title: Continuous shifts in the active set of spinal interneurons during changes in locomotor speed.
abstract: The classic 'size principle' of motor control describes how increasingly forceful movements arise by the recruitment of motoneurons of progressively larger size and force output into the active pool. We explored the activity of pools of spinal interneurons in larval zebrafish and found that increases in swimming speed were not associated with the simple addition of cells to the active pool. Instead, the recruitment of interneurons at faster speeds was accompanied by the silencing of those driving movements at slower speeds. This silencing occurred both between and within classes of rhythmically active premotor excitatory interneurons. Thus, unlike motoneurons, there is a continuous shift in the set of cells driving the behavior, even though changes in the speed of the movements and the frequency of the motor pattern appear to be smoothly graded. We conclude that fundamentally different principles may underlie the recruitment of motoneuron and interneuron pools.
authors.affiliation: Department of Neurobiology and Behavior, w103 Mudd Hall Cornell University, Ithaca, New York 14853, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: McLean
authors.forename: Mark A
authors.initials: MA
authors.lastname: Masino
authors.forename: Ingrid Y Y
authors.initials: IY
authors.lastname: Koh
authors.forename: W Brent
authors.initials: WB
authors.lastname: Lindquist
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Fetcho
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D001330:Electronic Data Processing / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D007395:Interneurons / Q000502:physiology*; D007814:Larva; D009046:Motor Neurons / Q000502:physiology; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018408:Patch-Clamp Techniques; D010507:Periodicity; D011810:Quinoxalines / Q000494:pharmacology; D011999:Recruitment, Neurophysiological / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology*; D013550:Swimming / Q000502:physiology*; D055366:Synaptic Potentials / Q000187:drug effects / Q000502:physiology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D015027:Zebrafish
chemical_list: D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; C056639:2-amino-5-phosphopentanoic acid; D014633:Valine