Spatial Frequency Tuning Follows Scale Invariance in the Human Visual Cortex

Abstract

Our visual system can recognize patterns across many spatial scales. A fundamental assumption in visual neuroscience is that this ability relies on the putative scale-invariant properties of receptive fields (RFs) in early vision, whereby the spatial area over which a visual neuron responds is proportional to the spatial scale of information it can encode (i.e., spatial frequency, SF). In other words, the resolution of spatial sampling of a RF is assumed to be constant in the visual cortex. However, this assumption has gone untested in the human visual cortex. To address this, we leveraged model-based fMRI techniques that characterize the spatial tuning and SF preferences of cortical subpopulations sampled within a voxel across eight participants (five females, three males). We find that the voxel-wise ratio between peak SF tuning and RF size—expressed as “cycles per RF”—remains constant across visual areas V1, V2, and V3, suggesting that, at the population level, SF preferences are inversely proportional to the RF size, a tenet of scale invariance in early human vision.