Verbal versus non-verbal visual evoked potentials: Kanji versus line drawings

Summary

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. Difference 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.