Determination of observer-rated alpha activity during sleep

Patients suffering from chronic fatigue syndrome (CFS) have been
described as having alpha intrusion into sleep. In a separate
study of the relationship between depression and CFS, we
investigated the sleep of CFS patients. We could not detect
any observable alpha anomaly in our group of CFS patients. It
is possible that there is a subgroup of CFS patients in whom
no alpha anomaly is present. However, the sleep
electroencephalogram (EEG) montage used in our study was
different to that employed by previous researchers. This paper
investigates the influence of electrode derivations on the
outcome of observable alpha ratings. We compared simultaneous
recordings of sleep EEG using three commonly employed
montages. Our results indicate that use of the mastoid
reference (montage 1) results in the highest observer-related
alpha. This may suggest that data regarding alpha intrusion
should always be collected using montage 1. However, there is
a possibility that the mastoid electrode is not electrically
silent and is contaminating the data of the referenced
channels. The implications of these findings are discussed in
relation to the validity of alpha intrusion measurement of CFS
and fibromyalgia.

Flanigan MJ, Morehouse RL, Shapiro CM

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