By K J Foxhall 
Deep within the temporal lobe sits the amygdala, an almond-shaped cluster of nuclei. For decades, scientists knew it was part of the limbic system (the brain’s emotional network), but it took specific, often tragic patient stories (isn’t it always the way), to reveal exactly how it orchestrates our responses to fear, memory, and aggression.
Here are the three most famous patient stories associated with the amygdala:
Patient S.M.: ‘The woman with no fear’
Patient S.M. is arguably the most famous amygdala patient in history. She suffers from a rare genetic condition called Urbach-Wiethe disease, which causes the gradual calcification and total destruction of both sides of her amygdala while leaving the rest of her brain completely intact.
Researchers spent decades studying S.M., exposing her to situations that would terrify an average person:
- The exotic pet store: S.M. claimed she hated snakes and spiders. Yet, when researchers took her to a pet store, she was overcome with curiosity, voluntarily holding a venomous snake and trying to touch a tarantula.
- The haunted house: She was walked through the Waverly Hills Sanatorium (a notoriously scary haunted house attraction). While other visitors screamed, S.M. laughed and even tried to poke one of the actors dressed as a monster out of curiosity.
- Horror movies: She watched clips from The Shining, The Blair Witch Project, and The Silence of the Lambs without showing a single dip in emotional comfort or a spike in heart rate.
The plot twist: Researchers eventually found a way to make S.M. feel panic. When they had her inhale a safe mixture of 35% carbon dioxide (which mimics the sensation of suffocation), she experienced a full-blown panic attack. This taught neuroscientists that the amygdala is responsible for processing external threats from the environment, while internal physical threats (like a lack of oxygen) come from deep brain structures like the hypothalamus, brainstem, and insular cortex.
S.M. later described it as a completely novel sensation, the first time she had felt fear in her adult life. This proved to science that while the amygdala is the gatekeeper for processing visual and auditory threats from the outside world, the brainstem and insular cortex can independently register internal, physiological survival threats (like suffocation).
Patient S.M. ‘s case fundamentally reshaped neuroscience by proving that the amygdala is the physical ‘engine’ of PTSD, revealing that without it, the disorder cannot exist.
Her exact identity remains heavily guarded by her research team to protect her privacy and safety, but she is alive and continues to participate in ongoing studies.
Patient H.M. (Henry Molaison): The placid mind
You may remember Henry from a previous magazine issue where we dived deeper into the hippocampus.
Henry Molaison is universally famous for his profound memory loss. In 1953, to cure his severe epilepsy, a surgeon removed his medial temporal lobes. This surgery famously destroyed his hippocampus (leaving him unable to form new memories), but it also removed most of his amygdala.
While his memory loss stole the headlines, his personality shift gave scientists huge clues about the amygdala:
- Before the surgery, H.M. suffered from intense emotional distress and outbursts related to his epilepsy.
- After the surgery, he became incredibly placid and docile. He never expressed anger, deep grief, or intense fear.
- Even when undergoing painful medical tests or receiving bad news, his emotional baseline remained completely flat.
His story offered early, definitive evidence that removing the amygdala essentially lowers the entire emotional sensitivity of the brain.
Charles Whitman: The Texas tower sniper
While S.M. and H.M. showed what happens when the amygdala is missing, Charles Whitman’s story is a chilling look at what happens when the amygdala is malfunctioning.
In 1966, Whitman, a seemingly normal, intelligent former U.S. Marine suddenly began experiencing overwhelming, violent impulses. Confused and distressed by his own changing mind, he wrote a note stating that he loved his wife and mother deeply but felt compelled to kill them, which he tragically did. He then climbed a clock tower at the University of Texas, killing 14 people and wounding over 30 others before being shot by police.
In his suicide note, Whitman explicitly requested an autopsy to see if something had changed in his brain.
The finding: The medical examiner discovered a glioblastoma (a malignant brain tumour) about the size of a walnut.
The amygdala connection: The tumour was pressing directly against his amygdala and eroding the surrounding brain tissue.
While neuroscientists still debate the exact extent of the tumour’s influence, his case is widely cited as evidence of how physical damage or pressure on the amygdala can severely disrupt emotional regulation, sending the brain’s fight-or-flight aggression responses into hyper drive.
Further reading: A Fitting Memorial, The Mental Health Legacy of the Whitman Murders by Rebecca Johnston