Novel protocol for random visual stimulation during visual evoked potential testing

The standard method of studying the visual evoked potentials (VEPs) of multiple visual stimuli is to separately record the VEP for each stimulus then compare the resultant signals. The resultant signals are subject to inter-presentation noise factors. These can include subject attention, electrode noise and subject movement. We have developed a technique, which allows all of the visual stimuli to be presented randomly in a single recording. The individual VEPs for each visual pattern are then extracted from the recorded signal. The method employs a custom written visual presentation program, which controls the video output and parallel port synchronization. By presenting all of the data during one experiment, the electrode noise, the subject´s movement and attentiveness are more uniform for all recorded signals. In this study, we examined the VEPs to a square-wave grating pattern embedded in different degrees of spatial noise. For each subject, we recorded the VEP response to the different stimulus patterns using a random presentation of the stimuli. This method of stimulation produced viable trends within 30 trials which is 50% to 200% fewer trials than standard methods currently require.