Imaging the neural mechanisms of TMS neglect-like bias in healthy volunteers with the interleaved TMS/fMRI technique: preliminary evidence
- 1Brain Stimulation Laboratory, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, USA
- 2Department of Psychology and Neuroscience Institute of Turin, University of Turin, Turin, Italy
- 3The Center for Advanced Imaging Research, Medical University of South Carolina, Charleston, SC, USA
- 4Stanford Systems Neuroscience and Pain Laboratory, Stanford School of Medicine, Palo Alto, CA, USA
Applying a precisely timed pulse of transcranial magnetic stimulation (TMS) over the right posterior parietal cortex (PPC) can produce temporary visuo-spatial neglect-like effects. Although the TMS is applied over PPC, it is not clear what other brain regions are involved. We applied TMS within a functional magnetic resonance imaging (fMRI) scanner to investigate brain activity during TMS induction of neglect-like bias in three healthy volunteers, while they performed a line bisection judgment task (i.e., the landmark task). Single-pulse TMS at 115% of motor threshold was applied 150 ms after the visual stimulus onset. Participants completed two different TMS/fMRI sessions while performing this task: one session while single-pulse TMS was intermittently and time-locked applied to the right PPC and a control session with TMS positioned over the vertex. Perceptual rightward bias was observed when TMS was delivered over the right PPC. During neglect-like behavior, the fMRI maps showed decreased neural activity within parieto-frontal areas, which are often lesioned or dysfunctional in patients with left neglect. Vertex TMS induced behavioral effects compatible with leftward response bias and increased BOLD signal in the left caudate (a site which has been linked to response bias). These results are discussed in relation to recent findings on neural networks subserving attention in space.
Keywords: TMS, fMRI, spatial attention, neglect, visuospatial orienting
Citation: Ricci R, Salatino A, Li X, Funk AP, Logan SL, Mu Q, Johnson KA, Bohning DE and George MS (2012) Imaging the neural mechanisms of TMS neglect-like bias in healthy volunteers with the interleaved TMS/fMRI technique: preliminary evidence. Front. Hum. Neurosci. 6:326. doi: 10.3389/fnhum.2012.00326
Received: 05 October 2012; Paper pending published: 28 October 2012;
Accepted: 22 November 2012; Published online: 17 December 2012.
Copyright © 2012 Ricci, Salatino, Li, Funk, Logan, Mu, Johnson, Bohning and George. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Raffaella Ricci, Department of Psychology, University of Turin, Via Po 14, Torino 10123, Italy. e-mail: firstname.lastname@example.org; email@example.com