tDCS Effects on Motion Perception
When we move, our self-induced motion provides a constant “flow” of visual information (e.g. objects, people, etc.) across the retina; these regular changes in the overall image on the retina are known as optic flow. Optic flow allows one to calculate distance to objects and judge time to collision - aiding in locomotion and balance. Results from both lesion and cerebellar trans-magnetic stimulation (TMS) studies indicate the cerebellum plays an important role in ability to perceive optic flow. The aim of this study was to investigate the role of cerebellar activity on the perception of optic flow. If the cerebellum generates inhibitory output towards other optic flow-processing areas, then increased activation of cerebellum should improve optic flow perception. Research indicates transcranial direct-current stimulation can modulate excitability in cortical cells; thereby a useful tool for modulating cerebellar activity. Task performance was measured under three stimulation conditions: anodal, cathodal, sham. A threshold for optic flow was measured through a motion discrimination task using random-dot-stimuli to simulate optic flow. Results showed that anodal stimulation resulted in significant increases in performance during and post stimulation for right/left motion. No effect of anodal stimulation was found for up/down motion. In addition, no effect of cathodal stimulation for either up/down, or right/left motion. These results demonstrate that cerebellar activity can be modulated with tDCS to enhance motion perception, but the direction of motion appears to be a critical factor. The results will be discussed in relation to cerebellar organization and connections with cortical motion areas.
Faculty Mentor: Dr. Jean-Francois Nankoo