Changes in Theta and Gamma Network Oscillations during the Development of Neurodegenerative Disorders (Review)

Abstract

Theta and gamma oscillations registered in the hippocampus and neocortex are necessary for cognitive processes in the brain; their alterations are revealed in many neurological and psychiatric diseases. The most common forms of neurodegenerative disorders, Alzheimer's disease (AD) and temporal lobe epilepsy (TLE) are characterized by the loss of cells and progressive violations of cognitive functions, such as memory. Early diagnosis of diseases is very important for their successful treatment. Many efforts have been done for defining early signs of these diseases. Significant advances have been made in the searching of some AD and TLE reliable biomarkers with using biochemical and imaging approaches. 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. In the present review, the data of recent literature specifying that the coherent analysis of the theta and gamma oscillations can be used in early diagnostics of TLE and AD are considered. These data show that in a brain with the developing neurodegenerative disorder the specific violations of the theta and gamma interaction are observed. We summarize here the data on the alterations of the theta and gamma coherence based on examples from TLE and AD and from models of these diseases. The specific disturbances in interactions of theta-gamma oscillations in hippocampal, hippocampal-entorhinal, hippocampal-prefrontal, and hippocampal-septal networks were revealed in the epileptic brain. In the AD models, marked changes were observed in the theta-gamma coupling in the subiculum, an output region of the hippocampus. In addition, a decreased theta-gamma interaction between the hippocampus and the parietal cortex as well as between the hippocampus and the prefrontal cortex was also shown.

Toward the Identification of Neurophysiological Biomarkers for Alzheimer’s Disease in Down Syndrome: A Potential Role for Cross-Frequency Phase-Amplitude Coupling Analysis

“…Synchronous activity of neural networks generates rhythmic voltage oscillations at multiple frequencies, which are conventionally classified as ultraslow (<1 Hz), delta (1-4 Hz), theta (4-8 Hz), alpha (8)(9)(10)(11)(12), beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), slow gamma , fast gamma , and ultra-fast gamma oscillations [25]. Switches between brain states are underlined by changes in the global pattern of neural activity, and these statedependent changes can be well distinguished by electrophysiological recordings [28].…”

“…Although further electrophysiological studies in humans may contribute to the open debate of to what extent theta and gamma oscillations detected by human scalp EEG recordings reflect rhythms generated by neocortical and/or hippocampal areas [90], one cannot ignore the potential that EEG-based measurements have shown as a tool for studying brain rhythms and their dynamic interactions. Accordingly, there has been an increasing interest in the study of theta-gamma PAC as a potential index in neurological and psychiatric disorders [11][12][13].…”

“…Such inter-frequency interaction can be achieved, for example, via phaseamplitude coupling (PAC), wherein the amplitude (or power) of a fast oscillation is modulated by the phase of a slower oscillation [4,5]. The modulation of gamma amplitude by theta phase, which is the most-studied type of PAC, has been implicated in multiple cognitive processes [5][6][7][8][9][10], and alterations in this interaction have been reported in many brain disorders [11][12][13]. For example, it has been suggested that cross-frequency interactions between neural oscillations may be impaired in early stages of Alzheimer's disease (AD) [14][15][16][17], and such changes have also been associated with the progression from mild cognitive impairment (MCI) to AD and dementia [18,19].…”

Brain Electrical Bioactivity Informational Specifics in Relation to Behavioural and Cognitive Functions in Children with Learning Difficulties

“…This, first of all, refers to the organization of the system of perception and attention, which allows us to consider this stage of development as extremely important for improving the information processes that form the basis of cognitive activity [9,10]. At the same time, great importance has always been attached to the ratio of involuntary and voluntary attention prevailing at this age since both of them bear features of immaturity at this age [11]. According to modern ideas about the age norm (normal development), the development of a child’s body, the age from 4 to 7 years, is considered the period of the first childhood and the period of 8-11 years - the second childhood [12].…”