Differential effects of electrical stimulation of amygdala or caudate on inhibitory shock avoidance: a role for state-dependent learning.

The present study examined the disruptive effects of low-intensity electrical stimulation in the caudate or amygdala on retention of inhibitory shock avoidance. Caudate stimulation administered during a training trial disrupted inhibitory avoidance on a retest trial. However, animals receiving caudate stimulation during both training and retention trials displayed good retention of this behavior and did not differ significantly from implanted controls. These data suggest a role for state-dependent learning in mediating the disruptive effects of caudate stimulation on inhibitory shock avoidance. No evidence was found for state-dependent effects with amygdaloid stimulation. Animals receiving stimulation only during training or during both training and retest trials showed comparable disruption of inhibitory shock avoidance. These data provide evidence for locus-specific state-dependent effects of electrical brain-stimulation. The implications of these state-dependent effects are discussed with respect to the use of electrical brain-stimulation to study the neural substrates of memory.