Hello there all my friends!

This is my very first post in Steemit, so the polite thing to do is to introduce myself, although I won’t disclose my full name. What I will tell you is that I’m a physician. If you looked at my profile, I can guess you just thought, “This guy doesn’t seem like a physician at all! He must be a musician or something!” That’s because I am. I've been playing the piano since I a lot of years ago and now I produce music; trying to do something interesting out of it. Like everyone in arts.

One can argue that science nurtures the mind and music nurtures the soul. Beyond this metaphoric concept of music being an art and thus a product of our right brain, arts do require some sort of dogmatic thinking in order to make sense. Imagine a sculptor who worked on a sculpture without following the right ways of his or her craft. The result? A total disaster. Now imagine a musician, a pianist, who went on to perform a Scott Joplin ragtime piece without following the proper theoretical knowledge required to play the piano. The result? You know the answer.

But this post is not intended to talk about that. This intended to discuss briefly what happens in our brains when we listen to a set of sounds ordered in both time and intensity. What we call music.

Sound reception occurs through two pathways

In the first part of our history, we must take into account why is important for an animal to hear, the evolutionary sense of it, which is to predict the presence of a predator in the environment in order to trigger a fight-or-flight response. What happens here is that the sounds are caught by the ears, the vibrations are caught by the ear, arriving at the inner ear by getting through the outer and middle ear. In the inner ear, the translation of these vibrations into electrical signals occurs. From there, the next step is the spread of the signals in the brain.

The inner ear comprises the vestibular system, responsible of syncing the head movements with body movements in a harmonious way, alongside with perceiving when and to where are we moving, and the cochlear system, which is responsible of catching the mechanical content of the sound and translating it into electrical signals. Both systems end up playing a role in sound perception. Because the vestibular system consists of a system of tubes that contain liquid and react according to movements, sounds can actually stimulate the vestibular system as well, although to a lesser extent than in the case of the stimulation of the cochlea.

The vestibular pathway

The next relay station after the vestibular apparatus itself are the vestibular nuclei. There are numerous connections that are active in relation to its main function, balance. However, when sound is received, the electrical signals that are generated in the vestibular nuclei are meant to trigger postural changes, most of them subtle in nature. This is the biological reason why we subconsciously follow the rhythm of a beat, and the likely reason why the humans started dancing. A 5-month infant is able to move according to a beat because of this, even when the perception of the sound itself is not totally possible because these structures aren’t mature enough.

What about reward?

Alongside these postural stabilization signals, some of the electric signals generated in the vestibular nuclei end up being processed as sound itself. Part of those signals are directed towards a part of the brain called the nucleus accumbens. Like all brain structures, we have a nucleus accumbens in both hemispheres, and this structure is part of a bigger array of neurons called the basal ganglia. Usual descriptions of the nucleus accumbens also involve the ventral striatum, other basal ganglia structure.

These names are important in the rewarding feeling that follows listening to a happy song, a positive song. When you hear a song and have goose-bumps because of it, the nucleus accumbens and ventral striatum are likely active in that moment. Through a brain imaging technique called positron emission tomography, or PET, it is possible to trace certain molecules inside the brain and fluctuations in their concentrations during specific events. PET analysis of voluntaries has shown increased activity of the neurotransmitter dopamine inside the brain during these music evoked goose-bumps.

That’s lovely but what about sadness and other feelings?

Do you remember that I told you that there were two pathways the sounds followed to get into our brains, right? Well, this second pathway, which follows the cochlear nuclei, is newer in evolution. It is involved in the actual processing of sound by our brain cortex, not only in eliciting reflex responses by our body. Part of a sound goes to the brain cortex where it gets translated into what we perceive as music, noise, or speech, and part of it goes to an area called the hippocampus.

The hippocampus was named like that because it resembles a sea horse, and it’s the major structure responsible for memory. In addition to memory, the hippocampus has shown to have increased activity in the presence of music. The emotional content of music, being it positive or negative, is able to elicit hippocampal activation. There’s more to it than just tears. There are connections from the hippocampus to the hypothalamus, which regulate hormone concentrations in the body, and these emotions can lead to actual changes in homone levels.

In addition to all this...

When music goes into our brains, signals go from a variety of places to a structure called the amygdala. The amygdala is further divided in several nuclei because each part is activated during different situations. In general, activation of the amygdala is associated with the emotional content of music but in a social context. It’s not the same listening to The Dark Side of the Moon alone in a room through close-back headphones than listening to it with some friends. Here comes another characteristic of emotions elicited by music: They tend to be contagious. It calls for homogeneity in the emotions felt. Everybody feeling what the music evokes, consistently.

All these circuits are interconnected, none of them functions alone. That’s one of the things to bear in mind when trying to understand how music does what it does. Understanding the principles of this can lead to using music as a therapeutic approach for certain conditions, a topic we’ll discuss later.