Segregation of the thalamic alpha rhythm from cortical alpha activity using the Savit-Green S-statistic and estimated correlation dimension

Author(s): Duke, D. W.

Journal/Book: Int J Psychophysiol. 1997; 26: PO Box 211, 1000 AE Amsterdam, Netherlands. Elsevier Science BV. 263-271.

Abstract: The large-amplitude, occipital alpha rhythm of the human electroencephalogram (EEG) is associated in normal subjects with a state of relaxed wakefulness. We analyzed resting eyes-open and eyes-closed human EEG data using three measures: power in the 8-12-Hz alpha frequency band, estimated correlation dimension (D-2), and the Savit-Green S-statistic. At occipital loci, two groups of points were evident in the scatterplot of S vs. Estimated D-2. Group A was of higher dimension and consisted of predominantly eyes-open records. Group B was of lower dimension and consisted of more eyes-closed than eyes-open records. Furthermore, Group B had a broad range of alpha power, with alpha power being negatively correlated with estimated D-2 (higher alpha power associated with lower dynamical complexity). In contrast, Group A had a very small range of low alpha power, and was positively correlated with estimated D-2 (higher alpha power associated with increased dynamical complexity). Our results indicate that Group B EEG (the alpha rhythm) and Group A EEG (EEG containing 'other' alpha activity) have fundamentally different dynamical properties.

Note: Article Pritchard WS, Rj Reynolds Tobacco Co, Bowman Gray Tech Ctr, Psychophysiol Lab, Res & Dev, Winston Salem,NC 27102 USA

Keyword(s): human electroencephalogram; Savit-Green S-statistic; alpha activity; EEG; MECHANISMS; ATTRACTOR; DYNAMICS; BRAIN

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