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. Author manuscript; available in PMC: 2008 Dec 12.
Published in final edited form as: Cereb Cortex. 2007 Jul 25;18(4):817–827. doi: 10.1093/cercor/bhm128

Figure 2. Group stereotactic analyses: Effects of IPS TMS intensity upon BOLD signal in occipital cortex depend on current visual context.

Figure 2

The images in both panels show the SPM(T)s quantifying (A) positive correlations of BOLD with TMS intensity during the absence of visual stimuli (Vis−) or (B) negative correlations of BOLD with TMS intensity during the presence of visual stimuli (Vis+). The SPM(T)s are plotted as 2-D projections onto a transparent schematic of the MNI template, and as renderings onto a transverse slice of the mean structural scan. All thresholds are set to T > 3 and p < 0.05 (cluster-level corrected for multiple comparisons across the image volume). The line plots displayed in each panel show the mean signal intensity during the different experimental conditions, extracted from a spherical region-of-interest (6mm radius) centred in the peak voxel of the corresponding SPM(T). The data for each subject is shown in a different colour, whereas the inter-subject mean is shown in black. For ease of visualisation (and for comparison with the same procedure in Ruff and others 2006), the signal is plotted averaged across the two lowest versus the two highest TMS intensities. Panel (A) shows a region in the calcarine sulcus that displayed activity increases with greater intensity of TMS over IPS, but only during the absence of visual stimulation, not when visual stimuli were present (significant positive correlation of BOLD with TMS intensity during blank-screen trials only, and significant interaction with absence/presence of visual stimuli). Note that the TMS effect is only apparent with a blank screen (asterisked leftmost pair of points in the corresponding plot). Panel (B) displays a bilateral region in occipito-temporal cortex, corresponding to V5/MT+, that showed negative correlations of BOLD signal with IPS-TMS intensity (i.e, reduced activity with higher intensity of TMS), but only when moving visual stimuli were concurrently presented (see asterisked rightmost pair of points in the plot). Note that applying the same TMS protocol over a different site (FEF) elicited occipital activity modulations that, by contrast, did not depend on visual context and had no effect on V5/MT+ (see main text and Figures 3 and 4).