The sequential processing of visual motion in the human electroretinogram and visual evoked potential

Abstract

Mechanisms of motion vision in the human have been studied extensively by psychophysical methods but less frequently by electrophysiological techniques. It is the purpose of the present investigation to study electrical potentials of the eye (electroretinogram, ERG) and of the brain (visual evoked potential, VEP) in response to moving regular square-wave stripe patterns spanning a wide range of contrasts, spatial frequencies, and speeds. The results show that ERG amplitudes increase linearly with contrast while VEPs, in agreement with the literature, show an amplitude saturation at low contrast. Furthermore, retinal responses oscillate with the fundamental temporal stimulus frequency of the moving pattern while brain responses do not. In both the retina and the brain, the response amplitudes are tuned to certain speeds which is in agreement with the nonlinear correlation-type motion detector. Along the ascending slopes (which means increasing amplitudes) of the tuning functions, the ERG curves overlap at all spatial frequencies if plotted as a function of temporal stimulation frequency. The ascending slopes of the tuning functions of the VEP overlap if plotted as a function of speed. The descending slopes (which means decreasing amplitudes) of the tuning functions show little (ERG) or no (VEP) overlap and the waveforms at high speeds approach pattern-offset-onset responses. These observations suggest that in the retina motion processing along the ascending slopes of the tuning curves takes place by coding the temporal stimulation frequency which depends on the spatial frequency of the moving pattern. In the brain, however, motion processing is by speed independent of spatial frequency. Simple calculations show that the VEP information is decoded from the ERG signal into a speed signal.

Visual detection of motion speed in humans: spatiotemporal analysis by fMRI and MEG

“…A similar response latency change was observed in a recent study on evoked potentials [Korth et al, 2000]. Recent physiological studies also showed that the response latencies of neurons in MT/V5 and MST of monkeys are inversely related to the speed of visual motion stimuli [Kawano et al, 1994;Lisberger and Movshon, 1999], which corresponds to our results.…”

How Motion Signals Are Integrated Across Frequencies: Study on Motion Perception and Ocular Following Responses Using Multiple-Slit Stimuli

“…Imaging studies have reported that motion-evoked activities localized around hMTϩ (the human homologous area of monkey MT) have a peak at a spatial frequency lower than those expected from contrast threshold sensitivity [MEG response (Amano et al 2007;Anderson et al 1996); EEG response (Korth et al 2000); fMRI response (Singh et al 2000)]. Moreover, the optimal speed for direction discrimination estimated here is around 30 -40°/s and is reasonably consistent with the range of preferred speeds of MT neurons (around 16 -32°/s) (Cheng et al 1994;Lagae et al 1993;Liu and Newsome 2003;Maunsell and Van Essen 1983;Perrone and Thiele 2001;Priebe et al 2003).…”

A primer on motion visual evoked potentials

“…No evidence for motion-specific processing was found. There is no directional adaptation [164] and the ERG amplitude changes linearly with contrast [165]. The shape of the ERG trace is substantially affected by the stimulus speed [164,165].…”

“…There is no directional adaptation [164] and the ERG amplitude changes linearly with contrast [165]. The shape of the ERG trace is substantially affected by the stimulus speed [164,165]. Interestingly, the motion-onset VEP is still recordable at luminance levels below the minimum luminance required for motion ERGs [91].…”