Auditory processing across the sleep-wake cycle: Simultaneous EEG and fMRImonitoring in humans

We combined fMRI and EEG recording to study the neurophysiological response s associated with auditory stimulation across the sleep-wake cycle. We foun d that presentation of auditory stimuli produces bilateral activation in au ditory cortex, thalamus, and caudate during both wakefulness and nonrapid e ye movement (NREM) sleep. However, the left parietal and, bilaterally, the prefrontal and cingulate cortices and the thalamus were less activated duri ng NREM sleep compared to wakefulness. These areas may play a role in the f urther processing of sensory information required to achieve conscious perc eption during wakefulness. Finally, during NREM sleep, the left amygdala an d the left prefrontal cortex were more activated by stimuli having special affective significance than by neutral stimuli. These data suggests that th e sleeping brain can process auditory stimuli and detect meaningful events.