title: Event-related and motor responses to probes in a forewarned reaction time task in schizophrenic patients.
abstract: Surface-negative brain potentials indicate increased excitability of the underlying cortical neural networks. Consequently, deviant patterns of event-related potentials in schizophrenic patients reveal an atypical regulation of cortical excitability. Twelve patients with a chronic schizophrenic disorder and 12 matched control subjects were investigated using a probe paradigm: A contingent negative variation (CNV) was evoked in a forewarned reaction time paradigm. Clicks were presented before, during and after elicitation of the CNV. Click-evoked responses allow one to 'probe' the current brain state, particularly neuronal excitability, which is also reflected by the slow potentials. During the measurements, subjects pressed one button in response to the offset of the visual warning stimulus and a different button in response to the acoustic probes, the latter button press being a behavioral indication of the brain's excitability. In the forewarned reaction time task, patients developed a CNV with a frontal maximum, while the CNV in control subjects was predominantly centro-parietal. This atypical topographical pattern of the CNV may indicate a different spatio-temporal regulation of cortical preparatory processes in schizophrenics. Motor responses were accelerated during negative potential shifts in both patients and controls, with responses being slower overall in patients. In patients, probe-evoked potentials revealed a smaller N100, but a larger P300, than in controls. The covariation of these brain waves with slow potentials, however, turned out to be similar for both groups.
authors.affiliation: Department of Psychology, University of Konstanz, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Rockstroh
authors.forename: M
authors.initials: M
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Wagner
authors.forename: R
authors.initials: R
authors.lastname: Cohen
authors.forename: T
authors.initials: T
authors.lastname: Elbert
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology; D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012559:Schizophrenia / Q000175:diagnosis / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012815:Signal Processing, Computer-Assisted