Amygdala lesions impair context aversions but not the ability of contexts to serve as occasion setters

Abstract

Rats with large amygdala lesions (Experiment 1) were compared with sham controls on a conditional discrimination task that allowed assessment of occasion-setting learning. A saccharin solution was paired with lithium chloride in one context, but with saline in a second context. All the groups learned to suppress fluid consumption in the first, relative to the second, context. Sham lesioned rats, but not amygdala-lesioned rats, also showed a large aversion to the first context on a choice test. Shamlesioned Pavlovian control groups, given direct pairings of Context 1 with lithium chloride and of Context 2 with saline, showed large aversions to Context 1, whereas similarly trained amygdala-lesioned rats did not avoid the context associated with lithium chloride. Rats with discrete lesions of either the central nucleus or the basolateral nucleus (Experiment 2) of the amygdala were not impaired on the conditional discrimination task but did show deficits on the place choice test. The data from amygdala-lesioned rats in the present study support previous behavioral data in suggesting that the aversive properties of contextual cues, as acquired through Pavlovian conditioning, are neither necessary nor sufficient for occasion-setting learning.