Intracerebral P3-like waveforms and the length of the stimulus-response interval in a visual oddball paradigm.
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.
Roman
Robert
R
Department of Physiology, Medical Faculty, Masaryk University, Komenského nám. 2 662 43 Brno, Czech Republic. roman@med.muni.cz
Brázdil
Milan
M
Jurák
Pavel
P
Rektor
Ivan
I
Kukleta
Miloslav
M
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