Surgeons can and do remove the amygdala, and the procedure has been performed for decades. It is most commonly done today as part of epilepsy surgery, where removing amygdala tissue along with parts of the hippocampus can dramatically reduce seizures in people whose epilepsy resists medication. What happens afterward depends heavily on how much tissue is taken, whether one or both sides are affected, and when in life the damage occurs. The consequences range from subtle shifts in emotional memory to a near-complete inability to recognize fear in other people’s faces.
Why Surgeons Remove It
The most common reason for amygdala removal today is mesial temporal lobe epilepsy, a form of seizure disorder that originates in the inner structures of the temporal lobe. When medications fail to control seizures, surgeons may perform what is called an amygdalohippocampectomy, removing the amygdala and hippocampus on one side of the brain. Stereotactic radiofrequency amygdalohippocampectomy is one alternative approach that has been used as an epilepsy treatment alongside traditional microsurgical resection.1PubMed Central. Relationship between remnant hippocampus and amygdala and memory outcomes after stereotactic surgery for mesial temporal lobe epilepsy
There is also a darker chapter in this history. Starting in the 1950s, stereotactic amygdalotomy, a procedure that destroys amygdala tissue using a probe guided by brain coordinates, was performed on patients with severe aggressive behavior. A review of thirteen clinical series found that reported improvement in aggression ranged from about a third to all patients, but complication rates went as high as 42 percent, and the mortality rate reached nearly 4 percent in some series.2PubMed. Stereotactic amygdalotomy in the management of severe aggressive behavioral disorders The earliest clinical series of amygdalotomy for aggression and temporal lobe epilepsy was reported by Narabayashi and colleagues, who used a frame-based stereotactic device.3PubMed. Historical evolution of stereotactic amygdalotomy for the management of severe aggression These procedures were ethically contentious even at the time, and the use of psychosurgery for behavioral control has largely been abandoned. Modern amygdala removal is almost exclusively performed for structural brain disease like epilepsy or tumors.
How the Surgery Is Performed
A traditional approach involves open microsurgery, where a neurosurgeon accesses the temporal lobe through a craniotomy and removes the amygdala along with any surrounding abnormal tissue. One team described a refined procedure for removing amygdalar-uncal lesions, reporting that lesions were completely removed in all fifteen patients without complications.4PubMed Central. Surgical Resection of Amygdala and Uncus This kind of open surgery remains common when the goal is complete tissue removal, especially for tumors.
A newer and less invasive option is laser thermal ablation. Rather than opening the skull widely, surgeons thread a small laser fiber through a tiny hole and use MRI guidance to heat and destroy targeted tissue. This approach has shown good seizure outcomes while being significantly less invasive than a traditional amygdalohippocampectomy.5American Epilepsy Society. Laser thermal ablation of amygdala and hippocampus – surgical outcome and memory deficits in mesial-temporal lobe epilepsy patients Laser ablation has become increasingly popular because it means shorter hospital stays, smaller incisions, and often a quicker recovery.
What Happens to Fear
The amygdala’s best-known role is processing threats and fear. Much of what we know about this comes from a single extraordinary patient known as SM, a woman with a rare genetic condition called Urbach-Wiethe disease that destroyed both of her amygdalae while leaving the rest of her brain intact. SM performs within the normal range on standard tests of IQ, memory, language, and perception. Yet she is severely impaired in fear conditioning, in recognizing fear in facial expressions, and in social behaviors that depend on fear-related emotions.6PubMed Central. The human amygdala and the induction and experience of fear
The mechanism behind this is surprisingly specific. Researchers found that SM’s difficulty recognizing fear in faces stems from the fact that she does not spontaneously look at the eye region of faces. Since the eyes are the most informative feature for identifying fear, this creates a selective blind spot. When SM was explicitly told to look at the eyes, her recognition of fearful faces returned to normal.7Nature. A mechanism for impaired fear recognition after amygdala damage That finding suggests the amygdala is not the “fear center” in the way pop neuroscience sometimes portrays it. It is more like a spotlight director, automatically steering attention toward the parts of the environment that matter for detecting danger. Without it, the raw ability to perceive a fearful face is still there, but the automatic drive to look where it counts is gone.
Animal research has added an interesting wrinkle to this picture. In mice, amygdala lesions do not simply eliminate fear responses; they change which fear responses appear. When exposed to carbon dioxide (a suffocation cue that triggers intense distress), mice with amygdala lesions froze much less than normal mice but instead displayed frantic jumping, as if attempting to escape. Mice with only one amygdala damaged showed both normal freezing and the jumping behavior.8PubMed Central. The amygdala differentially regulates defensive behaviors evoked by CO2 The amygdala does not appear to be the sole gateway to all fear; other brain circuits can still trigger panic-like responses through different pathways.
Emotional Memory Takes a Hit
You probably remember emotionally charged events more vividly than mundane ones. That boost in memory for emotional material depends on the amygdala. When the amygdala is damaged, people typically retain normal memory for everyday neutral information but lose the extra memory advantage that emotional events usually get.
Studies of patients with unilateral (one-sided) amygdala damage have shown this clearly. Patients with left amygdala damage were impaired in their memory for emotional stimuli, despite having entirely normal memory for neutral material.9PubMed Central. Impaired emotional declarative memory following unilateral amygdala damage The normal memory boost from emotion appears to build over time, taking more than thirty minutes to develop, which points to the amygdala’s role in the slow process of memory consolidation rather than in the initial moment of experiencing something.
Timing matters in another sense too. Research has found that amygdala lesions arising early in development, but not those acquired in adulthood, are associated with a loss of the expected superior retrieval of emotionally arousing material over neutral material.10PubMed. A critical period for the impact of amygdala damage on the emotional enhancement of memory This suggests there may be a critical period: lose the amygdala as a child, and the brain’s emotional memory system never fully develops its normal architecture. Lose it as an adult, and the brain may have already established workarounds or stored enough emotional-memory infrastructure elsewhere to partially compensate.
Decision-Making Without the Emotional Guardrails
The amygdala does not just process fear and emotional memories; it shapes the way people weigh risks and make financial and social decisions. Several lines of evidence from patients with amygdala damage paint a consistent picture: without the amygdala’s input, people become less sensitive to potential losses and more willing to take risks that most people would avoid.
One of the clearest demonstrations involves loss aversion, the well-known tendency to feel the sting of a loss about twice as strongly as the pleasure of an equivalent gain. Two patients with bilateral amygdala damage showed a dramatic reduction in loss aversion compared to matched controls, while retaining a normal ability to respond to changes in expected value and risk. The researchers concluded that the amygdala plays a key role in generating loss aversion by inhibiting actions with potentially harmful outcomes.11PubMed Central. Amygdala damage eliminates monetary loss aversion
This extends to broader decision-making. Patients with selective amygdala damage from Urbach-Wiethe disease showed lower scores in both decisions under ambiguity and decisions under risk, with risk-based decisions especially compromised in patients who also had trouble with executive functioning.12PubMed. Role of the amygdala in decisions under ambiguity and decisions under risk: evidence from patients with Urbach-Wiethe disease In social contexts, basolateral amygdala damage has been linked to increased generosity in economic games, and this was not simply explained by increased risk-taking in nonsocial situations.13PubMed Central. Generous economic investments after basolateral amygdala damage The picture that emerges is of the amygdala as a kind of caution engine: it generates the gut feeling that something could go wrong, and without it, people are more trusting, more generous, and less cautious about losses in ways that look socially warm but financially reckless.
Social Behavior and Personal Space
If you have ever felt uncomfortable when a stranger stands too close, that reaction is partly mediated by your amygdala. A study of a patient with complete bilateral amygdala lesions found that she lacked any sense of personal space. Healthy individuals showed amygdala activation when someone entered their personal zone, but this patient was comfortable at any distance and did not experience the discomfort that normally serves as a social boundary signal.14PubMed Central. Personal space regulation by the human amygdala The researchers suggested that the amygdala is needed to trigger the strong emotional reactions that normally follow personal space violations, effectively setting the invisible bubble most people maintain around themselves.
This ties into the broader pattern: the amygdala functions as an alarm and appraisal system for socially relevant signals. Without it, people may be described as unusually friendly and trusting, not because they have reasoned their way into openness, but because the visceral wariness that normally keeps strangers at arm’s length simply is not firing.
Moral Judgment Changes in Unexpected Ways
One of the more surprising findings involves how amygdala damage affects moral reasoning. In classic moral dilemmas (would you push one person off a bridge to save five?), healthy people frequently make the utilitarian choice, sacrificing one life to save many. But five humans with selective, bilateral basolateral amygdala damage showed a breakdown of these utilitarian sacrificial judgments. They withheld sacrificial decisions even when the cost was enormous, declining to sacrifice one person even at the cost of thousands of lives.15PubMed Central. Breakdown of utilitarian moral judgement after basolateral amygdala damage
This finding challenges the assumption that emotions primarily push people toward refusing to sacrifice (the squeamish response) while cold calculation drives utilitarian choices. Instead, the amygdala seems to be involved in the kind of flexible, model-based reasoning that allows people to evaluate trade-offs. Without it, moral judgments become more rigid and rule-bound: harm is bad, full stop, regardless of the arithmetic of lives saved.
One Side Versus Both Sides
Most epilepsy surgeries remove amygdala tissue on only one side of the brain, and the consequences of unilateral removal are far milder than bilateral loss. The two amygdalae are not identical in their roles, either. In rats, inactivation of the right amygdala impaired retention of fear-based learning 48 hours later, suggesting the right side may play a larger role in consolidating aversive memories.16PubMed. Differential effects of pretraining inactivation of the right or left amygdala on retention of inhibitory avoidance training
In humans, a study of two patients who received left amygdala lesions for epilepsy found that the surgery led to decreases in both trait and state anxiety, along with drops in respiratory rate and activity in the intact right amygdala. The researchers proposed that the right amygdala dominates anxiety and anxiety-related physiological responses but depends on excitatory signals from the left amygdala to function fully.17PubMed. Effects of left amygdala lesions on respiration, skin conductance, heart rate, anxiety, and activity of the right amygdala during anticipation of negative stimulus Losing one amygdala, in other words, does not just halve the system. It changes the dynamics of the surviving side.
Bilateral damage, whether from surgery, disease, or injury, produces the most dramatic effects. A case report described a patient with bilateral selective amygdala damage who developed a cluster of symptoms known as Klüver-Bucy syndrome: visual agnosia (difficulty recognizing objects by sight), hypersexuality, hyperorality (compulsively putting things in the mouth), a tendency to react to every visual stimulus, and memory deficits.18PubMed. Klüver-Bucy syndrome after bilateral selective damage of amygdala and its cortical connections This syndrome is rare in humans because bilateral amygdala damage from surgery is almost never intentional, but it illustrates the extremes of what can happen when both sides are lost.
How Mood Changes After Surgery
Given the amygdala’s deep involvement in negative emotions, you might expect that removing it would leave people emotionally flat or depressed. The evidence from epilepsy surgery tells a more nuanced story. A study of patients who underwent temporal lobectomy found that, on average, participants showed a significant post-surgical improvement in mood, with depression scores dropping from a mean of roughly 12 points before surgery to about 8 points after. About 56 percent of patients improved, while 38 percent experienced some mood worsening. The area most strongly associated with mood improvement was the right amygdala, specifically regions within it.19PubMed Central. Amygdala lesions are associated with improved mood after epilepsy surgery
These results need some context. Epilepsy itself causes depression at high rates, and simply becoming seizure-free after surgery can improve quality of life enormously. Separating the mood benefits of amygdala removal from the mood benefits of seizure freedom is genuinely difficult. There are also cases where things go the other direction: patients who were depressed after temporal lobectomy tended to have smaller remnant amygdala volumes on the side that was resected.20PubMed. Relationship between post-operative depression/anxiety and hippocampal/amygdala volumes in temporal lobectomy for epilepsy The relationship between amygdala tissue and post-surgical mood is not straightforward; both how much tissue is removed and how much remains seem to matter.
The Brain’s Ability to Compensate
One of the more remarkable findings in amygdala research is that the brain does not simply accept the loss and move on. There is evidence that other brain structures can partially pick up the slack. Animal research has shown that the bed nuclei of the stria terminalis, a nearby structure with close connections to the amygdala, can provide compensatory plasticity after the basolateral amygdala is damaged. With extensive training, fear learning that initially depended on the amygdala can be partially recovered through this alternative circuit.21PubMed Central. Compensation in the neural circuitry of fear conditioning awakens learning circuits in the bed nuclei of the stria terminalis
This compensation is not complete, and it takes time and repeated exposure. But it helps explain why patients who lose amygdala tissue in surgery do not typically experience the catastrophic emotional deficits you might predict from the animal literature. The brain is not modular in the clean way diagrams suggest; it is a network, and networks reroute.
The Amygdala’s Role in Pain
The amygdala receives pain signals and processes the emotional dimension of pain, the unpleasantness and distress rather than the raw sensation of where and how much something hurts. Research has shown that the central nucleus of the amygdala contributes only marginally to the sensory-discriminative components of pain but plays a significant role in the associated behavioral and emotional responses to painful stimuli.22PubMed Central. The amygdala between sensation and affect: a role in pain In practical terms, a person with amygdala damage might still feel pain in the physical sense but could experience less of the suffering and anxiety that normally accompanies it. This distinction between the sensation and the emotional weight of pain is one of the more underappreciated aspects of amygdala function.
Deep Brain Stimulation Instead of Removal
Removing the amygdala is irreversible. For conditions where amygdala overactivity is part of the problem but where destroying tissue seems too drastic, researchers have been exploring deep brain stimulation as an alternative. DBS involves implanting electrodes that deliver continuous electrical pulses to modulate a brain region’s activity without destroying it. In a rat model of post-traumatic stress disorder, amygdala DBS outperformed the common SSRI paroxetine. The idea is that by dampening amygdala function rather than eliminating it, DBS could treat the hyperactive amygdala activity thought to drive PTSD without the permanent consequences of tissue removal.23Brain Stimulation. Amygdala deep brain stimulation is superior to paroxetine treatment in a rat model of posttraumatic stress disorder
DBS for the amygdala is still experimental in humans for psychiatric conditions, and it carries its own risks including infection and hardware complications. But the concept is appealing: a dial rather than a switch. If the amygdala’s problem is running too hot, turning it down without cutting it out preserves the option of adjustment or reversal. Whether this approach will ever reach clinical practice for conditions like treatment-resistant PTSD or severe anxiety remains an open question, but the animal data is encouraging enough that several research groups are pursuing it.