Alterations of Coherent Theta and Gamma Network Oscillations as an Early Biomarker of Temporal Lobe Epilepsy and Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) and temporal lobe epilepsy (TLE) are the most common forms of neurodegenerative disorders characterized by the loss of cells and progressive irreversible alteration of cognitive functions, such as attention and memory. AD may be an important cause of epilepsy in the elderly. Early diagnosis of diseases is very important for their successful treatment. Many efforts have been done for defining new biomarkers of these diseases. Significant advances have been made in the searching of some AD and TLE reliable biomarkers, including cerebrospinal fluid and plasma measurements and glucose positron emission tomography. However, there is a great need for the biomarkers that would reflect changes of brain activity within few milliseconds to obtain information about cognitive disturbances. Successful early detection of AD and TLE requires specific biomarkers capable of distinguishing individuals with the progressing disease from ones with other pathologies that affect cognition. In this article, we review recent evidence suggesting that magnetoencephalographic recordings and coherent analysis coupled with behavioral evaluation can be a promising approach to an early detection of AD and TLE.Highlights Data reviewed include the results of clinical and experimental studies.Theta and gamma rhythms are disturbed in epilepsy and AD.Common and different behavioral and oscillatory features of pathologies are compared.Coherent analysis can be useful for an early diagnostics of diseases.

Amygdala Low-Frequency Stimulation Reduces Pathological Phase-Amplitude Coupling in the Pilocarpine Model of Epilepsy

“…The amygdala LFS reduced this pathologically increased phase-amplitude coupling in all epileptic animals and reduced seizures more effectively in animals having fewer IEDs during DBS, while it did not affect the PAC in healthy animals. The average theta power, which was suggested to be reduced during epileptogenesis [ 50 , 51 , 52 ], was increased in the 30 s periods following the stimulation trains. All these phenomena could have a role in reducing the pathologically increased synchrony observed in epilepsy.…”

“…As the amygdala and hippocampus are strongly interconnected [ 69 ] it is expected that the amygdala LFS could facilitate long-term depression in the hippocampus [ 70 ], and may modulate the network synchronicity in the limbic system [ 71 ]. It was reported by others that physiological theta-power decreased during the interictal periods of human TLE patients and in kainate and pilocarpine rat models of TLE [ 35 , 50 , 51 , 52 , 72 , 73 ]. In-vitro experiments had shown that diazepam (an antiepileptic drug) significantly increases the theta power [ 74 ].…”

Amyloid, APP, and Electrical Activity of the Brain

“…Indeed, AD patients exhibit prominent changes in the function of large brain networks, particularly those involved in memory formation (Sperling and others 2009; Zott and others 2018). These changes include deceleration of the alpha rhythm (8–12 Hz) toward theta frequency (4–8 Hz in humans), aberrant gamma (30–80 Hz) activity (Hamm and others 2015; Kitchigina 2018), and reduction of slow oscillations during sleep (Lucey and Holtzman 2015). Hyperactivity of local networks such as the hippocampus in parallel to dysfunctional connectivity between large brain networks are suggested to underlie cognitive dysfunction in AD (Zott and others 2018).…”

Pathological Aspects of Neuronal Hyperploidization in Alzheimer’s Disease Evidenced by Computer Simulation

“…This conclusion should be experimentally tested in the future. In areas such as the entorhinal cortex, where above 30% of neurons become hyperploid in AD patients (Arendt et al, 2010), this condition could have an important impact not only on the firing frequency but also on the oscillations observed in the neural networks (Kitchigina, 2018), which according to our in silico model requires a high proportion of silent neurons to be relevant.…”