Cholinergic basal forebrain is critical for social transmission of food preferences

Studies using selective lesions of basal forebrain cholinergic neurons sugg est that these neurons play a role in attentional processing, but not learn ing and memory. However, the tests of learning and memory used thus far hav e been restricted largely to spatial tasks. In the present study, we examin ed whether the cholinergic basal forebrain plays a role in a form of nonspa tial associative memory, the social transmission of food preferences. Sham- operated control rats were compared to rats with 192 IgG-saporin lesions of the medial septum/diagonal band cholinergic projections to hippocampus or nucleus basalis magnocellularis/ substantia innominata cholinergic projecti ons to neocortex. Both lesions impaired 24-h retention of a learned social food preference relative to controls, despite performance on an immediate r etention trial that was indistinguishable from controls. Moreover, 24-h ret ention of the socially learned food preference correlated strongly with cho linergic enzymatic activity in the neocortex, but not in the hippocampus. I mmunohistochemical data confirmed significant and selective lesion-induced cholinergic depletions in the intended brain regions. These data provide ev idence that the cholinergic basal forebrain, particularly the cholinergic p rojection to neocortex, is involved in the formation and/or retrieval of so cial memories related to food preference, and suggest a role for cortical a cetylcholine in consolidation of associative memory processes. Hippocampus 2000;10:729-738. (C) 2000 Wiley-Liss, Inc.