Who is you? A look at the intricacies of human behavior and one’s sense of self through the lens of neurotransmitters. 

Nikola Reko
Health Sciences, Class of 2024, McMaster University

A general acceptance of how different brain regions are involved in specific processes is a relatively easy concept for one to understand. Having areas specialized for speech, facial recognition, or different types of memories or feelings falls in line with how most other organs in the human body work.1 Despite the underlying mechanisms behind these functions being somewhat unknown, a delegation of tasks within the brain seems efficient and natural.2 The well-understood and differentiated organs of the rest of the body’s various systems, be they gastrointestinal, circulatory, respiratory, or more, make seeing the brain in that manner appear to be a logical conclusion.3 Unfortunately, it becomes gravely apparent that this simple organizational framework of the brain is severely lacking once the chemical mix of signaling molecules — neurotransmitters — of the body are taken into account.4 

Many different molecules have been discovered in the brain with their specific functions and mechanisms of action being mapped out in extreme detail down to the chemical level5. These neurotransmitters are simply molecules being released in the brain and nervous system which bind to other molecules to exert their effects.4 They include, but are certainly not limited to: glutamate, a principal excitatory neurotransmitter implicated in neuronal plasticity (the name given to the ability of the nervous systems to change over time much like molding plastic) and memory; GABA and glycine to inhibit over-signaling in throughout the nervous system; dopamine for rewards, emotions, and movement; serotonin with generally relaxing and peaceful effects; or catecholamines for their stress and focus inducing capabilities.6 The specifics of their biochemical reactions within the body is beyond the scope of this piece but a key takeaway is how almost every feeling and function humans experience or use depends massively on these chemicals.7

So far, the system does not seem complicated. With mapped out paths and effects of certain molecules then it is rational to assume that knowledge could be applied to help remedy common issues within the brain. Anxiety disorders, insomnias, or epilepsies have all been tied to insufficient activation of the neuronal pathways associated with the inhibitory neurotransmitter, GABA.6 Many of these conditions are treated, in part, with drugs which act on the nervous system in manners similar to GABA.8 Similarly, mood disorders and depressions have been aided by drugs which serve to increase the effects of the brain’s own serotonin.9 These selective serotonin reuptake inhibitors (SSRIs) are commonly used as depression medications and act specifically to block the brain’s reuptake or recycling of used serotonin to keep it around longer and exert more of its effects.10 Essentially most drugs seek to either increase or decrease its effects to keep one’s perceived sense of self as intact as possible.11 

Now, with the basics of neurotransmitters and their related clinical drugs having been briefly explained the concept of the self can start being addressed. Notice that most of the molecules and pathways drugs toy with are doing so in order to return one to their optimal state of being.11 It should not be outrageous to want to be able to live, laugh, and love without chemical imbalances ruining the experience. The thing is however that all of these chemicals are constantly fluctuating in the brain on a scale ranging from seconds to days.12 

As previously mentioned, these chemicals are largely responsible for all of the sensations and subsequent behaviors one feels.7 The perplexing thing about this line of thought is how it leads to bizarre conclusions regarding who one truly is. Most would agree that aside from physical characteristics of an external body it is the personality that makes someone up. Others might argue how actions define a person. In both cases these defining characteristics are, as they are currently understood, entirely dependent on chemicals which are not generally viewed as being part of oneself. Would an energetic individual still be themself if drugs suppressing their stimulant neurotransmitters were administered for a long time? At first, most would agree they are still that same individual and only their state of mind is somewhat altered for the present time period. But, eventually a new pattern of behaviors would cement a decidedly new personality caused solely by the shift in the levels of certain neurotransmitters.13, 14 It is unsettling when one realizes how primal experiences or pillars of individuality, like feelings and personalities respectively, depend on chemicals which are constantly fluctuating and could potentially be altered with molecules which are exogenously administered6.

Along the same train of thought, it can be difficult to distinguish between cause and effect with many brain states, and especially disordered brains.15 Are the various repeated patterns of neurotransmitters usually present in one’s brain that which makes one themself? Immediately, most would answer that these chemicals are not intrinsically a part of anyone. However, their extreme influence over who one is and what one does greatly muddles this self versus non-self distinction.15 While these neurotransmitters are correlated with various states of being they are difficult to isolate as being a true cause, consequence, or simply correlated with the inner workings of the brain.16 This distinction is not trivial philosophy either as it is a vital step in deepening the understanding of the brain. Ranging from disordered eating to chronic pains, and neurodegenerative diseases, like Alzheimer’s or Parkinson’s, there are many brain-related issues which are tied to dysregulated patterns of neurotransmitters in one way or another.6 Further research and inquiry leading to that deeper understanding of how and why the brain functions the way it does stands to benefit many who are affected by such problems.17 

A lot is already known about the mighty brain but there is still a long way to go before humankind can claim to understand the organ which grants it its humanity. From the more philosophical debate over who one truly is to the scientific advancement of understanding about neuronal and chemical interactions, the field of neuroscience is teetering on the edge of explosive new advancements which stand to greatly advance understandings of humanity.18 So, if one is ever in the mood for a mild existential crisis they could take a second to ponder over the electrochemical mix stewing in the delicate brain; if nothing else they might stimulate the release of those same chemicals within their organic circuitry. 

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