Alpha-frequency feedback to early visual cortex orchestrates coherent natural vision

For coherent visual experience to emerge, the brain needs to spatially integrate the complex and dynamic information it receives from the environment. To meet this challenge, the visual system uses contextual information from one part of the visual field to create feedback signals that guide analysis in other parts of the visual field. Here, we set out to characterize the nature of this feedback across brain rhythms and cortical regions. In EEG and fMRI experiments, we experimentally recreated the spatially distributed nature of visual inputs by presenting natural videos at different visual field locations. Critically, we manipulated the spatiotemporal congruency of the videos, so that they did or did not demand integration into a coherent percept. Decoding stimulus information from frequency-specific EEG patterns revealed a shift from representations in feedforward-related gamma activity for spatiotemporally inconsistent videos to representations in feedback-related alpha activity for spatiotemporally consistent videos. Our fMRI data suggest high-level scene-selective areas as the putative source of this feedback. Combining the EEG data with spatially resolved fMRI recordings, we demonstrate that alpha-frequency feedback is directly associated with representations in early visual cortex. Together this demonstrates how the human brain orchestrates coherent visual experience across space: it uses feedback to integrate information from high-level to early visual cortex through a dedicated rhythmic code in the alpha frequency range.