Repetitive anodal tDCS of perilesional cortex impairs recovery of function after parietal damage

Abstract

Unilateral spatial neglect is a common disorder, most often occurring after right hemispheric stroke and resulting in severe functional impairment and a poor prognosis of recovery. Previous research has shown that there are several methods of rehabilitation, one of the newer techniques being non-invasive brain stimulation. Specifically, transcranial direct current stimulation has been show to change neuronal activity in a polarity dependent manner. In this study we investigated whether passive anodal repetitive transcranial direct current stimulation of the perilesional parietal cortex ameliorated the symptoms of unilateral spatial neglect. Three cats were given focal right posterior parietal cortex lesions to produce neglect. After the plateau of spontaneous recovery of function, subjects received passive anodal transcranial direct current stimulation (2 mA for 20 min a day for 50 days). No overall collective effects of tDCS on visual performance were seen in the contralesional nor ipsilesional visual hemi-field. Yet when visual field quadrants were analyzed, tDCS exerted a deteriorative effect on performance in the right peripheral visual quadrant. These data show that passive anodal transcranial direct current stimulation in the perilesional cortex may come with a cost of function in performance to stimuli in the intact visual field. Future research is necessary to further investigate these effects.