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Magnetic stimulation of the left visual cortex impairs expert word recognition

Skarratt, Paul A.; Lavidor, Michal

Authors

Paul A. Skarratt P.Skarratt@hull.ac.uk

Michal Lavidor

Abstract

One of the hallmarks of expert reading is the ability to identify arrays of several letters quickly and in parallel. Such length-independent reading has only been found for word stimuli appearing in the right visual hemifield (RVF). With left hemifield presentation (LVF), response times increase as a function of word length. Here we investigated the comparative efficiency with which the two hemispheres are able to recognize visually presented words, as measured by word length effects. Repetitive transcranial magnetic stimulation (rTMS) of the left occipital cortex disrupted expert processing of the RVF such that a length effect was created (Experiment 1). Right occipital rTMS, on the other hand, had no such effect on RVF words and nor did it modulate the length effect already present in the LVF. Experiment 2 explored the time course of these TMS-induced effects by applying single pulses of TMS at various stimulus-onset asynchronies for the same task. We replicated the TMS-induced length effect for RVF words, but only when a single pulse was applied to the left visual cortex 80 msec after target presentation. This is the first demonstration of TMS-induced impairment producing a word length effect, and as such confirms the specialization of the left hemisphere in word recognition. It is likely that anatomical differences in the pathway linking retinal input to higher level cortical processing drive this effect.

Journal Article Type Article
Publication Date Oct 1, 2006
Journal JOURNAL OF PSYCHOPHYSIOLOGY
Print ISSN 0898-929X
Electronic ISSN 1530-8898
Publisher Massachusetts Institute of Technology Press (MIT Press)
Peer Reviewed Peer Reviewed
Volume 18
Issue 10
Pages 1749-1758
Institution Citation Skarratt, P. A., & Lavidor, M. (2006). Magnetic stimulation of the left visual cortex impairs expert word recognition. Journal of cognitive neuroscience, 18(10), 1749-1758. doi:10.1162/jocn.2006.18.10.1749
DOI https://doi.org/10.1162/jocn.2006.18.10.1749
Keywords Cognitive Neuroscience
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