Abstract
To analyze the event-related desynchronization/synchronization (ERD/ERS) attended with the mental load arising while solving two cognitive tasks. The features of the presented visual stimulus determined the type of cognitive task that should be solved. For each experimental task and everybody's subject FFT Analysis module calculated the total power histograms from a fixed frequency band (3-20 Hz or 8-13 Hz) for each 3-second EEG sample with 50 % overlay and all electrodes. From the histograms the software derived two FFT single values--the average Total Power (TP) and Frequency at Maximum Power (FMP). It has been shown that during the solution of cognitive tasks the marked changes of ongoing EEG activity appeared. The short lasting and localized amplitude decrease in rhythmic activity (ERD) and the change of EEG frequency were among the most frequent. The ERD extent was determined by an informational content of processed visual stimuli and by the site of scalp-recording electrode. A higher mental load related to the solution of cognitive tasks shifted the average FM to lower frequencies. The suitability of an analysis of ongoing EEG activity to uncover differences in people's brain activation patterns when engaged in performing cognitively demanding tasks was proved.
Highlights
Berger[2] was the first who proposed the idea that fast changes in brain activity as recorded in human electroencephalogram (EEG) might be related to specific mental activities
The review of Klimesch[6] and monographs of Faber[3, 4] and especially papers presented in the book “Event-Related Dynamics of Brain Oscillations”, edited by Neuper and Klimesch[13] in 2006, confirm it unambiguously
The analysis ran as follows: A visual elimination of distorted records, sorting records into groups according to the type of mental task, digital filtering of records, and cutting digitally filtered records for the Fast Fourier Transform analysis (FFT) – the starting points of the cut segments of EEG record were time-locked to the photodiode signal
Summary
Berger[2] was the first who proposed the idea that fast changes in brain activity as recorded in human electroencephalogram (EEG) might be related to specific mental activities. In 1977, Pfurtscheller and Aranibar[21] described the characteristic change of ongoing EEG (short-lasting decrease/increase in rhythmic activity) that occurs in relation to an event. They designate the change as the “event-related desynchronization/synchronization” or ERD/ERS. Detailed study of ERD, which followed(see e.g. 6, 8, 11, 12, 17, 22, 23, 24) showed that the ERD represents a good electrophysiological correlate of cortical activation related to stimulus processing It gives characteristics of cortical areas preparing to process sensory information or being ready to execute a motor command. The review of Klimesch[6] and monographs of Faber[3, 4] and especially papers presented in the book “Event-Related Dynamics of Brain Oscillations”, edited by Neuper and Klimesch[13] in 2006, confirm it unambiguously
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