BASAL FOREBRAIN CHOLINERGIC LESIONS ENHANCE CONDITIONED APPROACH RESPONSES TO STIMULI PREDICTIVE OF FOOD

This study examined the effects of lesions to different neuronal popul ations within the basal forebrain on reward-related learning. Rats rec eived bilateral alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic a cid (AMPA) or quinolinate lesions that preferentially destroy the chol inergic nucleus basalis magnocellularis (NBM) or noncholinergic ventra l pallidal neurons, respectively. Both lesions enhanced conditioned ap proach responses to stimuli predictive of food but did not increase th e locomotor stimulating effect of d-amphetamine. Although both lesions disrupted the discriminative control over behavior by a conditioned s timulus, they did not impair the subsequent acquisition of instrumenta l responding with conditioned reinforcement (CR). Indeed, both lesions were associated with an increased responding with CR following intra- accumbens infusions of d-amphetamine (0, 1, 3, 10, and 20 mu g). Quino linate lesions also increased responses on an inactive control lever. Neither lesion altered consummatory responses to food or sucrose. Resu lts suggest that NBM lesions may disrupt the balance between cortical and subcortical dopamine levels, and/or produce a deficit in attention al mechanisms that is manifested as increased responding to specific s timuli.