Spectral analysis of eeg signal in verbal information processing task

Abstract

The EEG is a non-invasive method to obtain information about neural activity associated with cognitive processes. Its great temporal resolution can provide data regarding the process itself within milliseconds but EEG has poor spatial resolution. The EEG is based on the voltage difference between two (or more) electrodes and represents the summation of numerous neuron activity. The objective of the study reported was to analyze the EEG signal in verbal information processing task using spectral analysis for frequency band and power spectrum extraction. Also we wanted to determine relation between different frequency bands (Theta – θ, Beta – β and Alpha - α) and their power spectrum in different parts of the task (perception, retention and reproduction) for different stimuli (syllables, words, non-words, sentences, picture situations and picture stories). The sample comprised of 9 subjects, right-handed, native speakers of Serbian language with no history of hearing and speech-language disorders. All subjects were not using any medication that may influence EEG signal. After the standard procedure of EEG electrodes placement, subjects listened to a set of auditory presented verbal stimuli. After each stimulus they had a 2 second retention period time followed by a reproduction period. They were given 5 seconds for viewing picture situations and a 15 second period for the picture story followed by a reproduction period. Differences between EEG frequency bands and power as well as their cortical representation in verbal information processing task will be discussed.