Investigating the Neural Substrates of Relapse Behavior

Reinstatement occurs when exposure to theunconditioned stimulus alone (i.e. contextconditioning) after extinction causes a recovery of responding to the conditioned stimulus. This model isfrequently used as a research model of relapse forthe treatment of drug abuse and anxiety disorders.Reinstatement of conditioned fear has been shown to depend on the hippocampal formation. Thehippocampal formation has also been implicated in theacquisition and expression of contextual freezing.Two experiments examined the role of the hippocampus and two of its efferent targets the bednucleus of the stria terminalis (BST) and nucleusaccumbens in two protocols for creating contextualfreezing and the reinstatement of conditioned fear in rats. The results of these experiments suggestthat hippocampal-BST neural circuitry is criticallyinvolved in the reinstatement effect and the production of a state that is more like anxietythan fear.