Verbal versus non-verbal visual evoked potentials: Kanji versus line drawings.
Cortical areas related to perception of verbal and non-verbal stimuli were studied using VEPs. Kanji characters, line drawings (LD), or a blank were displayed. Verbal VEPs were obtained by subtracting the blank-VEPs from the Kanji-VEPs, and non-verbal VEPs by subtracting the blank-VEPs from the LD-VEPs. Both the verbal and non-verbal VEPs showed a negative peak (100-300 msec) focally over bilateral occipital, posterior temporal and parietal areas, and a positive peak diffusely over frontal halves. Differences between the non-verbal from the verbal VEPs showed an initial peak (100-200 msec) focally over bilateral occipital and posterior temporal areas, followed by a peak (200-300 msec) focally over bilateral posterior temporal areas. The frontal areas diffusely showed peaks at 100-200, 200-300 and 300-400 msec. Left-right asymmetries of both the verbal and non-verbal VEPs showed peaks between 100 and 300 msec over posterior temporal, parietal, and occipital areas. Left-right asymmetries of the subtraction to the non-verbal from the verbal VEPs showed a peak (100 msec) over occipital and parietal areas, and a broader peak over posterior temporal area (100-200 msec). Bilateral occipital, posterior temporal, and parietal areas are focally activated by the two perceptions (100-300 msec), while frontal areas are activated diffusely. Further, different processes may be focally involved between the hemispheres over occipital (100-200 msec) and posterior temporal (100-200 and 200-300 msec) regions. Initial left-right asymmetries of the subtracted VEP between the two perception would occur over occipital and parietal areas (100 msec) and last for 200 msec over posterior temporal area.
Shimoyama
I
I
Department of Neurosurgery, Hamamatsu University School of Medicine, Shizuoka, Japan.
Morita
Y
Y
Uemura
K
K
Kojima
Y
Y
Nakamura
T
T
Nishizawa
S
S
Yokoyama
T
T
Ryu
H
H
Murayama
M
M
Uchizono
K
K
D000161:Acoustic Stimulation; D000328:Adult; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010775:Photic Stimulation; D013060:Speech; D013997:Time Factors