| 研究実績の概要 |
Final year: We started acute brain slice recordings to verify the in-vivo observation of increased cortical responses in NREM sleep. In acute brain slices we can record from identified neuron types and can apply pharmacological agents directly. From the in-vivo result we hypothesized the low cholinergic tone in NREM was responsible for the increased responses. Accordingly, in slice recordings the cholinergic agonist carbachol caused a reduction of evoked optogenetically induced responses. We are now investigating the contribution of excitatory and inhibitory circuits in the cholinergic (wake) depression of cortical responsiveness.
Overall: The cortical circuits are typically studied observing spontaneous oscillations. This only gives a limited view on their function. We optogenetically stimulated defined inputs to cortex to study the function of cortical circuits in wake and sleep. Our investigation produced four main results. 1. Responses in NREM sleep are much larger than in wake. 2. The change in response size is rapid and best explained by changes in neuromodulator tone. 3. The characteristic ON-OFF oscillations in NREM sleep do not modulate the responses in a major way, proving that the OFF state is not a state of active inhibition. 4. We found not sleep-need dependent modulation of cortical response size.
This NREM-disinhibition may help us understand the high prevalence of epileptic seizures in NREM sleep. In addition the shift in excitability in NREM is likely important for sleep functions such as memory consolidation and brain homeostasis.
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