Summary
One of the most extraordinary qualities of the mammalian nervous system is its ability to change with experience and throughout its life span. Mammalian brain plasticity is thought to be mainly mediated by neurons. Increased plasticity during specific windows of time during development called “critical periods” allows neuronal circuitry to be shaped. How this phase ends, however, has not been clear. On page 77 of this issue, Ribot et al. (1) show that an unsuspected cellular player—astrocytes—control when experience-dependent wiring of brain circuits is permitted in the developing primary visual cortex (V1). This finding points to possible similar roles of astrocytes or other nonneuronal cells in other neural circuits.