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Noah C Benson, Omar H Butt, Geoffrey K Aguirre; Spontaneous visual cortex activity predicts eccentricity and is related to receptive field size. Journal of Vision 2014;14(10):587. doi: 10.1167/14.10.587.
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© ARVO (1962-2015); The Authors (2016-present)
Spontaneous "rest" fMRI signals have a spatial correlation structure in retinotopic visual cortex that resembles the radial organization of eccentricity. We tested if individual differences in measured eccentricity organization are reflected in resting state maps. Further, we examined if the spatial arrangement of resting state maps is better explained by common receptive field size as opposed to common eccentricity position. We collected rest (eyes-closed in darkness; 200 minutes) and retinotopic mapping data to 10° eccentricity (27 minutes) from 3 subjects at 3 Tesla. The data were registered to a common cortical surface atlas (fsaverage). The second principal component (SPC2) of the spontaneous correlations for each subject had radial structure aligned with the eccentricity direction. Using a cross-validation approach to determine an appropriate scaling factor, the SPC2 could predict eccentricity values out to 10° with 1.1° error in the group and 0.8° error in individuals, suggesting that spontaneous signals both resemble eccentricity organization and reflect individual differences. The SPC2 structure, however, was observed to plateau beyond 20°, unlike eccentricity which increases steadily with distance from the foveal confluence. We considered that SPC2 reflects not eccentricity per se, but receptive field size, which is in turn related to retinal ganglion cell (RGC) density in the retina. We obtained the inverse of the RGC density [Curcio & Allen, 1990, J. Comp. Neurol. 300:5-25] as an approximation of receptive field size and find that it is nearly identical in shape to traces of SPC2 along iso-polar angle lines. We conclude that the correlations in spontaneous fMRI signals reflect shared receptive field size across polar angle position and visual areas, and demonstrate that these correlations may be employed to predict eccentricity with high accuracy within 10° of the fovea.
Meeting abstract presented at VSS 2014
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