Purpose: Previous investigations have utilized the chromatic pattern-onset visual evoked potential (VEP) to characterize development, maturation, and aging of the chromatic visual pathways. The utility of the chromatic onset VEP as a sensitive and objective measure of neural function has been demonstrated in both congenital and acquired color vision deficiencies from diseases such as diabetes and optic neuritis. Here we report extension of this technique to include multifocal recordings that provide topographic measures of chromatic response. Methods: Multifocal VEP recordings were made using the VERIS system. This system employs a binary m-sequence for stimulus presentation and software designed to extract VEP responses generated from different regions of the visual field. Stimuli were chromatic patterns in which colors were modulated along S cone, L-M cone and achromatic axes in the MBDKL color space. Patterns were presented in an onset-offset temporal mode. Results and Conclusions: Our data indicate that as with achromatic pattern-onset responses the character of the waveforms depends greatly on topographic location. The classic large -positive complex reported for full-field chromatic responses is inverted and reduced in the upper fields as has been reported for achromatic responses. Near the horizontal midline, the responses are partially cancelled and the largest contribution to the classicfull-field negative-positive complex appears to be generated in fact from neurons of the lower visual field. Nevertheless, the robust nature of the waveforms generated throughout much of the visual field suggest that the multifocal onset VEP may be useful for future clinical application and studies of aging.
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