Inhibitory TMS over Visual Area V5/MT Disrupts Visual Speech Recognition

During face-to-face communication, the perception and recognition of facial movements can facilitate individuals' understanding of what is said. Facial movements are a form of complex biological motion. Separate neural pathways are thought to processing (1) simple, nonbiological motion with an obligatory waypoint in the motion-sensitive visual middle temporal area (V5/MT); and (2) complex biological motion. Here, we present findings that challenge this dichotomy. Neuronavigated offline transcranial magnetic stimulation (TMS) over V5/MT on 24 participants (17 females and 7 males) led to increased response times in the recognition of simple, nonbiological motion as well as visual speech recognition compared with TMS over the vertex, an active control region. TMS of area V5/MT also reduced practice effects on response times, that are typically observed in both visual speech and motion recognition tasks over time. Our findings provide the first indication that area V5/MT causally influences the recognition of visual speech.