Exploring Learning and Unlearning of Fear

The present study investigates the effect of d-cycloserine on learning and unlearning of fear in healthy humans and its underlying effect on the amygdala. As a second objective, the effect of genotype on fear learning will be studied.

A growing body of evidence suggests that the extinction of fear is mediated by the N-methyl-D-aspartate (NMDA) receptor activity in the basolateral amygdala. Intra-amygdala infusions of antagonists of this glutamate receptor in small animals (eg: rats, mice) have demonstrated a blockage of fear acquisition and extinction. Agonists, on the other hand, facilitate conditioned fear extinction. The animal studies are all based on the simple fear learning paradigm of conditioning. However, it is not clear that human anxiety disorders are based on prior conditioning encounter. Therefore it is important to disentangle the effect of DCS on acquisition and extinction in the context of a simple learning paradigm, particular its effect on the human amygdala.