title: Visual Sampling Predicts Hippocampal Activity.
abstract: Eye movements serve to accumulate information from the visual world, contributing to the formation of coherent memory representations that support cognition and behavior. The hippocampus and the oculomotor network are well connected anatomically through an extensive set of polysynaptic pathways. However, the extent to which visual sampling behavior is related to functional responses in the hippocampus during encoding has not been studied directly in human neuroimaging. In the current study, participants engaged in a face processing task while brain responses were recorded with fMRI and eye movements were monitored simultaneously. The number of gaze fixations that a participant made on a given trial was correlated significantly with hippocampal activation such that more fixations were associated with stronger hippocampal activation. Similar results were also found in the fusiform face area, a face-selective perceptual processing region. Notably, the number of fixations was associated with stronger hippocampal activation when the presented faces were novel, but not when the faces were repeated. Increases in fixations during viewing of novel faces also led to larger repetition-related suppression in the hippocampus, indicating that this fixation-hippocampal relationship may reflect the ongoing development of lasting representations. Together, these results provide novel empirical support for the idea that visual exploration and hippocampal binding processes are inherently linked.
  
  
  
  The hippocampal and oculomotor networks have each been studied extensively for their roles in the binding of information and gaze function, respectively. Despite the evidence that individuals with amnesia whose damage includes the hippocampus show alterations in their eye movement patterns and recent findings that the two systems are anatomically connected, it has not been demonstrated whether visual exploration is related to hippocampal activity in neurologically intact adults. In this combined fMRI-eye-tracking study, we show how hippocampal responses scale with the number of gaze fixations made during viewing of novel, but not repeated, faces. These findings provide new evidence suggesting that the hippocampus plays an important role in the binding of information, as sampled by gaze fixations, during visual exploration.
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Ontario, Canada M6A 2E1, and zliu@research.baycrest.org.
authors.forename: Zhong-Xu
authors.initials: ZX
authors.lastname: Liu
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Ontario, Canada M6A 2E1, and.
authors.forename: Kelly
authors.initials: K
authors.lastname: Shen
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Ontario, Canada M6A 2E1, and.|Department of Psychology and.
authors.forename: Rosanna K
authors.identifier: 0000-0002-2918-4152
authors.initials: RK
authors.lastname: Olsen
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Ontario, Canada M6A 2E1, and.|Department of Psychology and.|Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada M5S 3G3.
authors.forename: Jennifer D
authors.identifier: 0000-0001-9244-7851
authors.initials: JD
authors.lastname: Ryan
mesh_terms: D000328:Adult; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005544:Forecasting; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D055815:Young Adult
keywords: eye movements; gaze fixations; hippocampus; memory encoding; oculomotor system; visual exploration