Similar Motor Cortical Control Mechanisms for Precise Limb Control during Reaching and Locomotion.
Throughout the course of evolution there has been a parallel development of the complexity and flexibility of the nervous system and the skeletomuscular system that it controls. This development is particularly evident for the cerebral cortical areas and the transformation of the use of the upper limbs from a purely locomotor function to one including, or restricted to, reaching and grasping. This study addresses the issue of whether the control of reaching has involved the development of new cortical circuits or whether the same neurons are used to control both locomotion and reaching. We recorded the activity of pyramidal tract neurons in the motor cortex of the cat both during voluntary gait modifications and during reaching. All cells showed generally similar patterns of activity in both tasks. More specifically, we showed that, in many cases, cells maintained a constant temporal relationship to the activity of synergistic muscle groups in each task. In addition, in some cells the relationship between the intensity of the cell discharge activity and the magnitude of the EMG activity was equally constant during gait modifications and reaching. As such, the results are compatible with the hypothesis that the corticospinal circuits used to control reaching evolved from those used to precisely modify gait.
Division of Exercise Physiology, Department of Human Performance, and Center for Neuroscience, West Virginia University, Morgantown, West Virginia 26506, and.
Sergiy
S
Yakovenko
Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montreal, Quebec H3C 3J7, Canada Trevor.Drew@umontreal.ca.
Trevor
T
Drew
D000818:Animals; D001696:Biomechanical Phenomena; D002415:Cats; D004576:Electromyography; D005121:Extremities / Q000294:innervation / Q000502:physiology*; D005684:Gait / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology / Q000502:physiology
cat; locomotion; motor cortex; reaching; visually guided