Neurons in primate visual cortex are tuned for spatial frequency, and this
tuning depends on eccentricity. Several studies have examined this
dependency using fMRI (Henriksson et al. 2008; Sasaki et al. 2001; D’Souza
et al. 2016), but they report preferred spatial frequencies (tuning curve
peaks) at a given eccentricity in V1 that differ by one to two octaves,
perhaps due to differences in stimuli or analysis methodology. Here, we
systematically map this dependency using a population receptive field
analysis of fMRI responses to a novel set of stimuli. The stimuli are
constructed as mixtures of circular and radial gratings (pure circular,
pure radial, or spirals). For any local region of the visual field, these
stimuli cover a broad range of spatial frequencies and orientations, and
the local spatial frequency of all stimuli varies inversely with
eccentricity. We then used an unsupervised denoising algorithm
(GLMdenoise; Kay et al. 2013) to estimate the response amplitude of each
voxel to each stimulus, and combine these data with subjects’ retinotopic
maps (Benson et al. 2014; Dumoulin and Wandell 2008) to determine the
relationship between the eccentricity of a voxel’s population receptive
field and its spatial frequency tuning at several orientations. We show
that over a range of eccentricities from two to eight degrees, the
preferred spatial frequency varies as the inverse of the eccentricity.
Given that population receptive fields grow approximately linearly with
eccentricity,
these results are broadly consistent with a simple scaling rule, whereby
peak spatial frequency tuning is inversely proportional to both population
receptive field size and to eccentricity.