Effect of level of consciousness on blood flow and oxygen consumption in the primary sensory area during sensory stimulation

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We investigated how brain responded to auditory stimuli during wakefulness and sleep. First, we explored the methods to obtain electroencephalogram (ECG) in magnetic resonance (MR) imaging system. Although pulse artifact migrated, ECG which could be used to detect sleep stages was obtained. After preliminary experiments, we measured signal change with functional magnetic resonance imaging in six sleep deprived male volunteers. They ranged in age between 25 to 44 years. None of them had sleep, hearing, or neurological problems. After applying electrodes, they laid supine with headphones for auditory stimulation. Measurement was performed with 1.5-T MR system. MR image acquisition was performed ever 12 seconds. Auditory stimulus was alternated every 36 seconds. Region of interest was set to be bilateral transverse gyri, in which primary auditory cortex exists. Results showed that percentage signal change, the number of activated pixels, and the maximal Z-score during sleep were significantly less than those during wakefulness.