Sensorimotor computation involves a dynamic interplay between incoming sensory information, internally generated knowledge, and task-related goals to formulate action plans. In the rodent whisker system, a pivotal model for active sensing, recent evidence indicates that neuromodulatory neurotransmitters play a key role in shaping whisker position control and influencing context-dependent changes in whisking behavior. As these neurotransmitters are primarily released from subcortical nuclei with widespread projections throughout the central nervous system, understanding the circuits of top-down neuromodulatory control is crucial for unraveling the mechanisms of active sensing. Leveraging the Allen Institute’s Mouse Connectivity database, we present an updated, cell-type-specific map of sensorimotor circuits in the mouse brain. This map encompasses 138 projections, including 54 not previously reported, spanning 18 principal and neuromodulatory neurotransmitter-releasing nuclei within the whisker system. Applying graph network analysis to this connectome, we identify cell-type-specific hubs, sources, and sinks. Our findings offer anatomical evidence of monosynaptic inhibitory projections across all stages of the ascending pathway and demonstrate that neuromodulatory projections enhance network-wide connectivity. These results underscore the significance of neuromodulatory networks in the whisker system, positioning them as pivotal nodes for the integration of sensory and motor information beyond their chemical modulatory roles.
Where top-down meets bottom-up: Cell-type specific connectivity map of the whisker system
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