The role of audio-visual and auditory-motor integration in speech perception: Is what we hear dominated by what we see or how we move?

The articulatory motor cortex plays a large role in speech perception. Disrupting this cortex using repetitive Transcranial Magnetic Stimulation (TMS) has shown significant decrease in performance on demanding speech perception tasks (Möttönen, Rogers, & Watkins, 2014). When hearing speech in difficult listening conditions, our auditory system recruits the articulatory motor cortex to assist with speech perception. Further TMS studies have been used to demonstrate this effect, finding that the excitability of the lip motor region increases distorted speech conditions compared to clear speech conditions (Nuttall et al., 2016). This suggests that in difficult speech conditions, the articulatory motor system interacted with the auditory speech systems more than in clear speech.