Effects of ibotenic acid lesions of the basal forebrain on serial reversal learning in marmosets.

Five common marmosets (Callithrix jacchus) received unilateral ibotenic acid lesions of the basal forebrain. Seven days post-operatively, choline acetyltransferase activity was reduced by 60% in frontal cortex and 40% in temporal cortex in the ipsilateral side compared with the contralateral side. Four animals receiving bilateral lesions of the same area were impaired on the first post-operative task of serial reversal learning when compared with four animals receiving bilateral saline injections. Although their performance improved with time, the lesioned animals were subequently impaired following administration of a low dose of scopolamine which did not affect the control group. These results show that lesions within the basal forebrain can affect cholinergic function in the cortex and impair learning ability.