title: Serotonin affects movement gain control in the spinal cord.
abstract: A fundamental challenge for the nervous system is to encode signals spanning many orders of magnitude with neurons of limited bandwidth. To meet this challenge, perceptual systems use gain control. However, whether the motor system uses an analogous mechanism is essentially unknown. Neuromodulators, such as serotonin, are prime candidates for gain control signals during force production. Serotonergic neurons project diffusely to motor pools, and, therefore, force production by one muscle should change the gain of others. Here we present behavioral and pharmaceutical evidence that serotonin modulates the input-output gain of motoneurons in humans. By selectively changing the efficacy of serotonin with drugs, we systematically modulated the amplitude of spinal reflexes. More importantly, force production in different limbs interacts systematically, as predicted by a spinal gain control mechanism. Psychophysics and pharmacology suggest that the motor system adopts gain control mechanisms, and serotonin is a primary driver for their implementation in force production.
authors.affiliation: Department of Psychology, Peking University, Beijing, China 100871, wei.kunlin@pku.edu.cn.
authors.forename: Kunlin
authors.initials: K
authors.lastname: Wei
authors.affiliation: Departments of Physical Medicine and Rehabilitation, Physiology, and Applied Mathematics, Northwestern University, Chicago, Illinois 60611, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and.
authors.forename: Joshua I
authors.initials: JI
authors.lastname: Glaser
authors.affiliation: Department of Psychology, Peking University, Beijing, China 100871.
authors.forename: Linna
authors.initials: L
authors.lastname: Deng
authors.affiliation: Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois 60607.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Thompson
authors.affiliation: Departments of Physical Medicine and Rehabilitation, Physiology, and Applied Mathematics, Northwestern University, Chicago, Illinois 60611, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and.
authors.forename: Ian H
authors.initials: IH
authors.lastname: Stevenson
authors.affiliation: Department of Psychology, Peking University, Beijing, China 100871.
authors.forename: Qining
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Departments of Physical Medicine and Rehabilitation, Physiology, and Applied Mathematics, Northwestern University, Chicago, Illinois 60611, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois 60607.
authors.forename: Thomas George
authors.initials: TG
authors.lastname: Hornby
authors.affiliation: Departments of Physical Medicine and Rehabilitation, Physiology, and Applied Mathematics, Northwestern University, Chicago, Illinois 60611, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Heckman
authors.affiliation: Departments of Physical Medicine and Rehabilitation, Physiology, and Applied Mathematics, Northwestern University, Chicago, Illinois 60611, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, and.
authors.forename: Konrad P
authors.initials: KP
authors.lastname: Kording
mesh_terms: D015283:Citalopram / Q000494:pharmacology; D003533:Cyproheptadine / Q000494:pharmacology; D004311:Double-Blind Method; D006801:Humans; D009046:Motor Neurons / Q000502:physiology; D009068:Movement / Q000187:drug effects / Q000502:physiology*; D011601:Psychophysics; D012026:Reflex, Stretch / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D014953:Wrist / Q000502:physiology
chemical_list: D015283:Citalopram; D003533:Cyproheptadine; D012701:Serotonin; D012702:Serotonin Antagonists; D017367:Selective Serotonin Reuptake Inhibitors
keywords: efficient control; gain control; neuromodulation; pharmacology; serotonin; spinal cord