Saccades are locked to the phase of alpha oscillations during natural reading

Abstract

We saccade three to five times per second when reading. However, little is known about the neuronal mechanisms coordinating the oculomotor and visual system during such rapid processing. Here we ask if brain oscillations play a role in the temporal coordination of the visuomotor integration. We simultaneously acquired MEG and eye-tracking data while participants read sentences silently. Every sentence was embedded with target words of either high or low lexical frequency. Our key finding demonstrated that saccade onsets were locked to the phase of alpha oscillations (8 - 13 Hz); in particular, for saccades towards low-frequency words. Source modelling demonstrated that the alpha oscillations to which the saccades were locked, were generated in the right-associative visual cortex (BA 19). Our findings suggest that the alpha oscillations serve to time the processing between the oculomotor and visual systems during natural reading, and that this coordination becomes more pronounced for demanding words. Significance StatementReading is an essential skill in modern society that allows us to acquire information from written language. While we effortlessly can acquire the meaning of a text, the task of reading requires precisely timed saccades as our eyes jump from word to word. By using a natural reading task, we demonstrate that the coordination between saccades and visual processing is clocked by ongoing ~10 Hz alpha oscillations in the visual cortex. The clocking of the saccades by brain oscillations became particularly pronounced when the participants made saccades to demanding words.