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Omar H Butt, Noah Benson, Ritobrato Datta, Geoffrey Karl Aguirre; V1 resting-state functional connectivity reflects polar angle and eccentricity both within and between hemispheres. Journal of Vision 2012;12(9):574. doi: https://doi.org/10.1167/12.9.574.
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Local functional connectivity is reported to represent retinotopic eccentricity (E) within visual cortex (Yeo et al, 2011 JNeurophysiol). We tested if V1 functional connectivity actually reflects cortical surface distance (D), or some combination of eccentricity and polar angle (PA), and if inter-hemispheric correlations are retinotopically organized. Eighteen subjects were scanned (150 or 160 TRs BOLD fMRI, TR=3, 3mm voxels, 3 Tesla) under constant darkness. Raw signals from each subject were combined within a V1 cortical-surface template (Hinds et al, 2009 Neuroimage). Following 2mm surface smoothing, cross-correlation matrices (3161x3161 cells) for within-hemisphere V1 vertices were generated for low temporal frequencies (0.01<f<0.08 Hz) for each subject. Each vertex was assigned a PA and E value based upon the location of the vertex within the V1 retinotopic surface template (Benson, Butt et al, submitted). The pattern of correlation values in the individual (and group averaged) resting matrices were then modeled with exponential decay functions of changes in E, PA, and D. The group data were fit with an R2 of 0.97, with significant loading upon ∆E, ∆PA, and ∆SD (p<0.001). Consistently, the ∆E component contributed more to the model than the ∆PA component (p=0.02), even accounting for the greater cortical extent of V1 along the E axis. The between-hemisphere correlation matrix was also obtained, in which each vertex was compared to a vertex in the opposite hemisphere. The correlation structure again reflected E and PA (p's <0.001), with a greater representation of E (p <0.001). As this resting retinotopic structure existed between hemispheres, the finding cannot be explained by (e.g.) physiologic artifact or digital smoothing. These results show that V1 functional connectivity reflects retinotopic organization, not just local smoothness.
Meeting abstract presented at VSS 2012
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