Research Report
Population: Not Applicable
John A Buford, PT, PhD, Associate Professor and Director, Division of Physical Therapy, The Ohio State University buford.5@osu.edu
Wendy Herbert, PT, PhD, Assistant Professor & Director of Clinical Education, Elon University wendyherbertpt@gmail.com
Lynnette Montgomery, PT, PhD, Post Doctoral Associate, University of Louisville lynnette.montgomery@louisville.edu
Keywords: Prevention
Purpose/Hypothesis: To determine the relative potential for contributions of corticospinal and reticulospinal systems in control of reaching in the intact nervous system and in recovery from stroke.
Subjects: Subjects were five adult non-human primates, Macaca fascicularis.
Materials/Methods: Three subjects were trained to perform a reaching task allowing simultaneous recording of neural activity and microstimulation within the brain in the cortical motor areas as well as in the reticulospinal system of the brainstem. EMG in both upper limbs was recorded from 24 muscles, flexors and extensors, proximal and distal. IN two subjects, an ischemic injury to primary motor cortex was induced with direct injection of a vasoconstrictor into the cortical tissue. Behavioral recovery was measured along with the motor output of the motor cortex and the reticulospinal system.
Results: In the intact nervous system, corticospinal and reticulospinal systems are both active in the control of skilled reaching, and both have motor outputs to the muscles of the upper limb bilaterally. Motor outputs from the corticospinal and reticulospinal systems to upper limb muscles can combine with each other for augmented recruitment, and can also compete such that motor outputs from one system cancel those from the other. The results will be presented with reference to how these combinations occur in the ipsilateral and contralateral limb, and based on which cortical motor area is studied. In the ischemic model, we present evidence that the role of the reticulospinal system in recruitment of the impaired upper limb increases after rehabilitation, even though there may be no return of motor function from the injured primary motor cortex.
Conclusions: The reticulospinal and corticospinal systems normally cooperate for the control of skilled reaching, with both systems making strong contributions to specific muscle recruitment in both upper limbs. The reticulospinal system’s influence is clearly not limited to posture and automatic movements. Further, increased reliance on reticulospinal control may be a normal part of motor recovery after cortical injury.
Clinical Relevance: Better understanding of how these systems work together normally and in recovery can provide valuable insight into mechanisms of recovery during neurologic rehabilitation.
Citation:
Buford, John A, PT, PhD; Herbert, Wendy J, PT, PhD; Montgomery, Lynnette R, PT, PhD. Corticospinal and Reticulospinal Cooperation for control of reaching in the normal nervous system and in a model of stroke.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/058_buford-et-al/