Abstract
To study frontal brain activity we measured event-related potentials (ERPs) to auditory target and novel stimuli in nine schizophrenic patients, five affective controls, and 13 normals. We predicted that schizophrenics, because of impaired frontal lobe function, would not show as much frontal augmentation of the P3 component to infrequent taskirrelevant novel stimuli as would normal subjects. Subjects were instructed to respond (finger lift) to infrequently occurring (10%) target tones (TS) while ignoring frequently occurring (80%) nontarget tones and infrequently occurring (10%) random electronic noise (NS). Ten channel EEG was collected until 30 correct and artifact-free trials to TS and NS were acquired. After transformation to average reference, the peak global field power between 276 and 450 milliseconds after stimulus onset was used to identify P300 latency. Potentials at this latency were compared across groups by repeated measures ANOVA. In agreement with previous studies, maximum positivity to NS shifted anteriorly relative to TS (p < .04). The topography of the P300 to NS varied with diagnosis (p < .007). The largest differences occurred at Cz, where the response to NS was larger than to TS across groups (p = .0003), but with smaller differences in schizophrenics (group x condition, p < .02). In fact, schizophrenics produced the shallowest potential maps (p < .04) and higher positivity in frontal relative to central leads (p < .05). Medicated schizophrenics (N = 5) differed from unmedicated schizophrenics (N = 4) only in prolonged latency (p = .002); there were no other latency differences between groups. These preliminary findings suggest a link between abnormalities of arousal and selective attention with frontal cortex functioning in schizophrenic patients.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call