Multisensory stimulation in hemianopic patients boosts orienting responses to the hemianopic field and reduces attentional resources to the intact field.

Abstract

Lateralised lesions can disrupt inhibitory cross-callosal fibres which maintain interhemispheric equilibrium in attention networks, with a consequent attentional bias towards the ipsilesional field. Some evidence of this imbalance has also been found in hemianopic patients (Tant et al., 2002). The aim of the present study was to reduce this attentional bias in hemianopic patients by using multisensory stimulation capable of activating subcortical structures responsible for orienting attention, such as the superior colliculus. Eight hemianopic patients underwent a course of multisensory stimulation treatment for two weeks and their behavioural and electrophysiological performance was tested at three time intervals: baseline 1 (before treatment), control baseline 2 (two weeks after baseline 1 and immediately before treatment as a control for practice effects) and finally after treatment. The results show improvements on various clinical measures, on orienting responses in the hemianopic field, and a reduction of electrophysiological activity (P3 amplitude) in response to stimuli presented in the intact visual field. These results suggest that the primary visual deficit in hemianopic patients might be accompanied by an ipsilesional attentional bias which might be reduced by multisensory stimulation.