Brains rely on old and new mechanisms for diminishing fear

September 10, 2008

A new study suggests that although humans may have developed complex thought processes that can help to regulate their emotions, these processes are linked with evolutionarily older mechanisms that are common across species. The research, published by Cell Press in the September 11th issue of the journal Neuron, provides new insight into way the brain manages fear and may guide exploration of novel pharmacological and therapeutic treatments for anxiety disorders.

"The ability to eliminate, control or diminish negative emotional responses is important for adaptive function and critical in the treatment of psychopathology," says study author, Dr. Mauricio Delgado from Rutgers University. "Recent research examining the neural mechanisms for diminishing fears has focused on two techniques: extinction, which has been explored across species, and cognitive emotion regulation strategies, which are unique to humans." Previous work in rodents and humans has implicated activity in the amygdala and ventral medial prefrontal cortex (vmPFC) in extinction. In contrast, neural circuits underlying cognitive strategies to regulate emotions are not as well understood.

Dr. Delgado, Dr. Elizabeth A. Phelps from New York University, and their colleagues were interested in examining the similarities and differences of diminishing fear through both techniques. They used similar experimental paradigms with different means of controlling fear to directly compare the neural mechanisms that mediate extinction and emotional regulation. A typical fear conditioning method was paired with a measurement of physiological arousal to examine extinction, while a cognitive emotion regulation strategy was also implemented. Functional magnetic resonance imaging (fMRI) was used to compare the neural activation patterns of extinction and emotional regulation.

The researchers observed that the lateral prefrontal cortex regions engaged by cognitive emotion regulation strategies influenced the amygdala and diminished fear through similar vmPFC connections that are thought to inhibit the amygdala during extinction. Taken together, the findings indicate that there is overlap in the neural circuitry of diminishing learned fears through emotion regulation and extinction and that vmPFC may play a general regulatory role in diminishing fear across a range of paradigms.

"Our results suggest that even though humans may have developed unique capabilities for using complex cognitive strategies to control emotion, these strategies may influence the amygdala through phylogenetically shared mechanisms of extinction," explains Dr. Phelps. "Extinction and cognitive emotion regulation may be, in part, complementary in that they rely on a common neural circuitry and, perhaps, similar neurophysiological and neurochemical mechanisms."
-end-
The researchers include Mauricio R. Delgado, Rutgers University, Newark, NJ; Katherine I. Nearing, University of Miami School of Medicine, Miami, FL; Joseph E. LeDoux, New York University, New York, NY; and Elizabeth A. Phelps, New York University, New York, NY.

Cell Press

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