Abstract

The visual evoked response (VEP) is notoriously variable, in part due to adaptation. However, it has not been possible to express adaptation of VEP amplitude in terms of visual thresholds. We have employed a technique which makes it possible to rapidly measure contrast threshold elevations using evoked potential responses. The method can detect threshold elevation caused by as little as 20 sec exposure to faint contrasts of 5% or less. Threshold shifts are demonstrated here in both acuity limits and contrast thresholds. The effect is both orientation and spatial frequency selective. Patients with epilepsy, a disorder which probably reflects disabled cortical inhibition, fail to show this adaptation effect. Drugs which alter the brain dopaminergic system also effect adaptation.

© 1987 Optical Society of America