Tyssowski, K. M. et al. Neuron 98, 530–546 (2018).

Genes such as Arc have been used as reporters for neural activity; however, hundreds of other genes are induced in response to neuronal activity. Tyssowski et al. analyzed the temporal sequence of these activity-regulated genes (ARGs) in response to sustained or brief activity. The researchers grouped the ARGs into three classes: rapid primary response genes (rPRGs), delayed primary response genes (dPRGs) and secondary response genes (SRGs). rPRGs, dPRGs and SRGs are all expressed after sustained neuronal activity, but only rPRGs are induced by brief activity. On the basis of their different expression profiles, neurons can be classified as either briefly active neurons or neurons with sustained activity via a nearest-neighbor classifier. In turn, analysis of gene expression by single-cell RNA-seq allows one to infer the activity history of neurons, which the researchers demonstrate both in cultured neurons and in mouse visual cortex. NV