LESION LOCATION INFLUENCES PERCEPTION OF HOMONYMOUS SCOTOMAS DURING FLICKERING RANDOM-DOT PATTERN STIMULATION

An attempt was made to clarify whether the site of postchiasmal lesion s affects subjective perception of homonymous visual field defects dur ing stimulation with flickering random dot patterns (white noise-field ). Out of 56 patients with homonymous hemianopia, 38 (68%) perceived s cotomata in this situation, but 18 (32%) discerned none at all. Neuror adiologic superposition of cerebral lesions detected by computed tomog raphy (CT) or magnetic resonance imaging (MRI) showed that nearly all patients who perceived their scotomata had lesions involving the prima ry visual cortex or the perigeniculate region, whereas those who recei ved no scotoma had lesions centered within the optic radiation. Functi onal MRT of six normal subjects during stimulation with flickering ran dom dot patterns indicated predominant activation of the primary visua l cortex. Since noise-field defects were most frequently perceived by patients whose lesion involved the primary visual cortex, it appears t hat the sensitivity of noise-field campimetry depends on the site of d amage in the visual pathway. The explanation for this may be that dama ge to long-range horizontal connections impairs filling-in processes. (C) 1998 Elsevier Science Ltd. All rights reserved.