Task specific Brain Synchronization in EEG based Speech and Speech Imagery Procedures

Abstract

Abstract Speech being a complicated cognitive skill of the brain, retrieving verbal information from spoken and imagined speech using electrophysiological signal is widely under research to assist the impaired. Electroencephalography has been a successful medium in analyzing the temporal and behavioral changes happening in the brain during any task. In this work an endeavor has been made to distinguish such changes while speaking and envisioning speaking the phoneme of vowel ‘a’. The brain activity was recorded from volunteers while speaking and envisioning speaking the vowel ‘a’ and the basic signal processing routines were applied. The EEG sub-band frequencies were extracted using Fast Fourier Transform (fft). The synchronization indices were assessed for the segmented signals of various sub-band frequencies and the behavioral changes were enlisted. It was seen that the left hemisphere of the brain functioned synchronously during speech task and an inverse phenomenon was observed during the imagery task. Hence the possibility of reconstructing the broken or incomplete speech from the directly recorded brain activity has reached a step ahead towards the milestone. This work exhibits the analysis of brain connectivity parameters while speaking and imagining a vowel ‘a’. Speech imagery can be used to decode the thoughts for patients who are unable to express their thoughts, using non-invasive techniques.