NREM sleep alpha and sigma activity in Parkinson's disease: evidence for conflicting electrophysiological activity?

Sleep EEG spectral patterns were investigated in eight newly diagnosed, non-depressed, non-demented, drug-naïve Parkinson's disease patients compared to nine controls.

Mean relative spectral power density calculated for 0.25 Hz frequency bins and for classical EEG frequency bands.

Differences between patients and controls were most prominent in non-REM sleep, specially around 8.6 Hz (slow alpha), 12.5 Hz (fast alpha/slow sigma) and 15 Hz (fast sigma). Slow alpha showed lower p-values over frontal and occipital electrodes, whereas fast sigma activity was more important on central and parietal sites. Significantly increased NREM sleep alpha activity was found in left and right frontal (Mann-Whitney U=12,000, p=.021; U=14,000, p=.036), left and right central (U=14,000, p=.036), left parietal and left occipital (U=13,000, p=.027; U=15,000, p=.046) areas. Increased sigma activity was found in right frontal (U=14,000, p=.036), left central (U=12,000, p=.021), left and right parietal (U=12,000, p=.021; U=13,000, p=.027) and left occipital (U=15,000, p=.046) areas.

Concomitantly increased scalp EEG alpha and sigma activity was found during NREM sleep in initial Parkinson's disease.

These non-REM sleep microstructure changes may represent evidence for altered electrophysiological mechanisms leading to sleep-wake instability in early disease stages.