Event:

Sleep slow waves are known to participate in memory consolidation, yet slow waves occurring under anesthetized states present no positive effects on memory. Here, we shed light onto this paradox, based on a combination of extracellular recordings in vivo, in vitro, and computational models. We find two types of slow waves, based on analyzing the temporal patterns of successive slow-wave events. The first type of slow waves is seen during sleep, while the second type prevails in anesthetized states. Network models of spiking neurons predict that the two slow wave types emerge due to a different gain on inhibitory vs excitatory cells and that different levels of spike-frequency adaptation in excitatory cells can account for dynamical distinctions between the two types. This prediction was tested in vitro by varying adaptation strength using an agonist of acetylcholine receptors, which demonstrated a neuromodulatory switch between the two types of slow waves.
Finally, we show that the first type of slow-wave dynamics is more sensitive to external stimuli, which can explain how slow waves in sleep and anesthesia differentially affect memory consolidation. Finally, we show some potential applications of sleep slow waves, by converting the slow-wave dynamics into sound sequences using computer-generated (electronic) music techniques. Such sound sequences were found to have relaxing effects and can help inducing sleep if the subject listens to its own slow-waves.
In conclusion, sleep slow-waves are useful, not only to understand aspects of computation in brain circuits, but also for applications in music-therapy.

Research supported by CNRS and the EU (Human Brain Project)