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 Flament, D Articles by Lemon, R N Search for Related Content PubMed PubMed Citation Articles by Flament, D Articles by Lemon, R N

Department of Anatomy, Cambridge University.

1. The effects of magnetic brain stimulation on electromyographic (EMG) activity recorded from arm and hand muscles have been investigated in five infant and six adult macaque monkeys under ketamine sedation. 2. In the adults, brief, short-latency EMG responses could be readily evoked with magnetic stimuli of 40-50% of the maximum stimulator output (1.5 T). 3. In a cross-sectional study of five infant macaques, it was difficult to evoke EMG responses in young infants (less than 5 months old). Clear short-latency responses were first evoked in an animal 5.75 months old. This change was accompanied by an increase in the probability of occurrence of the responses. 4. In a longitudinal study of two infant monkeys over a period ranging from 2.5 to 14.5 months of age we found that clear short-latency responses were first evoked at 4 and at 5.5 months, respectively. In both animals there was a steady fall in response threshold which reached the adult range at 6.5 and 8 months, respectively. EMG responses in animals older than 8 months were indistinguishable from those in adults. 5. In the longitudinal study we also noted that the latency of EMG responses to magnetic brain stimulation declined with age. Since there were no comparable changes in the peripheral conduction time in these animals, we attribute this result to a decrease in central conduction time. 6. Parallel behavioural observations of the natural behaviour of the same animals within a colony indicated that mature precision movements of the fingers were not used until 5-6 months of age. 7. In two adult monkeys, the latency of EMG responses evoked in the extensor digitorum and first dorsal interosseous muscles by direct stimulation of the corticospinal tract, via electrodes implanted in the medullary pyramids, was found to be 0.7-1.7 ms shorter than that of responses evoked by magnetic stimuli. It is argued that at least the earliest component of these latter responses is conducted over the cortico-motoneuronal pathway. 8. The mechanisms likely to contribute to the late appearance of EMG responses to brain stimulation are discussed. One of these is probably the establishment of mature cortico-motoneuronal connections, which are not present at birth.

This article has been cited by other articles:

				J. H. Martin The Corticospinal System: From Development to Motor Control Neuroscientist, April 1, 2005; 11(2): 161 - 173. [Abstract] [PDF]

				Z. Meng and J. H. Martin Postnatal Development of Corticospinal Postsynaptic Action J Neurophysiol, August 1, 2003; 90(2): 683 - 692. [Abstract] [Full Text] [PDF]

				S. Chakrabarty and J. H. Martin Postnatal Development of the Motor Representation in Primary Motor Cortex J Neurophysiol, November 1, 2000; 84(5): 2582 - 2594. [Abstract] [Full Text] [PDF]

				P. Ucles, J.-L. Serrano, and F. Rosa Central Conduction Time of Magnetic Brain Stimulation in Attention-Deficit Hyperactivity Disorder J Child Neurol, November 1, 2000; 15(11): 723 - 728. [Abstract] [PDF]

				T. Lamb and J. F. Yang Could Different Directions of Infant Stepping Be Controlled by the Same Locomotor Central Pattern Generator? J Neurophysiol, May 1, 2000; 83(5): 2814 - 2824. [Abstract] [Full Text] [PDF]

				J. A. Eyre, S. Miller, G. J. Clowry, E. A. Conway, and C. Watts Functional corticospinal projections are established prenatally in the human foetus permitting involvement in the development of spinal motor centres Brain, January 1, 2000; 123(1): 51 - 64. [Abstract] [Full Text] [PDF]

				M. S. George, S. H. Lisanby, and H. A. Sackeim Transcranial Magnetic Stimulation: Applications in Neuropsychiatry Arch Gen Psychiatry, April 1, 1999; 56(4): 300 - 311. [Abstract] [Full Text] [PDF]

				S K Tamer, S Misra, and S Jaiswal Central motor conduction time in malnourished children Arch. Dis. Child., October 1, 1997; 77(4): 323 - 325. [Abstract] [Full Text]

				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]

				E. Olivier, S. A. Edgley, J. Armand, and R. N. Lemon An Electrophysiological Study of the Postnatal Development of the Corticospinal System in the Macaque Monkey J. Neurosci., January 1, 1997; 17(1): 267 - 276. [Abstract] [Full Text] [PDF]