Eccentricity-dependent temporal contrast tuning in human visual cortex measured with fMRI.

Abstract Cells in the peripheral retina tend to have higher contrast sensitivity and respond at higher flicker frequencies than those closer to the fovea. Although this predicts increased behavioural temporal contrast sensitivity in the peripheral visual field, this effect is rarely observed in psychophysical experiments. It is unknown how temporal contrast sensitivity is represented across eccentricity within cortical visual field maps and whether such sensitivities reflect the response properties of retinal cells or psychophysical sensitivities. Here, we used functional magnetic resonance imaging (fMRI) to measure contrast sensitivity profiles at four temporal frequencies in five retinotopically-defined visual areas. We also measured population receptive field (pRF) parameters (polar angle, eccentricity, and size) in the same areas. Overall contrast sensitivity, independent of pRF parameters, peaked at 10 Hz in all visual areas. In V1, V2, V3, and V3a, peripherally-tuned voxels had higher contrast sensitivity at a high temporal frequency (20 Hz), while hV4 more closely reflected behavioural sensitivity profiles. We conclude that our data reflect a cortical representation of the increased peripheral temporal contrast sensitivity that is already present in the retina and that this bias must be compensated later in the cortical visual pathway. Highlights • Contrast sensitivity to 20Hz flicker is increased in peripheral voxels, when compared to foveal voxels, within V1, V2, V3, and V3a. • In hV4, contrast sensitivity at 20Hz is unchanged across eccentricity, similar to psychophysical sensitivities. • Our data suggest that the temporal response properties of peripheral retinal cells are represented in the cortical periphery of early visual areas. • Temporal filtering may occur in higher-order ventral visual areas, consistent with an eccentricity-dependent invariance to lower level visual properties such as temporal contrast. [ABSTRACT FROM AUTHOR]