title: Hippocampal gamma-band Synchrony and pupillary responses index memory during visual search.
abstract: Memory for scenes is supported by the hippocampus, among other interconnected structures, but the neural mechanisms related to this process are not well understood. To assess the role of the hippocampus in memory-guided scene search, we recorded local field potentials and multiunit activity from the hippocampus of macaques as they performed goal-directed search tasks using natural scenes. We additionally measured pupil size during scene presentation, which in humans is modulated by recognition memory. We found that both pupil dilation and search efficiency accompanied scene repetition, thereby indicating memory for scenes. Neural correlates included a brief increase in hippocampal multiunit activity and a sustained synchronization of unit activity to gamma band oscillations (50-70 Hz). The repetition effects on hippocampal gamma synchronization occurred when pupils were most dilated, suggesting an interaction between aroused, attentive processing and hippocampal correlates of recognition memory. These results suggest that the hippocampus may support memory-guided visual search through enhanced local gamma synchrony. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Centre for Vision Research, York University, Toronto, Ontario, Canada.
authors.forename: Rodrigo
authors.identifier: 0000-0001-8296-1195
authors.initials: R
authors.lastname: Montefusco-Siegmund
authors.affiliation: Department of Psychology, Centre for Vision Research, York University, Toronto, Ontario, Canada.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Leonard
authors.affiliation: Department of Psychology, Department of Biology, Centre for Vision Research, Toronto, Ontario, Canada.
authors.forename: Kari L
authors.identifier: 0000-0003-0560-8157
authors.initials: KL
authors.lastname: Hoffman
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001143:Arousal / Q000502:physiology; D001288:Attention / Q000502:physiology; D004567:Electrodes, Implanted; D053483:Eye Movement Measurements; D005133:Eye Movements / Q000502:physiology; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D008253:Macaca mulatta; D008568:Memory / Q000502:physiology*; D009483:Neuropsychological Tests; D009929:Organ Size; D011680:Pupil / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*
keywords: CA3; binding memory; change detection; dentate gyrus; episodic memory; fast gamma; relational memory; spike-field coherence; top-down