Redeeming The Amygdala. The tiny brain region that packs a big punch!
Dr Ana Lund & Dr Mike Tranter
Updated: January 4 2024
If you are reading this, chances are that you have already heard about the amygdala. You might also know of its involvement in fear. In fact, if you’re not a brain expert, it might be the only brain structure you can specifically name. But the amygdala is one of the most fascinating regions of the brain, and despite decades of study, we are just beginning to truly grasp how much it guides our behaviours around risk and reward, dangerous situations, and motivation in new environments, and some of those findings have been quite…..unexpected.
The story begins in the late 1960s’, when Dr. Arthur Kling, a pioneering researcher in the primate brain and behaviour, ventured to an island off the coast of Puerto Rico in search of the elusive function of the tiny almond-shaped brain structure called the amygdala. The island was a Mecca for primate behaviour researchers as it was inhabited only by monkeys, and so Dr. Kling was able to conduct groundbreaking research. Since then, studies into the function of the amygdala have gained even more traction, especially after the development of affective neuroscience as a discipline in the 1980s. Once Daniel Goleman coined the term “the Amygdala Hijack” in his 1995 book Emotional Intelligence, the term went viral. The reputation of the amygdala as the ‘bad boy’ of the brain has taken the world by storm ever since.
The amygdala has a particular reputation. Today, it is not uncommon to see popular psychology articles blaming the amygdala for many of our least desirable behaviours, such as fearful responses, anxiety, or aggression. The usual narrative goes: ancient humans lived in caves or the savannah, surrounded by predators and poisonous food. Under those circumstances, the brain’s alert system to set alarm bells ringing and engage us in a “fight or flight” response was necessary for our survival. The amygdala was essentially that alarm system. Fast forward to modern humans who live much more sheltered lives with no predators but still with brain circuitry that has not been updated accordingly since our ancestors’ time. According to this view, the amygdala is an outdated alarm system that is causing havoc in our modern life and has become maladaptive. It’s like a fire alarm ringing, with fire engines on their way, when all we might have done is light a small candle. Not technically wrong, just too much!
But is the story of the amygdala so simple? Is its only role to scan the environment for danger and keep us on our toes, always seconds away from triggering the “fight or flight” response. Or could it be that our bad boy, like every true anti-hero, plays a much more complex role in our behaviour? Is it actually helping us not only to survive but also to thrive?
Inspired by David Amaral’s book Living without an Amygdala [1] which explores the extraordinary life of someone who lives without the amygdala in her brain, this article sets out to answer this question by drawing on new and exciting research. We look at some of the challenges she faces and the somewhat bizarre behaviours that result from living without the amygdala. We also look at some of the cutting-edge neuroscience today, to shed some light on why the amygdala has so much influence over so many things we do.
A curious case of a girl without an amygdala
Dr. Arthur Kling pioneered the research into the amygdala function in a series of daring, if extremely cruel experiments, where he surgically removed both amygdalae (there is one in each hemisphere of the brain) from several vervet monkeys [2]. He then released the animals back into the wild. All animals, without exception, rapidly perished. Contrary to Kling’s expectation, death by predation was not the only cause of their demise. Animals would isolate themselves or become ostracised from the other monkeys because, without the amygdala, they could not fully comprehend the intricate relationships of dominance within the group. Interestingly, the monkeys also seemed unmotivated to eat, with some even dying of starvation. Kling found that the amygdala removal not only affected the fear response but also the bonding behaviour between the monkeys. It was clear that the amygdala was associated with feeding and pro-social behaviour, and the missing link to understanding all of it came from a little girl in the USA.
Around the same time as Kling’s experiments, a young girl was born in America with a rare genetic disease called Urbach-Wiethe Disease (UWD). The condition meant that her amygdala would be destroyed bilaterally (through calcification) during adolescence. When she turned 20 and now a young woman, she became a research subject in Antonio Damasio’s lab at the University of Iowa, USA. Antonio Damasio is one of the pioneers of affective neuroscience (emotions in the brain), the newest of all branches of neuroscience and the one that is the most relevant for psychotherapy. By the time she was 20, both amygdalae in her brain were completely destroyed. What’s more, is that, unlike any other human amygdala lesions known at that time, a perplexing feature of her UWD was that it confined the damage specifically to the amygdala, offering an unprecedented opportunity for scientists to explore its function. And explore they did.
The young woman became known in research circles as S.M. and over the next three decades, she took part in hundreds of research studies, contributing to a tremendous body of work that changed forever what we understand about the role of the amygdala. We will look into insights from her curious life in more detail below, as we try to imagine what life without an amygdala might look like for you or me.
Fear is never outdated!
A well-documented role of the amygdala is in fear processing and emotional regulation [3], and unsurprisingly, S.M. did not feel any fear. While life without feeling afraid seems like a good idea for a Marvel superhero, a window into S.M.’s daily existence provides a more accurate view of how many adversities she faced. S.M. once got into a car with a complete stranger, ignoring the obvious risks, who drove her to a distant location outside the city and tried to rape her. After a narrow escape, S.M. realised that she was outside in a remote area with no way to get back home, so she got back into the car with the same man, asking him to give her a lift back home. She reported to the researchers, how afterwards, she felt annoyed at the man and felt a strong dislike towards the situation, but experienced no fear. This story is just one of many similar events in S.M.’s life and is a good example of how the brain can retain its logic and reasoning skills (at least to some degree) but be lacking in fear about future consequences. This fear was diminished to such an extent that the mere inconvenience of travel was enough to mitigate the obvious risks of being attacked again.
The amygdala, along with other brain regions in the frontal cortex and memory centers, is critical for associating certain behaviours with bad experiences. We can also see this experimentally when risk-taking behaviours in animals (such as walking close to a predator’s scent) are increased after amygdala damage. While S.M. knew what fear was (she experienced it before the age of ten, the approximate age of the onset of her amygdala was calcification), she could not feel it anymore.
This incident was all but an exception in S.M.’s life. Although S.M. is alive and well today, in the five decades of her life, she has experienced a disproportionate number of dangerous but completely avoidable events. She was held at a gunpoint and knifepoint, and was a victim of serious domestic violence, the list goes on. What is perhaps even more astonishing is that S.M. never thought to report the perpetrators to the police, and thus, displayed a lack of instinct for self-preservation and healthy decision-making.
As we have already seen, the amygdala is critical for threat detection and guiding the next appropriate action, and we also know from previous studies that the amygdala is essential in fear processing. However, it does so much more than make us feel afraid, as we are about to find out.
Food, Money, Planning and Consequences
Like Dr Arthur Kling’s vervet monkeys of the 1960s, S.M. lacked motivation to find food, even when hungry. She would eat food if it was accessible, ruling out the presence of an eating disorder, but did not seem motivated to go out of her way to buy or prepare food. Sometimes S.M. would go entire days without eating, especially in times of financial hardship. Now, try to think for a moment about how you feel and behave when you start feeling hungry? And how this intensifies when the feeling of hunger grows stronger and stronger. Think about how, without any conscious effort, your motivation to go and get some food becomes stronger and stronger until it becomes the only thing on your mind. Of course, the growing urge to feed as we run out of fuel is completely natural – the food is necessary for the sustenance of life, after all. Yet, none of it was happening with S.M. This self-defeating behavior makes sense, however, in the light of what we know about the regulation of feeding behaviours in the brain. It relies on a network of regions such as the hypothalamus, reward pathways, frontal cortex, and amygdala. It is the broad integration of the amygdala with the reward pathways in the brain (like the dopamine pathways) that can motivate us to eat. We can see this in lab studies where brain implants are used to activate specific neurons. Researchers have shown that, in mice, activating the amygdala causes them to gorge on food, even if they don’t like the taste [4]. This excessive feeding is likely due to the positive feeling associated with eating.
For S.M., the absence of a healthy drive to feed herself fits into a broader picture of an inability to incorporate her priorities and hierarchy of needs for survival. One example of this was her terrible management of money. The money would just come and go. She would impulsively purchase non-essential items but ignore food and not feel alarmed by this behaviour or learn from her mistakes. This is because the amygdala plays a role in reward-learning and value-based decision making from communicating with the orbitofrontal cortex at the front of the brain, for adaptive decision making. Without proper functioning of the amygdala (because S.M. didn’t have one), any negative associations regarding the consequences were likely limited and the more rewarding and impulsive decisions were poorly regulated.
Relationships and social circles
Despite her caring nature, kindness, and desire to be with others, a consistent thread running throughout S.M.’s life was her inability to maintain stable relationships. Friendships, romantic relationships, and a relationship with her three children, were all short-lived. She spent the majority of her existence lonely, and it is, to this day, the greatest source of suffering for her.
Many factors can contribute to the de facto social ostracisation that S.M. experienced, uncannily echoing once more the sad fate of Dr Kling’s vervet monkeys. For example, S.M. struggles with accurately recognising emotions on people’s faces, especially fear and surprise, presenting a challenge when dealing with the complex web of human communication through facial expressions. Facial recognition relies on brain regions, such as the fusiform gyrus and temporal sulcus (on the side of the brain, roughly where your ears are). The amygdala seems to play a role in recognising specific emotions in facial expressions. Patients who have suffered a stroke affecting the amygdala, demonstrate poor recognition of angry faces [5], likely resulting from weakened connectivity between the amygdala and these facial recognition regions, which is also supported by various brain imaging studies [6].
S.M. is capable of reading a range of emotions and can feel empathy, but the threshold was high. Often, the subtle nuances of someone’s expression would be misread, and only if it was very obvious would S.M. react with attunement. Another intriguing feature of living without the amygdala turns out to be that one cannot have an accurate sense of personal space. Despite understanding the concept itself, S.M. would typically stand nose-to-nose and in direct eye contact with people, irrespective of whether she knew them personally or they were complete strangers. Interestingly, the lack of sense of the personal boundaries of another is mirrored by the inability to accurately gauge psychological boundaries. S.M. would indiscriminately disclose very intimate and personal details of her life to any new acquaintance, creating a feeling of awkwardness that would ultimately lead to a relationship breakdown.
Although a little heartbreaking, these observations are not too surprising. Actually, the observation of the scarcity of S.M.’s social life is consistent with a broader finding from Lisa Feldman Barrett’s lab [7]; the amygdala’s size and complexity correlate to the size and complexity of social networks. The bigger the amygdala, the bigger the social circle. And, while the size of the amygdala is most often associated with experiences of adversity and trauma, in the case of S.M., the size of the amygdala correlates to a positive trait – sociability. A wide range of studies suggest the importance of the amygdala during early life, especially during adolescence. This is a susceptible time for brain development (and the age at which S.M. suffered the amygdala damage), and dopamine circuits involving the amygdala are essential in establishing early life social behaviours that we build on during our lives [8]. By uncovering more about the various complex functions of the amygdala, studies like Barrets’ can help us to reimagine the colourful story of the amygdala, rather than seeing it in only black and white.
The bigger, the better
While the role of the amygdala in fear processing is, of course, undeniable and is probably its evolutionary raison d’etre, in primates and especially in humans, the role of the amygdala goes beyond just the bare survival against the physical threat. It is interwoven into how we behave in society and how we nonverbally sense and adjust our behaviour to others. As we have seen, the increased size of the amygdala is not only related to the experience of adverse life events but also to sociability and there are even studies showing that the size of the amygdala plays a role in creativity [9]. The bigger your amygdala, the more ‘outside of the box’ thinker you are. And so, if we circle back to Daniel Goleman’s “amygdala hijack” and quote the man himself: “not all limbic hijackings are distressing. When a joke strikes someone as so uproarious that their laughter is almost explosive, that, too, is a limbic response. It is at work also in moments of intense joy”.
If you stop to think about how many of your behaviours are influenced by the activity within your amygdala (fear, anxiety, motivation, reward pathways, feeding, emotional regulation, creativity and humour processing [10]), the next time you find yourself in the supermarket contemplating buying cakes and treats, laughing at a joke, or hiding behind a pillow during a horror movie, you can wonder, just what is my amygdala up to?
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References:
[1] David G. Amaral; Ralph Adolphs, eds. (2016). Living without an Amygdala. Guilford Publications. ISBN 9781462525959.
[2] Steklis, H. D. (1998). Arthur S. Kling: pioneer of the primate social brain. Am J Primatol; 44 (3):227-30
[3] Feinstein, J.S., Adolphs, R., Damasio, A., Tranel, D. (2011). The human amygdala and the induction and experience of fear. Curr Biol;21 (1): 34-8
[4] Douglass, A., Kucukdereli, H., Ponserre, M. et al. Central amygdala circuits modulate food consumption through a positive-valence mechanism. Nat Neurosci 20, 1384–1394 (2017).
[5] Tippett, D. C., Godin, B. R., Oishi. K., et al. (2018). Impaired Recognition of Emotional Faces after Stroke Involving Right Amygdala or Insula. Seminars in Speech and Language; 39 (1): 87-100
[6] Miyahara, M., Harada, T., Ruffman, T., et al. (2013). Functional connectivity between amygdala and facial regions involved in recognition of facial threat. Social Cognitive and Affective Neuroscience; 8 (2): 181-189
[7] Bickart, K.C., Wright, C.I., Dautoff, R.J., et al. (2011). Amygdala volume and social network size in humans. Nat Neurosci; 14 (2): 163-4
[8] Ferrara, N.C. & Opendk, M. (2023). Amygdala circuit transitions supporting developmentally-appropriate social behaviour. Neurobio of Learn and Mem; 201
[9] Asari, T., Konishi, S., Jimura. K., et al. (2010). Amygdala enlargement associated with unique perception. Cortex; 46 (1)
[10] Chan, Y., Zeitlen, D. C., Beaty, R. E. (2022). Amygdala-frontopareital effective connectivity in creativity and humour processing. Human Brain Mapp; 44, 2585-2606