Precise Subcellular Coordination of Excitation and Inhibition Supports Micron-Scale Dendritic Computations

Abstract

Neural computations are shaped by the competing actions of inhibitory and excitatory synapses. Recent studies indicate that the precise timing and location of inhibition (I) and excitation (E) on the dendritic tree significantly alters how they are transformed into spike output. Assessing the degree to which E/I are spatiotemporally coordinated in intact networks, however, is technically challenging. We measured Ca2+ signals in the dendrites of direction-selective ganglion cells in the mouse retina, which are known to rely on E/I balance for their computation. We found the direction of motion to be encoded by a large number of semi-independent, micron-scale subunits (<10 µm) distributed throughout the ganglion cell’s dendritic arbor, indicating dendritic E/I are coordinated on an exceptionally fine spatiotemporal scale. Computational modeling demonstrates that precise E/I coordination enables multiple computations along a single dendritic branch to occur quasi-independently, which enhances the strength and accuracy of direction encoding at the soma.