Abstract
Although much is now known about the neural basis of fear acquisition, the mechanisms
of fear inhibition or suppression remain largely obscure. Fear inhibition is studied
in the laboratory through the use of an extinction procedure, in which an animal (typically
a rat) is exposed to nonreinforced presentations of a conditioned stimulus (CS; e.g.,
a light or tone) that had previously been paired with a fear-inducing unconditioned
stimulus (US; e.g., a mild footshock). Over the course of such training, the conditioned
fear response exhibited by the rat in the presence of the CS is reduced in amplitude
and frequency. This procedure is analogous to those employed in the treatment of fear
dysregulation in humans, which typically involve exposure to the feared object in
the absence of any overt danger.
Recent work on the neural basis of extinction indicates that the neurotransmitters
γ-aminobutyric acid (GABA) and glutamate are critically involved. Gamma-aminobutyric
acid may act to inhibit brain areas involved in fear learning (e.g., the amygdala),
and glutamate, acting at N-methyl-d-aspartate receptors, may play a role in the neural plasticity that permits this GABA-mediated
inhibition to be exerted appropriately. These insights have significant implications
for the conduct of extinction-based clinical interventions for fear disorders.
Keywords
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Article info
Publication history
Accepted:
June 21,
2002
Received in revised form:
June 19,
2002
Received:
March 7,
2002
Identification
Copyright
© 2002 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
