Researchers at the University of California, Irvine have identified a key neural pathway in humans that explains how the brain processes feelings of fear and anxiety, a finding that could help scientists unlock new ways to treat mental health disorders. People are motivated to remember fearful events, because this information is useful for daily survival. Yet over-interpretation of fear may lead to anxiety and other mental disorders.
Understanding how the human brain processes fearful information has been a topic of intense scientific research. Until now, the brain circuit underlying fear has only been mapped in rodents. The study, “Amygdala-hippocampal dynamics during salient information processing,” appears today in the journal Nature Communications.
Researchers recorded neuronal activity using electrodes inserted into the amygdala and hippocampus of nine people as they watch scenes from horror movies to stimulate the recognition of fear. “Deep brain electrodes capture neurons firing millisecond by millisecond, revealing in real time how the brain attends to fearful stimuli,” said Jie Zheng, a UCI graduate student and the study’s first author. Researchers demonstrated that these two regions, which play a key role in recognizing emotional stimuli and encoding them in memories, are directly exchanging signals.
“In fact, neurons in the amygdala fired 120 milliseconds earlier than the hippocampus. It is truly remarkable that we can measure the brain dynamics with such precision,” said Zheng. “Further, the traffic pattern between the two brain regions are controlled by the emotion of the movie; a unidirectional flow of information from the amygdala to the hippocampus only occurred when people were watching fearful movie clips but not while watching peaceful scenes.”
Human and animal studies have established the amygdala’s role in fear processing and a parallel role the hippocampus plays in enhanced memory processing of emotional events.