Hemispheric asymmetry of the harmonic components ot the visual potentials evoked by the onset-offset of spatially periodic stimuli.
The distribution on the scalp of the first (H1) and second (H2) harmonic components of the steady-state visual evoked potential was studied. The stimulus was the onset-offset of a sinusoidal grating with spatial frequency of 4 c/deg, temporal frequency of 7.1 or 16.7 Hz and contrast of 0.2. The visual evoked potentials were recorded monopolarly from symmetric points at distances of 3, 6 and 9 cm laterally from Oz. It was found that while in the averaged data for all investigated subjects there were no differences in the distributions of H1 and H2 to the right and to the left of Oz, the different individuals had a characteristic asymmetry in the amplitude of the response. The statistical processing of the data revealed a significant prevalence of the second harmonic in the left hemisphere upon stimulation at 16.7 Hz for right-handed subjects. The hypothesis about the dominating role of the left cerebral hemisphere in the processing of signals with high temporal frequency was supported for this group of subjects.
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
V
V
Stomonyakov
A
A
Vassilev
D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D006801:Humans; D010775:Photic Stimulation; D013997:Time Factors