On the mechanism of go-no go symmetrically reinforced task in dogs.

The mechanism of differentiation with asymmetrical and symmetrical reinforcement was analysed on the basis of different impairments after medial and lateral prefrontal lesions. The medial prefrontal lesions impaired the retention of asymmetrical differentiation whereas the symmetrical differentiation was slightly or not impaired at all. The lateral prefrontal lesions impaired moderately the asymmetrical differentiation only with short intertrial intervals. The disturbances of symmetrical differentiation depended on the quality of the stimuli, the separation of their sources and the quality of instrumental responses. The results support the hypothesis that the medial prefrontal cortex is involved in inhibitory control of alimentary drive functions. It is concluded that the lateral prefrontal cortex takes part in the elaboration of direct connections between conditioned stimuli and instrumental responses.