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The Journal of Neuroscience, October 24, 2007, 27(43):11465-11472; doi:10.1523/JNEUROSCI.2827-07.2007

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Behavioral/Systems/Cognitive
Occipital Transcranial Magnetic Stimulation Has Opposing Effects on Visual and Auditory Stimulus Detection: Implications for Multisensory Interactions

Vincenzo Romei,¹ Micah M. Murray,^2,3,4 Lotfi B. Merabet,⁵ and Gregor Thut¹

¹Functional Brain Mapping Laboratory, Department of Neurology, University Hospital Geneva, and Department of Fundamental Neuroscience, University Medical School, 1211 Geneva, Switzerland, ²Electroencephalography Brain Mapping Core, Center for Biomedical Imaging of Lausanne and Geneva, 1011 Lausanne, Switzerland, ³Radiology Service and ⁴Neuropsychology and Neurorehabilitation Service, Centre Hospitalier Universitaire Vaudois and University of Lausanne, CH-1011 Lausanne, Switzerland, and ⁵Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215

Correspondence should be addressed to Dr. Vincenzo Romei, The Functional Brain Mapping Laboratory, Department of Fundamental Neuroscience, University Medical School, Rue Michel-Servet 1, 1206 Geneva, Switzerland. Email: vincenzo.romei{at}medecine.unige.ch

Multisensory interactions occur early in time and in low-level cortical areas, including primary cortices. To test current models of early auditory–visual (AV) convergence in unisensory visual brain areas, we studied the effect of transcranial magnetic stimulation (TMS) of visual cortex on behavioral responses to unisensory (auditory or visual) or multisensory (simultaneous auditory–visual) stimulus presentation. Single-pulse TMS was applied over the occipital pole at short delays (30–150 ms) after external stimulus onset. Relative to TMS over a control site, reactions times (RTs) to unisensory visual stimuli were prolonged by TMS at 60–75 ms poststimulus onset (visual suppression effect), confirming stimulation of functional visual cortex. Conversely, RTs to unisensory auditory stimuli were significantly shortened when visual cortex was stimulated by TMS at the same delays (beneficial interaction effect of auditory stimulation and occipital TMS). No TMS-effect on RTs was observed for AV stimulation. The beneficial interaction effect of combined unisensory auditory and TMS-induced visual cortex stimulation matched and was correlated with the RT-facilitation after external multisensory AV stimulation without TMS, suggestive of multisensory interactions between the stimulus-evoked auditory and TMS-induced visual cortex activities. A follow-up experiment showed that auditory input enhances excitability within visual cortex itself (using phosphene-induction via TMS as a measure) over a similarly early time-window (75–120 ms). The collective data support a mechanism of early auditory–visual interactions that is mediated by auditory-driven sensitivity changes in visual neurons that coincide in time with the initial volleys of visual input.

Key words: multisensory; auditory; visual; primary visual cortex; transcranial magnetic stimulation; TMS; crossmodal

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Received April 3, 2007; revised Aug. 21, 2007; accepted Aug. 30, 2007.

Correspondence should be addressed to Dr. Vincenzo Romei, The Functional Brain Mapping Laboratory, Department of Fundamental Neuroscience, University Medical School, Rue Michel-Servet 1, 1206 Geneva, Switzerland. Email: vincenzo.romei{at}medecine.unige.ch

Related articles in J. Neurosci.:

Listen to Your Visual Cortex: Effects of Occipital Transcranial Magnetic Stimulation on Auditory Stimulus Detection

Oliver Doehrmann
J. Neurosci. 2008 28: 1-2. [Full Text]  

This article has been cited by other articles:

				O. Doehrmann Listen to Your Visual Cortex: Effects of Occipital Transcranial Magnetic Stimulation on Auditory Stimulus Detection J. Neurosci., January 2, 2008; 28(1): 1 - 2. [Full Text] [PDF]

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