Cerebellar tDCS alters the perception of optic flow

Studies have shown that the cerebellar vermis is involved in the perception of motion. However, it is unclear how the cerebellum influences motion perception. tDCS is a non-invasive brain stimulation technique that can reduce (through cathodal stimulation) or increase neuronal excitability (through anodal stimulation). To explore the nature of the cerebellar involvement on large-field global motion perception (i.e., optic flow-like motion), we applied tDCS on the cerebellar midline while participants performed an optic flow motion discrimination task. Our results show that anodal tDCS improves discrimination threshold for optic flow perception, but only for left-right motion in contrast to up-down motion discrimination. This result was evident within the first 10 minutes of stimulation and was also found post-stimulation. Cathodal stimulation did not have any significant effects on performance in any direction. The results show that discrimination of planar optic flow can be improved with tDCS of the cerebellar midline and provide further support for the role of the human midline cerebellum in the perception of optic flow.