Binocular interaction reflected in visually evoked cortical potentials as studied with pseudorandom stimuli.

PURPOSE

To study the interaction of visual signals from both eyes with visual evoked cortical potentials (VECPs) elicited by pseudorandom binary sequence (PRBS) stimuli.

METHODS

A PRBS was used to drive two independent LED arrays to elicit VECPs. The right and left eyes were simultaneously stimulated by two different series of PRBS stimuli. The impulse response function of each eye was calculated from the raw data by cross-correlating the PRBS and the response. The effect of changing the luminosity of the LEDs parametrically on the responses obtained from the two eyes was evaluated.

RESULTS

The impulse response, obtained from 10 volunteers with normal vision, had characteristics similar to responses to the conventional VECP, with a major positive peak at 110 ms (P110). When two eyes were bilaterally exposed to two PRBS stimuli of the same luminosity, the P110 amplitudes of both eyes were decreased by the same amount from that obtained by stimulating only one eye. When the luminosity in the two eyes was different, the VECP amplitude in the eye with the dimmer stimuli decreased, and the amplitude in the contralateral eye increased.

CONCLUSIONS

The results clearly demonstrate that interocular luminance interaction can be detected electrophysiologically in normal subjects by using PRBS- driven stimuli in which the feasibility of recording response from the two eyes independently.