Organisation of Cortico-motoneuronal Projections from the Primary Motor Cortex: Evidence for Task-Related Function in Monkey and in Man

  • A. Turton
  • C. Fraser
  • D. Flament
  • W. Werner
  • K. M. B. Bennett
  • R. N. Lemon


In primates the fibres of the corticospinal tract are derived from extensive regions of the cerebral cortex including the motor, premotor, supplementary motor and cingulate areas in the frontal lobe and also from the postcentral gyrus of the parietal lobe. Dum and Strick (1991) have recently shown that in the macaque monkey only about half of the projections derived from the frontal lobe originate from the primary motor cortex. The corticospinal tract arises from large pyramidal neurones in the deepest part of layer V (Catsman-Berrevoets and Kuypers 1976; Jones and Wise 1977). The principal targets of corticospinal projections from the primary motor cortex appear to be interneurones and propriospinal neurones located in laminae VII and VIII (contralaterally) and lamina VIII (bilaterally; Schoen 1964; see Armand 1982). In addition, there are the direct cortico-motoneuronal (CM) projections. In the macaque monkey most of these direct CM projections influence motoneurones supplying muscles concerned with movements of the hand and fingers, but in man there are also strong projections to the more medial motoneuronal cell groups concerned with axial and truncal movements. Convincing evidence for the existence of these different projections has been obtained using magnetic stimulation in man (see Roth well et al. 1991).


Motor Cortex Macaque Monkey Hand Muscle Precision Grip Power Grip 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1993

Authors and Affiliations

  • A. Turton
    • 1
  • C. Fraser
    • 1
  • D. Flament
    • 1
  • W. Werner
    • 1
  • K. M. B. Bennett
    • 1
  • R. N. Lemon
    • 1
  1. 1.Anatomy Dept.Cambridge UniversityCambridgeEngland, UK

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