Segregation of the thalamic alpha rhythms from cortical alpha activity using the Savit-Green S-statistic and estimated correlation dimension.
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 (D2), and the Savit-Green S-statistic. At occipital loci, two groups of points were evident in the scatterplot of S vs. estimated D2. 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 D2 (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 D2 (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.
Pritchard
W S
WS
Psychophysiology Laboratory, Bowman Gray Technical Center, R.J. Reynolds Tobacco Company, Winston-Salem, NC 27102, USA. wally@rjrt.com
Duke
D W
DW
D000328:Adult; D000513:Alpha Rhythm / Q000706:statistics & numerical data*; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography / Q000706:statistics & numerical data; D006801:Humans; D009799:Ocular Physiological Phenomena; D010775:Photic Stimulation; D013788:Thalamus / Q000502:physiology*