Haloperidol reinstates latent inhibition impaired by hippocampal lesions: Data and theory

The effect of haloperidol administration on the impairment of latent inhibi tion produced by aspirative lesions of the hippocampus was examined in the rat eyeblink response preparation. During the preexposure phase, rats with hippocampal or control lesions were either exposed to a tone or allowed to sit in the training apparatus. During the conditioning phase, the tone was paired with an airpuff to the eye after the rats were injected with either saline or haloperidol. Although saline-injected rats with hippocampal lesio ns did not show latent inhibition, the phenomenon was reinstated in rats th at received haloperidol injections. A possible locus of the interaction bet ween hippocampal lesions and haloperidol is the nucleus accumbens. The repo rted data are well described by a neural network model of classical conditi oning. This study contributes to the understanding of the neurophysiology o f latent inhibition as well as the neuropsychological bases of schizophreni a.