 |
|||||
|
|||||
|
|||||
|
|||||
|
|||||
Previous Article | Next Article
The Journal of Neuroscience, October 15, 1998, 18(20):8402-8416
Directional Tuning of Single Motor Units
Uta Herrmann and Martha Flanders Neuroscience Graduate Program, University of Minnesota, Minneapolis, Minnesota 55455
The directional activity of whole muscles has been shown to be broadly and often multimodally tuned, raising the question of how this tuning is subserved at the level of single motor units (SMUs). Previously defined rules of SMU activation would predict that units of the same muscle (or at least of the same neuromuscular compartment) are activated homogeneously with activity peaks in the same "best" direction(s). In the present study, the best directions of SMUs in human biceps (both heads) and deltoid (anterior, medial, and posterior portions) were determined by measuring the firing rate and threshold force of units for recruitment during isometric force ramps in many different directions. For all muscles studied, neighboring motor units could have significantly different best directions, suggesting that each muscle receives multiple directional commands. Furthermore, 17% of the units sampled clearly had a second-best direction, consistent with a convergence of different directional commands onto the same motoneuron. The best directions of the units changed gradually with location in the muscle. Best directions did not cluster into separate groups, thus, not supporting the existence of clearly distinguished neuromuscular compartments. Instead, the results reveal a more gradually distributed activation of the biceps and deltoid motoneuron pools. A model is proposed in which the central control mechanism optimizes the fulfillment of the continuously changing directional force requirements of a movement by gradually recruiting and derecruiting those units ideally suited for the production of the required force vector at any given time.
Key words: motor control; arm movement; reaching; single motor unit; directional tuning; motoneurons
Copyright © 1998 Society for Neuroscience 0270-6474/98/18208402-15$05.00/0
This article has been cited by other articles:
J. A. Pruszynski, I. Kurtzer, T. P. Lillicrap, and S. H. Scott
Temporal Evolution of "Automatic Gain-Scaling"
J Neurophysiol, August 1, 2009; 102(2): 992 - 1003.
[Abstract] [Full Text] [PDF]
S. A. Winges, S. E. Eonta, J. F. Soechting, and M. Flanders
Effects of Object Compliance on Three-Digit Grasping
J Neurophysiol, May 1, 2009; 101(5): 2447 - 2458.
[Abstract] [Full Text] [PDF]
R. M. Enoka, P. Bawa, J. M. Wakeling, D. A. Gabriel, G. Kamen, F. Meyer, D. F. Stegeman, T. van Wessel, M. J. Zwarts, A. Rainoldi, et al.
Spectral properties of the surface EMG can characterize motor unit recruitment strategies.
J Appl Physiol, November 1, 2008; 105(5): 1676 - 1677.
[Full Text] [PDF]
J. E. Butler and S. C. Gandevia
The output from human inspiratory motoneurone pools
J. Physiol., March 1, 2008; 586(5): 1257 - 1264.
[Abstract] [Full Text] [PDF]
M. D. Klein Breteler, K. J. Simura, and M. Flanders
Timing of Muscle Activation in a Hand Movement Sequence
Cereb Cortex, April 1, 2007; 17(4): 803 - 815.
[Abstract] [Full Text] [PDF]
I. Kurtzer, J. A. Pruszynski, T. M. Herter, and S. H. Scott
Primate Upper Limb Muscles Exhibit Activity Patterns That Differ From Their Anatomical Action During a Postural Task
J Neurophysiol, January 1, 2006; 95(1): 493 - 504.
[Abstract] [Full Text] [PDF]
L. E. Sergio, C. Hamel-Paquet, and J. F. Kalaska
Motor Cortex Neural Correlates of Output Kinematics and Kinetics During Isometric-Force and Arm-Reaching Tasks
J Neurophysiol, October 1, 2005; 94(4): 2353 - 2378.
[Abstract] [Full Text] [PDF]
D. Nozaki, K. Nakazawa, and M. Akai
Uncertainty of knee joint muscle activity during knee joint torque exertion: the significance of controlling adjacent joint torque
J Appl Physiol, September 1, 2005; 99(3): 1093 - 1103.
[Abstract] [Full Text] [PDF]
D. Nozaki, K. Nakazawa, and M. Akai
Muscle Activity Determined by Cosine Tuning With a Nontrivial Preferred Direction During Isometric Force Exertion by Lower Limb
J Neurophysiol, May 1, 2005; 93(5): 2614 - 2624.
[Abstract] [Full Text] [PDF]
E. J. Weiss and M. Flanders
Muscular and Postural Synergies of the Human Hand
J Neurophysiol, July 1, 2004; 92(1): 523 - 535.
[Abstract] [Full Text] [PDF]
K. T. Reilly and M. H. Schieber
Incomplete Functional Subdivision of the Human Multitendoned Finger Muscle Flexor Digitorum Profundus: An Electromyographic Study
J Neurophysiol, October 1, 2003; 90(4): 2560 - 2570.
[Abstract] [Full Text] [PDF]
I. Phanachet, T. Whittle, K. Wanigaratne, and G. M. Murray
Functional Properties of Single Motor Units in Inferior Head of Human Lateral Pterygoid Muscle: Task Relations and Thresholds
J Neurophysiol, November 1, 2001; 86(5): 2204 - 2218.
[Abstract] [Full Text] [PDF]
K. E Jones, J. Wessberg, and A. B Vallbo
Directional tuning of human forearm muscle afferents during voluntary wrist movements
J. Physiol., October 15, 2001; 536(2): 635 - 647.
[Abstract] [Full Text] [PDF]
M. L. Hines and N. T. Carnevale
Neuron: A Tool for Neuroscientists
Neuroscientist, April 1, 2001; 7(2): 123 - 135.
[Abstract] [PDF]
|
|
|
|
 |
|