A Heart That Thinks

In 1991, Dr. Armour introduced the term “Heart Brain” by discovering an intrinsic cardiac nervous system of over 40,000 neurons called “sensory neurites.” These neurons were thought to be simple afferent neurons (neurons that send electrical signals from the autonomic nervous system, which is responsible for unconscious bodily functions such as one’s heartbeat, to the central nervous system: brain and spinal cord). However, sensory neurites present a rather peculiar role: they send meaningful messages to the brain upon which it acts and to which it obeys. 

The Little Brain 

After proving that the neurons of the heart eventually have a say in behavioural sequences and dynamics, especially in the sensation of emotional pain, it was no surprise when Dr. Armour started referring to the intrinsic cardiac nervous system as the “little brain.” This name became even more fitting when they recently discovered that the heart secretes, among many other hormones, oxytocin, also known as the “love hormone.” The concentration of oxytocin in the heart was surprisingly as high as in the brain. 

What is Oxytocin?

You might know it as the “love hormone”, or you might associate it with childbirth and lactation. Oxytocin is a hormone secreted by the brain and more recently discovered, by the heart. It affects cognitive function, adaptation, tolerance, endurance, and the maintenance of complex sexual and maternal emotions and behaviours. Oxytocin also plays an important role in social learning and the development of behavioural cues, as well as the establishment of human bonds between pairs. 

The Heart and the Amygdala: an Underrated Friendship 

Research has proven that the heart and amygdala are linked strongly and directly by a bundle of afferent neurons. The amygdala is the area of the brain that controls how our nervous, immune, and behavioural systems react to environmental threats. It does so by comparing incoming emotional stimuli and signals to the stored emotional information in our memory systems. The amygdala assesses the threat level instantaneously and acts accordingly through the autonomic nervous system to elicit a fight or flight response. 

Since the heart is connected intensively to the amygdala, it can activate the autonomic nervous system before the signal even reaches the brain.

The Heart’s Intuition 

Intuition is regarded in the field of neuroscience as the processing and decoding of energetic information that is perceived beyond space and time about an event before it occurs. In 2004, researchers McCraty, Atkinson, and Bradley not only managed to prove that intuition is a physiological event, but they also found that the heart receives intuition information before the brain itself. 

So apparently the heart has more to it than we thought, and maybe Aristotle wasn’t so wrong to assume that the heart is the seat of our mental processes and house of thought.