Sleep and basal forebrain activity: Different patterns of neural activity in the brain control the sleep-wake cycle. However, how this activity contributes to sleep homeostasis remains largely unknown. Adenosine in the basal forebrain is a prominent physiological mediator of sleep homeostasis. Using a newly developed indicator, Peng et al. monitored adenosine concentration in the mouse basal forebrain. There was a clear correlation with wake state and REM sleep. Activity-dependent release of adenosine could also be elicited after optogenetic stimulation of basal forebrain glutamatergic, but not cholinergic, neurons. These findings offer new insights into how neuronal activity during wakefulness contributes to sleep pressure through the release of sleep-inducing factors. Science , this issue p. eabb0556

A fundamental challenge in fluorescence microscopy is the photon shot noise arising from the inevitable stochasticity of photon detection. Noise increases measurement uncertainty and limits imaging resolution, speed and sensitivity. To achieve high-sensitivity fluorescence imaging beyond the shot-noise limit, we present DeepCAD-RT, a self-supervised deep learning method for real-time noise suppression. Based on our previous framework DeepCAD, we reduced the number of network parameters by 94%, memory consumption by 27-fold and processing time by a factor of 20, allowing real-time processing on a two-photon microscope. A high imaging signal-to-noise ratio can be acquired with tenfold fewer photons than in standard imaging approaches. We demonstrate the utility of DeepCAD-RT in a series of photon-limited experiments, including in vivo calcium imaging of mice, zebrafish larva and fruit flies, recording of three-dimensional (3D) migration of neutrophils after acute brain injury and imaging of 3D dynamics of cortical ATP release. DeepCAD-RT will facilitate the morphological and functional interrogation of biological dynamics with a minimal photon budget.