Research articleCorticospinal excitability during the processing of handwritten and typed words and non-words

- TMS was applied to left primary motor cortex during observation of videos of handwritten and typed words and non-words.
- MEPs from the FDI muscle were measured.
- Facilitation of MEPs was observed for handwritten stimuli for both words and non-words.
- Facilitation was not observed for typed stimuli.
- Motor system plays a strong role in perception of written language.

A number of studies have suggested that perception of actions is accompanied by motor simulation of those actions. To further explore this proposal, we applied Transcranial magnetic stimulation (TMS) to the left primary motor cortex during the observation of handwritten and typed language stimuli, including words and non-word consonant clusters. We recorded motor-evoked potentials (MEPs) from the right first dorsal interosseous (FDI) muscle to measure cortico-spinal excitability during written text perception. We observed a facilitation in MEPs for handwritten stimuli, regardless of whether the stimuli were words or non-words, suggesting potential motor simulation during observation. We did not observe a similar facilitation for the typed stimuli, suggesting that motor simulation was not occurring during observation of typed text. By demonstrating potential simulation of written language text during observation, these findings add to a growing literature suggesting that the motor system plays a strong role in the perception of written language.