Investigating Occipito-temporal Contributions to Reading with TMS

The debate regarding the role of ventral occipito-temporal cortex (vOTC) in visual word recognition arises, in part, from difficulty delineating the functional contributions of vOTC as separate from other areas of the reading network. Here, we investigated the feasibility of using TMS to interfere with vOTC processing in order to explore its specific contributions to visual word recognition. Three visual lexical decision experiments were conducted using neuronavigated TMS. The first demonstrated that repetitive stimulation of vOTC successfully slowed word, but not nonword, responses. The second confirmed and extended these findings by demonstrating the effect was specific to vOTC and not present in the adjacent lateral occipital complex. The final experiment used paired-pulse TMS to investigate the time course of vOTC processing for words and revealed activation starting as early as 80–120 msec poststimulus onset—significantly earlier than that expected based on electrophysiological and magnetoencephalography studies. Taken together, these results clearly indicate that TMS can be successfully used to stimulate parts of vOTC previously believed to be inaccessible and provide a new tool for systematically investigating the information processing characteristics of vOTC. In addition, the findings provide strong evidence that lexical status and frequency significantly affect vOTC processing, findings difficult to reconcile with prelexical accounts of vOTC function.