Topographical distribution of fast and slow sleep spindles in medicated depressive patients

To compare the properties of sleep spindles between healthy subjects and medicated patients with major depressive episode, including frequency range, spectra power, and spatial distribution of spindle power.

Continuous 16-channel EEG was used to record nocturnal sleep in healthy control subjects and medicated depressive patients. Recordings were analyzed for changes in EEG power spectra and power topography. Additionally, we graphically demonstrated the pattern of spatial distribution of each type of sleep spindle, divided into fast (12.5-14 Hz) and slow spindles (11-12.5 Hz).

Sleep EEG records of depressive subjects exhibited a significantly higher amplitude of slow spindles in the prefrontal region, compared with the healthy controls (P < 0.01). Fast spindles were dominant in the centroparietal region in both depressive patients and the control group. Enhanced slow spindles in the prefrontal region were observed in the medicated depressive patients and not in the healthy controls. The frequency of fast spindles in depressive patients was globally higher than that in healthy participants.

The alteration in sleep spindles seen in medicated depressive subjects may reflect a pharmacological modulation of synaptic function involving the thalamic-reticular and thalamocortical mechanisms.