Jerusalem, 4 November, 2025 (TPS-IL) — Scientists have uncovered how the brain’s reaction to potential loss drives risky and sometimes irrational behavior — a process that may also underlie anxiety and post-traumatic stress disorder (PTSD). Using rare recordings from electrodes implanted deep in the human brain, researchers observed neurons firing in ways that explain why people fear losses more than they value gains, and why that fear can sometimes override logic.
These neural mechanisms are not just abstract phenomena — they have real-world consequences, contributing to the prevalence of anxiety and trauma-related disorders across populations. An estimated 4% of people worldwide suffer from anxiety disorders, and 5.6% of trauma survivors develop PTSD. In Israel, experts estimate that about 5.3% of the population may experience post-traumatic symptoms following the October 7 attacks and the ongoing war.
The studies, published in the peer-reviewed Nature and Current Biology journals, were led by Prof. Rony Paz and Dr. Tamar Reitich-Stolero of the Weizmann Institute of Science, together with brain surgeon Prof. Ido Strauss and neurologist Dr. Piras Pahom of Tel Aviv’s Sourasky Medical Center (Ichilov). They reveal that the amygdala — a brain region long associated with fear and emotional processing—generates bursts of “neural noise” when people face the possibility of losing something.
Neural noise is the random variability in the firing of neurons, causing fluctuations in brain activity that can influence decision-making and perception. Neural noise becomes problematic when its fluctuations are excessive or poorly regulated, because it can distort how the brain interprets information. This leads to heightened uncertainty, irrational decision-making, over-exploration, and the overgeneralization of threats—mechanisms linked to anxiety, compulsive behaviors, and PTSD.
“We know from behavioral economics that people fear losses more than they value gains,” said Reitich-Stolero. “What we’ve now found is the biological mechanism behind that: when faced with potential loss, the brain literally becomes noisier, and this noise drives exploratory, sometimes irrational, behavior.”
To investigate, the team took advantage of deep-brain electrodes implanted in patients with severe epilepsy to identify seizure origins. “Unlike electrodes placed on the scalp, deep electrodes measure the activity of individual neurons,” explained Strauss. “That allows us to see how specific brain cells compute decisions in real time.”
During the experiment, participants performed learning tasks involving either potential gains or losses. Each trial began with a tone indicating whether they could earn or lose points, followed by a choice between two shapes representing different probabilities of success. Over time, participants learned which choices improved their outcomes.
But when loss was on the line, logic gave way to emotion. Even after learning which option minimized loss, participants repeatedly ignored it, trying new strategies that often worsened their results. “They were desperately trying to find some strategy that would completely prevent a loss,” Reitich-Stolero said. “In gain situations, they stuck with what worked.”
By tracking hundreds of neurons, the researchers found that certain cells in the amygdala and temporal cortex became active before participants chose to explore new options. The intensity of that signal was similar in gain and loss situations, leading the team to look for another explanation.
“We realized the key difference was neural noise,” said Reitich-Stolero. “Under loss conditions, the amygdala’s activity became more erratic, and that unpredictability was linked to the feeling of uncertainty and the urge to keep searching for a perfect, loss-free solution.”
A second experiment examined how people generalize from past experiences of gain or loss. Participants heard sounds associated with each outcome, followed later by new sounds. They were more likely to mistake new tones for familiar ones if they resembled the “loss” sounds, suggesting the brain broadens its perception of threat after loss.
“The broad generalization of danger signals is an excellent defense mechanism, but when it’s applied excessively, as in PTSD, it leads to stress and anxiety in everyday life,” said Prof. Paz. Recordings showed that amygdala neurons fired more strongly in response to sounds similar to those linked with loss—activity that predicted whether a person would mistakenly interpret them as familiar or threatening.
“These results show, for the first time in humans, how the brain’s electrical instability during loss can distort decision-making and perception,” said Paz. “It gives us a neural explanation for why anxiety and PTSD feel so uncontrollable — and how they might one day be treated.”
The study’s findings could have significant implications for mental health treatment. By identifying neural noise in the amygdala as a driver of over-exploration and irrational behavior under threat of loss, clinicians may be able to develop therapies that reduce maladaptive responses to uncertainty, improving treatment for anxiety disorders.
Understanding why people with PTSD overgeneralize danger signals may provide new approaches to desensitize patients to perceived threats and prevent excessive stress reactions. Additionally, pinpointing the amygdala’s role opens the possibility for pharmacological interventions.
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