PRIMING REVEALS ATTENTIONAL MODULATION OF HUMAN MOTION SENSITIVITY

Although recent fMRI and single unit recording studies have shown that attention modulates neural activity in motion sensitive areas of extr astriate cortex, these approaches cannot reveal qualitative or quantit ative effects of attention on perception of motion. To investigate thi s, we asked observers to select one of two orthogonal directions in a brief, transparent dot display (prime) and then measured their sensiti vity to global directional motion in a second uni-directional dot disp lay (probe) presented a short time later. When probe direction matched the attended prime direction, sensitivity was degraded. But, when pro be direction matched the ignored prime direction, sensitivity was enha nced, even though both components were of equal physical strength. Sen sitivity was unchanged for directions opposite to either previously se en direction. Neither sensory adaptation nor opponent direction mechan isms can account for these data. Rather, processes initiated by Visual selection must underlie these dramatic changes in motion sensitivity. (C) 1998 Elsevier Science Ltd. All rights reserved.