Event-related desynchronization/synchronization (ERD/ERS)
Research Papers
Changes in EEG Spectrograms, Event-Related Potentials and Event-Related Desynchronization Induced by Relative Beta Training in ADHD Children
Background. During the last three decades EEG-based biofeedback (neurofeedback) was used as an alternative treatment for reducing symptoms of ADHD. The goal of this study was to objectively assess the efficacy of biofeedback training by comparing spectrograms, ERPs and ERDs, measured before and after 20 sessions of neurotherapy in a group of ADHD children. Method. Electroencephalogram (EEG), Event related potentials (ERPs) and event related synchronisation/desynchronisation (ERD/ERS) were recorded and computed in auditory GO/NOGO task before and after 15-22 sessions of EEG biofeedback. Eighty-six ADHD children participated in the study. Each session consisted of 30 min of relative beta training. The patients were divided into two groups (good performers and poor performers) depending on their ability to elevate beta activity during sessions. Results. Amplitude of late positive components of evoked potentials in response to NOGOstimuli increased, and event-related synchronisation in alpha frequency band measured at central areas decreased after the whole set of sessions of neurofeedback training in the group of good performers but did not change for the poor performers group. Evoked potential differences between post- and pre-treatment conditions for good performers were distributed over frontal-central areas, reflecting activation of frontal cortical areas associated with beta training. Conclusion. Relative beta training with electrodes located above the frontal areas was associated with an increase of the late positive NOGO component. This activation likely indicates recovery of normal functioning of the executive system
View Full Paper →Long-term stability and consistency of EEG event-related (de-)synchronization across different cognitive tasks
Objective We examined whether task-related band power changes (event-related desynchronization/synchronization; ERD/ERS) that have been linked to individual differences in cognitive ability demonstrate satisfying temporal stability and cross-situational consistency. Methods Multi-channel EEG recordings from 29 adults, assessed at three different occasions over 2 years were examined. Between-session correlations and consistency coefficients (Cronbach's alpha) across the three experiments were evaluated for both, spectral power features of the resting EEG and ERD/ERS estimates while the participants performed some cognitive task (i.e. different elementary cognitive tasks that put comparable demands on the participants). Results ERD/ERS values, while subjects performed a cognitive task, demonstrated satisfactory stability and consistency (i.e. >0.7), whereby the degree of consistency varied as a function of frequency band and brain region. Highest consistency was found for the 8–10Hz ERD in parieto-occipital recording sites (i.e. >0.9). In resting EEG, mean alpha (gravity) frequency was the most stable EEG feature. Conclusions The present data suggest that ERD/ERS phenomena in different narrow frequency bands are rather stable over time and across different situations. The relatively high reproducibility of ERD/ERS promotes the usefulness of this measure in assessing individual differences of physiological activation patterns accompanying cognitive performance. Significance This study addresses the issue of reproducibility of EEG in general and ERD/ERS experiments in particular, which is a prerequisite for both basic research and clinical studies.
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