Inherent characteristics of visual stimulus systems and their effect on the visual evoked potential.

The inherent stimulus characteristics of three common types of visual stimulus systems, based upon a slide projector, a television and a photic stimulator, were measured. The effect of these characteristics upon pattern visual evoked potentials (VEPS) elicited by the systems was also investigated. Considerable differences in both spatial and temporal luminance characteristics were found between the systems. The differences in spatial luminance properties produced no significant changes in the VEP waveform, but the temporal luminance properties of the television system, in particular, produced maleficent effects on the VEP. Methods of dealing with these problems and of overcoming some of the traditional disadvantages of a strobe stimulus are discussed.