High-frequency network oscillation in the hippocampus

Buzsáki, György; Horváth, Zsolt; Urioste, Ronald; Hetke, J.F.; Wise, K.D.

doi:10.1126/science.1589772

Cited by 1,080 publications

(931 citation statements)

References 33 publications

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“…Spontaneous mesiotemporal ripple oscillations have been described in the CA1 (Buzsáki et al, 1992), CA3, subiculum and enthorinal cortex (Chrobak and Buzsáki, 1996;Csicsvari et al, 1999) of normal rat hippocampus during episodes of awake immobility and slow-wave sleep, probably involved in information processing and consolidation of memory (Buzsaki, 1996;Siapas and Wilson, 1998). Physiological HFOs occur also in normal neocortex.…”

Section: Discussionmentioning

confidence: 99%

Continuous High Frequency Activity: A peculiar SEEG pattern related to specific brain regions

Melani

Zelmann

Mari

et al. 2013

Clinical Neurophysiology

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Objective-While visually marking the high frequency oscillations in the stereo-EEG of epileptic patients, we observed a continuous/semicontinuous activity in the ripple band (80-250 Hz), which we defined continuous High Frequency Activity (HFA). We aim to analyze in all brain regions the occurrence and significance of this particular pattern.Methods-Twenty patients implanted in mesial temporal and neocortical areas were studied. One minute of slow-wave sleep was reviewed. The background was classified as continuous/ semicontinuous, irregular, or sporadic based on the duration of the fast oscillations. Each channel was classified as inside/outside the seizure onset zone (SOZ) or a lesion.Results-The continuous/semicontinuous HFA occurred in 54 of the 790 channels analyzed, with a clearly higher prevalence in hippocampus and occipital lobe. No correlation was found with the SOZ or lesions. In the occipital lobe the continuous/semicontinuous HFA was present independently of whether eyes were open or closed. Conclusions-We describe what appears to be a new physiological High Frequency Activity, independent of epileptogenicity, present almost exclusively in the hippocampus and occipital cortex but independent of the alpha rhythm.Significance-The continuous HFA may be an intrinsic characteristic of specific brain regions, reflecting a particular type of physiological neuronal activity.

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Section: Discussionmentioning

confidence: 99%

Continuous High Frequency Activity: A peculiar SEEG pattern related to specific brain regions

Melani

Zelmann

Mari

et al. 2013

Clinical Neurophysiology

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“…Beyond this observation, it was also shown that γ oscillations may operate as a general mechanism that is capable of binding together, by a process of phase synchronization, not only the firing of neurons at the local level, but also neural activities of spatially separate cortical areas (Roelfsema et al, 1997). Furthermore, the discovery of hippocampal ripples during behavioral immobility, consummatory behaviors and slow-wave sleep (Buzsáki et al, 1992), kindled the interest for understanding the functional significance of HFOs in the process of memory consolidation. The subsequent finding that similar short transient oscillations, named "fast ripples", can be observed in the local field potential recorded from the hippocampus and the temporal cortex of epileptic humans and rodents (Bragin et al, 1999b) stimulated the interest for these oscillatory phenomena as possible biomarkers of epileptogenic neural networks.…”

Section: Introductionmentioning

confidence: 98%

Mechanisms of physiological and epileptic HFO generation

Jefferys

Prida

Wendling

et al. 2012

Progress in Neurobiology

270

238

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High frequency oscillations (HFO) have a variety of characteristics: band-limited or broad-band, transient burst-like phenomenon or steady-state. HFOs may be encountered under physiological or under pathological conditions (pHFO). Here we review the underlying mechanisms of oscillations, at the level of cells and networks, investigated in a variety of experimental in vitro and in vivo models. Diverse mechanisms are described, from intrinsic membrane oscillations to network processes involving different types of synaptic interactions, gap junctions and ephaptic coupling. HFOs with similar frequency ranges can differ considerably in their physiological mechanisms. The fact that in most cases the combination of intrinsic neuronal membrane oscillations and synaptic circuits are necessary to sustain network oscillations is emphasized. Evidence for pathological HFOs, particularly fast ripples, in experimental models of epilepsy and in human epileptic patients is scrutinized. The underlying mechanisms of fast ripples are examined both in the light of animal observations, in vivo and in vitro, and in epileptic patients, with emphasis on single cell dynamics. Experimental observations and computational modeling have led to hypotheses for these mechanisms, several of which are considered here, namely the role of out-ofphase firing in neuronal clusters, the importance of strong excitatory AMPA-synaptic currents and recurrent inhibitory connectivity in combination with the fast time scales of IPSPs, ephaptic coupling and the contribution of interneuronal coupling through gap junctions. The statistical behaviour of fast ripple events can provide useful information on the underlying mechanism and can help to further improve classification of the diverse forms of HFOs.

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“…Ripples have been thought to be more physiological in nature and involved in memory, while FRs appear to be pathological, except for FRs in sensory evoked potentials (Axmacher et al, 2008;Buzsaki et al, 1992;Curio et al, 1997;Engel et al, 2009;Worrell et al, 2008). HFOs often co-occur with epileptic spikes, but there are HFOs without spikes and spikes without HFOs (Jacobs et al, 2008;Urrestarazu et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Ictal and interictal high frequency oscillations in patients with focal epilepsy

Zijlmans¹,

Jacobs²,

Kahn³

et al. 2011

Clinical Neurophysiology

165

128

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Objective-High frequency oscillations (HFOs) can be recorded with depth electrodes in focal epilepsy patients. They occur during seizures and interictally and seem important in seizure genesis. We investigated whether interictal and ictal HFOs occur in the same regions and how they relate to epileptiform spikes.Methods-In 25 patients, spikes, ripples (80-250 Hz) and fast ripples (FR: 250-500 Hz) and their co-occurrences were marked during interictal slow wave sleep (5-10 min), during 10 preictal seconds and 5 s following seizure onset. We compared occurrence and spatial distribution between these periods.Results-HFOs and spikes increased from interictal to ictal periods: the percentage of time occupied by ripples increased from 2.3% to 6.5%, FR from 0.2% to 0.8%, spikes from 1.1% to 4.8%. HFOs increased from interictal to preictal periods in contrast to spikes. Spikes were in different channels in the interictal, preictal and ictal periods whereas HFOs largely remained in the same channels.Conclusions-HFOs remain confined to the same, possibly epileptogenic, area, during interictal and ictal periods, while spikes are more widespread during seizures than interictally.Significance-Ictal and interictal HFOs represent the same (epileptogenic) area and are probably similar phenomena.

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High-frequency network oscillation in the hippocampus

Cited by 1,080 publications

References 33 publications

Continuous High Frequency Activity: A peculiar SEEG pattern related to specific brain regions

Continuous High Frequency Activity: A peculiar SEEG pattern related to specific brain regions

Mechanisms of physiological and epileptic HFO generation

Ictal and interictal high frequency oscillations in patients with focal epilepsy

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