HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Palmer, E Articles by Ashby, P Search for Related Content PubMed PubMed Citation Articles by Palmer, E Articles by Ashby, P

Playfair Neuroscience Unit, University of Toronto, Toronto Western Hospital, Canada.

1. Magnetic stimulation was applied over the motor cortex in forty-five normal human subjects and peristimulus time histograms (PSTHs) of the discharges of single motor units were used to record changes in the firing probability of individual spinal motoneurones of contralateral upper limb muscles. Recordings were obtained from 153 motor units from fourteen upper limb muscles. 2. For the majority of motor units the initial effect was a short latency facilitation. The estimated central conduction velocities and the rise times of the underlying excitatory postsynaptic potentials (EPSPs) were compatible with monosynaptic facilitation by a fast corticospinal pathway. In some motor units the initial effect was a short latency inhibition. Other units showed no statistically significant changes in firing probability. The proportion of the tested motor units in each of these categories depended on the muscle. All of the sampled units of first dorsal interosseous (1DI) showed short latency facilitation, as did the majority of units in the forearm and the biceps brachii. More than half of the sampled motor units of triceps brachii and deltoid showed either no effect or were inhibited. 3. To compare the net short latency actions of the neurones activated by magnetic stimulation on various motoneurone pools, the magnitude of the short latency facilitation or inhibition in a given motor unit was normalized to the magnitude of the short latency facilitation in the 1DI motor unit of the same subject at the same stimulus intensity, and these data were pooled for a number of subjects. 4. 1DI motoneurones received strong net facilitation (estimated mean EPSP amplitude 2.9 +/- 0.2 mV), the motoneurones of forearm muscles and biceps brachii received weaker net facilitation and triceps brachii and deltoid received no net effect. 5. It is concluded that the short latency corticospinal projections to upper limb motoneurones in humans have a distinct pattern which is similar to that in other primates.

This article has been cited by other articles:

				K. E. Personius, J. L. Karnes, and S. D. Parker NMDA Receptor Blockade Maintains Correlated Motor Neuron Firing and Delays Synapse Competition at Developing Neuromuscular Junctions J. Neurosci., September 3, 2008; 28(36): 8983 - 8992. [Abstract] [Full Text] [PDF]

				P. G. Martin, J. E. Butler, S. C. Gandevia, and J. L. Taylor Noninvasive Stimulation of Human Corticospinal Axons Innervating Leg Muscles J Neurophysiol, August 1, 2008; 100(2): 1080 - 1086. [Abstract] [Full Text] [PDF]

				T. J. Dartnall, M. A. Nordstrom, and J. G. Semmler Motor Unit Synchronization Is Increased in Biceps Brachii After Exercise-Induced Damage to Elbow Flexor Muscles J Neurophysiol, February 1, 2008; 99(2): 1008 - 1019. [Abstract] [Full Text] [PDF]

				M. A. Krutky and E. J. Perreault Motor Cortical Measures of Use-Dependent Plasticity Are Graded From Distal to Proximal in the Human Upper Limb J Neurophysiol, December 1, 2007; 98(6): 3230 - 3241. [Abstract] [Full Text] [PDF]

				J. E. Butler, T. S. Larsen, S. C. Gandevia, and N. T. Petersen The nature of corticospinal paths driving human motoneurones during voluntary contractions J. Physiol., October 15, 2007; 584(2): 651 - 659. [Abstract] [Full Text] [PDF]

				P. G. Martin, S. C. Gandevia, and J. L. Taylor Muscle fatigue changes cutaneous suppression of propriospinal drive to human upper limb muscles J. Physiol., April 1, 2007; 580(1): 211 - 223. [Abstract] [Full Text] [PDF]

				M. L. Harris-Love, M. A. Perez, R. Chen, and L. G. Cohen Interhemispheric Inhibition in Distal and Proximal Arm Representations in the Primary Motor Cortex J Neurophysiol, March 1, 2007; 97(3): 2511 - 2515. [Abstract] [Full Text] [PDF]

				T. L. McIsaac and A. J. Fuglevand Motor-Unit Synchrony Within and Across Compartments of the Human Flexor Digitorum Superficialis J Neurophysiol, January 1, 2007; 97(1): 550 - 556. [Abstract] [Full Text] [PDF]

				C. E. Lang, J. M. Wagner, D. F. Edwards, S. A. Sahrmann, and A. W. Dromerick Recovery of Grasp versus Reach in People with Hemiparesis Poststroke. Neurorehabil Neural Repair, December 1, 2006; 20(4): 444 - 454. [Abstract] [PDF]

				A. G. Richardson, S. A. Overduin, A. Valero-Cabre, C. Padoa-Schioppa, A. Pascual-Leone, E. Bizzi, and D. Z. Press Disruption of Primary Motor Cortex before Learning Impairs Memory of Movement Dynamics J. Neurosci., November 29, 2006; 26(48): 12466 - 12470. [Abstract] [Full Text] [PDF]

				C. I.E. Renner, H. Woldag, and H. Hummelsheim Central Compensation at Short Muscle Range Is Differentially Affected in Cortical Versus Subcortical Strokes Stroke, August 1, 2006; 37(8): 2076 - 2080. [Abstract] [Full Text] [PDF]

				P. G. Martin, J. L. Smith, J. E. Butler, S. C. Gandevia, and J. L. Taylor Fatigue-sensitive afferents inhibit extensor but not flexor motoneurons in humans. J. Neurosci., May 3, 2006; 26(18): 4796 - 4802. [Abstract] [Full Text] [PDF]

				J. A. Johnston, S. A. Winges, and M. Santello Periodic Modulation of Motor-Unit Activity in Extrinsic Hand Muscles During Multidigit Grasping J Neurophysiol, July 1, 2005; 94(1): 206 - 218. [Abstract] [Full Text] [PDF]

				M. C. Park, A. Belhaj-Saif, and P. D. Cheney Properties of Primary Motor Cortex Output to Forelimb Muscles in Rhesus Macaques J Neurophysiol, November 1, 2004; 92(5): 2968 - 2984. [Abstract] [Full Text] [PDF]

				U. Ziemann, T. V. Ilic, H. Alle, and F. Meintzschel Cortico-motoneuronal excitation of three hand muscles determined by a novel penta-stimulation technique Brain, August 1, 2004; 127(8): 1887 - 1898. [Abstract] [Full Text] [PDF]

				G. Todd, J. L. Taylor, and S. C. Gandevia Reproducible measurement of voluntary activation of human elbow flexors with motor cortical stimulation J Appl Physiol, July 1, 2004; 97(1): 236 - 242. [Abstract] [Full Text] [PDF]

				C. E. Lang and M. H. Schieber Reduced Muscle Selectivity During Individuated Finger Movements in Humans After Damage to the Motor Cortex or Corticospinal Tract J Neurophysiol, April 1, 2004; 91(4): 1722 - 1733. [Abstract] [Full Text] [PDF]

				P. Grosse, R. Guerrini, L. Parmeggiani, P. Bonanni, A. Pogosyan, and P. Brown Abnormal corticomuscular and intermuscular coupling in high-frequency rhythmic myoclonus Brain, February 1, 2003; 126(2): 326 - 342. [Abstract] [Full Text] [PDF]

				J. M. Jakobi and C. L. Rice Voluntary muscle activation varies with age and muscle group J Appl Physiol, August 1, 2002; 93(2): 457 - 462. [Abstract] [Full Text] [PDF]

				P. Bawa, G. R. Chalmers, H. Stewart, and A. A. Eisen Responses of Ankle Extensor and Flexor Motoneurons to Transcranial Magnetic Stimulation J Neurophysiol, July 1, 2002; 88(1): 124 - 132. [Abstract] [Full Text] [PDF]

				B. Calancie, M. R. Molano, and J. G. Broton Interlimb reflexes and synaptic plasticity become evident months after human spinal cord injury Brain, May 1, 2002; 125(5): 1150 - 1161. [Abstract] [Full Text] [PDF]

				S. C. Gandevia Spinal and Supraspinal Factors in Human Muscle Fatigue Physiol Rev, October 1, 2001; 81(4): 1725 - 1789. [Abstract] [Full Text] [PDF]

				K. Nakajima, M. A. Maier, P. A. Kirkwood, and R. N. Lemon Striking Differences in Transmission of Corticospinal Excitation to Upper Limb Motoneurons in Two Primate Species J Neurophysiol, August 1, 2000; 84(2): 698 - 709. [Abstract] [Full Text] [PDF]

				J. L. Taylor, G. M. Allen, J. E. Butler, and S. C. Gandevia Supraspinal fatigue during intermittent maximal voluntary contractions of the human elbow flexors J Appl Physiol, July 1, 2000; 89(1): 305 - 313. [Abstract] [Full Text] [PDF]

				M. Weber, A. Eisen, H. G. Stewart, and P. M. Andersen Preserved slow conducting corticomotoneuronal projections in amyotrophic lateral sclerosis with autosomal recessive D90A CuZn-superoxide dismutase mutation Brain, July 1, 2000; 123(7): 1505 - 1515. [Abstract] [Full Text] [PDF]

				R. Chen and R. Garg Facilitatory I Wave Interaction in Proximal Arm and Lower Limb Muscle Representations of the Human Motor Cortex J Neurophysiol, March 1, 2000; 83(3): 1426 - 1434. [Abstract] [Full Text] [PDF]

				A. M. de Noordhout, G. Rapisarda, D. Bogacz, P. Gerard, V. De Pasqua, G. Pennisi, and P. J. Delwaide Corticomotoneuronal synaptic connections in normal man: An electrophysiological study Brain, July 1, 1999; 122(7): 1327 - 1340. [Abstract] [Full Text] [PDF]

				B. J. McKiernan, J. K. Marcario, J. H. Karrer, and P. D. Cheney Corticomotoneuronal Postspike Effects in Shoulder, Elbow, Wrist, Digit, and Intrinsic Hand Muscles During a Reach and Prehension Task J Neurophysiol, October 1, 1998; 80(4): 1961 - 1980. [Abstract] [Full Text] [PDF]

				R. N. Lemon REVIEW {blacksquare} : Mechanisms of Cortical Control of Hand Function Neuroscientist, November 1, 1997; 3(6): 389 - 398. [Abstract] [PDF]

				K. E. Jones and P. Bawa Computer Simulation of the Responses of Human Motoneurons to Composite 1A EPSPS: Effects of Background Firing Rate J Neurophysiol, January 1, 1997; 77(1): 405 - 420. [Abstract] [Full Text] [PDF]

				J. Armand, E. Olivier, S. A. Edgley, and R. N. Lemon Postnatal Development of Corticospinal Projections from Motor Cortex to the Cervical Enlargement in the Macaque Monkey J. Neurosci., January 1, 1997; 17(1): 251 - 266. [Abstract] [Full Text] [PDF]