A spinal synergy of excitatory and inhibitory neurons coordinates ipsilateral body movements

Abstract

Innate and goal-directed movements require a high-degree of trunk and appendicular muscle coordination to preserve body stability while ensuring the correct execution of the motor action. The spinal neural circuits underlying motor execution and postural stability are finely modulated by propriospinal, sensory and descending feedback, yet how distinct spinal neuron populations cooperate to control body stability and limb coordination remains unclear. Here, we identified a spinal microcircuit composed of V2 lineage-derived excitatory (V2a) and inhibitory (V2b) neurons that together coordinate ipsilateral body movements during locomotion. Inactivation of the entire V2 neuron lineage does not impair intralimb coordination but destabilizes body balance and ipsilateral limb coupling, causing mice to adopt a compensatory festinating gait and be unable to execute skilled locomotor tasks. Taken together our data suggest that during locomotion the excitatory V2a and inhibitory V2b neurons act antagonistically to control intralimb coordination, and synergistically to coordinate forelimb and hindlimb movements. Thus, we suggest a new circuit architecture, by which neurons with distinct neurotransmitter identities employ a dual-mode of operation, exerting either synergistic or opposing functions to control different facets of the same motor behavior.

Spinal cords: Symphonies of interneurons across species

“…V3 neurons, for example, are divided into a local and an ascending population that is important for trot in mice ( Zhang et al, 2022 ). The V2a class, in addition to their role in regulating flexor-extensor activity, has long-range V2a and V2b neurons that are important for ipsilateral body coordination ( Hayashi et al, 2023 ). In limbed vertebrates, that require coordination at and across highly variant regions of the body, it is likely that more examples of such local and long-range divisions with distinct functions will be found for other classes in the future.…”

Neural circuit mechanisms underlying context-specific halting inDrosophila

“…Walking recruits distributed neural activity across the brain [7][8][9][10][11][12] and spinal [13][14][15][16] /nerve cord 17 . When an animal halts, the net output of this widely distributed neural activity dramatically changes to drive the arrest of leg stepping movements.…”