Recurrent Inhibition in Motor Control

MARTINA RADICE; AGUSTÍN SANCHEZ MERLINSKY; LIDIA SZCZUPAK

Congreso; The International Congress of Neuroethology 2022; 2022

The execution of rhythmic motor behaviors requires multiple control mechanisms to adjust the behavioral output, narrowing down the degrees of freedom of a system that involves many units. Leeches crawl on solid surfaces through a succession of elongation and contraction body waves, anchored on the posterior and anterior suckers. Each segmental ganglion contains all the neurons required to produce this rhythmic motor pattern and dopamine evokes fictive crawling (crawling) in isolated midbody ganglia. The pair of premotor NS (nonspiking) neurons, similar to vertebrate Renshaw cells, are connected to motoneurons through a central network that provides recurrent inhibitory signals onto the motoneurons. We aim at understanding the role of NS in the context of crawling. During crawling NS neurons receive inhibitory signals, tuned to its contraction phase, monitored through the DE-3 motoneuron. The results suggest that the inhibitory signals in NS are delivered by the rhythmogenic circuit that controls the motoneuron output. Thus, excitatory signals onto DE-3 are correlated with inhibitory signals in NS that, in turn, could restrict the motoneuron activity. Extracellular recordings combined with spike sorting analysis allowed the simultaneous study of multiple motoneurons in the course of crawling. An NS manipulation that transiently removes the recurrent inhibitory pathway enhanced the firing frequency of motoneurons firing during the contraction phase, including DE-3, and expanded the duty cycle.