The effects of a multisensory training for hemianopia on spatial attention

Abstract

The aim of the study is to assess the neural mechanisms underlying the recovery of visual function after multisensory stimulation (MS) in hemianopic patients. As a result of a hyperactivation of the intact hemisphere, with concurrent hypoactivation of the damaged hemisphere, hemianopic patients focus their attention on the ipsilesional field and the contralesional field lacks sufficient attentional resources. The unbalanced excitability of the two hemispheres can be restored by a multisensory stimulation, mediated by the collicular-extrastriate pathway, which largely contributes to spatial orienting behaviors. We administered a course of MS treatment (Bolognini et al., 2005) to a sample of seven hemianopic participants for 4 hours daily, over a period of nearly 2 weeks and we collected both behavioural and electrophysiological data, before and after the intervention, in order to index the stimulation effects. The results showed an improvement of visual oculomotor exploration that allowed patients to efficiently compensate for the loss of vision. In addition, amplitudes of P3 event related potentials elicited by a simple visual detection paradigm were significantly reduced after the treatment when the stimuli were presented to the intact field. The behavioural improvement in the hemianopic field, and ERP amplitude reduction in the intact field, can be explained as driven by a shift in spatial attention away from the hyperactivated intact visual field, induced by the intensive multisensory training.