Our present understanding of segmental motor control has been greatly influenced by investigations of the lumbosacral spinal cord and hindlimb muscles of the cat. While such a focus has been of great benefit towards the understanding of motor behavior in general, it may also result in a potentially limited view of the segmental motor control system. At different levels of the neuraxis, there are potentially different strategies for the control of muscle force. For a fuller understanding of the segmental motor control system, this project focuses on one aspect of this system in the cat forelimb. The main objective of this project is to determine how the motoneuron and muscle unit portions of single distal forelimb motor units interact to modulate muscle force. This will be accomplished by using electrophysiological techniques. Our long-term objective is to conduct a thorough investigation of the cervical spinal cord and muscles of the cat forelimb. Hopefully, this effort will contribute to our understanding of the synaptic organization of distal forelimb motor units and how muscle force is controlled through their recruitment and rate modulation. Furthermore, it should be possible to determine what organizational principles are common between the forelimb and other areas of motor organization, and what specializations are unique to the forelimb because of the motor tasks it must perform. Without a clear understanding of the basic properties and design features of the segmental motor control system at all levels of the neuraxis, we will not be able to fully understand how this system is affected under a variety of neurological and injury-related disorders.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Neurology B Subcommittee 1 (NEUB)
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University of Texas Sw Medical Center Dallas
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United States
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Botterman, B R (1995) Task-dependent nature of fatigue in single motor units. Adv Exp Med Biol 384:351-60
Cope, T C; Webb, C B; Botterman, B R (1991) Control of motor-unit tension by rate modulation during sustained contractions in reinnervated cat muscle. J Neurophysiol 65:648-56
Cope, T C; Webb, C B; Yee, A K et al. (1991) Nonuniform fatigue characteristics of slow-twitch motor units activated at a fixed percentage of their maximum tetanic tension. J Neurophysiol 66:1483-92
Cope, T C; Hickman, K R; Botterman, B R (1988) Acute effects of spinal transection on EPSPs produced by single homonymous Ia-fibers in soleus alpha-motoneurons in the cat. J Neurophysiol 60:1678-94
Botterman, B R; Cope, T C (1988) Maximum tension predicts relative endurance of fast-twitch motor units in the cat. J Neurophysiol 60:1215-26
Botterman, B R; Cope, T C (1988) Motor-unit stimulation patterns during fatiguing contractions of constant tension. J Neurophysiol 60:1198-214
Botterman, B R; Iwamoto, G A; Gonyea, W J (1986) Gradation of isometric tension by different activation rates in motor units of cat flexor carpi radialis muscle. J Neurophysiol 56:494-506
Botterman, B R; Iwamoto, G A; Gonyea, W J (1985) Classification of motor units in flexor carpi radialis muscle of the cat. J Neurophysiol 54:676-90