refrontal Mechanisms in Extinction f Conditioned Fear

nterest in the medial prefrontal cortex (mPFC) as a source of behavioral inhibition has increased with the mounting evidence for a unctional role of the mPFC in extinction of conditioned fear. In fear extinction, a tone-conditioned stimulus (CS) previously paired ith a footshock is presented repeatedly in the absence of footshock, causing fear responses to diminish. Here, we review converging vidence from different laboratories implicating the mPFC in memory circuits for fear extinction: (1) lesions of mPFC impair recall f extinction under various conditions, (2) extinction potentiates mPFC physiological responses to the CS, (3) mPFC potentiation is orrelated with extinction behavior, and (4) stimulation of mPFC strengthens extinction memory. These findings support Pavlov’s riginal notion that extinction is new learning, rather than erasure of conditioning. In people suffering from posttraumatic stress isorder (PTSD), homologous areas of ventral mPFC show morphological and functional abnormalities, suggesting that extinction ircuits are compromised in PTSD. Strategies for augmenting prefrontal function for clinical benefit are discussed.