Work

Hippocampal Theta Distinguishes between Memory-Guided and Exploratory Saccades in Humans

Year: 2026

Type: article

Abstract: Memory shapes how we explore the visual world, but the neural mechanisms linking mnemonic processes to eye movements during naturalistic viewing remain poorly understood. Theta-band oscillatory activity in the hippocampus is time-locked with eye movements in primates, suggesting a putative mechanism for coordinating mnemonic processing and oculomotor behavior. Yet, it remains unknown whether this coupling generalizes to episodic memory-guided viewing in humans, whether slow (3-6 Hz) and fast (6-10 Hz) theta bands play dissociable functions, and whether this coupling is sensitive to the direction of upcoming eye movements. Here, we used intracranial EEG and eye-tracking data from 11 neurosurgical patients of either sex (Keles et al., 2024) to address these questions. Using fixation-locked analyses, we found that hippocampal theta dynamics differentiate memory-guided from memory-independent fixations of episodically encoded naturalistic scenes (i.e., movies) through power and coherence mechanisms that are temporally and spectrally dissociable. First, immediately after fixations (∼0-250 ms), slow-theta power was more strongly suppressed during memory-guided trials (i.e., true positive, TP) than correct memory-independent trials (i.e., true negative, TN). Second, in the period around fixations (-80 to 60 ms), theta phase coherence increased independent of power during TP versus TN trials. This increase in coherence was most pronounced for contraversive relative to ipsiversive fixations, consistent with direction-sensitive hippocampal-oculomotor coordination during memory-guided viewing. Together, these findings suggest that hippocampal theta plays dissociable, time-locked roles in memory-guided fixations during naturalistic retrieval, supporting an ecologically relevant role of the hippocampus in coordinating memory and active visual behavior.

Source: Journal of Neuroscience

DOI: 10.1523/jneurosci.0047-26.2026

Authors: Camilo A. Castelblanco Riveros, Peter A. Angeli, Matthijs A. A. van der Meer, Krzysztof A. Bujarski, Caroline E. Robertson

Institutions: Dartmouth College, Dartmouth–Hitchcock Medical Center

Language: English

Topic: Memory and Neural Mechanisms

Subfield: Cognitive Neuroscience

Field: Neuroscience

Domain: Life Sciences

Open Access status: hybrid

Funders: National Science Foundation, National Institute of Mental Health

Awards: CAREER: The Neural Basis of Memory for Visual Environments, How Visuospatial Memory Shapes Perception of Real-World Environments