Effects of check size on pattern reversal visual evoked magnetic field andpotential

The effects of different check sizes on the 100m component of pattern rever sal visual evoked magnetic fields (VEF) and the P100 component of visual ev oked potentials (VEP) in terms of latency, amplitude and source localizatio n were analyzed. Half field stimuli with or without central occlusion with cheek sizes of 15', 30', 60', 90' and 180' of visual are were given to 7 he althy subjects. VEF and VEP were recorded simultaneously. The effect of the check size on the peak latency of both 100m and P100 was significant (P<0. 01, ANOVA). The latencies for the smaller checks were significantly longer than those for the larger checks. The effect of the check size on the ampli tude of the 100m to the stimulation with central occlusion was significant (P<0.05, ANOVA), but was not to the stimulation without central occlusion. That is, the amplitudes for the smaller checks were significantly smaller t han those for the larger checks when using the stimulation with central occ lusion, but not the stimulation without central occlusion. The effect of th e check size on the P100 amplitude was not significant to the stimulation w ith and without central occlusion. The equivalent current dipoles were loca ted around the calcarine fissure and did not differ significantly in locati on with check size. In conclusion: check size significantly affects the lat ency and amplitude of the 100m and/or P100, but not the receptive areas for the stimulation. (C) 2000 Elsevier Science B.V. All rights reserved.