Comparison of the pattern reversal visual evoked potential mediated by separate cone systems.
With the purpose of recording responses mediated by the 3 cone systems visual evoked potentials (VEPs) were elicited by the reversal of monochromatic checkerboards superimposed upon strong monochromatic backgrounds (yellow, purple and blue-green). The sensitivity to light of various wave lengths were measured as the reciprocal of the intensity necessary to elicit a VEP amplitude of 3 microV. The spectral sensitivity curves based on this VEP amplitude criterion in the presence of blue-green, purple and yellow adaptation showed peak sensitivities in the red, the green and the blue part of the spectrum, respectively. This indicates that the responses reflect separate modulation of the 3 different cone mechanisms. The potentials obtained with yellow adaptation differed from those obtained with purple and blue-green adaptation. The amplitude versus log intensity function was flatter and the latency of the major positive peak was increased by 20-25 msec. Repeated examinations of 4 subjects suggest that the method yields reliable latency measurements of responses mediated by separate cone mechanisms.
Johnsen
B
B
Department of Clinical Neurophysiology, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.
Frederiksen
J L
JL
Larsson
H B
HB
D000328:Adult; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology