Isolating motion responses in visual evoked potentials by preadapting flicker-sensitive mechanisms.
Onset of visual motion evokes a component in the EEG, the motion onset VEP. Exploring its motion specificity with a direction-specific adaptation paradigm, previous work demonstrated that less than 50% of the motion onset VEP represents actual motion detection. Here, we tested whether preadaptation of flicker-sensitive mechanisms can help to isolate motion-specific responses in the VEP. Flicker preadaptation was accomplished by limiting dot lifetime in the random-dot kinematograms that we used to study the direction specificity of motion adaptation. With unlimited dot lifetime, motion adaptation reduced the VEP amplitude to 35% (adapted direction) and 50% (opposite direction). With the shortest dot lifetime (40 ms), motion adaptation reduced the amplitude to 55% (adapted direction) and 70% (opposite direction). These findings suggest that random-dot kinematograms with short dot lifetimes could improve the investigation of human motion processing, be it in electrophysiology or other fields. While such stimuli successfully preadapt flicker-related components, they still evoke a sizable response, of which an estimated 70% is motion-specific.
Maurer
J Peter
JP
Elektrophysiologisches Labor, Universitäts-Augenklinik, Killianstr. 5, 79106, Freiburg, Germany.
Bach
Michael
M
D004585:Electrooculography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation