Investigating Occipito-temporal Contributions to Reading with TMS

Abstract

Abstract■ 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. ■

How Does Learning to Read Affect Speech Perception?

“…An additional seven participants were excluded after analyzing their data from the visual lexical decision TMS experiment. 11 of 18 participants who received vOTC stimulation showed the expected slowdown on words, with an average increase of 40 ms for TMS relative to no-TMS trials (t (10) ϭ 4.0, p ϭ 0.003), similar to that seen previously (Duncan et al, 2010). The remaining seven either showed no effect of TMS or had faster RTs with stimulation, probably due to a nonspecific intersensory facilitation.…”

“…Two versions of stimuli were created to guarantee that each stimulus was equally presented in TMS and no-TMS trials across participants. Previously, we have shown that rTMS to vOTC increased reaction times (RTs) in this task whereas stimulation of LOC had no significant effect on RTs (Duncan et al, 2010). Consequently, subjects who did not show a disruptive effect of ventral occipitotemporal rTMS on words were excluded from the analysis of the main experiment on the assumption that we had targeted the site incorrectly in these participants.…”

Colateralization of Broca’s area and the visual word form area in left-handers: fMRI evidence

“…Others believe that the vOT is not dedicated to visual word form processing because it also responds to picture naming, repeating auditory words etc. (e.g., Devlin, Jamison, Gonnerman & Matthews, 2006;Duncan, Pattamadilok & Devlin, 2010;Price & Devlin, 2003Twomey, Duncan, Price & Devlin, 2011). The latter view considers the 1 Note that the direction of laterality within an activated region can be influenced by both excitatory and inhibitory connections from the LH/RH homologue areas.…”

Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course

“…Other studies have measured the effects of stimulation on eye movements 63,64 . Most cognitive neuroscience experiments with TMS, however, use reaction times as their dependent measure 13,48,65,66 . Typically, the effects are on the order of tens of msec, or roughly a 10% change in reaction times 67 .…”

“…The duration of this disruption limits the temporal resolution of the technique to 10s of msec, roughly an order of magnitude coarser than electroencephalography (EEG) and magnetoencephalography (MEG). On the other hand, the timings observed in chronometric TMS studies tend to match those from invasive neurophysiological recordings better than EEG and MEG 9,13 . Presumably this is because EEG and MEG measure large scale neuronal synchrony that lags behind the earliest onset of activity , it was quickly adopted as a valuable tool for cognitive neuroscience.…”