Information processing enabling brain sensory and cognitive performances is typically thought to fully rely on neurons. Yet, the other major cell type in the brain, the astrocytes, has now been shown to play a key role in brain activity and pathology. Astroglial cells can indeed sense neuronal inputs through membrane ion channels, transporters and receptors. They can also respond by transduction pathways, involving for instance calcium signaling, and modulate in turn adjacent neuronal elements by various mechanisms, including uptake or release of neuroactive factors, contact-mediated signaling or plastic physical coverage of neurons. However, comprehensive molecular description of such regulations, their occurrence and impact during physiological or pathological conditions remains to be further described. Furthermore, little is known about the impact of such regulation on perception, behavior and cognition. Unraveling how astrocytes control the activity of neuronal circuits and brain functions is important, not only to advance our comprehension of cognitive functions, but also to provide a novel framework for identifying dysfunctions underlying neurological disorders as well as alternative therapeutic targets.