Imaging the sleeping brain

Abstract

In the December issue of Neuron, a research group at the Institute of Neurology, UK, has reported that a human sleeping brain can be influenced by external auditory stimuli in a stimulus-specific manner. Using fMRI images, researchers found that saying the participant's name evoked a greater activation compared with a generic beep in orbitofrontal regions and the amygdaloid complex in both awake and sleep states. Amazingly, the activation in response to the name stimulus was greatest during non-REM sleep, when these regions are normally deactivated. This suggests that during sleep, important external information can reactivate neural circuits to a higher level compared with that achieved when awake. The implications of this study extend beyond sleep research and auditory processing to touch upon issues of consciousness in normal and altered states.