Saccades are coordinated with directed circuit dynamics and stable but distinct hippocampal patterns that promote memory formation

Abstract

During natural viewing, humans explore their environment by moving the eyes - a process that involves saccades to guide attention and shape memory. Saccades are controlled by visuo-oculomotor regions and are known to impact medial temporal lobe processing, but the circuit dynamics in humans are unclear. Here, we asked which of the functional routes between the visual cortex, frontal eye fields, and the hippocampus facilitates memory encoding during visual exploration and whether saccades affect neural representations. Forty-eight human participants underwent functional magnetic resonance imaging (fMRI) and continuous monitoring of eye gaze while studying scenes and performing a recognition memory test thereafter. We discovered saccade-related excitatory coupling from the visual cortex and frontal eye fields towards the hippocampus, independent of memory. This was complemented by hippocampal inhibition of the visual cortex that determined whether participants would later remember or forget. Moreover, saccades were associated with overall stable but distinct hippocampal voxel patterns during memory formation and the degree of pattern distinctiveness positively scaled with inhibition along the hippocampus-to-visual cortex route. This suggests that eye movements are timed to the orchestration of circuit connectivity and neural representations, setting the stage for memory formation.