Scientists studying fear responses in rats have discovered that although the amygdala plays a central role in emotional learning and processes and expresses fear, a region of the cortex may be involved in learned fear.

By teaching rats to fear a tone by associating it with a shock to the foot at the end of the tone, scientists were able to observe the rats’ response. Ater learning to fear the tone, the rats would spend 70% percent of the time the tone sounded in a frozen state, a typical fear response.

When the researchers chemically blocked activity in the prelimbic cortex, located near the front of the brain, the rats spent only 14% of the time frozen. However, their innate fears were not affected by the blocking of the prelimbic cortex, they still exhibited fear at the sight of a cat or a large open area.

The findings suggest that hyperactivity in that region of the prefrontal cortex might contribute to learned fear disorders in humans, such as post-traumatic stress disorder and anxiety disorders.

The study was authored by Kevin A. Corcoran, PhD, and Gregory Quirk, PhD, of the Ponce School of Medicine in Puerto Rico. Their report appears in the January 24 issue of The Journal of Neuroscience.