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Modeling the locomotor CPG integrated with spinal circuits |
In collaboration with
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David
A. McCrea |
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Experimental studies
| Dr.
McCrea and his collaborators at the Spinal Cord Research Center ( SCRC ) at the University of Manitoba perform
comprehensive experimental studies of neural circuits in the mammalian spinal cord
comprising the locomotor CPG. They also study afferent control of the CPG and interactions
between the CPG and circuits of spinal reflexes. These studies are performed using
"fictive locomotion" preparations of cats in which the locomotor
activity is evoked by continuous stimulation of the midbrain locomotor region (MLR). |
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 The movie is created by Dr. McCrea. |
An example of fictive locomotor pattern Note the presence of "deletions" - missing bursts that spontaneously occur in the activity of multiple agonist motoneurons (in this case - flexors, shown red). The deletions of agonist motoneuron activity are usually accompanied by sustained firing in antagonist motoneurons (here - extensors, shown blue). Interestingly, the locomotor CPG is able to maintain the phase of post-deletion oscillations (and burst timing) after most of the deletions. This finding led to the concept of a two-level organization of the locomotor CPG .
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The
concept of two-level locomotor CPG |
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It is suggested that the locomotor CPG consists of a half-center rhythm generator (RG) and a pattern formation (PF) network controlling groups of synergist motoneurons. The two-level organization allows various proprioceptive afferents to perform separate control of the durations of step cycle and locomotor phases and the degree of activation of different motoneuron groups . |
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| Related Publications: Rybak, I. A., Shevtsova, N. A., Lafreniere-Roula, M., and McCrea, D. A.
(2006) Modelling spinal circuitry involved in locomotor pattern generation: insights from
deletions during fictive locomotion. J. Physiol. Lond. 577(Pt. 2): 617-639. Rybak, I. A., Stecina, K., Shevtsova, N. A., and
McCrea, D. A. (2006) Modelling spinal circuitry involved in locomotor pattern generation:
insights from the effects of afferent stimulation. J. Physiol. Lond. 577(Pt. 2):
641-658. McCrea, D. A., and Rybak, I. A. (2007) Modeling the
mammalian locomotor CPG: insights from mistakes and perturbations. Prog. Brain Res. 165: 235-253. McCrea, D. A., and Rybak, I. A. (2008) Organization
of mammalian locomotor rhythm and pattern generation. Brain Res.
Reviews 57: 134-146. |
