Ws. Pritchard et Dw. Duke, SEGREGATION OF THE THALAMIC ALPHA-RHYTHM FROM CORTICAL ALPHA-ACTIVITYUSING THE SAVIT-GREEN S-STATISTIC AND ESTIMATED CORRELATION DIMENSION, International journal of psychophysiology, 26(1-3), 1997, pp. 263-271
The large-amplitude, occipital alpha rhythm of the human electroenceph
alogram (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 scatterp
lot of S vs. estimated D-2. Group A was of higher dimension and consis
ted 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 neg
atively correlated with estimated D-2 (higher alpha power associated w
ith lower dynamical complexity). In contrast, Group A had a very small
range of low alpha power, and was positively correlated with estimate
d D-2 (higher alpha power associated with increased dynamical complexi
ty). Our results indicate that Group B EEG (the alpha rhythm) and Grou
p A EEG (EEG containing 'other' alpha activity) have fundamentally dif
ferent dynamical properties. (C) 1997 Elsevier Science B.V.