Sleep Spindles in Magnetoencephalography and Electroencephalography

Abstract

Sleep spindles are one of the characteristic EEG transients of sleep. They are found at a frequency range of 12.5–16.0 Hz and primarily at the vertex. This important pattern, however, is poorly understood neurophysiologically and its origin remains controversial. A previous neuromagnetic study (Hughes et al., 1976) indicated there are few sleep spindles in MEG recordings, however, we observed many MEG spindles above the central vertex (Nakasato et al., 1988). We also indicated that sleep spindles were under three distinct conditions: (i) when they were detected simultaneously in MEG and EEG, (ii) when they were detected alone in MEG without comparable EEG activity, (iii) when they were detected alone in EEG without comparable MEG activity. In this study, we measured the MEG at larger number of point over the scalp to show the spatial distribution of sleep spindles in MEG.