Steady or changing? Long-term monitoring of neuronal population activity

Highlights • We review in vivo chronic extracellular recording and two-photon calcium-imaging studies that address the question of the stability of neuronal population activity. • Chronic two-photon calcium imaging has become a powerful tool for analyzing the long-term stability and plasticity of neuronal activity. • Sensory cortex contains stable subnetworks of highly active neurons embedded in a sea of relatively unresponsive cells. • Throughout the cortex, neuronal activity may be adaptively stabilized by learning.