Robotic Rehabilitator of the Rodent Upper Extremity: A System and Method for Assessing and Training Forelimb Force Production after Neurological Injury

Abstract

Rodent models of spinal cord injury are critical for the development of treatments for upper limb motor impairment in humans, but there are few methods for measuring forelimb strength of rodents, an important outcome measure. We developed a novel robotic device-the Robotic Rehabilitator of the Rodent Upper Extremity (RUE)-that requires rats to voluntarily reach for and pull a bar to retrieve a food reward; the resistance of the bar can be programmed. We used RUE to train forelimb strength of 16 rats three times per week for 23 weeks before and 38 weeks after a mild (100 kdyne) unilateral contusion at the cervical level 5 (C5). We measured maximum force produced when RUE movement was unexpectedly blocked. We compared this blocked pulling force (BPF) to weekly measures of forelimb strength obtained with a previous, well-established method: the grip strength meter (GSM). Before injury, BPF was 2.6 times higher (BPF, 444.6 -19.1 g; GSM, 168.4 -3.1 g) and 4.9 times more variable ( p < 0.001) than pulling force measured with the GSM; the two measurement methods were uncorrelated (R 2 = 0.03; p = 0.84). After injury, there was a significant decrease in BPF of 134.35 g -14.71 g ( p < 0.001). Together, our findings document BPF as a repeatable measure of forelimb force production, sensitive to a mild spinal cord injury, which comes closer to measuring maximum force than the GSM and thus may provide a useful measure for quantifying the effects of treatment in rodent models of SCI.

Neuroplastic Changes Following Brain Ischemia and their Contribution to Stroke Recovery: Novel Approaches in Neurorehabilitation

“…Similarly to the Hays’s work, Reinkensmeyer’s group recently developed another robotic interface, the Robotic Rehabilitator of the Rodent Upper Extremity (RUE), This 1 DOF system allows rats to voluntarily perform a task of reaching followed by the pulling of a bar in order to retrieve a food reward (Sharp et al, 2016 ). The bar is connected to an interface by means of which the force required to accomplish the pulling task can be changed, simply varying the stiffness of a voice coil actuator used to generate the resistance force.…”

Translational Challenges of Rat Models of Upper Extremity Dysfunction After Spinal Cord Injury

“…Although the finesse in digital control is far less developed in rodents when compared to humans and non-human primates, 14 there are many functional assessments of the forelimb in the rodent models of SCI (see Table 1). 20,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] Mouse models of SCI permit the use of genetically engineered models allowing for the evaluation of molecular and cellular changes following SCI, and they are beginning to be used for understanding forelimb movement and dexterous behavior. 51 However, mice display a wound healing process that is different following SCI when compared to other species including rats and humans.…”

Experimental Spinal Cord Injury Models in Rodents: Anatomical Correlations and Assessment of Motor Recovery

“…For forelimb training, a robotic rehabilitation system was recently developed, in which the animal has to pull a bar to receive food. This setup could also be used to measure forelimb strength [72].…”