Reaction-times and bioelectrical brain signals of drug-naive schizophrenic first-onset patients in identification and classification tasks
The question of the present study is whether disturbances of response-selection in schizophrenic patients are discernible only if overt motor-actions are required, or also if covert cognitive actions are necessary. Visual identification (digits) and classification (dot-enumeration) tasks were presented to 18 drug-naive, first-onset schizophrenic patients and healthy controls. It is assumed that enumeration of more than three dots requires additional cognitive processes as buffering and re-focusing of attention. Reaction-times and 21-channel-EEG were measured. For eye-movement artefact-elimination a new non-parametric regression approach was applied. Reaction-times revealed that in the patient group response selection is lengthened in both tasks. Perception of dot numbers is not affected. Bioelectrical data depicted a left-lateralization of posterior P100 and N 100 in the patient group as well as an enhanced fronto-central P200. Whereas in reaction-times of patients only a disturbance of response selection is discernible, bioelectrical measurements also point to an altered organization of perceptive processes.