title: Changes in muscle directional tuning parallel feedforward adaptation to a visuomotor rotation.
abstract: When people learn to reach in a novel sensorimotor environment, there are changes in the muscle activity required to achieve task goals. Here, we assessed the time course of changes in muscle directional tuning during acquisition of a new mapping between visual information and isometric force production in the absence of feedback-based error corrections. We also measured the influence of visuomotor adaptation on corticospinal excitability, to test whether any changes in muscle directional tuning are associated with adaptations in the final output components of the sensorimotor control system. Nine right-handed subjects performed a ballistic, center-out isometric target acquisition task with the right wrist (16 targets spaced every 22.5 degrees in the joint space). Surface electromyography was recorded from four major wrist muscles, and motor evoked potentials induced by transcranial magnetic stimulation were measured at baseline, after task execution in the absence of the rotation (A1), after adaptation to the rotation (B), and after a final block of trials without rotation (A2). Changes in the directional tuning of muscles closely matched the rotation of the directional error in force, indicating that the functional contribution of muscles remained consistent over the adaptation period. In contrast to previous motor learning studies, we found only minor changes in the amount of muscular activity and no increase in corticospinal excitability. These results suggest that increased muscle co-activation occurs only when the dynamics of the limb are perturbed and/or that online error corrections or altered force requirements are necessary to elicit a component of the adaptation in the final steps of the transformation between motor goal and muscle activation.
authors.affiliation: Perception and Motor Systems Laboratory, School of Human Movement Studies, University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia. aymar@hms.uq.edu.au
authors.forename: Aymar
authors.initials: A
authors.lastname: de Rugy
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Carroll
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D025461:Feedback, Physiological / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology*; D012399:Rotation; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult
references.citation: J Neurosci. 2005 Nov 23;25(47):10941-51
references.pmid: 16306407
references.citation: Curr Biol. 2004 Feb 3;14(3):252-6
references.pmid: 14761660
references.citation: J Neurosci. 2004 Feb 18;24(7):1666-72
references.pmid: 14973238
references.citation: Adv Exp Med Biol. 2009;629:405-21
references.pmid: 19227512
references.citation: J Neurophysiol. 1995 Jun;73(6):2535-9
references.pmid: 7666158
references.citation: Exp Brain Res. 2001 Feb;136(4):431-8
references.pmid: 11291723
references.citation: J Appl Physiol (1985). 2005 Oct;99(4):1558-68
references.pmid: 15890749
references.citation: Proc Natl Acad Sci U S A. 2000 Feb 29;97(5):2259-63
references.pmid: 10681435
references.citation: Proc Natl Acad Sci U S A. 2009 Feb 3;106(5):1590-5
references.pmid: 19164589
references.citation: Exp Brain Res. 1998 Sep;122(1):23-30
references.pmid: 9772108
references.citation: J Electromyogr Kinesiol. 2000 Aug;10(4):249-53
references.pmid: 10969198
references.citation: J Neurophysiol. 2002 Aug;88(2):991-1004
references.pmid: 12163548
references.citation: Eur J Neurosci. 2004 May;19(10):2888-92
references.pmid: 15147322
references.citation: J Neurophysiol. 2005 Dec;94(6):4244-55
references.pmid: 16079196
references.citation: J Neurophysiol. 2009 May;101(5):2263-9
references.pmid: 19225174
references.citation: J Physiol Paris. 2004 Jul-Nov;98(4-6):331-48
references.pmid: 16298517
references.citation: J Cogn Neurosci. 2006 Dec;18(12):2167-76
references.pmid: 17129198
references.citation: J Neurophysiol. 1999 Jan;81(1):319-33
references.pmid: 9914292
references.citation: Exp Brain Res. 2010 Mar;201(2):191-207
references.pmid: 19830412
references.citation: J Neurophysiol. 2003 Nov;90(5):3270-82
references.pmid: 14615432
references.citation: Exp Brain Res. 2008 Sep;190(2):153-63
references.pmid: 18584164
references.citation: Brain Res. 2008 Mar 4;1197:123-34
references.pmid: 18241844
references.citation: J Physiol. 2000 Sep 15;527 Pt 3:633-9
references.pmid: 10990547
references.citation: J Mot Behav. 1993 Jun;25(2):97-106
references.pmid: 15064201
references.citation: Neuron. 2001 May;30(2):593-607
references.pmid: 11395017
references.citation: J Neurosci. 1999 Oct 1;19(19):8573-88
references.pmid: 10493757
references.citation: Nat Neurosci. 1999 Nov;2(11):1026-31
references.pmid: 10526344
references.citation: J Neurosci. 2007 Dec 5;27(49):13413-9
references.pmid: 18057199
references.citation: J Neurosci. 1991 Sep;11(9):2680-93
references.pmid: 1880544
references.citation: Exp Brain Res. 2006 Aug;173(2):215-22
references.pmid: 16733699
references.citation: J Neurophysiol. 1995 Sep;74(3):1037-45
references.pmid: 7500130
references.citation: Annu Rev Neurosci. 2000;23:393-415
references.pmid: 10845069
references.citation: J Physiol. 2009 Jun 15;587(Pt 12):2949-61
references.pmid: 19403605
references.citation: J Neurophysiol. 1989 Dec;62(6):1201-12
references.pmid: 2600619
references.citation: Nature. 2002 Feb 7;415(6872):640-4
references.pmid: 11807497
references.citation: J Neurophysiol. 2007 Jul;98(1):54-62
references.pmid: 17507504
references.citation: Nat Neurosci. 2003 Aug;6(8):882-90
references.pmid: 12872127
references.citation: Nat Neurosci. 1998 Jul;1(3):230-4
references.pmid: 10195148
references.citation: J Neurosci Methods. 2005 Dec 15;149(2):95-100
references.pmid: 16026850