Can I change the way you think about this bad boy of neuroscience? Countering the simplistic narratives around the amygdala.
Co-written Ana x Mike Tranter
If there is only one brain area you have heard of, I bet it is the amygdala. This little structure has shot to global fame, but it gets a bad rap. Its often cast as the villain—the culprit behind almost any account (especially the more simplistic ones) about how neuroscience and brain come into play for many of the least desirable maladaptive reactions or behaviours such as anxiety, fearful reactions or aggression. It's an explanation to anything and everything.
And there is a whole neuro-psycho-babble surrounding it. We are offered the "tools to calm or tame the amygdala", or warned that we might be "hijacked" by it. We hear that the amygdala is the brain’s fear center (it is not) or the brain’s smoke alarm.
Cross my heart, I once heard a mindfulness teacher from a reputable meditation training institution say that every time we meditate, we “literally spray our amygdala with a soothing neurotransmitter.” Literally? What does that even mean...
So let’s set the record straight. While fear and threat conditioning are crucial functions of the amygdala—and far from outdated, as we explain later—it also plays a key role in many other essential processes. The amygdala is not the brain’s villain and is long overdue for some redemption.
Let’s start at the beginning.
A Little Neuroanatomy and Little History
Believe it or not, the amygdala did not always command so much attention. Let the story about its rise to fame begin in the late 1960s, when Arthur Kling, a pioneering researcher in primate brain and behaviour, set out to uncover the elusive function of this tiny, almond-shaped structure. His search took him to an island off the coast of Puerto Rico, a Mecca for primate behavior research, inhabited solely by monkeys. There, Dr. Kling conducted groundbreaking studies on what happens when vervet monkeys lose their amygdala and are released into the wild (more on that later).
Once Daniel Goleman coined the term “the Amygdala Hijack” in his 1995 book Emotional Intelligence, the term went viral for the general public. The reputation of the amygdala as the ‘bad boy’ of the brain has taken the world by storm ever since.
Neuroanatomycaly, the amygdala is a relatively small structure (approx 1.7cm3) situated deep in the temporal lobes, towards the centre of the brain and adjacent to the hippocampus. Despite being small, the amygdala is complex and it has been argued that it is a composite structure with up to dozen of structurally and functionally distinct subregions formed by different cell types.
The function—or 'power', if you will—of the amygdala in defensive behaviours lies in its connections to other brain structures. It receives sensory input from both the sensory cortex and the thalamus. Downstream, it sends projections to the hypothalamus, the 'master key' to the body’s endocrine system and autonomic arousal. In other words, the amygdala has privileged access to sympathetic activation—the system that mobilises the body’s resources to spring into action.
But while this specific pathway is one of the most heavily researched, the amygdala’s network of neural connections is far more complex and cannot be reduced to just threat conditioning.
Cavemen Needed the Amygdala, But Do We?
Today, the amygdala gets a bad rap, and its origin story often goes like this:
Ancient humans lived in caves or on the savannah, surrounded by predators and poisonous food. In that world, the brain’s alert system—designed to sound the alarm and trigger a “fight or flight” response—was essential for survival. The amygdala, in this view, was that alarm system.
Fast forward to modern humans: We live far more sheltered lives, free from predators, yet we’re still wired with the same brain circuitry as our distant ancestors. According to this perspective, the amygdala is an outdated alarm system, wreaking havoc in our daily lives and becoming maladaptive. It’s like a fire alarm blaring and fire engines rushing in—when all we’ve done is light a small candle. It is just too much over the top.
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 its role is much more complex and one the scientists are only beginning to fathom? Is it actually helping us not only to survive but also to thrive?
A Girl Without the 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. 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, one of the pioneers of affective neuroscience (neuroscience of emotions). 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 , 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 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. 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.
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 heartbreaking, these observations are not that surprising. Actually, the observation of the scarcity of S.M.’s social life is consistent with a broader finding :
amygdala's size and complexity correlate to the size and complexity of social networks. The bigger the amygdala, the bigger the social circle.
Bigger Can Sometimes Be Better, And It Aint't All Black and White
That brings us to an important point: the size of the amygdala is often heard about in the context of trauma, exposure to chronic stress or other adverse life experiences and that might lead us to create a cognitive shortcut of "bigger the amygdala, bigger the problem".
Yet, the situation is more complex.
In the example above, 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 dopamine circuits involving the amygdala are essential in establishing early life social behaviours that we build on during our lives. Uncovering more about its various complex functions can help us to reimagine the colourful story of the amygdala, rather than seeing it in only black and white.
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 is associated with creativity.
For a moment, consider how many of your behaviours are influenced by your amygdala: fear, anxiety, motivation, reward pathways, feeding, emotional regulation, sociality, creativity, even humour processing. The next time you feel someone is too close (or too far) from your personal space, get a food craving, laugh at a joke, or instinctively hide behind a pillow during a horror movie, you will know that what you experience is, to some extent, mediated by the amygdala.
Hopefully, by now, you see what we mean when we say that the amygdala isn’t that bad boy that it is made out to be. If anything, it deserves a little redemption.
As always, thank you for reading. For updates you can follow me on BlueSky , via my substack or subscribe to my mailing list.
References
In this article we draw heavily on the book Living without an Amygdala.
Dr Mike Tranter, originally from the UK, is neuroscientist and best-selling author, who now resides in San Diego, California. His research interests focus on decision making in the brain, particularly in mental illness. Mike has just had his new book out, A Billion Things To Ask A Neuroscientist, where he answers some of the following questions: How is the brain different between introverts and extroverts? Are psychedelics the miracle cure we’ve been waiting for? What happens during a near death experience? What happens when we listen to music? and many more. You can follow Mike on Instagram or LinkedIn.
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