Real-Time Single Trial Phase Synchrony Detection in Physiological Signals

Abstract

Physiological signals are recorded through electrodes that sense electrical activity in the biological systems. Synchronization among physiological signals is important for studying the communication mechanisms occurring within and between different physiological systems (e.g. EEG-EEG or EEG-EMG). The aim of this study is to compute the level of synchronization in physiological signals during single trials in real time. Synchronization is the rhythmic adjustments of self-sustained oscillators because of coupling (e.g. classic clock pendulum). Phase synchronization is the relative temporal constancy of phases of two physiological signals that shows the electrical/oscillatory activity in the body. This oscillatory/electrical activity is called “phase locked” if it occurs time-locked to a stimulus event. A method called Single Trial Phase Locking Value (SPLV) is used in this study for computation of synchrony levels among physiological signals during single trials in real-time. Two types of physiological signals i.e. EEG and EMG are used in this study. First, SPLV method was developed for offline studies of phase synchronization for EEG data. Based on SPLV results for offline data, SPLV offline method was optimized for use in real-time. For real-time, EEG and EMG signals were used following a finger tapping protocol. For EMG, SPLV’s were computed by placing electrodes at mid-belly point and First Dorsal Interosseous (FDI) muscles of both hands. For EEG, electrodes were placed at left and right sensory motor cortex (C3 and C4 according to international 10-20 system). Subjects were asked to perform the same finger tapping task. Abstract xii Real-time single trial phase synchronization can be used to study the plasticity induced in different parts of the brain. This study can be further utilized for neuro-muscular studies for rehabilitation applications. This method can also be used to study diverse functions such as motor activity, working memory, associative memory, attention, object recognition, awareness, perceptual organization or muscular activity during a specific task in real-time.