COMPARISON OF THE EFFECTS OF FRONTAL CORTICAL AND THALAMIC LESIONS ONMEASURES OF OLFACTORY LEARNING AND MEMORY IN THE RAT

Rats were trained on an olfactory continuous delayed nonmatching-to-sa mple (DNMTS) task and then given 1 of 4 treatments: sham surgery or ra dio-frequency lesion of the lateral internal medullary lamina of the t halamus or of the frontal cortex along the medial wall or dorsal to th e rhinal sulcus. Thalamic lesions produced persistent deficits on the continuous DNMTS task, and both the cortical lesions resulted in trans ient impairments that disappeared with continued training. Manipulatio ns of stimulus set size and the delay between trials affected continuo us DNMTS performance but did not exacerbate group differences. All 3 l esion groups performed normally when next trained on a discrimination task with odorants and go-no-go procedures comparable to continuous DN MTS. These results indicate that lesions did not affect ability to per form go-no-go procedures, to discriminate among odorants, or to use re ference memory to respond on the basis of a fixed stimulus-response ru le.