Hippocampal and Entorhinal Cortex High-Frequency Oscillations (100-500 Hz) in Human Epileptic Brain and in Kainic Acid-Treated Rats with Chronic Seizures
TL;DR: Property of oscillations with frequencies >100 Hz were studied in kainic acid (KA)‐treated rats and compared with those recorded in normal and kindled rats as well as in patients with epilepsy to determine differences associated with epilepsy.
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Abstract: Summary: Purpose: Properties of oscillations with frequencies >100 Hz were studied in kainic acid (KA)-treated rats and compared with those recorded in normal and kindled rats as well as in patients with epilepsy to determine differences associated with epilepsy.
Methods: Prolonged in vivo wideband recordings of electrical activity were made in hippocampus and entorhinal cortex (EC) of (a) normal rats, (b) kindled rats, (c) rats having chronic recurrent spontaneous seizures after intrahippocampal KA injections, and (d) patients with epilepsy undergoing depth electrode evaluation in preparation for surgical treatment.
Results: Intermittent oscillatory activity ranging from 100 to 200 Hz in frequency and 50–150 ms in duration was recorded in CA1 and EC of all three animal groups, and in epileptic human hippocampus and EC. This activity had the same characteristics in all groups, resembled previously observed “ripples” described by Buzsaki et al., and appeared to represent field potentials of inhibitory postsynaptic potentials (IPSPs) on principal cells. Unexpectedly, higher frequency intermittent oscillatory activity ranging from 200 to 500 Hz and 10–100 ms in duration was encountered only in KA-treated rats and patients with epilepsy. These oscillations, termed fast ripples (FRs), were found only adjacent to the epileptogenic lesion in hippocampus, EC, and dentate gyrus, and appeared to represent field potential population spikes. Their local origin was indicated by correspondence with the negative phase of burst discharges of putative pyramidal cells.
Conclusions: The persistence of normal-appearing ripples in epileptic brain support the view that inhibitory processes are preserved. FRs appear to be field potentials reflecting hypersynchronous bursting of excitatory neurons and provide an opportunity to study the role of this pathophysiologic phenomenon in epilepsy and seizure initiation. Furthermore, if FR activity is unique to brain areas capable of generating spontaneous seizures, its identification could be a powerful functional indicator of the epileptic region in patients evaluated for surgical treatment.
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Citations
Synchronization in hybrid neuronal networks of the hippocampal formation.
Theoden I. Netoff,Matthew I. Banks,Alan D. Dorval,Corey D. Acker,Julie S. Haas,Nancy Kopell,John A. White +6 more
TL;DR: The results imply that excitatory SCs, but not inhibitory O-LM interneurons, are capable of synchronizing in phase via monosynaptic mutual connections of the biologically appropriate polarity.
Prospective observational study: Fast ripple localization delineates the epileptogenic zone.
Hiroki Nariai,Shaun A. Hussain,Danilo Bernardo,Aria Fallah,Kristina K. Murata,Jimmy C. Nguyen,Rajsekar R. Rajaraman,Lekha M. Rao,Joyce H. Matsumoto,Jason T. Lerner,Noriko Salamon,David Elashoff,Raman Sankar,Joyce Y. Wu +13 more
TL;DR: Prospective visual analysis of interictal FRs was feasible, and it seemed to accurately localize epileptogenic zones, and topological extent of epileptic region may exceed what is discernible by multimodal neuroimaging.
Determining the Quantitative Threshold of High-Frequency Oscillation Distribution to Delineate the Epileptogenic Zone by Automated Detection.
Chenxi Jiang,Xiaonan Li,Jiaqing Yan,Tao Yu,Xueyuan Wang,Zhiwei Ren,Donghong Li,Chang Liu,Wei Du,Xiaoxia Zhou,Yue Xing,Guoping Ren,Guojun Zhang,Xiaofeng Yang +13 more
TL;DR: An improved automated high frequency oscillations (HFOs) detector that could not only be applied to various intracranial electrodes, but also automatically remove false HFOs caused by high-pass filtering is proposed.
Automatic 80-250Hz "ripple" high frequency oscillation detection in invasive subdural grid and strip recordings in epilepsy by a radial basis function neural network.
TL;DR: An algorithm for automatic HFO detection that allows the automatic evaluation of brain areas with high HFO frequency, which is of high relevance for the demarcation of the epileptogenic zone.
Timing differences between HFOs and interictal epileptiform discharges generated in vitro by different mechanisms in rat hippocampal slices: A novel approach
TL;DR: Several of the metrics used, particularly those regarding the timing between HFOs & IEDs, appear to correlate with the synchronizing mechanism and it is proposed that they may be useful when investigating antiepileptic substance effects on neuronal network activity.
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