Ventral tegmental area lesions do not enhance appetitive classically conditioned responses in the rat

An autoshaping procedure, in which presentation of a retractable lever signalled food delivery, was used to assess the effects of ventral tegmental area lesions on appetitive classically conditioned responses in 28 rats. Rats with ventral tegmental area lesions did not differ from sham-lesioned rats in acquiring classically conditioned lever press responses, or in learning to withold these responses when an omission contingency was in effect. This lack of effect in an appetitive setting stands in contrast to our previous finding that aversive classically conditioned responses are facilitated by this lesion, and suggests that the ventral tegmental area lesion selectively enhances aversively motivated behaviors.