Brain dynamics in theta and alpha frequency bands and working memory performance in humans

In this study non-linear and linear global electroencephalogram (EEG) chang es during a visual working memory task were studied using a separate analys is of theta, lower alpha and upper alpha band filtered data. EEGs were reco rded in 21 healthy subjects (62.5 year; SD 2.1; 12 females, nine males) dur ing an eyes-closed no-task condition and a working memory condition. Coarse -grained dimension was estimated for both conditions from spatially embedde d EEG data filtered in the theta band and both alpha bands. Linear measures of coupling and mean amplitude were also computed. During the working memo ry condition lower alpha band dimension increased. Linear analysis showed a lpha1 band desynchronization, Female subjects had a higher dimension in the theta band as well as more desynchronization in the theta and alpha1 band. Working memory capacity correlated with a lower theta band dimension durin g the no-task condition in female subjects. The increase in alpha1 band com plexity can be interpreted as increased desynchronization corresponding wit h attentional processes. Higher complexity/desynchronization in females see ms to be a more structural phenomenon and may be more intimately related to task performance. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.