Binocular interaction in the VEP to grating stimulation. II. Spatial frequency effects.

The size specificity of the binocular interaction in the VEP was investigated. VEPs elicited by sine wave gratings were recorded on 3 subjects, with the exception of one experiment where 6 subjects were tested. The recording technique made it possible to obtain responses from each eye, even during binocular stimulation. The VEP amplitude for each eye during monocular stimulation was compared with the response of the same eye during binocular stimulation. A low binocular/monocular ratio indicated a high binocular interaction. When each eye was stimulated by the same spatial frequency, the binocular interaction was highest in the spatial frequency band of 2-4 c/d. When each eye was stimulated by a different spatial frequency, the binocular interaction decreased as the frequencies were made progressively more unequal. The bandwidth at half amplitude was about 1 octave around the center frequency.