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Abstract

Previous studies have shown that population level activity in the primary cortex (V1) encodes information about natural stimuli into two distinct frequency regions, one above and one below 40Hz [1]. However, the origins and function of these two frequency bands are as yet unknown. We investigated the encoding of visual information across the joint domains of frequency and depth within a single cortical column of V1. Using laminar electrodes (150 micron spacing), we recorded broadband local field potentials and spiking activity in 4 anaesthetised macaques during the presentation of a naturalistic movie. We found information was highest for low frequencies (4-16Hz) in the granular region (layer 4) while for higher frequencies (60-200Hz) at was highest in the supra-granular region (layers 1-3). This suggests the independent channels of information are generated in distinct cortical laminae. Importantly, the distribution of information along cortical depth was different from the distribution of power. Additionally, we investigated how much information was contained in the neural activity about changes in the stimulus at various spatial frequencies. We found that neural activity in frequency bands below 40Hz contained most information about low spatial frequency components, peaking around 0.2 cycles per degree. Neural oscillations at frequencies above 40Hz contained most information about higher spatial frequencies, peaking around 2 cycles per degrees. These results shows that 1) visual information in V1 can be decomposed into two broad frequency bands, likely arising through different mechanisms, and 2) the information encoded in these bands is differs in spatial content.