[Sequential spatial maps of visual potentials evoked by checkerboard-pattern reversal: effect of the retinal field...

Sequential color maps of visual potentials evoked by the reversal of various checkerboard patterns were recorded in 10 young adults using a 16 channel montage. It was found that each of the components of the N75-P100-N145 occipital complex had a specific spatial distribution on the scalp and was selectively influenced by the size, the spatial frequency, the luminance and possibly the wave length of the stimulus. Component N75 was found to be elicited by the more peripheral area of the TV stimulus (12 degrees X 16 degrees). Component P100 was associated with a frontal negativity of similar latency favoring the hypothesis of a dipolar occipital generator. With half-field stimulations the dipole orientation was modified, leading to a 'paradoxical' lateralization of P100 in most cases. However the reverse situation (P100 contralateral to the stimulated half-field) was observed in 4 and 3 subjects out of 10 with left and right half-field stimulations respectively. Thus VEP to full-field TV pattern reversal cannot be recommended to investigate hemianopic patients. Component N145 was of maximal amplitude when elicited by the reversal of small foveal patterns (2.18 degrees), especially red light emitting diodes.