Sleep and Waking

Sleep-like states occur in the life of almost every animal studied. While the function of waking is obvious, the function of sleep is unknown. Sleep has been suggested to serve a restorative function in the nervous system. Our lab is trying to understand the function and regulation of sleep by studying different model organisms. We have started our studies by looking at a developmentally regulated sleep-like state in the larva of the nematode Caenorhabditis elegans.

Wake-like state

Sleep-like state

L1 C. elegans larvae cultured inside microcompartments (190 x 190 microns) observed with DIC microscopy. Both movies are speeded up 5 times. Note the reduced movement and lack of feeding (pharyngeal pumping) during the sleep-like state (lower movie).

C. elegans to study sleep-like states

The major advantages of C.elegans as a model to study sleep-like states are the easy genetics allowing the identification of genes that control sleep and the simple nervous system inside the transparent worm allowing non-invasive in vivo observation of neural activity together with behavior. Using this combination of genetics, behavior analysis, and physiology, we hope to uncover important aspects of sleep regulation.

Control of sensory responsiveness through down-regulation of calcium transients in sensory neurons

Reduced spontaneous activity and reduced sensory responsiveness are defining criteria of sleep. We are trying to find out how information processing differs during sleep. We found that information processing is changed during sleep at the level of sensory neurons. Both spontaneous and reduced activity of sensory neurons is reduced during sleep. We are investigating the molecular mechanism of these state-dependent activities. 

Reduced spontaneous and evoked activity of the mechanosensory neuron ALM. Animals expressing the calcium indicator (GCaMP3.35) panneuronally (ALM is shown by the arrow) were cultured in microcompartments and worms were stimulated by dish tapping. The waking worm (upper movie) responds with a backwards movement (escape reflex) and high increase in ALM activity. The sleeping worm (lower movie) does not respond with a backwards movement and ALM responds only weakly to tapping.
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