| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Faculty of Dentistry, University of Toronto, Canada
Institut de Physiologie, Université de Fribourg, Switzerland
1. The details of the organization of the motor cortex and its anterior and posterior border were investigated in three monkeys by a combination of techniques including intracortical microstimulation (i.c.m.s.), electrophysiological recording of cutaneous and muscle afferent inputs to single cortical neurones, and electrophysiological and anatomical identification of corticospinal neurones; in addition, data from these methods were related to cortical cytoarchitecture.
2. Almost 5000 individual cortical loci were tested with i.c.m.s. in the unanaesthetized monkeys. In this paper, we particularly consider the organization of the forelimb motor representation, and its relation to the representation of other parts of the body. I.c.m.s. thresholds of about 5 µA were common for evoking twitch movements and e.m.g. responses in distal forelimb and face, jaw and tongue muscles, but proximal forelimb, trunk and hind-limb movements also sometimes had such low thresholds.
3. The fingers were found to be represented nearest the central sulcus, with horseshoe-shaped bands of cortical tissue representing progressively more proximal muscles situated around this central `finger core'.
4. Cytoarchitectonically, the cortex having these low-threshold motor effects was characteristic of area 4. There was also a close fit between the extent of this `excitable cortex' and the extent of densely spaced corticospinal neurones identified electro-physiologically or with horseradish peroxidase labelling. In subsequent mapping of forelimb afferents to the cortex when the animal was deeply anaesthetized, low-threshold and short-latency responses to muscle nerve stimulation were rarely found in this `excitable cortex'.
5. The anterior border could be clearly established by i.c.m.s. and by the sharp boundary of corticospinal neurones. It was noted that the motor cortex extends rostrally beyond area 4 and its anterior border appears to reside in the posterior part of area 6a
(Vogt & Vogt, 1919) although it is difficult to establish the precise transition from area 4 to area 6.
6. Posteriorly, the `micro-excitable cortex' was found to be limited to regions cytoarchitectonically delineated as area 4 and did not include area 3a. On the other hand, low-threshold forelimb proprioceptive afferent inputs appeared restricted to area 3a neurones in the deeply anaesthetized animal. Corticospinal neurones were very dense in area 4, and there was a clear decrease in their occurrence in more caudal areas. However, scattered nests of corticospinal neurones were noted in areas 3a, 3b, 2, 1 and 5. It remains to be seen whether these scattered nests could be directly involved in motor control or whether they may modulate ascending somatosensory transmission, and whether they rely on sensory feed-back or inputs from other central areas for their spinal effects.
This article has been cited by other articles:
|
|
 |
|
  R. D. Andreatta Sensorimotor Elements of the Orofacial System: Reviewing the Basics Speech Science and Orofacial Disorders, October 1, 2008; 18(2): 51 - 61. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. D. Meier, T. N. Aflalo, S. Kastner, and M. S. A. Graziano Complex Organization of Human Primary Motor Cortex: A High-Resolution fMRI Study J Neurophysiol, October 1, 2008; 100(4): 1800 - 1812. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Adachi, G. M. Murray, J.-C. Lee, and B. J. Sessle Noxious Lingual Stimulation Influences the Excitability of the Face Primary Motor Cerebral Cortex (Face MI) in the Rat J Neurophysiol, September 1, 2008; 100(3): 1234 - 1244. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Alkadhi, G. R. Crelier, S. H. Boendermaker, X. Golay, M.-C. Hepp-Reymond, and S. S. Kollias Reproducibility of Primary Motor Cortex Somatotopy Under Controlled Conditions AJNR Am. J. Neuroradiol., October 1, 2002; 23(9): 1524 - 1532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Yao, K. Yamamura, N. Narita, R. E. Martin, G. M. Murray, and B. J. Sessle Neuronal Activity Patterns in Primate Primary Motor Cortex Related to Trained or Semiautomatic Jaw and Tongue Movements J Neurophysiol, May 1, 2002; 87(5): 2531 - 2541. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. H. Schieber Constraints on Somatotopic Organization in the Primary Motor Cortex J Neurophysiol, November 1, 2001; 86(5): 2125 - 2143. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.-J. Boudreau, T. Brochier, M. Pare, and A. M. Smith Activity in Ventral and Dorsal Premotor Cortex in Response to Predictable Force-Pulse Perturbations in a Precision Grip Task J Neurophysiol, September 1, 2001; 86(3): 1067 - 1078. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.-J. Boudreau and A. M. Smith Activity in Rostral Motor Cortex in Response to Predictable Force-Pulse Perturbations in a Precision Grip Task J Neurophysiol, September 1, 2001; 86(3): 1079 - 1085. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-X. Qi, I. Stepniewska, and J. H. Kaas Reorganization of Primary Motor Cortex in Adult Macaque Monkeys With Long-Standing Amputations J Neurophysiol, October 1, 2000; 84(4): 2133 - 2147. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Tokuno and A. Nambu Organization of Nonprimary Motor Cortical Inputs on Pyramidal and Nonpyramidal Tract Neurons of Primary Motor Cortex: An Electrophysiological Study in the Macaque Monkey Cereb Cortex, January 1, 2000; 10(1): 58 - 68. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. E. Martin, P. Kemppainen, Y. Masuda, D. Yao, G. M. Murray, and B. J. Sessle Features of Cortically Evoked Swallowing in the Awake Primate (Macaca fascicularis) J Neurophysiol, September 1, 1999; 82(3): 1529 - 1541. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. C. Cramer, S. P. Finklestein, J. D. Schaechter, G. Bush, and B. R. Rosen Activation of Distinct Motor Cortex Regions During Ipsilateral and Contralateral Finger Movements J Neurophysiol, January 1, 1999; 81(1): 383 - 387. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Boussaoud, C. Jouffrais, and F. Bremmer Eye Position Effects on the Neuronal Activity of Dorsal Premotor Cortex in the Macaque Monkey J Neurophysiol, September 1, 1998; 80(3): 1132 - 1150. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. W. Huntley Differential Effects of Abnormal Tactile Experience on Shaping Representation Patterns in Developing and Adult Motor Cortex J. Neurosci., December 1, 1997; 17(23): 9220 - 9232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. E. Martin, G. M. Murray, P. Kemppainen, Y. Masuda, and B. J. Sessle Functional Properties of Neurons in the Primate Tongue Primary Motor Cortex During Swallowing J Neurophysiol, September 1, 1997; 78(3): 1516 - 1530. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. L. Widener and P. D. Cheney Effects on Muscle Activity From Microstimuli Applied to Somatosensory and Motor Cortex During Voluntary Movement in the Monkey J Neurophysiol, May 1, 1997; 77(5): 2446 - 2465. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. N. Sanes and J. P. Donoghue Dynamic Motor Cortical Organization Neuroscientist, May 1, 1997; 3(3): 158 - 165. [Abstract] [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]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
