| Slow waves are the most prominent feature of nonREM sleep and are visible at the level of the scalp EEG as large amplitude fluctuations at frequencies ranging from slow (< 1 Hz) to delta (1-4 Hz) activity. At the cellular level they are characterized by slow membrane potential fluctuations of cortical neurons consisting of depolarized up states and hyperpolarized down states alternating synchronously over vast cortical territories with a frequency below 1 Hz. Their role in sleep homeostasis, however, is uncertain. Aim of the present analysis was to investigate changes in the activation of brain structures during slow oscillations following sleep deprivation. EEG recordings during baseline sleep and recovery sleep after 40 hours of wakefulness were analyzed (27 channels, 7 healthy young men, slow wave sleep (stages 3 and 4) of the first nonREM sleep episode). Slow oscillations were detected based on the Hilbert transformed EEG of derivation Cz (linked mastoids; band-pass filter 0.5-4.5 Hz; peak-to-peak amplitude > 75 ìV). Source localization using the software LORETA was performed for the down-states (short time interval around the negative peak). Preliminary analysis revealed significant clusters of increased activation after sleep deprivation in the right frontal lobe and decreased activation in both parietal lobes, left limbic and temporal lobes. Further analyses are needed to investigate the contribution of the up-states. Supported by SNSF grant 320000-112674. |
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