Recurrent inhibition in motor systems, a functional analysis in the leech nervous system

LIDIA SZCZUPAK

Sapporo

Congreso; XI International Congress of Neuroethology; 2014

International Society of Neuroethology

Motor systems of invertebrates and vertebrates are constituted by hierarchicalnetworks, where stimulation of neurons at their highest level activates complexsets of movements; at the bottom of the hierarchy, motoneurons and premotorneurons form local networks that determine the spatio-temporal pattern of musclecontraction. Local circuits present a variety of phylogenetically conservedfunctions, among which recurrent inhibition has been repeatedly identified, and yeta clear description of its function(s) has been elusive. Different than classicalreflexes, recurrent inhibition is a feedback mechanism where the activity of themotoneurons is modulated by their output and not by the activity of their targets.In leeches, a recurrent inhibitory circuit has been described, centered around a pairof nonspiking (NS) neurons, that combines chemical and electrical synapses.Functional analysis of this circuit has shown that it exhibits a variety of functions: i)heteronymous motoneurons in leeches are electrically coupled and this coupling ismodulated by NS membrane potential; ii) in the course of crawling NS influencesthe activity of motoneurons through a direct path, and iii) it also influences theactivity of the central pattern generator responsible of this rhythmic behavior