We examined which aspects of cortical processing are affected by sleep deprivation (SD), and whether they can already be identified in early sensory regions. We recorded spiking activity in rat auditory cortex along with polysomnography while presenting sounds during SD followed by recovery sleep. We found that certain aspects of auditory processing (frequency tuning, onset responses, and spontaneous firing rates) were largely unaffected by SD. By contrast, SD reliably decreased entrainment to rapid (≥20 Hz) click-trains, increased population synchrony, and increased silent periods induced by the sounds as is often observed during sleep, even when ongoing activity was similar. Recovery NREM sleep was associated with similar effects as SD with even greater magnitude, while auditory processing during REM sleep was similar to vigilant wakefulness.