title: Intracerebral P3-like waveforms and the length of the stimulus-response interval in a visual oddball paradigm.
abstract: OBJECTIVE
  This study investigated the possible linkage of intracerebrally recorded P3-like waveforms to the processes induced by stimulus perception or motor response formation.
  
  
  METHODS
  Event-related potentials were recorded from 560 cerebral sites in 17 patients suffering from intractable epilepsy during visual oddball task. Potentials evoked by the target stimuli were sorted according to button-pressing response times, and the P3 waveform was analyzed both in stimulus-locked and response-locked averages, which were separately averaged for fast and slow responses.
  
  
  RESULTS
  P3-like waveforms were identified in 180 sites in 17 patients. Three different types of P3-like waveforms, diffusely distributed within the brain, were found: (1) time-locked to the stimulus (30 sites in 11 patients); (2) time-locked to the motor response (52 sites in 13 patients); and (3) with ambiguous time relationship to stimulus and motor response (98 sites in 16 patients).
  
  
  CONCLUSIONS
  The intracerebral P3-like waveform could represent different processes involved in performing active oddball tasks. Therefore, our results support the hypothesis that the P3 waveform registered by surface electrodes could be a heterogeneous phenomenon.
  
  
  CONCLUSIONS
  These results provide evidence that the P3 waveform is not only related to stimulus processing, which differs from what has been generally claimed in the literature.
authors.affiliation: Department of Physiology, Medical Faculty, Masaryk University, Komenského nám. 2 662 43 Brno, Czech Republic. roman@med.muni.cz
authors.forename: Robert
authors.initials: R
authors.lastname: Roman
authors.forename: Milan
authors.initials: M
authors.lastname: Brázdil
authors.forename: Pavel
authors.initials: P
authors.lastname: Jurák
authors.forename: Ivan
authors.initials: I
authors.lastname: Rektor
authors.forename: Miloslav
authors.initials: M
authors.lastname: Kukleta
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors