EEG Sleep Spindle Frequency Differs between Pure and Diffuse Spindles

E.J. Huupponen, A.J. Saastamoinen, J. Hasan, A.O. Värri, and S.-L.J. Himanen (Finland)


Sleep EEG, sleep spindles, detection, Matching Pursuit


The frequencies of automatically detected synchronous and diffuse EEG sleep spindles were studied in the pre sent work. The term synchronous refers here to a spindle occurring simultaneously in both brain hemispheres in the corresponding EEG-derivations. A pure spindle is such that there is simultaneously a synchronous frontopolar or synchronous central spindle but not both. Simultaneous occurrence of a synchronous frontopolar as well as a syn chronous central spindle is considered to be a diffuse spindle. 12 all-night sleep EEG recordings with a total duration of 91 h 30 min were studied. A total of 24132 synchronous spindles were detected of which 4677 were diffuse spindles. Matching pursuit (MP) approach was used to determine the frequency of each spindle. Between brain hemispheres the spindle frequencies were similar. Both pure and diffuse spindles had higher frequencies centrally than frontally. Interestingly, however, this anter oposterior spindle frequency difference was statistically significantly smaller in diffuse spindles than in pure spin dles, which is a new finding. This may reflect thalamic spindle generation mechanisms.

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