, Volume 1, Issue 1, pp 63-75

Conflicting results in EEG alpha feedback studies

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Abstract

Success or failure of EEG feedback training for alpha enhancement can depend on how alpha activity is quantified and fed back. Alpha-enhancement failures usually employ a percent time(%) technique; successes typically use amplitude integration(ε). To dramatize the differences between percent and integration techniques, we derived both measures simultaneously from left occipital(O 1 ) and left central(C 3 ) sites for 16 male subjects who were given 5.6 hours of integrated alpha feedback from the midline occipital(Oz ) site. At both the O 1 and C 3 sites the integrated and percent measures were not equivalent and not linearly related. Statistically significant differences in the(integrated, percent) correlation coefficients(z-transformed) were observed under the different recording conditions: alpha enhancement, alpha enhancement, alpha suppression, and baselines. Theoretical discussion of integration and percent techniques is given and the adoption of amplitude integration measures and feedback stimuli is strongly advocated.

This study was supported by the following grants and contracts: National Institute of Mental Health (NIMH) Predoctoral Fellowship #1 F01 MH51704-01, NIMH General Research Support Grant #LPNI 185, and a Langley Porter Neuropsychiatric Institute Postdoctoral Fellowship (Interdisciplinary Training Program, NIMH #7082) to James V. Hardt, and by NIMH Research Scientist Development Award 2K02 MH38897, NIMH Research Grant #1 R01 MH24820, Office of Naval Research (ARPA) Contract N00014-70-C-0350, and Instruction and Research Funds, Computer Center Accounts (UCSF) #1431 and #1437 to Joe Kamiya.