Examples of compressed 24-h electroencephalogram (EEG)/electromyogram (EMG) recordings and corresponding hypnograms of control, striatal, nucleus accumbens core (NAc) and globus pallidus (GP) lesions. As compared with controls, the striatal and GP lesions resulted in frequent sleep–wake transitions and the appearance of pronounced ultradian oscillation of wakefulness and sleep. In addition, striatal lesions eliminated ultra-long wake bouts (*), which were commonly observed in the control animals. Although the NAc lesions induced more frequent sleep–wake transitions, they did not affect the diurnal pattern and ultra-long wake bouts were preserved. Similar to NAc lesions, GP lesions did not eliminate ultra-long wake bouts. NREM, non-rapid eye movement; REM, rapid eye movement.