Developments within the field of neurobiology and neuropsychology have shown that the brain is the center of wisdom, insight, cognition, and emotion. However, if one were to look back over the last millennia, the heart has traditionally stood as the symbol and driver of such feelings — especially of love.

The heart played a central role in ancient Egyptian religion, where it was weighed against the feather of ma’at (an Egyptian concept that included truth and justice) to see if one was worthy of entering the afterlife. Poets and artists have understood that the heart has the power to even heal and mend the suffering of our human condition — as the Spanish poet, Antonio Machado, once wrote: “Last night as I was sleeping, I dreamt … that I had a beehive here inside my heart; And the golden bees were making white combs and sweet honey from my old failures.”

Surprisingly, recent investigations studying brain-heart interactions have shown that the heart does in fact play a key role in modulating how we think, behave, and feel about some of the deepest human emotions and sensations — that of love and pain. A study of the physiological mechanisms by which the heart communicates with the brain provide us with the scientific basis to explain how and why the heart affects love, connection, and compassion for ourselves and those around us. This in turn may provide us with new means of managing some of the most difficult psychophysiological health conditions today such as pain, social isolation, and depression.

An integral review published by Rollin McCraty and others titled “The Coherent Heart” introduced the term “psychophysiological coherence” as an investigation of how sustained positive emotions such as appreciation, care, compassion, and love, can generate smooth, sine-wave-like cardiac patterns. Research on the cardiac correlates of positive emotions show that when certain positive emotional states (appreciation, compassion, or love) are intentionally maintained and shown neurologically, coherent heart rhythm patterns are sustained for longer periods. This also leads to increased synchronization and entrainment between multiple bodily systems. Psychophysiological coherence is characterized by distinctive psychological and behavioral correlates as well as by specific patterns of physiological activity throughout the body.

This reflects an increased activity in higher-order control systems in the brain, an increase synchronization between the two branches of the autonomic nervous system, and a shift in autonomic balance toward increased parasympathetic activity (the relaxation response).

As heart-brain coherence tends to naturally emerge with the activation of heart-felt positive emotions such as appreciation, compassion, and love, it suggests that such feelings increase the harmony in our own bodies as well as that of others. Recent research performed by McCraty published in Clinical Applications of Bioelectromagnetic Medicine, titled “The Energetic Heart: Bioelectromagnetic Communication Within and Between People,” investigates the magnetic field that the pumping heart produces and describes how there is a direct relationship between the heart-rhythm patterns and the spectral information encoded in the frequency spectra of the magnetic field radiated by the heart.

Therefore, information about a person’s emotional state can be encoded in the heart’s magnetic field where it can be communicated throughout the body and into the external environment. In turn, this may affect how people sense how and what we are feeling along with their physical indicators, which include facial expressions, body distance, and verbal tone. In order to better understand this complicated intro and interpersonal communication between the heart and the brain, Julian Thayer, professor of psychology at The Ohio State University, developed a heart-brain interaction model known as “neurovisceral integration.”

Thayer’s neurovisceral integration model describes how a set of neural structures within the brain involved in cognitive (reasoning), affective (emotions), and autonomic (stress and relaxation) regulation are deeply related to heart-rate variability (HRV). HRV is the change in the time intervals between adjacent heartbeats and is a strong indicator of psychophysiological well-being, parasympathetic tone, emotional flexibility, and cardiac health.

Thayer and his team have investigated how three functional networks — namely the central autonomic network, the anterior executive network, and the emotional circuit — regulate how our brains control motor, endocrine, and especially behavioral responses that are critical for goal-directed behavior, adaptability, and well-being (among three of the most essential elements involved in building and sustaining loving social relationships). The activity of the central autonomic network is mediated through the 10th cranial nerve of our body, known as the vagal nerve, which then in turn produces HRV. The functional network, called the anterior executive region, regulates our pro-social behavior by monitoring the motivational quality of internal and external stimuli. It stimulates activity in the anterior, insular, orbitofrontal cortices, amygdala, periaquaductal gray, ventral striatum, and autonomic brainstem motor nuclei.

Through a series of studies using pharmacological and neuroimaging approaches, Thayer and his team have shown that prefrontal-cortical activity is associated with HRV. Furthermore, his studies suggest that medial-prefrontal-cortical activity, involved in the sensation and generation of love, may be able to inhibit subcortical (amygdala) activity associated with defensive, disconnect, anger, and threat behaviors. This medial-prefrontal brain activity is also strongly associated with HRV.