VISUAL EXTINCTION AND PRIOR ENTRY - IMPAIRED PERCEPTION OF TEMPORAL-ORDER WITH INTACT MOTION PERCEPTION AFTER UNILATERAL PARIETAL DAMAGE

Two patients with left-sided visual extinction after right parietal da mage were each given two 'prior entry' tasks that have recently been u sed to study attentional biases in normals. The first task presented t wo unconnected bars, one in each visual held, with the patients asked to judge which appeared sooner. Both patients reported that the right bar preceded the left unless the latter led by over 200 msec, suggesti ng a severe bias to the right affecting the time-course of visual awar eness. The second task presented one continuous line in a scrolling fo rmat across the same spatial extent, with the patients asked to judge which direction the line moved in. The patients now performed normally . Thus, the perception of temporal order for separate events was impai red by the lesions, but without disrupting motion perception within si ngle events. The implications are discussed for theories of normal and pathological attention, visual awareness, and motion perception. (C) 1997 Elsevier Science Ltd.