Spatial Frequency Tuning Follows Scale Invariance in the Human Visual Cortex.

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.