Effects of Consistency vs. Variability in Robotically Controlled Training of Stepping in Adult Spinal Mice

Abstract

This paper studies the possible benefit that can be obtained by introducing variability into the robotic control of trajectories used to train hindlimb locomotion in adult spinal mice. The spinal cords of adult female SwissWebster mice were completely transected at a mid-thoracic level. Fourteen days post-transection, the spinal mice were robotically trained to step in the presence of a 5-HT agonist, quipazine, for a period of six weeks. In this pilot study nine animals were divided into three groups, each receiving a different control strategy: a fixed training trajectory (Group A), a variable training trajectory without interlimb coordination imposed (Group B) and a variable training trajectory with hindlimb bilateral coordination imposed (Group C). Preliminary results indicate that Group A recovers more slowly than the two groups receiving variable modes of robotic training. Groups B and C show higher levels of recovery than Group A in terms of the number of steps performed during testing sessions, as well as in their step periodicity and shape consistency. Group C displays a higher incidence of alternating stepping than Group B. These results indicate that variable trajectory robotic training paradigms may be more effective than fixed trajectory paradigms in promoting robust post-injury stepping behavior. Furthermore, it appears that the inclusion of interlimb coordination is an important contribution to successful training.

Implications of Assist-As-Needed Robotic Step Training after a Complete Spinal Cord Injury on Intrinsic Strategies of Motor Learning

“…It has been shown that adult spinal mice can be trained to step on a moving treadmill belt with the use of a robotic device (Fong et al, 2005). In addition, there is a positive interaction effect between robotic training and the administration of quipazine, a broad serotonin agonist.…”

“…Typically, this speed was ϳ3 cm/s. A detailed description of the robot and mouse attachment has been published previously (Fong et al, 2005).…”

“…Surgical procedure was the same as in Fong et al (2005). Briefly, the mice were maintained in a deep anesthetic state throughout the surgery with isoflurane gas (2-5% isoflurane mixed with 0.4% O 2 via face mask).…”

“…Gelfoam then was inserted into the gap to ensure complete separation of the proximal and distal stumps (de la Torre and Goldsmith, 1990). The musculature and fascia were repositioned, and the wound was closed by using 5-0 Dexon internal and 5-0 Ethilon external sutures (Fong et al, 2005). All animal procedures used in this study were conducted in accordance with the Animal Care Guidelines of the American Physiological Society and were reviewed and approved by the Animal Research Committee at the University of California, Los Angeles.…”

“…In this study quipazine, a broad spectrum serotonin agonist, was used to facilitate stepping in all mice. Based on our own dose-response tests, as well as dose-response studies reported for rats (Orsal et al, 2002;Fong et al, 2005), a dose of 0.5 mg/kg body weight was administered intraperitoneally 10 min before each training or testing session.…”