Attentional deficits are a proeminent aspect of cognitive dysfunction in schizophrenia. Inhibition of irrelevant processing appears to be an important, if not exclusive, function of selective attention (Neill, Valdes & Terry, 1993). Neuropsychological research has identified the associative cortex of frontal lobes, the prefrontal cortex, as the primary locus of cognitive inhibition. Structural and functional abnormalities have been reported in this region in schizophrenia. Patients with schizophrenia fail to activate the prefrontal cortex during a selective attention or another cognitive task performance that implies the cognitive inhibitory mechanisms. In the present study, Stroop stimuli, an intentional forgetting task, and the Short Inventory of Minor Lapses (Reason, 1993) have been used to evaluate the efficiency of inhibitory mechanisms at 7 positive and 9 negative schizophrenics, 8 patients with other psychiatric illness, and 16 healthy control subjects. The study reveals the inefficiency of inhibitory mechanisms at schizophrenics, and the increase of this efficiency through neuroleptic medication only at positive schizophrenics.
KEYWORDS: cognitive inhibition, hypofrontality, schizophrenia, dopamine systems