Remodelling the attentional system after left hemispheric stroke: Effect of leftward prismatic adaptation

Left hemispheric stroke is known to be associated with right neglect and/or not lateralized attentional deficits. The former appears to respond favourably to leftward prismatic adaptation (L-PA), as reported in a case of a large left stroke. In normal subjects, brief exposure to L-PA was shown to enhance the representation of the right visual field within the right inferior parietal lobule, emphasizing thus right hemispheric dominance within the ventral attentional system. We have investigated whether L-PA does the same in left hemispheric stroke by comparing neural responses to left, central and right stimuli before and after a brief exposure to L-PA. Neural responses to visual stimuli were significantly modulated within a large part of the occipito-temporal cortex and in smaller clusters in the angular gyrus, the anterior temporal lobe and the insula, corresponding to decrease in activity. Within the occipito-temporal region the decrease concerned predominantly neural activity elicited by left stimuli, downregulating thus the representation of the contralateral visual field, which is characteristic of the higher-order visual areas in this region.