title: Impact of precision grip tasks on cervical spinal network excitability in humans.
abstract: Motor skill acquisition in the lower limb may induce modifications of spinal network excitability. We hypothesized that short-term motor adaptation in precision grip tasks would also induce modifications of cervical spinal network excitability. In a first series of experiments, we studied the impact of two different precision grip force control tasks (a visuomotor force-tracking task and a control force task without visual feedback) on cervical spinal network excitability in healthy subjects. We separately tested the efficacy of two key components of the spinal circuitry: (i) presynaptic inhibition on flexor carpi radialis (FCR) Ia terminals, and (ii) disynaptic inhibition directed from extensor carpi radialis (ECR) to FCR. We found that disynaptic inhibition decreased temporarily after both force control tasks, independently of the presence of visual feedback. In contrast, the amount of presynaptic inhibition on FCR Ia terminals decreased only after the visuomotor force tracking task. This temporary decrease was correlated with improved tracking accuracy during the task (i.e. short-term motor adaptation). A second series of experiments confirmed these results and showed that the visuomotor force-tracking task resulted also in an increase of the Hmax/Mmax ratio and the slope of the ascending part of the H-reflex recruitment curve. In order to address the role of presynaptic inhibition in the motor adaptation process, we conducted a third series of experiments during which presynaptic inhibition was recorded before and after two consecutive sessions of visuomotor force tracking. The results showed that (i) improved tracking accuracy occurred during both sessions, and (ii) presynaptic inhibition decreased only after the first session of visuomotor force tracking. Taken together, these results suggest thus that the nature of the motor task performed has a specific impact on the excitability of these cervical spinal circuits. These findings also suggest that early motor adaptation is associated with a modulation of presynaptic Ia inhibition in the upper limb.
authors: ER-6 UPMC: Physiologie et physiopathologie de la motricité chez l'Homme-Médecine Physique et Réadaptation, Hôpital Pitié Salpêtrière, 75013 Paris, France. roche.nicolas@rpc.aphp.fr
authors: N
authors: N
authors: Roche
authors: B
authors: B
authors: Bussel
authors: M A
authors: MA
authors: Maier
authors: R
authors: R
authors: Katz
authors: P
authors: P
authors: Lindberg
references: Acta Physiol (Oxf). 2007 Feb;189(2):155-69
references: 17250566
references: Annu Rev Neurosci. 2001;24:807-43
references: 11520919
references: J Physiol. 2005 Oct 1;568(Pt 1):343-54
references: 16051628
references: J Neurosci. 2009 May 6;29(18):5784-92
references: 19420246
references: Trends Neurosci. 2004 Oct;27(10):637-43
references: 15374677
references: J Electromyogr Kinesiol. 2007 Jun;17(3):348-54
references: 16616519
references: Acta Physiol Scand. 1965 Aug;64(4):345-55
references: 5853025
references: J Neurophysiol. 1983 Oct;50(4):743-69
references: 6313870
references: Exp Brain Res. 2004 Nov;159(2):197-205
references: 15549279
references: J Physiol. 1984 Apr;349:519-34
references: 6737302
references: Exp Brain Res. 1995;106(3):418-24
references: 8983985
references: Brain. 2004 Jan;127(Pt 1):182-92
references: 14570822
references: J Physiol. 1987 Oct;391:71-83
references: 3443961
references: Exp Brain Res. 2009 Feb;193(2):213-24
references: 18953529
references: Neurosci Lett. 1994 Apr 11;170(2):203-7
references: 8058188
references: J Physiol. 2007 Mar 1;579(Pt 2):375-88
references: 17170047
references: J Neurophysiol. 2008 Apr;99(4):2000-5
references: 18234977
references: J Neurophysiol. 1994 Jul;72(1):431-42
references: 7965025
references: Clin Neurophysiol. 2006 Aug;117(8):1682-91
references: 16793333
references: Exp Brain Res. 1998 Apr;119(4):415-26
references: 9588776
references: J Physiol. 1989 Sep;416:255-72
references: 2607451
references: Exp Brain Res. 1990;81(1):35-45
references: 2394229
references: J Physiol. 1987 Aug;389:757-72
references: 3681742
references: Trends Neurosci. 1997 Dec;20(12):588-94
references: 9416673
references: J Physiol. 1997 Feb 15;499 ( Pt 1):267-82
references: 9061654
references: J Neurophysiol. 2003 Nov;90(5):3572-8
references: 12917382
references: J Physiol. 1995 Aug 15;487(1):221-35
references: 7473251
references: J Neurophysiol. 2010 May;103(5):2675-83
references: 20237314
references: Brain Res. 1995 Apr 17;677(1):69-81
references: 7606470
references: J Physiol. 1985 Apr;361:379-401
references: 3989732
references: Sports Med. 1985 Mar-Apr;2(2):120-32
references: 3847097
references: Exp Brain Res. 1999 Nov;129(1):1-37
references: 10550500
references: Exp Brain Res. 2006 Jan;168(1-2):203-17
references: 16096782
references: Exp Brain Res. 2001 Mar;137(1):127-31
references: 11310168