title: Hippocampal sharp wave-ripple: A cognitive biomarker for episodic memory and planning.
abstract: Sharp wave ripples (SPW-Rs) represent the most synchronous population pattern in the mammalian brain. Their excitatory output affects a wide area of the cortex and several subcortical nuclei. SPW-Rs occur during "off-line" states of the brain, associated with consummatory behaviors and non-REM sleep, and are influenced by numerous neurotransmitters and neuromodulators. They arise from the excitatory recurrent system of the CA3 region and the SPW-induced excitation brings about a fast network oscillation (ripple) in CA1. The spike content of SPW-Rs is temporally and spatially coordinated by a consortium of interneurons to replay fragments of waking neuronal sequences in a compressed format. SPW-Rs assist in transferring this compressed hippocampal representation to distributed circuits to support memory consolidation; selective disruption of SPW-Rs interferes with memory. Recently acquired and pre-existing information are combined during SPW-R replay to influence decisions, plan actions and, potentially, allow for creative thoughts. In addition to the widely studied contribution to memory, SPW-Rs may also affect endocrine function via activation of hypothalamic circuits. Alteration of the physiological mechanisms supporting SPW-Rs leads to their pathological conversion, "p-ripples," which are a marker of epileptogenic tissue and can be observed in rodent models of schizophrenia and Alzheimer's Disease. Mechanisms for SPW-R genesis and function are discussed in this review.
authors.affiliation: The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, New York.
authors.forename: György
authors.initials: G
authors.lastname: Buzsáki
mesh_terms: D000818:Animals; D015415:Biomarkers; D058256:Brain Waves / Q000502:physiology*; D056344:Executive Function / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology* / Q000503:physiopathology; D006801:Humans; D061212:Memory, Episodic
chemical_list: D015415:Biomarkers
keywords: epilepsy; imagining; learning; memory; planning