April 15, 2024
Section I
Unraveling the Mysteries of the Amygdala: A review of a section of the book Behave by Robert Sapolsky
In the world of neuroscience, Robert Sapolsky stands as a luminary, a maestro of unraveling the intricate dance of our brain's circuitry. Among the many deep dives that he delves into, his perspective on the amygdala resonates profoundly for me.
The amygdala emerges not as a mere anatomical curiosity as he decides that rather than reducing the amygdala to a simplistic seat of fear and aggression, he highlights its diverse functions, emphasizing its involvement in the vast array of behaviors and experiences. It is a narrative view of the why the brain developed as it did to aid us in the fight against pathogens, predators and stress. Sapolsky's take on the amygdala is nothing short of revelatory, akin to a seasoned detective peeling away layers of a perplexing case. There are diverse neuronal pathways in this almond-shaped structure nestled deep within our temporal lobes and they have profound purpose. The amygdala emerges not merely as a primal seat of fear and aggression, but as a nuanced orchestrator of our emotional lives. All mammals have emotional responses that are split second to threat, joy and relationship. This is mediated
subconsciously at the level of the vagal nerve and primitive brainstem. The amygdala is front and center. Failure of science and psychiatry to recognize this truth has been the real reason why we fail so often with cortical based cognitive behavioral therapy.
Dr. Sapolsky traverses the terrain of neurotransmitters and neural circuits, deftly navigating the intersections of biology, psychology, and behavior. The amygdala is the central actor in the grand theater of human experience. Its role in shaping our responses to stress, encoding memories, and even influencing social dynamics is the start point for a new series of theories understanding the how to in order to unwind fear, anxiety and human behavior.
When looking directly at the amygdala during aggression, anxiety, panic and other experiences, research has noted that this brain region consumes the most oxygen and glucose as energy for activity. When the amygdala is lesioned by brain surgery, the aggression in the recipient decreases. The reverse also holds true that experiments stimulating the amygdala increases aggression. The amygdala sits at the cross roads of humans understanding events at a primal level. It helps us lay down memory to prevent future experiences that could be traumatic. It is the fork in the road for understanding emotions and emotional responses. It helps us understand safety versus danger allowing us to enter into social contracts and relationships for long term survival.
The amygdala helps us process fear, both the innate and the learned varieties. This is a major function for this brain region as fear is an ever present reality for most of human existence. The older part of the evolved amygdala is the process point for innate fear while the newer part called the BLA or basolateral amygdala processes learned fears. It neuroceptively feels, then fears and thus sends a signal to the central amygdala leading to stress hormone release, neurotransmitter release and memory development related to the fear response. The amygdala can learn about a fear or safety issue long before the thinking cortex gets involved posing benefits and threats. He uses an example, think about a policeman who in a previous experience in a dark alley was presented with a gun wielding person that shot at him. Now, in a similar alley a teen walks up with a phone as the policeman turns to see him. The amygdala may fear a gun before the neocortical perception is brought in to override the response and the teen may get shot. The learned fear with solid memory can have an unfortunate outcome as stated. The BLA and amygdala have very enhanced neuroceptive pathways for a more rapid and robust fear response for survival.
Neuroception is a key here.
The amygdala is directly tied to our neuroception of the outside world whether that is directly from visual input or from feelings from skin, gut and other neuroceptive systems in the body. The normal route for neuroception is both to the thinking part of the brain as well as the more primitive structures as needed based on the type of input. If the neuroceptive response is fear based, the neocortex is bypassed in preference to the amygdala for a speedy response from threat. The vagus nerve mediates the transmission of this neuroception to the amygdala leading to the responses that are seen. Whether your neocortex gets involved in the perceiving of the event depends on the nature of the event. Severe trauma can stop the brain from understanding the event so much as baking in a coded response.
Let us look at the hippocampus, an area where memories are stored. The amygdala will take the fear based neuroceptive inputs and turn on the hippocampus in order to learn dispassionate facts about the event. i.e. what did the alley look like, what did the sky look like, the teen, etc.. The result is a focalized learning of the event and the surroundings for future risk avoidance. The motor cortex also has short cuts and enhanced pathways from the amygdala. Thus, we can run rapidly from threat. The vagus nerve and sympathetic SNS fibers are critical to mediating many of these rapid responses. Thus, Sapolsky says that the amygdala's nerve fiber routes pose an interesting question. When does the SNS fire full blast? During fear, flight, fight and sex. He states that a full 25% of the amygdala associated hypothalamic nucleus neurons are involved in sex and aggression. Hmm. Interesting. Sex and agression are two sides of a coin flowing through the same pathways of brain understanding and behavioral outcomes. Sapolsky states:"The second consequence reflects the core idea of this book. Your heart does roughly the same thing whether you are in a murderous rage or having an orgasm. Again, the opposite of love is not hate, it's indifference." (Sapolsky R. 2017)
Through Sapolsky's eyes, the amygdala is a linchpin in our understanding of human behavior and cognition. Its influence permeates every aspect of our lives, from the mundane to the profound, shaping our perceptions, decisions, and interactions with the world. His perspective
on the amygdala stands as a testament to the boundless complexity of the human brain.
For me this work ties heavily into Stephen Porges work on polyvagal theory. To unwind profound trauma and fear driven by the amygdala and hippocampal memory, we need to look to the neuroceptive vagal system.
More to come as I explore this book.
Dr. M
