title: Spontaneous fast gamma activity in the septal hippocampal region correlates with spatial learning in humans.
abstract: Hippocampal neuronal populations exhibit multiple kinds of activity patterns, from the dominant theta rhythm during active exploration to high-frequency ripple-like activity during periods of relative inactivity. In animals, evidence is rapidly accruing that these high-frequency ripple activity patterns subserve retention of spatial learning performance. In a translational effort to address the possible function of offline hippocampal processes in humans, we measured spontaneous gamma activity during an awake rest period within a virtual spatial learning context. Whole-head magnetoencephalographic (MEG) recordings were taken while healthy participants (N=24) quietly rested (eyes open) between encoding and retrieval phases of a hippocampal-dependent virtual Morris water maze task. Results are that fast gamma activity (80-140 Hz) in the septal or posterior region of the hippocampus (bilaterally) was positively correlated across participants with subsequent within-session spatial learning rate. Fast gamma did not predict initial retrieval performance following rest, failing to provide evidence of a direct link between spontaneous high-frequency activity patterns during awake rest and consolidation of previous spatial memories. The findings nevertheless are consistent with a prospective role for offline human hippocampal processes in spatial learning and indicate that higher spontaneous gamma activity in the septal hippocampal region is related to faster updating of spatial knowledge in familiar virtual surroundings.
authors.affiliation: Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Hawthorn, VIC 3122, Australia; Section on Neurobiology of Fear and Anxiety, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: bcornwell@swin.edu.au.
authors.forename: B R
authors.initials: BR
authors.lastname: Cornwell
authors.affiliation: Section on Neurobiology of Fear and Anxiety, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: C
authors.initials: C
authors.lastname: Overstreet
authors.affiliation: Section on Neurobiology of Fear and Anxiety, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: C
authors.initials: C
authors.lastname: Grillon
mesh_terms: D000328:Adult; D000465:Algorithms; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D012044:Regression Analysis; D013028:Space Perception / Q000502:physiology*; D014584:User-Computer Interface; D055815:Young Adult
keywords: Gamma activity; Hippocampus; Magnetoencephalography; Memory consolidation; Spatial learning; Virtual reality