Coordination of local and global responses in individual mouse thalamic local interneurons

Inhibitory interneurons, featuring presynaptic release sites and spiking activity in dendrites, present a puzzle in their signal organization and coordination. We investigated this in local interneurons (LINs) of the primary visual thalamus using two-photon calcium imaging in awake mice with both local and full-screen visual stimuli. Dendrites in single LINs showed consistent global responses to full-screen stimuli but varied responses to local stimuli. Dendrites from the same LIN exhibited different receptive fields that followed retinotopic progression. The similarity between dendritic and somatic responses decreased with increasing distance. Weak local stimuli could excite dendrites locally, while salient local stimuli triggered global responses. Salient global stimuli further enhanced motion selectivity, preference consistency, and peak responses. Thus, LINs leverage both local and global dendritic activation to perform spatially-organized, feature-selective, and size-dependent motion processing, providing new insights into the complexity and precision of sensory processing in the early visual system.