Theta phase gamma power synchronization in clinical electroencephalography

Abstract

The electroencephalography (EEG) bears the possibility to investigate oscillatory processes in the human brain. There has been a growing body of evidence that suggests EEG and quantitative electroencephalography (QEEG) abnormalities are found in a high proportion of psychiatric patients. But it has been often regarded as too nonspecific. Therefore, in spite of having abundant advantages such as non-invasiveness, less-discomfort, and economy of time and cost, the clinical application of QEEG is considered to be limited and adjunctive. Recently, The potential role of cross-frequency phase-amplitude synchronization for the explanation of cortical information processing has been emerging in the human EEG. There has been particular interest in the modula-tion of the amplitude of high-frequency oscillations by the phase of low-frequency oscillations. In the present work, theta-phase gamma-amplitude coupling (TGC) was introduced to the scalp EEG and was evaluated for clinical application. At first, we investigated the relationship between TGC and scores on memory tasks. A total of 31 elderly subjects performed a spatial delayed match-to-sample task (SDMST) during EEG recording. We also evaluated performance on the delayed figure recall (DFR) and delayed verbal recall (DVR) tasks for memory ability. Correlation analysis showed that increases in TGC in the parietal area were significantly corre-lated with increases in the DFR score. In addition, TGC was significantly correlated with the accuracy rate on the SDMST and age. The results indicate that TGC could be a useful biophysiological marker of memory ability. Second, we used resting EEG to examine the relationship between risk-taking propensity and TGC. Recent evidence has suggested that a deficiency in the top-down control of the prefrontal cortex on the subcortical structures may be responsible for risky human behavior. This weakness in top-down control may be reflected as changes to the TGC in scalp EEG. We record...