Advanced time-series analysis of MEG data as a method to explore olfactory function in healthy controls and Parkinson's disease patients.
OBJECTIVE
To determine whether time-series analysis of magnetoencephalography (MEG) data is a suitable method to study brain activity related to olfactory information processing, and to detect differences in odor-induced brain activity between patients with Parkinson's disease (PD) and controls.


METHODS
Whole head 151-channel MEG recordings were obtained in 21 controls and 20 patients with PD during a 10-min olfactory stimulus paradigm, consisting of 10 alternating rest-stimulus cycles (30 s each), using phenylethyl alcohol administered by means of a Burghart olfactometer. Relative spectral power and synchronization likelihood (SL; an unbiased measure of functional connectivity) were calculated for delta, theta, alpha1, alpha2, beta, and gamma frequency bands.


RESULTS
In controls, olfactory stimulation produced an increase in theta power and a decrease in beta power. In patients with PD, there was a decrease in alpha1 power. No significant interaction between group and condition was found for spectral power. SL analysis revealed a significantly different response to olfactory stimulation in patients with PD compared to controls. In controls, the odor stimulus induced a decrease in local beta band SL. The response in patients with PD involved a decrease in intrahemispheric alpha2 band SL.


CONCLUSIONS
This is the first study to show that time-series analysis of MEG data, including spectral power and SL, can be used to detect odor-induced changes in brain activity. In addition, differences in odor-induced brain activity were found between patients with PD and controls using analysis of SL, but not of spectral power.
Boesveldt
Sanne
S
Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands. sboesveldt@monell.org
Stam
Cornelis J
CJ
Knol
Dirk L
DL
Verbunt
Jeroen P A
JP
Berendse
Henk W
HW
D000368:Aged; D001921:Brain / Q000033:anatomy & histology / Q000503:physiopathology; D001931:Brain Mapping / Q000379:methods*; D004185:Disability Evaluation; D018450:Disease Progression; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D008875:Middle Aged; D009812:Odorants; D000857:Olfaction Disorders / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D009833:Olfactory Pathways / Q000033:anatomy & histology / Q000503:physiopathology; D010300:Parkinson Disease / Q000209:etiology / Q000503:physiopathology*; D010812:Physical Stimulation; D011237:Predictive Value of Tests; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012903:Smell / Q000502:physiology*; D013997:Time Factors