NUCLEUS BASALIS LESIONS ATTENUATE AQUISITION, BUT NOT RETENTION, OF PAVLOVIAN HEART-RATE CONDITIONING AND HAVE NO EFFECT ON EYEBLINK CONDITIONING

Rabbits with lesions of the anterior nucleus basalis of Meynert (nBM) were compared with animals with sham lesions or unoperated control animals on a classical conditioning task in which heart rate (HR) and eyeblink (EB) conditioned responses (CRs) were assessed. The nBM lesions impaired the magnitude of the decelerative HR CR, but had no effect on the EB CR. A second experiment, in which animals were lesioned after acquisition was complete, showed that anterior nBM lesions had no effect on retention of either the HR or EB CR. These data suggest that the anterior nBM may participate in the early stages of information processing in which stimuli are evaluated for their significance based on their association with a reinforcer. However, the anterior nBM is apparently not involved in the selection of a somatomotor response to deal effectively with such changing stimulus contingencies.