Transcranial magnetic stimulation of the occipital cortex interferes with foot movements in blind individuals

Abstract

Research has shown that the occipital cortex can be reorganized and repurposed for nonvisual perception and cognitive functions following visual loss in blind individuals. However, no studies have directly examined the involvement of the visual cortex in motor function. Here, we show that a rhythmic foot movement performed by acquired blind individuals can be disrupted by transcranial magnetic stimulation (TMS) to their primary and secondary visual cortex (V1/V2). This disruptive effect was absent for congenitally blind or sighted individuals. As a control, TMS to the neck muscles of acquired blind individuals confirms that this disruptive effect was not caused solely by the sensory (tactile/auditory) sensations accompanying the stimulation. Our results provide the direct evidence that functional repurposing of the human visual cortex is not restricted to perception and cognitive functions but also extends to motor function. Moreover, our findings suggest the nessecity of the visual experience before visual loss for the functional reorganization of the visual cortex for motor function. Significance statementThe brain can adapt remarkably after sensory loss. One striking example is that after visual loss, the visual cortex--deprived of visual input--is often reused for nonvisual perception and higher cognition. Here, we show that it can also support motor control. Using transcranial magnetic stimulation, we transiently disrupted processing in the visual cortex while participants performed rhythmic foot movements. This disruption impaired performance in people who became blind after birth, but not in sighted individuals or those blind from birth. These findings demonstrate that the visual cortex can take on a motor function after vision is lost, but only with prior visual experience.