Abstract
Trial-to-trial response variability – generally referred to as “noise” – is pervasive in the visual system. Although it has long been known that in the human brain noise is correlated across voxels, the structure of noise correlations is not fully understood. In particular, it is not known if noise correlations have the same structure as signal correlations. To address this question, we used the massive 7T fMRI Natural Scenes Dataset to characterize signal and noise in multiple visual areas. We find that voxel-to-voxel correlation structure in noise is well aligned with voxel- to-voxel correlation structure in signals evoked by natural scenes. This finding generalizes to correlation structure observed in spontaneous activity during rest (viewing a blank screen). Importantly, we find that noise correlations do not match the correlation structure in signals evoked by artificial stimuli. These results suggest that noise in the visual system encodes naturalistic visual representations that are not directly related to the current visual input. We speculate that variation in these putative visual representations is driven by ongoing cognitive processing.