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. 2013 Jan 30;33(5):2188–2198. doi: 10.1523/JNEUROSCI.3388-12.2013

Figure 1.

Figure 1.

Correlation structure of cortical activity during MIB. A, Snapshot of the dynamic MIB stimulus. A salient yellow target was surrounded by a moving dot pattern (blue), which appeared as a rotating sphere. The target was presented in different visual field quadrants for different subjects. While viewing this stimulus, subjects repeatedly experienced and reported the spontaneous disappearance and reappearance of the target. B, Cortical subregions. Separate localizer protocols delineated the subregions corresponding retinotopically to the MIB target and the surrounding mask, within each of V1, V2, V3, and V4 (highlighted for V1). The figure shows an example map of cortical responses to a flickering probe stimulus presented at the spatial location of the MIB target. Colors represent correlation between measured activity and stimulus alternations (threshold: r > 0.5). The map is superimposed on a flattened representation of the subject's occipital lobe. The borders of areas V1, V2, V3, and V4 are indicated as white outlines. The probe in the lower left visual field quadrant evoked responses in the dorsal subregions of right hemisphere visual areas V1–V3, and in the corresponding subregion of area V4. C, Example fMRI time series during one run of MIB. Left, Raw fMRI time series of the eight cortical subregions (yellow traces, target subregions; blue traces, mask subregions). The black bars at the bottom mark epochs of strong global fluctuations shared by all subregions. Right, Residual time series after removing the global mean across all subregions. The green bars and arrows mark epochs of anti-correlated fluctuations in the target and mask subregions of V4 (compare traces for target and mask subregions). Vertical bars in bottom left corner of each panel, 1 SD of fMRI image intensity modulation. Note that the scales are different in the two panels. D, Correlation matrix showing pairwise correlation coefficients, for each pair of ROIs, averaged across all MIB runs and the six subjects. E, Spatial mode, averaged across subjects. Left, Map of the spatial mode weights. The spatial modes are vectors, whose elements are reorganized as matrices (4 cortical areas × 2 subregions) for illustration. Right, Bar graph of the spatial mode weights. Error bars indicate SEM, N = 6. Inset, histogram of the eigenvalues. Gray bar, eigenvalue corresponding to the first spatial mode.