Egner T. The effects of neurofeedback training on the spectral topography of the electroencephalogram

Clinical Neurophysiology 115 (2004) 2452–2460
Tobias Egnera,*, T.F. Zechb, J.H. Gruzeliera
aDivision of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College London, UK
Department of Clinical Psychology and Psychotherapy, Philipps-University of Marburg, Marburg, Germany
Accepted 16 May 2004
Available online 17 July 2004Abstract
Objective: To investigate the impact of EEG frequency band biofeedback (neurofeedback) training on spectral EEG topography, which is
presumed to mediate cognitive-behavioural training effects. In order to assess the effect of commonly applied neurofeedback protocols on
spectral EEG composition, two studies involving healthy participants were carried out.
Methods: In Experiment 1, subjects were trained on low beta (12–15 Hz), beta1 (15–18 Hz), and alpha/theta (8–11 Hz/5–8 Hz)
protocols, with spectral resting EEG assessed before and after training. The specific associations between learning indices of each individual
training protocol and changes in absolute and relative spectral EEG topography was assessed by means of partial correlation analyses.
Results of Experiment 1 served to generate hypotheses for Experiment 2, where subjects were randomly allocated to independent groups of
low beta, beta1, and alpha/theta training. Spectral resting EEG measures were contrasted prior and subsequent to training within each group.
Results: Only few associations between particular protocols and spectral EEG changes were found to be consistent across the two studies,
and these did not correspond to expectations based on the operant contingencies trained. Low-beta training was found to be somewhat
associated with reduced post-training low-beta activity, while more reliably, alpha/theta training was associated with reduced relative frontal
beta band activity.
Conclusions: The results document that neurofeedback training of frequency components does affect spectral EEG topography in healthy
subjects, but that these effects do not necessarily correspond to either the frequencies or the scalp locations addressed by the training
contingencies. The association between alpha/theta training and replicable reductions in frontal beta activity constitutes novel empirical
neurophysiological evidence supporting inter alia the training’s purported role in reducing agitation and anxiety.
Significance: These results underline the complexity of the neural dynamics involved EEG self-regulation and emphasize the need for
empirical validation of predictable neurophysiological outcomes of training EEG biofeedback protocols.
q 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
Keywords: Physiological self-regulation; EEG biofeedback; Spectral EEG topography; Low beta; beta1; Alpha/theta