title: Dual origins of measured phase-amplitude coupling reveal distinct neural mechanisms underlying episodic memory in the human cortex.
abstract: Phase-amplitude coupling (PAC) is hypothesized to coordinate neural activity, but its role in successful memory formation in the human cortex is unknown. Measures of PAC are difficult to interpret, however. Both increases and decreases in PAC have been linked to memory encoding, and PAC may arise due to different neural mechanisms. Here, we use a waveform analysis to examine PAC in the human cortex as participants with intracranial electrodes performed a paired associates memory task. We found that successful memory formation exhibited significant decreases in left temporal lobe and prefrontal cortical PAC, and these two regions exhibited changes in PAC within different frequency bands. Two underlying neural mechanisms, nested oscillations and sharp waveforms, were responsible for the changes in these regions. Our data therefore suggest that decreases in measured cortical PAC during episodic memory reflect two distinct underlying mechanisms that are anatomically segregated in the human brain.
authors.affiliation: Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USA; Medical Scientist Training Program, Duke University School of Medicine, Durham, NC 27710, USA.
authors.forename: Alex P
authors.initials: AP
authors.lastname: Vaz
authors.affiliation: Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USA; Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Yaffe
authors.affiliation: Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Wittig
authors.affiliation: Office of the Clinical Director, NINDS, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Sara K
authors.initials: SK
authors.lastname: Inati
authors.affiliation: Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: kareem.zaghloul@nih.gov.
authors.forename: Kareem A
authors.initials: KA
authors.lastname: Zaghloul
mesh_terms: D000328:Adult; D000465:Algorithms; D001244:Association; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D000069279:Drug Resistant Epilepsy / Q000000981:diagnostic imaging / Q000601:surgery; D004567:Electrodes, Implanted; D004569:Electroencephalography; D019277:Entropy; D005260:Female; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D011597:Psychomotor Performance / Q000502:physiology; D058067:Wavelet Analysis
keywords: Nested oscillations; Sharp waveforms; iEEG