Lesions of the amygdaloid complex impair acquisition of serial pattern learning in rats

Normal and amygdala-lesioned rats were trained in a runway to respond to a three-element pattern ending in 2, 12, or 0 Noyes pellets (45 mg), respectively. The amygdalectomized rats' performance was inferior to that of normal controls during the early and middle stages of training, that is, amygdalectomized rats ran more slowly on rewarded trials and developed patterned running later than control rats. In the later stages of training, the lesioned rats demonstrated tracking of the series elements, reflected by differential running times similar to those of the control animals. Results are discussed in terms of some of the current theories involving the role of the amygdaloid complex in learning and reinforcement.