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Séminaire - Edgardo TalpalarSpinal circuits generating rhythm and pattern for motor activities

Abstract :

Motor responses serve vital functions and are the output of most behaviors. Reconstructing the central nervous system (CNS) when damaged by injury or disease requires knowing the architecture of its circuits. The motor system displays eloquent experimental instances of how the CNS generates function. Basic motor acts show sequential temporal repetition of stereotypical events (rhythm) and of each moving segment with respect of other parts of the body (pattern). The neural circuits that produce rhythm and pattern for locomotion, postural control and other basic motor functions are now partially understood. But many basic questions are still unanswered. Keeping static upright position may rely only on supraspinal excitation of motor neurons.

Are other spinal neurons needed for posture? Moreover, the repetitive fashion of locomotor cycles requires neural components to close the ‘locomotor loop’. Which are these components? Are circuit components of locomotor, postural and other basic motor acts recombined and shared (modularity), or independent of each other?
To answer these questions we use intersectional genetics together with molecular, cellular and molecular methods, electrophysiology and behavior in perinatal and adult mice. Our results show that spinal Vglut2-dependent excitatory neurons are essential for locomotion and posture, while both excitatory and inhibitory spinal neurons are essential for full-range locomotor rhythm generation.
The V0 neurons, shown to mediate left-right alternating pattern for locomotion, are also indispensable for proper postural control and scratch-reflex performance.

These results show the essentiality of spinal neurons for specific motor acts, but also that at least certain subgroups are recombined and shared for the generation of different motor acts suggesting modularity. This basic knowledge is crucial for design of treatments for CNS degeneration.