High‐frequency oscillations recorded in human medial temporal lobe during sleep

Abstract

The presence of fast ripple oscillations (FRs, 200-500 Hz) has been confirmed in rodent epilepsy models but has not been observed in nonepileptic rodents, suggesting that FRs are associated with epileptogenesis. Although studies in human epileptic patients have reported that both FRs and ripples (80-200 Hz) chiefly occur during non-rapid eye movement sleep (NREM), and that ripple oscillations in human hippocampus resemble those found in nonprimate slow wave sleep, quantitative studies of these oscillations previously have not been conducted during polysomnographically defined sleep and waking states. Spontaneous FRs and ripples were detected using automated computer techniques in patients with medial temporal lobe epilepsy during sleep and waking, and results showed that the incidence of ripples, which are thought to represent normal activity in animal and human hippocampus, was similar between epileptogenic and nonepileptogenic temporal lobe, whereas rates of FR occurrence were significantly associated with epileptogenic areas. The generation of both FRs and ripples showed the highest rates of occurrence during NREM sleep. During REM sleep, ripple rates were lowest, whereas FR rates remained elevated and were equivalent to rates observed during waking. The predominance of FRs within the epileptogenic zone not only during NREM sleep, but also during epileptiform-suppressing desynchronized episodes of waking and REM sleep supports the view that FRs are the product of pathological neuronal hypersynchronization associated with seizure-generating areas.

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

“…The SEEG was analyzed in bipolar montages of consecutive contacts. We selected epochs of 10 min of slow-wave sleep, considering that HFOs occur more frequently during this stage (Staba et al, 2004;Bagshaw et al, 2009). We used the Harmonie software to compute spectral trends in the delta, alpha, and beta bands for the intracranial EEG and the power of the chin EMG with a 30-s time resolution.…”

Glutamatergic pre-ictal discharges emerge at the transition to seizure in human epilepsy

“…6a left). A subset of pyramidal cells (7/39) increased firing in the 25 ms before the onset of PID field potentials (19±26 Hz, 95% CI: [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], n=30 events from 3 cells; Fig. 6a right).…”

A Simple Statistical Method for the Automatic Detection of Ripples in Human Intracranial EEG

“…This is somewhat expected because the RMS detector was initially designed for use with microwire data, and it has been shown that the characteristics of high frequency activity depend on electrode size (Worrell et al 2008). However, the RMS detector has been successfully implemented in various recording schemes, including microwire electrodes (Staba et al 2002;Staba et al 2004) and macro-and microelectrodes Gliske et al 2016). Importantly, the results of our tests demonstrate that good performance is dependent on proper optimization of all parameters, not just the threshold.…”

“…Finally, to be qualified as HFOs, the events were required to have at least six rectified peaks above a second threshold, which was three standard deviations above the mean of the rectified filtered signal. Originally, the detector was designed to identify HFOs in hippocampus and entorhinal cortex microwire recordings in humans (Staba et al 2002), and it was used in the studies of microelectrode recordings in temporal regions (Staba et al 2004;Staba et al 2007). …”