CONICET | Buscador de Institutos y Recursos Humanos

The execution of rhythmic motor behaviors requires multiple control mechanisms to adjust the behavioral output, narrowing down the degrees of freedom of a system with multiple active 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 in isolated midbody ganglia. The pair of premotor NS (nonspiking) neurons 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 fictive crawling NS neurons receive inhibitory signals, tuned to the contraction phase of crawling, 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 to DE-3 are correlated to inhibitory signals in NS that, in turn, can restrict the motoneuron activity. To this point the data indicates that the premotor NS neuron acts as an homeostatic element, restricting the motor output. Our future work will determine if this is a global effect onto the motoneuron population or whether it is directed to specific motoneurons, sculpturing the motor pattern.