Biomedical subjects

Keir Pearson

Publications and source records attributed to Keir Pearson.

3 recordsLinked to original sources

PubMed2006

Assessing sensory function in locomotor systems using neuro-mechanical simulations.

Computer simulations are being used increasingly to gain an understanding of the complex interactions between the neuronal, sensory, muscular and mechanical components of locomotor systems. Recent neuro-mechanical simulations of walking in humans, cats and insects, and of swimming in lampreys, have provided new information on the functional role of specific groups of sensory receptors in regulating locomotion. As we discuss in this review, these studies also make it clear that a full understanding of the neural and mechanical mechanisms that underlie locomotion can be achieved only by using simulations in parallel with physiological investigations. The widespread implementation of this approach would be enhanced by the development of freely available and easy-to-use software tools.

Animals↗

PubMed2005

Computer simulation of stepping in the hind legs of the cat: an examination of mechanisms regulating the stance-to-swing transition.

Physiological studies in walking cats have indicated that two sensory signals are involved in terminating stance in the hind legs: one related to unloading of the leg and the other to hip extension. To study the relative importance of these two signals, we developed a three-dimensional computer simulation of the cat hind legs in which the timing of the swing-to-stance transition was controlled by signals related to the force in ankle extensor muscles, the angle at the hip joint, or a combination of both. Even in the absence of direct coupling between the controllers for each leg, stable stepping was easily obtained using either a combination of ankle force and hip position signals or the ankle force signal alone. Stable walking did not occur when the hip position signal was used alone. Coupling the two controllers by mutual inhibition restored stability, but it did not restore the correct timing of stepping of the two hind legs. Small perturbations applied during the swing phase altered the movement of the contralateral leg in a manner that tended to maintain alternating stepping when the ankle force signal was included but tended to shift coordination away from alternating when the hip position signal was used alone. We conclude that coordination of stepping of the hind legs depends critically on load-sensitive signals from each leg and that mechanical linkages between the legs, mediated by these signals, play a significant role in establishing the alternating gait.

Animals↗

PubMed2004

Restoring walking after spinal cord injury.

One of the most obvious deficits following a spinal cord injury is the difficulty in walking, forcing many patients to use wheelchairs for locomotion. Over the past decade considerable effort has been directed at promoting the recovery of walking and to find effective treatments for spinal cord injury. Advances in our knowledge of the neuronal control of walking have led to the development of a promising rehabilitative strategy in patients with partial spinal cord injury, namely treadmill training with partial weight support. The current focus is on developing more efficient training protocols and automating the training to reduce the physical demand for the therapists. Mechanisms underlying training-induced improvements in walking have been revealed to some extent in animal studies. Another strategy for improving the walking in spinal cord injured patients is the use of functional electric stimulation of nerves and muscles to assist stepping movements. This field has advanced significantly over the past decade as a result of developments in computer technology and the miniaturization of electronics. Finally, basic research on animals with damaged spinal cords has focused on enhancing walking and other motor functions by promoting growth and regeneration of damaged axons. Numerous important findings have been reported yielding optimism that techniques for repairing the injured spinal cord will be developed in the near future. However, at present no strategy involving direct treatment of the injured spinal cord has been established for routine use in spinal cord injured patients. It now seems likely that any successful protocol in humans will require a combination of a treatment to promote re-establishing functional connections to neuronal networks in the spinal cord and specialized rehabilitation training to shape the motor patterns generated by these networks for specific behavioral tasks.

Animals↗