A rhythmic framework of visual sampling in the reading brain

Reading is essentially a 'spatiotemporal sampling' problem, which relies on the brain's capacity to detect, arrange and transform sensory data, such as letter sequences and word sounds, in quick succession. While temporal sampling accounts of language processing focused on the auditory modality, where speech provides an externally driven rhythmic structure, reading constitutes a fundamentally different case, in which sampling is self-paced and actively controlled through eye movements rather than being externally constrained. Specifically, reading extensively involves visual sampling of written material on multiple spatiotemporal scales, enabling one to correctly segregate or integrate letters and words and to plan precise and fluid eye movements. We present a rhythmic framework describing how neural synchronization might support spatiotemporal abilities in reading across the visual, attentional and oculomotor networks. We propose that gamma oscillations (>30 Hz), integrated over theta or alpha cycles, are likely responsible for the extraction of basic grapheme features. Beta oscillations (∼15-25 Hz) may subserve the fast-track localization of elements in the visual space reflecting dorsal visual stream activity culminating in the superior parietal areas. Alpha oscillations (∼8-13 Hz) may implement precise visual input segregation influencing graphemic parsing in the ventral visual stream. Theta oscillations (∼4-7 Hz) may regulate fronto-parietal dorsal attentional networks and the initiation of saccadic eye movements. Although sampling depends primarily on the synchronization of neural oscillations across sensorimotor and associative areas, we also discuss how neural noise can interfere with such synchronization. This framework can improve our understanding of reading and its deficits, as well as other complex functions reliant on sensorimotor sampling.