Neuromechanical control of locomotion in the rat

Effect of axon misdirection on recovery of electromyographic activity and kinematics after peripheral nerve injury

In this study, patterns of activity in the soleus (Sol) and tibialis anterior (TA) muscles and hindlimb kinematics were evaluated during slope walking in rats after transection and surgical repair either of the entire sciatic nerve (Sci group) or of its two branches separately, the tibial and common fibular nerves (T/CF group). With the latter method, axons from the tibial and common fibular nerves could not reinnervate targets of the other nerve branch after injury, reducing the opportunity for misdirection. Activity in the TA shifted from the swing phase in intact rats to nearly the entire step cycle in both injured groups. Since these changes occur without misdirection of regenerating axons, they are interpreted as centrally generated. Sol activity was changed from reciprocal to that of TA in intact rats to coactivate with TA, but only in the Sci group rats. In the T/CF group rats, Sol activity was not altered from that observed in intact rats. Despite effects of injury that limited foot movements, hindlimb kinematics were conserved during downslope walking in both injury groups and during level walking in the T/CF group. During level walking in the Sci group and during upslope walking in both groups of injured rats, the ability to compensate for the effects of the nerve injury was less effective and resulted in longer limb lengths held at more acute angles throughout the step cycle. Changes in limb movements occur irrespective of axon misdirection and reflect compensatory changes in the outputs of the neural circuits that drive locomotion.

How spinalized rats can walk: biomechanics, cortex, and hindlimb muscle scaling--implications for rehabilitation

Neonatal spinalized (NST) rats can achieve autonomous weight-supported locomotion never seen after adult injury. Mechanisms that support function in NST rats include increased importance of cortical trunk control and altered biomechanical control strategies for stance and locomotion. Hindlimbs are isolated from perturbations in quiet stance and act in opposition to forelimbs in locomotion in NST rats. Control of roll and yaw of the hindlimbs is crucial in their locomotion. The biomechanics of the hind limbs of NST rats are also likely crucial. We present new data showing the whole leg musculature scales proportional to normal rat musculature in NST rats, regardless of function. This scaling is a prerequisite for the NST rats to most effectively use pattern generation mechanisms and motor patterns that are similar to those present in intact rats. Pattern generation may be built into the lumbar spinal cord by evolution and matched to the limb biomechanics, so preserved muscle scaling may be essential to the NST function observed.

Transient decreases in forelimb gait and ground reaction forces following rotator cuff injury and repair in a rat model

Due to inadequate healing, surgical repairs of torn rotator cuff tendons often fail, limiting the recovery of upper extremity function. The rat is frequently used to study rotator cuff healing; however, there are few systems capable of quantifying forelimb function necessary to interpret the clinical significance of tissue level healing. We constructed a device to capture images, ground reaction forces and torques, as animals ambulated in a confined walkway, and used it to evaluate forelimb function in uninjured control and surgically injured/repaired animals. Ambulatory data were recorded before (D-1), and 3, 7, 14, 28 and 56 days after surgery. Speed as well as step width and length were determined by analyzing ventral images, and ground reaction forces were normalized to body weight. Speed averaged 22+/-6 cm/s and was not affected by repair or time. Step width and length of uninjured animals compared well to values measured with our previous system. Forelimbs were used primarily for braking (-1.6+/-1.5% vs +2.5+/-0.6%), bore less weight than hind limbs (49+/-5% vs 58+/-4%), and showed no differences between sides (49+/-5% vs 46+/-5%) for uninjured control animals. Step length and ground reaction forces of the repaired animals were significantly less than control initially (days 3, 7 and 14 post-surgery), but not by day 28. Our new device provided uninjured ambulatory data consistent with our previous system and available literature, and measured reductions in forelimb function consistent with the deficit expected by our surgical model.

Gait analysis in normal and spinal contused mice using the TreadScan system

Advances in spinal cord injury (SCI) research are dependent on quality animal models, which in turn rely on sensitive outcome measures able to detect functional differences in animals following injury. To date, most measurements of dysfunction following SCI rely either on the subjective rating of observers or the slow throughput of manual gait assessment. The present study compares the gait of normal and contusion-injured mice using the TreadScan system. TreadScan utilizes a transparent treadmill belt and a high-speed camera to capture the footprints of animals and automatically analyze gait characteristics. Adult female C57Bl/6 mice were introduced to the treadmill prior to receiving either a standardized mild, moderate, or sham contusion spinal cord injury. TreadScan gait analyses were performed weekly for 10 weeks and compared with scores on the Basso Mouse Scale (BMS). Results indicate that this software successfully differentiates sham animals from injured animals on a number of gait characteristics, including hindlimb swing time, stride length, toe spread, and track width. Differences were found between mild and moderate contusion injuries, indicating a high degree of sensitivity within the system. Rear track width, a measure of the animal's hindlimb base of support, correlated strongly both with spared white matter percentage and with terminal BMS. TreadScan allows for an objective and rapid behavioral assessment of locomotor function following mild-moderate contusive SCI, where the majority of mice still exhibit hindlimb weight support and plantar paw placement during stepping.

High-speed X-ray video demonstrates significant skin movement errors with standard optical kinematics during rat locomotion

The sophistication of current rodent injury and disease models outpaces that of the most commonly used behavioral assays. The first objective of this study was to measure rat locomotion using high-speed X-ray video to establish an accurate baseline for rat hindlimb kinematics. The second objective was to quantify the kinematics errors due to skin movement artefacts by simultaneously recording and comparing hindlimb kinematics derived from skin markers and from direct visualization of skeletal landmarks. Joint angle calculations from skin-derived kinematics yielded errors as high as 39 degrees in the knee and 31 degrees in the hip around paw contact with respect to the X-ray data. Triangulation of knee position from the ankle and hip skin markers provided closer, albeit still inaccurate, approximations of bone-derived, X-ray kinematics. We found that soft tissue movement errors are the result of multiple factors, the most impressive of which is overall limb posture. Treadmill speed had surprisingly little effect on kinematics errors. These findings illustrate the significance and context of skin movement error in rodent kinematics.

Quantitative assessment of stereotyped and challenged locomotion after lesion of the striatum: a 3D kinematic study in rats

BACKGROUND

Although the striatum is in position to regulate motor function, the role of the structure in locomotor behaviour is poorly understood. Therefore, a detailed analysis of locomotion- and obstacle avoidance-related parameters was performed after unilateral lesion of the striatum in rats.

METHODS AND RESULTS

Using the three dimensional motion capture technology, kinematics of walking and clearing obstacles, head and body orientation were analyzed before and up to 60 days after the lesion. Recordings were performed in treadmill running rats with or without obstacles attached to the treadmill belt. The lesion, which was induced by the direct injection of the mitochondrial toxin malonate into the left caudoputamen resulted in the complete destruction of the dorsal striatum. During the first three days following the lesion, rats were unable to run on the treadmill. Thereafter, rats showed normal looking locomotion, yet the contralesional limbs exhibited changes in length and timing parameters, and were overflexed. Moreover, the head of lesioned rats was orientated towards the side of the lesion, and their postural vertical shifted towards the contralesional side. During obstructed running, the contralesional limbs when they were leading the crossing manoeuvre stepped on the obstacle rather than to overcome obstacle without touching it, yet more frequently with the forelimb than the hindlimb. Unsuccessful crossings appeared to be due to a paw placement farther away from the front of the obstacles, and not to an inappropriate limb elevation. Importantly, deficit in locomotor behaviour did not regress over the time.

CONCLUSION

Our results argue that the striatum of one hemisphere controls kinematics of contralateral limbs during stereotyped locomotion and plays a prominent role in the selection of the right motor program so that these limbs successfully cross over obstacle.

Neuromuscular stimulation therapy after incomplete spinal cord injury promotes recovery of interlimb coordination during locomotion

The mechanisms underlying the effects of neuromuscular electrical stimulation (NMES) induced repetitive limb movement therapy after incomplete spinal cord injury (iSCI) are unknown. This study establishes the capability of using therapeutic NMES in rodents with iSCI and evaluates its ability to promote recovery of interlimb control during locomotion. Ten adult female Long Evans rats received thoracic spinal contusion injuries (T9; 156 +/- 9.52 Kdyne). 7 days post-recovery, 6/10 animals received NMES therapy for 15 min/day for 5 days, via electrodes implanted bilaterally into hip flexors and extensors. Six intact animals served as controls. Motor function was evaluated using the BBB locomotor scale for the first 6 days and on 14th day post-injury. 3D kinematic analysis of treadmill walking was performed on day 14 post-injury. Rodents receiving NMES therapy exhibited improved interlimb coordination in control of the hip joint, which was the specific NMES target. Symmetry indices improved significantly in the therapy group. Additionally, injured rodents receiving therapy more consistently displayed a high percentage of 1:1 coordinated steps, and more consistently achieved proper hindlimb touchdown timing. These results suggest that NMES techniques could provide an effective therapeutic tool for neuromotor treatment following iSCI.

Chronic neuromuscular electrical stimulation of paralyzed hindlimbs in a rodent model

Neuromuscular electrical stimulation (NMES) can be used to activate paralyzed or paretic muscles to generate functional or therapeutic movements. The goal of this research was to develop a rodent model of NMES-assisted movement therapy after spinal cord injury (SCI) that will enable investigation of mechanisms of NMES-induced plasticity, from the molecular to systems level. Development of the model requires accurate mapping of electrode and muscle stimulation sites, the capability to selectively activate muscles to produce graded contractions of sufficient strength, stable anchoring of the implanted electrode within the muscles and stable performance with functional reliability over several weeks of the therapy window. Custom designed electrodes were implanted chronically in hindlimb muscles of spinal cord transected rats. Mechanical and electrical stability of electrodes and the ability to achieve appropriate muscle recruitment and joint angle excursion were assessed by characterizing the strength duration curves, isometric torque recruitment curves and kinematics of joint angle excursion over 6-8 weeks post implantation. Results indicate that the custom designed electrodes and implantation techniques provided sufficient anchoring and produced stable and reliable recruitment of muscles both in the absence of daily NMES (for 8 weeks) as well as with daily NMES that is initiated 3 weeks post implantation (for 6 weeks). The completed work establishes a rodent model that can be used to investigate mechanisms of neuroplasticity that underlie NMES-based movement therapy after spinal cord injury and to optimize the timing of its delivery.

Quantitative evaluation of movement and strength of the upper limb after transection of the C-7 nerve: is it possible in an animal model?

Object

Contralateral C-7 nerve transfer has been used clinically for more than 20 years. The increased interest in studies of transfer effectiveness at different target muscles, posttransfer cocontraction, and brain plasticity has prompted the need for an animal model. In addition to the conventional electrophysiological, histomorphometric, and biomechanical evaluation modalities, quantitative functional and behavioral evaluation will be crucial in applying this kind of model. The aim of this study was to establish a C-7 transection animal model and quantify the changes in upper-limb joint movement and muscle power.

Methods

A C-7 nerve transection model was created in Sprague-Dawley rats, the brachial plexus of which resembles the human brachial plexus. The impact of C-7 transection on donor limb function—namely, strength, movement, and coordination—was evaluated in 6 rats. Muscle strength (power reported in g) was measured as a grasping task. The active range of motion (ROM; angle reported in °) of the elbow, wrist, and metacarpophalangeal joints was quantified by computerized video motion analysis. Antiresistance coordinated movement (speed reported in seconds) was assessed by the vertical rope-climbing test. These tests were carried out before surgery and at 2, 4, 6, 8, 10, 14, 21, and 28 days after C-7 transection. Repeated-measures 1-way analysis of variance was applied for statistical analysis. When the overall probability value was < 0.05, the Dunnett multiple-comparison posttest was used to compare postoperative values with preoperative baseline values.

Results

Immediately after C-7 transection, the mean ± SD grip strength declined from 378.50 ± 20.55 g to 297.77 ± 15.04 g. Active elbow extension was impaired, as shown by a significant decrease of the elbow extension angle. The speed of vertical rope climbing was also reduced. Elbow flexion, wrist flexion and extension, and metacarpophalangeal joint flexion and extension were not impaired. Fast recovery of motor function was observed thereafter. Grip strength, range of active elbow extension, and speed of rope climbing returned to baseline values at postoperative Days 4, 8, and 8, respectively.

Conclusions

The ROM and muscle strength of the upper limb in rats can be measured quantitatively in studies that simulate clinical situations. Application of these functional evaluation modalities in a C-7 nerve transection rat model confirmed that transection of C-7 causes only temporary functional dysfunction to the donor limb. The results obtained in this animal model mimic those seen in humans who undergo contralateral C-7 nerve harvesting.

An in vitro spinal cord-hindlimb preparation for studying behaviorally relevant rat locomotor function

Although the spinal cord contains the pattern-generating circuitry for producing locomotion, sensory feedback reinforces and refines the spatiotemporal features of motor output to match environmental demands. In vitro preparations, such as the isolated rodent spinal cord, offer many advantages for investigating locomotor circuitry, but they lack the natural afferent feedback provided by ongoing locomotor movements. We developed a novel preparation consisting of an isolated in vitro neonatal rat spinal cord oriented dorsal-up with intact hindlimbs free to step on a custom-built treadmill. This preparation combines the neural accessibility of in vitro preparations with the modulatory influence of sensory feedback from physiological hindlimb movement. Locomotion induced by N-methyl D-aspartate and serotonin showed kinematics similar to that of normal adult rat locomotion. Changing orientation and ground interaction (dorsal-up locomotion vs ventral-up air-stepping) resulted in significant kinematic and electromyographic changes that were comparable to those reported under similar mechanical conditions in vivo. We then used two mechanosensory perturbations to demonstrate the influence of sensory feedback on in vitro motor output patterns. First, swing assistive forces induced more regular, robust muscle activation patterns. Second, altering treadmill speed induced corresponding changes in stride frequency, confirming that changes in sensory feedback can alter stride timing in vitro. In summary, intact hindlimbs in vitro can generate behaviorally appropriate locomotor kinematics and responses to sensory perturbations. Future studies combining the neural and chemical accessibility of the in vitro spinal cord with the influence of behaviorally appropriate hindlimb movements will provide further insight into the operation of spinal motor pattern-generating circuits.

Adaptive control of movement for neuromuscular stimulation-assisted therapy in a rodent model

Neuromotor therapy after spinal cord or brain injury often attempts to utilize activity-dependent plasticity to promote functional recovery. Neuromuscular electrical stimulation that activates paralyzed or paretic muscles may enhance passive assistance therapy by activating more muscle mass and enriching the sensory pattern with appropriately timed muscle spindle activation. To enable studies of activity-dependent plasticity, a rodent model for stimulation-assisted locomotor therapy was developed previously. To be effective, however, such a system must allow lengthy sessions of repetitive movements. In this study, we implemented an adaptive pattern generator/pattern shaper (PG/PS) control system for a rodent model of neuromotor therapy and evaluated its ability to generate accurate and repeatable hip movements in lengthy sessions by adjusting the activation patterns of an agonist/antagonist muscle pair. In 100-cycle movement trials, the PG/PS control system provided excellent movement tracking (<<10% error), but stimulation levels steadily increased to account for muscle fatigue. In trials using an intermittent movement paradigm (100 sets of five-cycle bouts interspersed by 20-s rest periods), excellent performance (<<8% error) was also observed with less stimulation, thus indicating reduced muscle fatigue. These results demonstrate the ability of the PG/PS control system to utilize an agonist/antagonist muscle pair to control movement at a joint in a rodent model. The demonstration of repeatable movements over lengthy intermittent sessions suggests that it may be well suited to provide efficient neuromotor therapy.

Neuromuscular electrical stimulation of the hindlimb muscles for movement therapy in a rodent model

Neuromuscular electrical stimulation (NMES) can provide functional movements in people after central nervous system injury. The neuroplastic effects of long-term NMES-induced repetitive limb movement are not well understood. A rodent model of neurotrauma in which NMES can be implemented may be effective for such investigations. We present a rodent model for NMES of the flexor and extensor muscles of the hip, knee, and ankle hindlimb muscles. Custom fabricated intramuscular stimulating electrodes for rodents were implanted near identified motor points of targeted muscles in ten adult, female Long Evans rats. The effects of altering NMES pulse stimulation parameters were characterized using strength duration curves, isometric joint torque recruitment curves and joint angle measures. The data indicate that short pulse widths have the advantage of producing graded torque recruitment curves when current is used as the control parameter. A stimulus frequency of 75 Hz or more produces fused contractions. The data demonstrate ability to accurately implant the electrodes and obtain selective, graded, repeatable, strong muscle contractions. Knee and ankle angular excursions comparable to those obtained in normal treadmill walking in the same rodent species can be obtained by stimulating the target muscles. Joint torques (normalized to body weight) obtained were larger than those reported in the literature for small tailed therian mammals and for peak isometric ankle plantarflexion in a different rodent species. This model system could be used for investigations of NMES assisted hindlimb movement therapy.

Coordination strategies for limb forces during weight-bearing locomotion in normal rats, and in rats spinalized as neonates

Some rats spinally transected as neonates (ST rats) achieve weight-supporting independent locomotion. The mechanisms of coordinated hind-limb weight support in such rats are not well understood. To examine these we compared ST rats (with better than 60% of weight supported steps) and normal rats that were trained to cross an instrumented runway. Ground reaction forces, coordination of hind-limb and forelimb forces and the motions of the center of pressure (CoP) were assessed. Normal rats crossed the runway with a diagonal trot. On average hind-limbs bore about 80% of the vertical load carried by forelimbs (45% body weight on hind-limbs 55% on forelimbs), although this varied. Forelimbs and hind-limbs acted synergistically to generate decelerative and propulsive rostrocaudal forces, which averaged 15% of body weight with maximums of 50%. Lateral forces were very small (<8% of body weight). Center of pressure progressed in jumps along a straight line with mean lateral deviations <1 cm. ST rats hind-limbs bore about 60% of the vertical load of forelimbs (37% body weight on hind-limbs, 63% on forelimbs), significantly less compared to intact rats (P < 0.05). ST rats showed similar mean rostrocaudal forces, but with significantly larger maximum fluctuations of up to 80% of body weight (P < 0.05). Joint force-plate recordings showed forelimbs and hind-limb rostrocaudal forces in ST rats were opposing and significantly different from intact rats (P < 0.05). Lateral forces were approximately 20% of body weight and significantly larger than in normal rats (P < 0.05). Center of pressure zig-zagged, with mean lateral deviations of approximately 2 cm and a significantly larger range (P < 0.05). The haunches were also observed to roll more than normal rats. The locomotor strategy of injured rats using limbs in opposition was presumably less efficient but their complex gait was statically stable. Because forelimbs and hind-limbs acted in opposition, the trunk was held compressed. Force coordination was likely managed largely by the voluntary control in forelimbs and trunk.

Trunk sensorimotor cortex is essential for autonomous weight-supported locomotion in adult rats spinalized as P1/P2 neonates

Unlike adult spinalized rats, approximately 20% of rats spinalized as postnatal day 1 or 2 (P1/P2) neonates achieve autonomous hindlimb weight support. Cortical representations of mid/low trunk occur only in such rats with high weight support. However, the importance of hindlimb/trunk motor cortex in function of spinalized rats remains unclear. We tested the importance of trunk sensorimotor cortex in their locomotion using lesions guided by cortical microstimulation in P1/P2 weight-supporting neonatal spinalized rats and controls. In four intact control rats, lesions of hindlimb/trunk cortex caused no treadmill deficits. All spinalized rats lesioned in trunk cortex (n = 16: 4 transplant, 6 transect, 6 transect + fibrin glue) lost an average of about 40% of their weight support. Intact trunk cortex was essential to their level of function. Lesion of trunk cortex substantially increased roll of the hindquarters, which correlated to diminished weight support, but other kinematic stepping parameters showed little change. Embryonic day 14 (E14) transplants support development of the trunk motor representations in their normal location. We tested the role of novel relay circuits arising from the grafts in such cortical representations in E14 transplants using the rats that received (noncellular) fibrin glue grafting at P1/P2 (8 allografts and 32 xenografts). Fibrin-repaired rats with autonomous weight support also had trunk cortical representations similar to those of E14 transplant rats. Thus acellular repair and intrinsic plasticity were sufficient to support the observed features. Our data show that effective cortical mechanisms for trunk control are essential for autonomous weight support in P1/P2 spinalized rats and these can be achieved by intrinsic plasticity.

A three-dimensional model of the rat hindlimb: musculoskeletal geometry and muscle moment arms

As a first step towards developing a dynamic model of the rat hindlimb, we measured muscle attachment and joint center coordinates relative to bony landmarks using stereophotogrammetry. Using these measurements, we analyzed muscle moment arms as functions of joint angle for most hindlimb muscles, and tested the hypothesis that postural change alone is sufficient to alter the function of selected muscles of the leg. We described muscle attachment sites as second-order curves. The length of the fit parabola and residual errors in the orthogonal directions give an estimate of muscle attachment sizes, which are consistent with observations made during dissection. We modeled each joint as a moving point dependent on joint angle; relative endpoint errors less than 7% indicate this method as accurate. Most muscles have moment arms with a large range across the physiological domain of joint angles, but their moment arms peak and vary little within the locomotion domain. The small variation in moment arms during locomotion potentially simplifies the neural control requirements during this phase. The moment arms of a number of muscles cross zero as angle varies within the quadrupedal locomotion domain, indicating they are intrinsically stabilizing. However, in the bipedal locomotion domain, the moment arms of these muscles do not cross zero and thus are no longer intrinsically stabilizing. We found that muscle function is largely determined by the change in moment arm with joint angle, particularly the transition from quadrupedal to bipedal posture, which may alter an intrinsically stabilizing arrangement or change the control burden.

Neuromuscular electrical stimulation induced forelimb movement in a rodent model

Upper extremity neuromuscular electrical stimulation (FNS) has long been utilized as a neuroprosthesis to restore hand-grasp function in individuals with neurological disorders and injuries. More recently, electrical stimulation is being used as a rehabilitative therapy to tap into central nervous system plasticity. Here, we present initial development of a rodent model for neuromuscular stimulation induced forelimb movement that can be used as a platform to investigate stimulation-induced plasticity. The motor points for flexors and extensors of the shoulder, elbow, and digits were identified and implanted with custom-built stimulation electrodes. The strength-duration curves were determined and from these curves the appropriate stimulation parameters required to produce consistent isolated contraction of each muscle with adequate joint movement were determined. Using these parameters and previous locomotor EMG data, stimulation was performed on each joint muscle pair to produce reciprocal flexion/extension movements in the shoulder, elbow, and digits, while 3D joint kinematics were assessed. Additionally, co-stimulation of multiple muscles across multiple forelimb joints was performed to produce stable multi-joint movements similar to those observed during reach-grasp-release movements. Future work will utilize this model to investigate the efficacy and underlying mechanisms of forelimb neuromuscular stimulation therapy to promote recovery and plasticity after neural injury in rodents.

Rat Models of Traumatic Spinal Cord Injury to Assess Motor Recovery

Devastating motor, sensory, and autonomic dysfunctions render long-term personal hardships to the survivors of traumatic spinal cord injury (SCI). The suffering also extends to the survivors' families and friends, who endure emotional, physical, and financial burdens in providing for necessary surgeries, care, and rehabilitation. After the primary mechanical SCI, there is a complex secondary injury cascade that leads to the progressive death of otherwise potentially viable axons and cells and that impairs endogenous recovery processes. Investigations of possible cures and of ways to alleviate the hardships of traumatic SCI include those of interventions that attenuate or overcome the secondary injury cascade, enhance the endogenous repair mechanisms, regenerate axons, replace lost cells, and rehabilitate. These investigations have led to the creation of laboratory animal models of the different types of traumatic human SCI and components of the secondary injury cascade. However, no particular model completely addresses all aspects of traumatic SCI. In this article, we describe adult rat SCI models and the motor, and in some cases sensory and autonomic, deficits that each produces. Importantly, as researchers in this area move toward clinical trials to alleviate the hardships of traumatic SCI, there is a need for standardized small and large animal SCI models as well as quantitative behavioral and electrophysiological assessments of their outcomes so that investigators testing various interventions can directly compare their results and correlate them with the molecular, biochemical, and histological alterations.

A comparison analysis of hindlimb kinematics during overground and treadmill locomotion in rats

The convenience of the motor-driven treadmill makes it an attractive instrument for investigating rat locomotion. However, no data are available to indicate whether hindlimb treadmill kinematic findings may be compared or generalized to overground locomotion. In this investigation, we compared overground and treadmill locomotion for differences in the two-dimensional angular kinematics and temporal and spatial measurements for the hindlimb. Ten female rats were evaluated at the same speed for natural overground and treadmill walking. The walking velocity, swing duration and stride length were statistically indistinguishable between the two testing conditions. Significant differences were found between overground and treadmill locomotion for step cycle duration and stance phase duration parameters. During the stance phase of walking, the angular movement of the hip, knee and ankle joints were significantly different in the two conditions, with greater flexion occurring on the overground. Despite this, the sagittal joint movements of the hindlimb were similar between the two walking conditions, with only three parameters being significantly different in the swing. Hip height and angle-angle cyclograms were also only found to display subtle differences. This study suggests that reliable kinematic measurements can be obtained from the treadmill gait analysis in rats.

Functional considerations of stem cell transplantation therapy for spinal cord repair

Stem cells hold great promise for therapeutic repair after spinal cord injury (SCI). This review compares the current experimental approaches taken towards a stem cell-based therapy for SCI. It critically evaluates stem cell sources, injury paradigms, and functional measurements applied to detect behavioral changes after transplantation into the spinal cord. Many of the documented improvements do not exclusively depend on lineage-specific cellular differentiation. In most of the studies, the functional tests used cannot unequivocally demonstrate how differentiation of the transplanted cells contributes to the observed effects. Standardized cell isolation and transplantation protocols could facilitate the assessment of the true contribution of various experimental parameters on recovery. We conclude that at present embryonic stem (ES)-derived cells hold the most promise for therapeutic utility, but that non-neural cells may ultimately be optimal if the mechanism of possible transdifferentiation can be elucidated.