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Jeff A Nessler

Publications and source records attributed to Jeff A Nessler.

6 recordsLinked to original sources
PubMed2006

Robot-assisted hindlimb extension increases the probability of swing initiation during treadmill walking by spinal cord contused rats.

Training and evaluation of locomotion in animals with spinal cord injury will likely be improved with the development of techniques that increase stepping activity. We hypothesized that robot-assisted extension of the hindlimbs of spinal cord injured rats during stance would increase the probability that the swing phase of gait would be initiated. Thirty-three adult, Sprague-Dawley rats received a contusion injury to the mid-thoracic spinal cord. The animals' hindlimbs were pulled into extension using small robotic arms to pull at the ankle, as the rat stepped on either a reciprocating, robotic paw platform or a conventional treadmill belt. The animals demonstrated an increase in the probability of swing initiation with spontaneous recovery during the first 4 weeks following injury (p < 0.0001). The probability of swing initiation was found to be greater with the use of robot-assisted extension versus no extension force at the ankle (75+/-16.9% versus 38.9+/-16.6%, p < 0.001). Swing initiation occurred most frequently at a particular distance of hindlimb extension (50 mm caudal from the neutral position at stance), but was broadly tuned about this distance. These results indicate that a greater amount of stepping activity can be elicited by robot-assisted extension, thereby providing possible benefits to evaluation and training of gait following SCI.

Algorithms↗
PubMed2006

Robotic gait analysis of bipedal treadmill stepping by spinal contused rats: characterization of intrinsic recovery and comparison with BBB.

There is a critical need to develop objective, quantitative techniques to assess motor function after spinal cord injury. Here, we assess the ability of a recently developed robotic device (the "rat stepper") to characterize locomotor impairment following contusion injury in rats. In particular, we analyzed how the kinematic features of hindlimb movement during bipedal, weight-supported treadmill stepping change following contusion, and whether these changes correlate with the recovery of open field locomotion. Female, Sprague-Dawley rats (n=29, 8 weeks of age) received mid thoracic contusion injuries of differing severities (11 mild, nine moderate, nine severe, and four sham). In a first experiment, 16 of the animals were evaluated weekly for 12 weeks using the robotic stepping device. In a second experiment, 17 of the animals were evaluated every other day for 4 weeks. The contused animals recovered open field locomotion based on the Basso, Beattie, and Bresnahan Scale (BBB) analysis, with most of the recovery occurring by 4 weeks post-injury. Analysis of 14 robotic measures of stepping revealed that several measures improved significantly during the same 4 weeks: swing velocity, step height, step length, hindlimb coordination, and the ability to support body weight. These measures were also significantly correlated with the BBB score. The number of steps taken during testing was not directly related to intrinsic recovery or correlated to the BBB score. These results suggest that it is the quality of weight-supported steps, rather than the quantity, that best reflects locomotor recovery after contusion injury, and that the quality of these steps is determined by the integrity of extensor, flexor, and bilateral coordination pathways. Thus, by measuring only a few weight-supported steps with motion capture, a sensitive, valid measure of locomotor recovery following contusion injury can be obtained across a broad range of impairment levels.

Animals↗
PubMed2005

Hindlimb loading determines stepping quantity and quality following spinal cord transection.

We compared the bipedal hindlimb stepping ability of untrained and trained (step-trained 6 min/day) spinal rats (mid-thoracic spinal cord transection at post-natal day 5) at different levels of body weight support on a treadmill over a 40-day period, starting at 69 days of age. A robotic device provided precise levels of body weight support and recorded hindlimb movement. We assessed stepping ability using: (1) step quantity determined from the measured hindlimb movement, (2) ordinal scales of paw placement, weight-bearing, and limb flexion, and (3) the lowest level of body weight support at which stepping was maintained. Stepping quantity and quality depended strongly on the level of support provided. Stepping ability improved with time, but only at the higher levels of weight-bearing, and independently of training. Increasing limb loading by gradually decreasing body weight support altered the spatiotemporal properties of the steps, resulting in an increase in step length and stance duration and a decrease in swing and step cycle duration. The rats progressively improved their ability to support more load before collapsing from a maximum of about 42 g ( approximately 25% of body weight) at Day 1 to 73 g ( approximately 35% of body weight) at Day 40. We conclude that the level of hindlimb loading provided to a spinally transected rat strongly influences the quantity and quality of stepping. Furthermore, the relationship between stepping ability and loading conditions changes with time after spinal cord transection and is unaltered by small amounts of step training. Finally, load-bearing failure point can be a quantitative measure of locomotor recovery following spinal cord injury, especially for severely impaired animals that cannot step unassisted.

Animals↗
PubMed2002

Web-based telerehabilitation for the upper extremity after stroke.

Stroke is a leading cause of disability in the United States and yet little technology is currently available for individuals with stroke to practice and monitor rehabilitation therapy on their own. This paper provides a detailed design description of a telerehabilitation system for arm and hand therapy following stroke. The system consists of a Web-based library of status tests, therapy games, and progress charts, and can be used with a variety of input devices, including a low-cost force-feedback joystick capable of assisting or resisting in movement. Data from home-based usage by a chronic stroke subject are presented that demonstrate the feasibility of using the system to direct a therapy program, mechanically assist in movement, and track improvements in movement ability.

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PubMedDate not supplied

Tools for understanding and optimizing robotic gait training.

This article reviews several tools we have developed to improve the understanding of locomotor training following spinal cord injury (SCI), with a view toward implementing locomotor training with robotic devices. We have developed (1) a small-scale robotic device that allows testing of locomotor training techniques in rodent models, (2) an instrumentation system that measures the forces and motions used by experienced human therapists as they manually assist leg movement during locomotor training, (3) a powerful, lightweight leg robot that allows investigation of motor adaptation during stepping in response to force-field perturbations, and (4) computational models for locomotor training. Results from the initial use of these tools suggest that an optimal gait-training robot will minimize disruptive sensory input, facilitate appropriate sensory input and gait mechanics, and intelligently grade and time its assistance. Currently, we are developing a pneumatic robot designed to meet these specifications as it assists leg and pelvic motion of people with SCI.

Computer Simulation↗