Estimation of the impulse response of the visual system using stochastic modulation of stimulus spatial frequency

Visual evoked responses known as VESPAs, which are typically evoked from the electroencephalogram (EEG) using continuous, stochastic modulation of the luminance or contrast of a stimulus, have been shown to have a number of advantages over traditional visual evoked potential (VEP) methods. In this study, we investigate the possibility that such VESPAs can be evoked using modulation of other characteristics of a visual stimulus. Specifically, we obtain clean, consistent responses with high signal-to-noise ratio in response to stimuli whose spatial frequencies are stochastically and continuously modulated. These responses should have applicability to basic research on the human visual system and, possibly, in studies of clinical populations.