A neural complexity measure applied to MEG data in Alzheimer's disease.
OBJECTIVE
A measure of neural complexity (C(N)) (Proc. Natl Acad. Sci. USA 91 (1994) 5033) was applied to magnetoencephalography (MEG) data to test the hypothesis that C(N) decreases when information processing in the brain is impaired, as is the case in patients with Alzheimer's Disease (AD).


METHODS
One hundred and fifty-one channel MEGs were recorded in 20 AD patients and 20 healthy age-matched controls in a resting condition with eyes open (EO) and eyes closed (EC). Artifact-free epochs of 117 channels were selected for analysis. C(N) and D(2) were computed in different frequency bands, and correlated with the MMSE.


RESULTS
The Group x Frequency band interaction was significant for both C(N) and D(2). C(N) was higher in AD, as compared with controls, in the 2-4 and 4-8Hz bands, and D(2) was higher in AD patients in the 14-20 and 20-30Hz bands. The C(N) was higher in the EC condition compared to the EO condition, whereas the D(2) was higher in the EO condition.


CONCLUSIONS
The hypothesis of Tononi et al. (Proc. Natl Acad. Sci. USA 91 (1994) 5033) that the neural complexity decreases in AD patients has to be rejected. However, both neural complexity and the correlation dimension did show differences between controls and AD patients which depended on frequency band.
van Cappellen van Walsum
A-M
AM
Department of Clinical Neurophysiology, VU University Medical Centre, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. am.vancappellen@vumc.nl
Pijnenburg
Y A L
YA
Berendse
H W
HW
van Dijk
B W
BW
Knol
D L
DL
Scheltens
Ph
P
Stam
C J
CJ
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping; D016022:Case-Control Studies; D005123:Eye / Q000503:physiopathology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D018709:Statistics, Nonparametric