• Voltage imaging and optogenetics reveal state-dependent CA1 dynamics • Intracellular theta oscillation in PCs and VIP cells is strongly shaped by inhibition • Locomotion induces divisive, burst-specific gain reduction in PCs • Coordinated somatic and dendritic E/I input drives the burst-specific gain control Voltage imaging and optogenetics reveal state-dependent CA1 dynamics Intracellular theta oscillation in PCs and VIP cells is strongly shaped by inhibition Locomotion induces divisive, burst-specific gain reduction in PCs Coordinated somatic and dendritic E/I input drives the burst-specific gain control Understanding how behavior modulates neuronal integration is a fundamental goal in neuroscience. We combined voltage imaging with optogenetics to reveal how excitatory (E) and inhibitory (I) inputs modulate spiking output, subthreshold dynamics, and gain in genetically defined CA1 neurons. We imaged pyramidal cells (PCs), vasoactive intestinal peptide (VIP), somatostatin (SST), and parvalbumin (PV) interneurons (INs) and found that locomotion reduced firing in PCs and VIP INs while increasing activity in SST and PV INs. Prolonged optical depolarization revealed that inhibitory inputs substantially contribute to intracellular theta oscillations in PCs and VIP cells. Firing rate-laser intensity (F-I) curves revealed distinct gain modulation across cell types, with a divisive gain reduction in PC bursting during locomotion, while simple spikes are unaffected. A two-compartment model suggested that this effect results from a balanced increase in E/I input to the soma and dendrite. These findings reveal how behavior coordinates E/I signaling to modulate hippocampal computations.
Yang et al. (Sun,) studied this question.