a, Excitatory pyramidal neurons transmit signals to inhibitory somatostatin-positive (SST) neurons, and vice versa, through neurotransmitting junctions called synapses. In addition, excitatory neurons synapse to one another in a positive feedback loop. b, Spiegel et al.3 report that neural excitation induces expression of the transcription factor Npas4 in both cell types, triggering neuron-specific gene programs. Npas4 expression in SST neurons causes an increase in the number of excitatory synapses to these neurons (blue dashed synapse). Conversely, Npas4 expression in pyramidal neurons increases their inhibition (red dashed synapses). Overall, these dynamic changes dampen excitation.