Latent inhibition and schizophrenia

The phenomenon of latent inhibition (LI) refers to a decrement in associability of a stimulus previously preexposed without being followed by an event of consequence, and it reflects a process of learning not to attend to, or to ignore, irrelevant stimuli. Recently it was demonstrated that amphetamine-treated animals fail to develop LI. This finding has been used to provide additional support for the analogy between the animal amphetamine model of schizophrenia and the human clinical syndrome. The present experiment tested whether schizophrenics would show a similar failure to develop LI. Groups of paranoid schizophrenics, nonparanoid schizophrenics, and normals were either preexposed or not preexposed to a to-be-associated stimulus. For all three populations, learning a new association to the preexposed stimulus was markedly inferior to learning an association to the same stimulus when it was not preexposed. Thus, contrary to expectations, schizophrenics as well as normal subjects demonstrated a strong LI effect. It was suggested that the failure to find an absence of LI in schizophrenics may be due to the fact that these subjects were on a drug regimen that normalizes attentional processes.