Amazing stuff!
"... researchers from Beth Israel Deaconess Medical Center and Auburn University, have now identified specific neurons that are crucial for this balanced relationship between sleep and wakefulness.
"We have identified neuronal populations that monitor prolonged wakefulness and actively promote sleep," ... "This is an important missing piece of the puzzle in understanding why we become sleepy." ...
This highlighted specific brain areas that reflected time spent awake. Within one of these regions, they further identified two distinct neuronal populations that influence sleep drive: GABAergic and serotonergic neurons in the brainstem.
The activation of both neuronal populations increased the longer the animals stayed awake and declined again after sleep onset. ..."
From the abstract:
"Prolonged wakefulness increases sleep drive and is normally compensated for by increased sleep. This homeostatic regulation of sleep shapes our lives profoundly, but the underlying neural circuit mechanisms remain poorly understood.
Here, we identify wake-activated neurons that regulate sleep drive in mice, using whole-brain activity mapping, targeted neuronal manipulations and electrophysiology.
By comparing whole-brain responses to sleep deprivation, recovery sleep and circadian behaviour, we identify the anterior medial preoptic area and the median raphe as candidate regions that encode sleep deficit. Activating sleep-deprivation-responsive cells in these regions induces increases in sleep duration and intensity that resemble recovery sleep. Conversely, inhibiting deprivation-responsive cells reduces sleep and abolishes the increased sleep propensity usually observed during deprivation.
Neurons in the median raphe that are responsive to sleep deprivation project to subcortical sleep-associated regions and act through the preoptic hypothalamus. These deprivation-sensitive cells include serotonergic neurons and a distinct population of GABAergic neurons, whose intrinsic excitability increases during sleep deprivation.
Co-activation of GABAergic and serotonergic neurons synergistically promotes sleep, whereas
co-inhibition chronically decreases sleep by nearly 70%.
Remarkably, most mice survive despite this marked reduction in sleep, without the compensatory increases in sleep drive or the behavioural deficits typically associated with severe sleep deprivation.
Together, these results define neuronal populations that are activated during wakefulness and are crucial for sleep drive."
Why do we get sleepy? How neurons control sleep drive (original news release) "Why does staying awake inevitably make us sleepy? Researchers ... have identified neuronal populations in the brain that become activated during prolonged wakefulness and are crucial for sleep drive. Their findings provide new insights on how the brain generates the need for sleep."
Sleep-promoting neurons (green) and recently activated neurons (magenta) in the mouse brain.
Fig. 1: Mapping of whole-brain activity reveals correlates of sleep deprivation and recovery.
Fig. 2: Deprivation-TRAP cells promote NREM sleep and slow-wave activity.
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