Study of Electrical Brain Signal during Verbal Cognitive Assignment

Abstract

Time frequency analysis is used to study the time varying properties of neurophysiological signals.When subject is reading, thinking or watching; various parts of brain gets stimulated.That creates electrical signals known as electroencephalogram. Based on frequency range there are five major brain waves such as alpha, delta, theta, beta and gamma. The purpose of the study was to explore the phase & magnitude synchrony, power spectral density, cross-correlation related changes during different cognitive activities in various frequency bands of EEG. The present study explored bivariate connectivity analysis of EEG signal. EEG was acquired for 7 healthy right handed multilingual subjects during the two cognitive activities such as analytical and syntax-morphology based activity. Linear and non-linear measures of synchronization were applied on the acquired data. Changes in magnitude and phase coherence were noted in frontal, occipital and temporal lobe during the activity. Activity related changes were more prominent in alpha and theta frequency band and less prominent in beta, delta band. During the syntax-morphology increased gamma band activity was observed in coherence. It show the importance of connectivity analysis in the simultaneously acquired electrical brain signals. Such analysis can provide diagnostic value in various neuronal disorders.