| 研究実績の概要 |
We are able to optogenetically activate cortex at pseudo-random intervals and follow the response during waking, NREM sleep and REM sleep. The behavior of the animal was not affected - in particular wake and sleep times were unchanged between unstimulated control recordings and periods of stimulation. We could measure the fluctuation of sleep need by observing the power of delta (0.5-4 Hz) oscillations in the EEG. Delta oscillations and therefore sleep need were highest (as expected) at the beginning of the 12 h light phase and decreased to a minimum at the beginning of the 12 h dark phase. Cortical response amplitude also varied - roughly in parallel with this natural sleep need oscillation. We then sleep deprived animals for 4 h at the beginning of the light phase (normal sleep time for mice) we saw an increase in delta oscillations after the animals were allowed to sleep, indicating increased sleep need. The cortical response did not show an increase under these circumastances.
In conclusion: Either the daily variation in cortical response size is a consequence of circadian rhythms and not sleep need per se, or sleep deprivation was too stressful and stress interferes with this phenomenon.
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