title: Two distinct interneuron circuits in human motor cortex are linked to different subsets of physiological and behavioral plasticity.
abstract: How does a single brain region participate in multiple behaviors? Here we argue that two separate interneuron circuits in the primary motor cortex (M1) contribute differently to two varieties of physiological and behavioral plasticity. To test this in human brain noninvasively, we used transcranial magnetic stimulation (TMS) of M1 hand area to activate two independent sets of synaptic inputs to corticospinal neurons by changing the direction of current induced in the brain: posterior-to-anterior current (PA inputs) and anterior-to-posterior current (AP inputs). We demonstrate that excitability changes produced by repetitive activation of AP inputs depend on cerebellar activity and selectively alter model-based motor learning. In contrast, the changes observed with repetitive stimulation of PA inputs are independent of cerebellar activity and specifically modulate model-free motor learning. The findings are highly suggestive that separate circuits in M1 subserve different forms of motor learning.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom, Department of Neurology, Graduate School of Medicine, University of Tokyo, Tokyo, 113-8655, Japan, mhamada-tky@umin.net.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hamada
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom, School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Joseph M
authors.identifier: http://orcid.org/0000-0002-0009-4049
authors.initials: JM
authors.lastname: Galea
authors.affiliation: Institute of Neurology, Campus Bio-Medico University, 00128 Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Lazzaro
authors.affiliation: Neurochirurgia CTO, 00145 Rome, Italy, and.
authors.forename: Paolo
authors.initials: P
authors.lastname: Mazzone
authors.affiliation: Department of Neurology and Stroke, and Hertie-Institute for Clinical Brain Research, Eberhard-Karls-University Tübingen, 72076 Germany.
authors.forename: Ulf
authors.identifier: http://orcid.org/0000-0001-8372-3615
authors.initials: U
authors.lastname: Ziemann
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000293:Adolescent; D000328:Adult; D002531:Cerebellum / Q000502:physiology; D018592:Cross-Over Studies; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007395:Interneurons / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: motor cortex; motor learning; plasticity; transcranial magnetic stimulation