522 (2001). Two areas of association cortical areas were shown to have crucial roles in superior colliculus multisensory integration.

102 Jiang, W., Jiang, H. & Stein, B. E. Two corticotectal areas facilitate multisensory orientation behavior. J. Cogn. Neurosci. 14, 1240–1255 (2002).

103 Jiang, W. & Stein, B. E. Cortex controls multisensory depression in superior colliculus. J. Neurophysiol. 90, 2123–2135 (2003).

104 Stein, B. E., Wallace, M. W., Stanford, T. R. & Jiang, W. Cortex governs multisensory integration in the midbrain. Neuroscientist 8, 306–314 (2002).

105 Stein, B. E. The development of a dialogue between cortex and midbrain to integrate multisensory information. Exp. Brain Res. 166, 305–315 (2005).

106 Wallace, M. T. & Stein, B. E. Cross-modal synthesis in the midbrain depends on input from cortex. J. Neurophysiol. 71, 429–432 (1994).

107 Clemo, H. R. & Stein, B. E. Topographic organization of somatosensory corticotectal influences in cat. J. Neurophysiol. 51, 843–858 (1984).

108 Mucke, L., Norita, M., Benedek, G. & Creutzfeldt, O. Physiologic and anatomic investigation of a visual cortical area situated in the ventral bank of the anterior ectosylvian sulcus of the cat. Exp. Brain Res. 46, 1–11 (1982).

109 Olson, C. R. & Graybiel, A. M. Ectosylvian visual area of the cat: location, retinotopic organization, and connections. J. Comp. Neurol. 261, 277–294 (1987).

110 Wallace, M. T., Meredith, M. A. & Stein, B. E. Converging influences from visual, auditory, and somatosensory cortices onto output neurons of the superior colliculus. J. Neurophysiol. 69, 1797–1809 (1993).

111 Alvarado, J. C., Rowland, B. A., Stanford, T. R. & Stein, B. E. A neural network model of multisensory integration also accounts for unisensory integration in superior colliculus. Brain Res. 1242, 13–23 (2008).

112 McHaffie, J. G. et al. in The New Handbook of Multisensory Processing 31–47 (ed. Stein, B.) (MIT Press, 2012).

113 Fuentes-Santamaria, V., Alvarado, J. C., Stein, B. E. & McHaffie, J. G. Cortex contacts both output neurons and nitrergic interneurons in the superior colliculus: direct and indirect routes for multisensory integration. Cereb. Cortex 18, 1640–1652 (2008).

114 Fuentes-Santamaria, V., McHaffie, J. G. & Stein, B. E. Maturation of multisensory integration in the superior colliculus: expression of nitric oxide synthase and neurofilament SMI-32. Brain Res. 1242, 45–53 (2008).

115 McHaffie, J. G., Kruger, L., Clemo, H. R. & Stein, B. E. Corticothalamic and corticotectal somatosensory projections from the anterior ectosylvian sulcus (SIV cortex) in neonatal cats: an anatomical demonstration with HRP and 3H-leucine. J. Comp. Neurol. 274, 115–126 (1988).

116 Jiang, W., Jiang, H., Rowland, B. A. & Stein, B. E. Multisensory orientation behavior is disrupted by neonatal cortical ablation. J. Neurophysiol. 97, 557–562 (2007).

117 Wilkinson, L. K., Meredith, M. A. & Stein, B. E. The role of anterior ectosylvian cortex in cross-modality orientation and approach behavior. Exp. Brain Res. 112, 1–10 (1996).

118 Rauschecker, J. P. Developmental plasticity and memory. Behav. Brain Res. 66, 7–12 (1995).

119 Wiesel, T. N. & Hubel, D. H. Single-cell responses in striate cortex of kittens deprived of vision in one eye. J. Neurophysiol. 26, 1003–1017 (1963).

120 Wallace, M. T., Perrault, T. J. Jr, Hairston, W. D. & Stein, B. E. Visual experience is necessary for the development of multisensory integration. J. Neurosci. 24, 9580–9584 (2004).

121 Feldman, D. E. The spike-timing dependence of plasticity. Neuron 75, 556–571 (2012).

122 Crair, M. C. Neuronal activity during development: permissive or instructive? Curr. Opin. Neurobiol. 9, 88–93 (1999).

123 Hua, J. Y. & Smith, S. J. Neural activity and the dynamics of central nervous system development. Nature Neurosci. 7, 327–332 (2004).

124 Kirkwood, A., Lee, H. K. & Bear, M. F. Co-regulation of long-term potentiation and experience-dependent synaptic plasticity in visual cortex by age and experience. Nature 375, 328–331 (1995).

125 Knudsen, E. I. & Brainard, M. S. Visual instruction of the neural map of auditory space in the developing optic tectum. Science 253, 85–87 (1991).

126 Withington, D. J. The effect of binocular lid suture on auditory responses in the guinea-pig superior colliculus. Neurosci. Lett. 136, 153–156 (1992).

127 Rauschecker, J. P. & Harris, L. R. Auditory compensation of the effects of visual deprivation in the cat's superior colliculus. Exp. Brain Res. 50, 69–83 (1983). This article provides an early demonstration of the ability of superior colliculus neurons to engage in cross-modal compensation by expanding one sensory representation as a result of restricted experience in another.

128 Champoux, F., Bacon, B. A., Lepore, F. & Guillemot, J.-P. Effects of early binocular enucleation on auditory and somatosensory coding in the superior colliculus of the rat. Brain Res. 1191, 84–95 (2008).

129 Mundiñano, I. C. & Martínez-Millán, L. Somatosensory cross-modal plasticity in the superior colliculus of visually deafferented rats. Neuroscience 165, 1457–1470 (2010).

130 Merabet, L. B. & Pascual-Leone, A. Neural reorganization following sensory loss: the opportunity of change. Nature Rev. Neurosci. 11, 44–52 (2010).

131 Chang, E. F. & Merzenich, M. M. Environmental noise retards auditory cortical development. Science 300, 498–502 (2003).

132 Efrati, A. & Gutfreund, Y. Early life exposure to noise alters the representation of auditory localization cues in the auditory space map of the barn owl. J. Neurophysiol. 105, 2522–2535 (2011).

133 Xu, J., Yu, L., Rowland, B. A., Stanford, T. R. & Stein, B. E. Noise-rearing disrupts the maturation of multisensory integration. Eur. J. Neurosci. 39, 602–613 (2014). This was the first study to demonstrate that superior colliculus neurons require experience with co-varying cross-modal signals to develop the circuitry needed to integrate the information they provide.

134 Wallace, M. T. & Stein, B. E. Early experience determines how the senses will interact. J. Neurophysiol. 97, 921–926 (2007).

135 Benedetti, F. & Ferro, I. The effects of early postnatal modification of body shape on the somatosensory-visual organization in mouse superior colliculus. Eur. J. Neurosci. 7, 412–418 (1995).

136 Benedetti, F. Orienting behaviour and superior colliculus sensory representations in mice with the vibrissae bent into the contralateral hemispace. Eur. J. Neurosci. 7, 1512–1519 (1995).

137 Brainard, M. S. & Knudsen, E. I. Sensitive periods for visual calibration of the auditory space map in the barn owl optic tectum. J. Neurosci. 18, 3929–3942 (1998).

138 King, A. J. Neural plasticity: how the eye tells the brain about sound location. Curr. Biol. 12, R393–R395 (2002).

139 Beauchamp, M. S., Lee, K. E., Argall, B. D. & Martin, A. Integration of auditory and visual information about objects in superior temporal sulcus. Neuron 41, 809–823 (2004).

140 De Gelder, B. & Bertelson, P. Multisensory integration, perception and ecological validity. Trends Cogn. Sci. 7, 460–467 (2003).

141 King, A. J. & Calvert, G. A. Multisensory integration: perceptual grouping by eye and ear. Curr. Biol. 11, R322–R325 (2001).

142 Baier, B., Kleinschmidt, A. & Müller, N. G. Cross-modal processing in early visual and auditory cortices depends on expected statistical relationship of multisensory information. J. Neurosci. 26, 12260–12265 (2006).

143 Fiebelkorn, I. C., Foxe, J. J. & Molholm, S. Dual mechanisms for the cross-sensory spread of attention: how much do learned associations matter? Cereb. Cortex 20, 109–120 (2010).

144 Barraclough, N. E., Xiao, D., Baker, C. I., Oram, M. W. & Perrett, D. I. Integration of visual and auditory information by superior temporal sulcus neurons responsive to the sight of actions. J. Cogn. Neurosci. 17, 377–391 (2005).

145 Yu, L., Rowland, B. A., Xu, J. & Stein, B. E. Multisensory plasticity in adulthood: cross-modal experience enhances neuronal excitability and exposes silent inputs. J. Neurophysiol. 109, 464–474 (2013).

146 Rowland, B., Jiang, W. & Stein, B. Brief cortical deactivation early in life has long-lasting effects on multisensory behavior. J. Neurosci. 34, 7198–7202 (2014). There is a sensitive period during early life when cross-modal experience, through the association cortex, normally alters the multisensory circuit of the superior colliculus so that it can engage in multisensory integration.

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