[Visual system in the light of the study of evoked potentials after stimulation by pattern stimuli in healthy...

In 65 healthy subjects aged 18-70 the characteristics of VEPs elicited with two kind of "pattern reversal" stimulus, checkerboard and gratings, in 13 various configurations were tested. In the recordings the latency and amplitude of peaks P1, N1, P100 and N2, and the difference between maximum and minimum amplitude and correlation coefficient for the cerebral hemispheres were analysed. It was found that checkerboard and gratings elicited in the both hemispheres the responses of comparable latencies and their amplitudes were consequently greater over the left hemisphere. Analyses of the correlation between VEPs and gender showed no influence on latencies and the occurrence of greater amplitudes in females and lower correlation coefficients in males. Differences were noted between potentials evoked by monocular and binocular stimulation, and for the responses elicited with the patterns of checkerboard and gratings, which reflects the activation of two separate channels of the visual system. It was also shown that the characteristics of VEPs obtained using for stimulation the fractionated visual field (checkerboard in the individual hemi-fields and quadrants) was consistent with the topography of visual pathways and retinotopic organisation of the striate cortex, which would suggest a location of the main generator of VEPs in Brodmann's area 17.