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The Journal of Neuroscience, July 15, 2000, 20(14):5483-5495

The Midbrain Precommand Nucleus of the Mormyrid Electromotor Network

Gerhard von der Emde¹, Leonel Gómez Sena^{2, 3}, Rafaella Niso², and Kirsty Grant²

¹ Institut für Zoologie, Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany, ² Unité des Neurosciences Intégratives et Computationnelles, Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette, Cedex, France, and ³ Department of Biomathematics, Faculty of Science, University of the Republic, Montevideo, Uruguay

The functional role of the midbrain precommand nucleus (PCN) of the electromotor system was explored in the weakly electric mormyrid fish Gnathonemus petersii, using extracellular recording of field potentials, single unit activity, and microstimulation in vivo.

Electromotor-related field potentials in PCN are linked in a one-to-one manner and with a fixed time relationship to the electric organ discharge (EOD) command cycle, but occur later than EOD command activity in the medulla. It is suggested that PCN electromotor-related field potentials arise from two sources: (1) antidromically, by backpropagation across electrotonic synapses between PCN axons and command nucleus neurons, and (2) as corollary discharge-driven feedback arriving from the command nucleus indirectly, via multisynaptic pathways.

PCN neurons can be activated by electrosensory input, but this does not necessarily activate the whole motor command chain. Microstimulation of PCN modulates the endogenous pattern of electromotor command in a way that can mimic the structure of certain stereotyped behavioral patterns. PCN activity is regulated, and to a certain extent synchronized, by corollary discharge feedback inhibition. However, PCN does not generally function as a synchronized pacemaker driving the electromotor command chain. We propose that PCN neurons integrate information of various origins and individually relay this to the command nucleus in the medulla. Some may also have intrinsic, although normally nonsynchronized, pacemaker properties. This descending activity, integrated in the electromotor command nucleus, will play an important modulatory role in the central pattern generator decision process.

Key words: electric fish; motor command; pacemaker; corollary discharge; central pattern generator; mormyrid; premotor pathways; sensory motor integration

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Copyright © 2000 Society for Neuroscience  0270-6474/00/20145483-13$05.00/0

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				J. Engelmann, J. Bacelo, E. van den Burg, and K. Grant Sensory and Motor Effects of Etomidate Anesthesia J Neurophysiol, February 1, 2006; 95(2): 1231 - 1243. [Abstract] [Full Text] [PDF]

				B. A. Carlson and C. D. Hopkins Central control of electric signaling behavior in the mormyrid Brienomyrus brachyistius: segregation of behavior-specific inputs and the role of modifiable recurrent inhibition J. Exp. Biol., March 1, 2004; 207(7): 1073 - 1084. [Abstract] [Full Text] [PDF]

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