Characterizing Hippocampal Oscillatory Signatures Underlying Seizures in Temporal Lobe Epilepsy

Abstract

Temporal Lobe Epilepsy (TLE) is a neurological condition characterized by focal brain hyperexcitability, resulting in abnormal neuronal discharge and uncontrollable seizures. The hippocampus, with its inherently highly synchronized firing patterns and relatively high excitability, is prone to epileptic seizures, and it is usually the focus of TLE. Researchers have identified hippocampal high-frequency oscillations (HFOs) as a salient feature in people with TLE and animal models of this disease, arising before or at the onset of the epileptic event. To a certain extent, these pathological HFOs have served as a marker and a potential target for seizure attenuation using electrical or optogenetic interventions. However, many questions remain about whether we can reliably distinguish pathological from non-pathological HFOs and whether they can tell us about the development of the disease. While this would be an arduous task to perform in humans, animal models of TLE provide an excellent opportunity to study the characteristics of HFOs in predicting how epilepsy evolves. This minireview will (1) summarize what we know about the oscillatory disruption in TLE, (2) summarize knowledge about oscillatory changes in the latent period and their role in predicting seizures, and (3) propose future studies essential to uncovering potential treatments based on early detection of pathological HFOs.

Daily biofeedback to modulate heart rate oscillations affects structural volume in hippocampal subregions targeted by the locus coeruleus in older adults but not younger adults

“…Neuronal over-excitation in the hippocampus is a hallmark of early-stage Alzheimer’s disease and aging (Goutagny and Krantic, 2013; Leal and Yassa, 2015). The hippocampus has various properties that make it prone to high excitability that produces seizures (Huberfeld et al, 2015; Mokhothu and Tanaka, 2021). Consistent with the observations of hippocampal hyperexcitation in Alzheimer’s disease, the disease is associated with increased risk of epileptic seizures (Xu et al, 2021).…”

Preventing Long-Term Brain Damage by Nerve Agent–Induced Status Epilepticus in Rat Models Applicable to Infants: Significant Neuroprotection by Tezampanel Combined with Caramiphen but Not by Midazolam Treatment

“…neuronal loss and atrophy were focused on the hippocampus and the amygdala because: 1) Both structures are severely damaged by nerve agent-induced SE (Shih et al, 2003;Aroniadou-Anderjaska et al, 2009;Apland et al, 2010); 2) the hippocampus plays a central role in mnemonic functions (Kesner and Hopkins, 2006), but it is also prone to generating seizures (Mokhothu and Tanaka, 2021) and is involved in the modulation of anxiety (Engin and Treit, 2007;Fournier and Duman, 2013); and 3) the amygdala is central to seizure initiation and propagation (McDonough et al, 1987;Aroniadou-Anderjaska et al, 2008;Prager et al, 2013), emotional behavior (Šimić et al, 2021), and, particularly, heightened anxiety, which is associated with hyperexcitability in the BLA nucleus (Zhou et al, 2010;Aroniadou-Anderjaska et al, 2012;Pidoplichko et al, 2014;Prager et al, 2014b;Babaev et al, 2018;Daviu et al, 2019). The functions of these two structures are relevant to the most common long-term morbidities that have been found in human victims of the sarin terrorist attacks in Japan, in 1994 and 1995, which are epileptiform abnormalities in the EEG and increased anxiety (Ohtani et al, 2004;Hoffman et al, 2007;Aroniadou-Anderjaska et al, 2016).…”

Unraveling the Neural Circuits: Techniques, Opportunities and Challenges in Epilepsy Research

“…Optogenetic tools have enabled an unprecedented degree of functional circuits mapping in epilepsy research. Temporal lobe epilepsy (TLE), one of the most common forms of focal epilepsy, has been extensively probed by optogenetics (Mokhothu and Tanaka 2021 ; Christenson Wick et al 2017 ). Chen et al investigated the complex circuitry of TLE, suggesting that the long-range SNr-PF inhibitory circuit is involved in regulating seizures in TLE and the deactivation of this circuit could lessen seizure severity (Chen et al 2020 ).…”