title: Reaction-times and bioelectrical brain signals of drug-naive schizophrenic first-onset patients in identification and classification tasks.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Centre for Psychiatry, Justus-Liebig-University Giessen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Krieger
authors.forename: S
authors.initials: S
authors.lastname: Lis
authors.forename: B
authors.initials: B
authors.lastname: Gallhofer
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology; D004569:Electroencephalography; D004585:Electrooculography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011930:Reaction Time; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology