title: Cathodal HD-tDCS on the right V5 improves motion perception in humans.
abstract: Brain lesions in the visual associative cortex are known to impair visual perception, i.e., the capacity to correctly perceive different aspects of the visual world, such as motion, color, or shapes. Visual perception can be influenced by non-invasive brain stimulation such as transcranial direct current stimulation (tDCS). In a recently developed technique called high definition (HD) tDCS, small HD-electrodes are used instead of the sponge electrodes in the conventional approach. This is believed to achieve high focality and precision over the target area. In this paper we tested the effects of cathodal and anodal HD-tDCS over the right V5 on motion and shape perception in a single blind, within-subject, sham controlled, cross-over trial. The purpose of the study was to prove the high focality of the stimulation only over the target area. Twenty one healthy volunteers received 20 min of 2 mA cathodal, anodal and sham stimulation over the right V5 and their performance on a visual test was recorded. The results showed significant improvement in motion perception in the left hemifield after cathodal HD-tDCS, but not in shape perception. Sham and anodal HD-tDCS did not affect performance. The specific effect of influencing performance of visual tasks by modulating the excitability of the neurons in the visual cortex might be explained by the complexity of perceptual information needed for the tasks. This provokes a "noisy" activation state of the encoding neuronal patterns. We speculate that in this case cathodal HD-tDCS may focus the correct perception by decreasing global excitation and thus diminishing the "noise" below threshold.
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland.
authors.forename: Giuseppe A
authors.initials: GA
authors.lastname: Zito
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland.
authors.forename: Theresa
authors.initials: T
authors.lastname: Senti
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland.
authors.forename: Dario
authors.initials: D
authors.lastname: Cazzoli
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland ; Division of Cognitive and Restorative Neurology, Department of Neurology, University Hospital Inselspital, University of Bern Bern, Switzerland.
authors.forename: René M
authors.initials: RM
authors.lastname: Müri
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland ; University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern Bern, Switzerland.
authors.forename: Urs P
authors.initials: UP
authors.lastname: Mosimann
authors.affiliation: Center of Neurology and Neurorehabilitation, Luzerner Kantonsspital Luzern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nyffeler
authors.affiliation: Gerontechnology and Rehabilitation Group, University of Bern Bern, Switzerland ; ARTORG Center for Biomedical Engineering Research, University of Bern Bern, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Nef
keywords: HD-tDCS; motion perception; shape perception; unilateral brain stimulation; visual test