Unilateral occipital lesion causing hemianopia affects the acoustic saccadic programming

Abstract

Infrared oculographic recordings of saccades evoked by auditory or visual targets in four patients with hemianopia due to an occipital lesion showed that these patients employed a different strategy to find visual and auditory targets in each hemifield. In the seeing hemifield, the patients acquired auditory targets with both monosaccadic and multiple saccadic refixations. The first saccade, the largest, brought the eyes toward the target; the following smaller saccades completed the search as in normal subjects. Saccades to visual targets consisted of one orthometric saccade or two saccades. By contrast, in the blind hemifield the patients acquired auditory targets by a staircase strategy consisting of stepwise saccadic search movements similar to those used for visual targets in the same hemifield. The similarity of strategy to auditory and visual targets suggests a common motor program controlled by the visual input. The latency, accuracy, and velocities of visual and acoustic responses were equal in both hemifields.