THE EFFECT OF MOVEMENT ADAPTATION ON HUMAN CORTICAL POTENTIALS EVOKED BY PATTERN MOVEMENT

Human visually evoked cortical potentials (VEPs) were elicited by the onset of movement of grating patterns (test stimuli). The most prominent VEP waves N2 and P2 increased with accelerating test stimulus velocity (within a range of 0.2-4 deg/s). Two kinds of rums were presented. Reference runs involved only test stimuli and stationary pattern periods between them. In test runs moving gratings were ad- ditionally presented between the test stimuli effecting a stable level of movement adaptation. The additional movement stimulation reduced the VEP amplitudes throughout. The relative amplitude reduction was ne- arly constant for all test stimulus velocities if a fixed velocity of the adaptation stimulus was used. When the adaptation stimulus velocity was raised (within a range of 0.1-4 deg/s), the relative VEP amplitude became smaller. The results support the additive model of velocity coding in human occipital cortex rather than the substitutive model.