David McCrea, Professor

 My research goal is on understanding how spinal cord motor systems are organized to produce purposeful movements. We use fictive locomotion to examine the activity of identified spinal interneurons. Fictive locomotion is a rhythmic and coordinated activity of limb motoneurons similar to that occuring during normal overground walking. Our research focus is on: identifying new types of spinal neurons; determining the connections between neurons; their activity during fictive locomotion; and the effects of reflexes on their activity.

Academic Achievements

  • Ph. D. (Physiology), Univ. of Manitoba, 1979
  • Postdoctoral Fellow, Univ. of Göteborg, Sweden, 1979-81
  • Research Associate, Univ. of Toronto, 1981-83
  • Professor (Physiology), Univ. of Manitoba, 1983-present
  • Research Interests

    A key goal of our research is to see how spinal reflexes operate during walking. We known that the spinal cord contains all of the neuronal circuits needed to produce coordinated walking and that the brain activates these spinal motor centres. Once activated, the spinal cord produces the detailed pattern of muscle activation occurring during walking and other rhythmic motor activities. The spinal nerve cells that make the spinal stepping generator have not been identified. Unravelling this mystery and identifying how spinal cells are connected together to produce locomotion is essential to restoring locomotion following spinal cord injury in man. The spinal cord circuitry responsible for walking appears to be almost identical in higher mammals and man. One goal of our research is to construct the "wiring diagram" of the motor systems in the mammalian spinal cord. This involves recording the electrical activity of identified spinal neurons in order to determine the connections and interactions between neurons that produce locomotion.

    These studies also examine how the activity of leg muscles during locomotion is adjusted by reflexes in order to compensate for changing conditions. For example, more extensor muscle activity is required when walking up than when walking down a hill or when carrying a backpack. There are specialized nerve sensors located in the muscles that measure muscle length and force. As we walk, information about the length of each muscle and how much force is being generated is sent to the spinal cord. Through a system of reflexes, this sensory information automatically adjusts the activity of muscles to produce smooth and stable walking as conditions change without the need to consciously think each step.

    Through the type of experiments done in our laboratory, we now know that the spinal nerve cells that produce these reflexes and those that produce rhythmic walking are strongly interconnected and in some cases, the same neurons. We strongly believe that the eventual restoration of walking in spinal injured man will require understanding spinal reflex and walking circuitry and the application of techniques to artificially activate these cells. Our research is specifically aimed at understanding how these systems are used and interact in uninjured mammals. Our previous results have already been used (by others) to develop new rehabilitation strategies to train spinal injured man to walk. Our future studies will greatly expand on past results and are exploring a wide variety of spinal reflexes as well as the organization of spinal motor pattern generation circuitry.

    See Also:
    Spinal Cord Research Centre Profile
    COS Expertise Record for Dr. McCrea
    Search PubMed for publications by McCrea D

    David McCrea

    University of Manitoba
    Department of Physiology
    409 Basic Medical Sciences Building
    745 Bannatyne  Avenue
    Winnipeg MB  CANADA
    R3E 0J9

    Tel:    204 789 3770
    Fax:   204 789 3930