Proceedings of the Annual Meeting of the Cognitive Science Society

Many different functional roles have been ascribed to themotor system due to its prevalent recruitment in perceptualand cognitive tasks other than motor production. We discussfindings that suggest the motor system might take on multipleroles that vary with context and the brain networks involved.Using single-pulse TMS, we measured the corticospinalexcitability of the FDI muscle in primary motor cortex asparticipants viewed words that were either typed orhandwritten. We observed consistent facilitation ofcorticospinal excitability during reading of handwritten text.Although we observed facilitation in corticospinal excitabilityduring the presentation of typed text, this effect decreasedwith repetitive presentations of stimuli. We suggest that thefacilitation during presentation of typed words is a case ofaction simulation, and that the diminishing facilitation in thecase of typed stimuli is representative of sensory predictionby the motor system. These findings suggest that we shouldconsider multiple roles for motor recruitment during theobservation of visual stimuli, taking context intoconsideration.