title: Hippocampal gamma oscillations increase with memory load.
abstract: Although the hippocampus plays a crucial role in encoding and retrieval of contextually mediated episodic memories, considerable controversy surrounds the role of the hippocampus in short-term or working memory. To examine both hippocampal and neocortical contributions to working memory function, we recorded electrocorticographic activity from widespread cortical and subcortical sites as 20 neurosurgical patients performed working memory tasks. These recordings revealed significant increases in 48-90 Hz gamma oscillatory power with memory load for two classes of stimuli: letters and faces. Sites exhibiting gamma increases with memory load appeared primarily in the hippocampus and medial temporal lobe. These findings implicate gamma oscillatory activity in the maintenance of both letters and faces in working memory and provide the first direct evidence for modulation of hippocampal gamma oscillations as humans perform a working memory task.
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey 08540, USA. mkvan@princeton.edu
authors.forename: Marieke K
authors.initials: MK
authors.lastname: van Vugt
authors.forename: Andreas
authors.initials: A
authors.lastname: Schulze-Bonhage
authors.forename: Brian
authors.initials: B
authors.lastname: Litt
authors.forename: Armin
authors.initials: A
authors.lastname: Brandt
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kahana
mesh_terms: D000328:Adult; D001683:Biological Clocks / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D019579:Neocortex / Q000502:physiology; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012044:Regression Analysis; D055815:Young Adult