Coherent Phasic Excitation during Hippocampal Ripples

Maier, Nikolaus; Tejero-Cantero, Álvaro; Dorrn, Anja L.; Winterer, Jochen; Beed, Prateep; Morris, Genela; Kempter, Richard; Poulet, James F.A.; Leibold, Christian; Schmitz, Dietmar

doi:10.1016/j.neuron.2011.08.016

Cited by 117 publications

(155 citation statements)

References 57 publications

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“…These properties have fostered the hypothetical role of ripples in processes underlying memory formation (see above). We and others have focused on the cellular mechanisms of sharp wave-ripple complexes over the past years [27,40,41,42]. We have mostly worked on the experimental model system of hippocampal slices of mice (and rats).…”

Section: Cellular Mechanisms Of 200 Hz Ripplesmentioning

confidence: 99%

Fast network oscillations in the hippocampus

et al. 2013

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Neuronal networks often express coherent oscillatory activity. These rhythms can provide a temporal reference for the activity of single neurons and allow the formation of spatiotemporal activity patterns with a defined phase relationship of action potentials. In a single brain nucleus, oscillations at different frequencies might be simultaneously generated, but isolated rhythms might also be characteristic for specific functional brain states. During the last two decades the mammalian hippocampus has become an important model system for the study of neuronal network oscillations. In this brain area, cellular mechanisms underlying neuronal synchronization have been described, but also models were developed to explain the contribution of oscillations in encoding, consolidation, and recall of memories. Neuronal rhythmic activities provide an important field of analysis bringing together cellular mechanisms and systemic functions of the brain. Here, we use a particularly fast type of neuronal oscillation, hippocampal “ripples”, as an example to outline current knowledge and open questions related with this research field.

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Section: Cellular Mechanisms Of 200 Hz Ripplesmentioning

confidence: 99%

Fast network oscillations in the hippocampus

et al. 2013

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“…Previous reports have used intracellular blockers of Cl − -mediated inhibition to investigate excitatory network input at the singlecell level (48,49). We applied this tool to corroborate the excitatory nature of ripple-locked currents in O-LM neurons.…”

Section: Resultsmentioning

confidence: 99%

“…To characterize contributions of excitatory and inhibitory input onto O-LM neurons during SWRs, we compared this input with the input in pyramidal neurons (41,(43)(44)(45)(46)(47)(48) (SI Materials and Methods, Data Analysis and Fig. S1).…”

Section: Resultsmentioning

confidence: 99%

“…For direct comparison, we pooled data from seven O-LM and seven Timing of Synaptic Input and Spikes in O-LM Cells During Ripples. We recently showed that excitatory input onto CA1 principal neurons during ripples is phasic, coherent across cells, and phaselocked to the LFP (48). To similarly characterize the compound excitatory postsynaptic currents (cEPSCs) onto O-LM neurons, we collected cEPSCs recorded close to the reversal potential of Cl − (−74 mV; Fig.…”

Section: Resultsmentioning

confidence: 99%

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Recruitment of oriens-lacunosum-moleculare interneurons during hippocampal ripples

Pangalos

Donoso

Winterer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Sharp wave-associated ∼200-Hz ripple oscillations in the hippocampus have been implicated in the consolidation of memories. However, knowledge on mechanisms underlying ripples is still scarce, in particular with respect to synaptic involvement of specific cell types. Here, we used cell-attached and whole-cell recordings in vitro to study activity of pyramidal cells and oriens-lacunosum-moleculare (O-LM) interneurons during ripples. O-LM cells received ripple-associated synaptic input that arrived delayed (3.3 ± 0.3 ms) with respect to the maximum amplitude of field ripples and was locked to the ascending phase of field oscillations (mean phase: 209 ± 6°). In line, O-LM cells episodically discharged late during ripples (∼6.5 ms after the ripple maximum), and firing was phase-locked to field oscillations (mean phase: 219 ± 9°). Our data unveil recruitment of O-LM neurons during ripples, suggesting a previously uncharacterized role of this cell type during sharp wave-associated activity.

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“…The roles played by these mechanisms in pathologic HFOs are still under study but evidence obtained to date suggests that pathologic HFOs in the ripple band -like those recorded under physiological conditions [30,31,46,47] (but see ref. 48 for a different interpretation) -may represent population IPSPs generated by principal neurons entrained by synchronously active interneuron networks (Fig. 3C).…”

Section: High Frequency Oscillationsmentioning

confidence: 99%

Mechanisms of Epileptiform Synchronization in Cortical Neuronal Networks

Avoli

2014

CMC

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Neuronal synchronization supports different physiological states such as cognitive functions and sleep, and it is mirrored by identifiable EEG patterns ranging from gamma to delta oscillations. However, excessive neuronal synchronization is often the hallmark of epileptic activity in both generalized and partial epileptic disorders. Here, I will review the synchronizing mechanisms involved in generating epileptiform activity in the limbic system, which is closely involved in the pathophysiogenesis of temporal lobe epilepsy (TLE). TLE is often associated to a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory adult form of partial epilepsy. This epileptic disorder can be reproduced in animals by topical or systemic injection of pilocarpine or kainic acid, or by repetitive electrical stimulation; these procedures induce an initial status epilepticus and cause 1-4 weeks later a chronic condition of recurrent limbic seizures. Remarkably, a similar, seizure-free, latent period can be identified in TLE patients who suffered an initial insult in childhood and develop partial seizures in adolescence or early adulthood. Specifically, I will focus here on the neuronal mechanisms underlying three abnormal types of neuronal synchronization seen in both TLE patients and animal models mimicking this disorder: (i) interictal spikes; (ii) high frequency oscillations (80-500 Hz); and (iii) ictal (i.e., seizure) discharges. In addition, I will discuss the relationship between interictal spikes and ictal activity as well as recent evidence suggesting that specific seizure onsets in the pilocarpine model of TLE are characterized by distinctive patterns of spiking (also termed preictal) and high frequency oscillations.

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Coherent Phasic Excitation during Hippocampal Ripples

Cited by 117 publications

References 57 publications

Fast network oscillations in the hippocampus

Fast network oscillations in the hippocampus

Recruitment of oriens-lacunosum-moleculare interneurons during hippocampal ripples

Mechanisms of Epileptiform Synchronization in Cortical Neuronal Networks

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