GaitNet+ARL: A Deep Learning Algorithm for Interpretable Gait Analysis of Chronic Ankle Instability

Chronic ankle instability (CAI) is a major public health concern and adversely affects people's mobility and quality of life. Traditional assessment methods are subjective and qualitative by means of clinician observation and patient self-reporting, which may lead to inaccurate assessment and reduce the effectiveness of treatment in clinical practice. Gait analysis becomes a commonly used approach for monitoring human motion behaviors, which can be applied to specific diagnosis and assessment of CAI. However, it is still challenging to recognize the pathological gait pattern for CAI subjects. In this paper, we propose an integrated deep learning framework to solve the CAI recognition problem using kinematic data. Specifically, inspired by the biomechanics of human body system, we create a simple graph neural network (GNN), termed GaitNet, that operates on a spatial domain and exploits interactions among 3-D joint coordinates. We also develop an attention reinforcement learning (ARL) model that determines attention weights of frames on a temporal domain, which is combined with GaitNet for prediction. The effectiveness of our method is validated on the kinematic NEU-CAI dataset which is collected in our institution using a stereophotogrammetric system. According to extensive experiments, we demonstrate that the selected key phases (i.e., sequences of frames with high attentions) significantly increase the predictability of the proposed biomechanics-based GNN model to differentiate between CAI cohort and control cohort. Moreover, we show a significant prediction accuracy improvement (20%-25%) by our approach compared to state-of-the-art machine learning and deep learning methods.

Inter-joint coordination variability is associated with pain severity and joint loading in persons with knee osteoarthritis

As the lower extremity is a linked-joint system, the contribution of movements at the hip and ankle, in addition to the knee, to gait patterns should be considered for persons with knee osteoarthritis (OA). However, the relationships of joint coordination variability to OA symptoms, particularly knee pain, and joint loading is unknown. The purpose of this study was to determine the relationship of joint coordination variability to knee pain severity and joint loading in persons with knee OA. Thirty-four participants with knee OA underwent gait analysis. Vector coding was used to assess coordination variability during the early, mid, and late stance phase. Hip-knee coupling angle variability (CAV) during midstance was associated with Knee Injury and Osteoarthritis Outcome Score (KOOS) pain (r = -0.50, p = 0.002) and Visual Analog Scale pain (r = 0.36, p = 0.04). Knee-ankle CAV during midstance was associated with KOOS pain (r = -0.34, p = 0.05). Hip-knee CAV during early and midstance were associated with knee flexion moment (KFM) impulses (r = -0.46, p = 0.01). Knee-ankle CAV during early and midstance were associated with peak KFM (r = -0.51, p < 0.01; r = -0.70, p < 0.01). Moreover, knee-ankle CAV during early, mid, and late stance phase were associated with KFM impulses (r = -0.53, p < 0.01; r = -0.70, p < 0.01; r = -0.54, p < 0.01). These findings suggest that joint coordination variability may be a factor that influences pain and knee joint loading in persons with knee OA. Statement of Clinical Significance: Movement coordination of the hip, knee, and ankle should be considered in the clinical management and future research related to knee OA.

Association Rule Mining to Examine Predictors for the Outcome of Gait Rehabilitation Programs in Stroke Survivors

ABSTRACT

This study presents a novel application of association rule data mining to determine the predictors of the response to locomotor training and home exercise for improving gait after stroke. The study was a secondary data analysis on the Locomotor Experience Applied Post Stroke Trial dataset. The association rule analysis was applied to analyze three interventions: (1) early locomotor training, (2) late locomotor training, and (3) home exercise program. The outcome variable was whether participants poststroke had greater than median improvement in the self-selected comfortable gait speed. Three types of predictors were investigated: (1) demographics, (2) behavioral and medical history, and (3) clinical assessments at baseline. Association rules were generated when they meet two criteria determined based on the data: 10% of support and 70% of confidence. The identified rules showed that the predictors of the response were different across the three interventions, which was inconsistent with the previous report based on traditional logistic regression. However, the rules were identified with high confidence but low support, indicating that they were reliable but did not appear often in the Locomotor Experience Applied Post Stroke Trial dataset. Further investigation of these rules with a larger sample size is warranted before applying them to clinical settings.

Recurrence Quantification Analysis of Ankle Kinematics During Gait in Individuals With Chronic Ankle Instability

Purpose

An investigation of the ankle dynamics in a motor task may generate insights into the etiology of chronic ankle instability (CAI). This study presents a novel application of recurrence quantification analysis (RQA) to examine the ankle dynamics during walking. We hypothesized that CAI is associated with changes in the ankle dynamics as assessed by measures of determinism and laminarity using RQA.

Methods

We recorded and analyzed the ankle position trajectories in the frontal and sagittal planes from 12 participants with CAI and 12 healthy controls during treadmill walking. We used time-delay embedding to reconstruct the position trajectories to a phase space that represents the states of the ankle dynamics. Based on the phase space trajectory, a recurrence plot was constructed and two RQA variables, the percent determinism (%DET) and the percent laminarity (%LAM), were derived from the recurrence plot to quantify the ankle dynamics.

Results

In the frontal plane, the %LAM in the CAI group was significantly lower than that in the control group (p < 0.05. effect size = 0.86). This indicated that the ankle dynamics in individuals with CAI is less likely to remain in the same state. No significant results were found in the %DET or in the sagittal plane.

Conclusion

A lower frontal-plane %LAM may reflect more frequent switching between different patterns of neuromuscular control states due to the instabilities associated with CAI. With further study and development, %LAM may have the potential to become a useful biomarker for CAI.

Exploiting telerobotics for sensorimotor rehabilitation: a locomotor embodiment

Background

Manual treadmill training is used for rehabilitating locomotor impairments but can be physically demanding for trainers. This has been addressed by enlisting robots, but in doing so, the ability of trainers to use their experience and judgment to modulate locomotor assistance on the fly has been lost. This paper explores the feasibility of a telerobotics approach for locomotor training that allows patients to receive remote physical assistance from trainers.

Methods

In the approach, a trainer holds a small robotic manipulandum that shadows the motion of a large robotic arm magnetically attached to a locomoting patient's leg. When the trainer deflects the manipulandum, the robotic arm applies a proportional force to the patient. An initial evaluation of the telerobotic system’s transparency (ability to follow the leg during unassisted locomotion) was performed with two unimpaired participants. Transparency was quantified by the magnitude of unwanted robot interaction forces. In a small six-session feasibility study, six individuals who had prior strokes telerobotically interacted with two trainers (separately), who assisted in altering a targeted gait feature: an increase in the affected leg’s swing length.

Results

During unassisted walking, unwanted robot interaction forces averaged 3−4 N (swing–stance) for unimpaired individuals and 2−3 N for the patients who survived strokes. Transients averaging about 10 N were sometimes present at heel-strike/toe-off. For five of six patients, these forces increased with treadmill speed during stance (R² = .99; p < 0.001) and increased with patient height during swing (R² = .71; p = 0.073). During assisted walking, the trainers applied 3.0 ± 2.8 N (mean ± standard deviation across patients) and 14.1 ± 3.4 N of force anteriorly and upwards, respectively. The patients exhibited a 20 ± 21% increase in unassisted swing length between Days 1−6 (p = 0.058).

Conclusions

The results support the feasibility of locomotor assistance with a telerobotics approach. Simultaneous measurement of trainer manipulative actions, patient motor responses, and the forces associated with these interactions may prove useful for testing sensorimotor rehabilitation hypotheses. Further research with clinicians as operators and randomized controlled trials are needed before conclusions regarding efficacy can be made.

Use of thrust joint manipulation by student physical therapists in the United States during clinical education experiences

Introduction: Thrust joint manipulation (TJM) is used in physical therapy practice and taught in entry-level curricula in the United States (US); however, research regarding implementation by student physical therapists (SPT)s is scarce. Objectives: To explore the use of TJM in SPT clinical education and factors influencing implementation. Methods: In a cross-sectional exploratory study, accredited physical therapy (PT) programs in the US (n = 227) were invited to participate in an electronic survey. SPTs were queried about TJM use and their clinical instructor's (CI) credentials during their final musculoskeletal clinical experience. Results: Forty-five programs participated in the study, consisting of 2,147 SPTs. Of those, 414 (19.3%) responses were used for analysis and 69% reported using TJM. SPTs who utilized TJM were more likely to have a CI who used TJM (p < 0.001) and/or had advanced certification/training in manual therapy (p < .001). A majority of students agreed or strongly agreed that their academic preparation provided them with clinical reasoning tools (84%) and psychomotor skills (69%) necessary to perform TJM. SPT use of TJM was facilitated by CI clinical practice, SPT competence in psychomotor skill, confidence in clinical reasoning, and practice setting. A main barrier to student use of TJM was CI lack of TJM use. Conclusions: Clinical practice of the CI appears to be a key factor in determining student use of TJM. Level of evidence: 2b.

Visuomotor control of ankle joint using position vs. force

Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g., due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position, as the findings in upper limb may not be generalizable to the lower limb. This study aimed to characterize the skilled performance of ankle joint in visuomotor position and force control. A two-degree-of-freedom (DOF) robotic footplate was used to measure individuals' force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. In contrast to comparable performance in 1-DOF control tasks, the performance in 2-DOF tasks was different and had characteristic patterns in the position and force conditions, with a significantly better performance for position. Subjective questionnaires on the perceived difficulty matched the objective experimental results, suggesting that the poor performance in force control was not due to experimental set-up or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in visuomotor coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks and therapeutic protocols.

Handgrip Strength: A Comparison of Values Obtained From the NHANES and NIH Toolbox Studies

IMPORTANCE

Handgrip dynamometry is probably the most commonly used method to characterize overall human muscle strength.

OBJECTIVE

To compare and summarize grip strength measurements obtained from two population-based studies.

DESIGN

Secondary data analysis.

SETTING AND PARTICIPANTS

Data from (1) the 2011-2014 National Health and Nutrition Examination Survey (NHANES) with 13,918 participants and (2) the 2011 normative phase of the National Institutes of Health (NIH) Toolbox project with 3,594 participants.

OUTCOMES AND MEASURES

The NHANES values used were the mean and best of three trials; the NIH Toolbox value used was the one maximum trial after a practice trial.

RESULTS

General linear model analysis revealed that values obtained from the NIH Toolbox differed from NHANES best values but not from NHANES mean values. The analysis also indicated, regardless of the values used, that grip strength differed significantly between dominant and nondominant sides, males and females, and age groups. We provide updated reference values for handgrip strength.

CONCLUSIONS AND RELEVANCE

On the basis of these analyses, we summarize grip strength measures obtained from the NHANES and NIH Toolbox for side, gender, and age group strata. Reference values are essential to assist in the interpretation of testing results and clinical decision making.

Between-side differences in hand-grip strength across the age span: Findings from 2011-2014 NHANES and 2011 NIH Toolbox studies

This project was undertaken to describe percentage differences in the grip strength between the dominant and nondominant-sides of left- and right-handed males and females across the age span. Data used in the project were from population-based samples of participants: 13,653 from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) and 3,571 from the 2011 normative phase of the National Institutes of Health (NIH) Toolbox project. Depending on how percentage differences were calculated, the overall grip strength was a mean 5.0-5.6% greater on the dominant than nondominant side. The percentage differences were significantly greater for individuals who were right-hand dominant rather than left-hand dominant. The differences also varied according to gender. We present summary data for percentage differences stratified by study, handedness, and gender. The values can be used to determine whether grip strength on one side is limited relative to the other.

An examination of muscle force control in individuals with a functionally unstable ankle

Previous studies suggest that functional ankle instability (FAI) may be associated with deficits in the ability to sense muscle forces. We tested individuals with FAI to determine if they have reduced ability to control ankle muscle forces, which is a function of force sense. Our test was performed isometrically to minimize the involvement of joint position sense and kinesthesia. A FAI group and a control group were recruited to perform an ankle force control task using a platform-based ankle robot. They were asked to move a cursor to hit 24 targets as accurately and as fast as possible in a virtual maze. The cursor movement was based on the direction and magnitude of the forces applied to the robot. Participants underwent three conditions: pre-test (baseline), practice (skill acquisition), and post-test (post skill acquisition). The force control ability was quantified based on the accuracy performance during the task. The accuracy performance was negatively associated with the collision count of the cursor with the maze wall. The FAI group showed reduced ability to control ankle muscle forces compared to the control group in the pre-test condition, but the difference became non-significant in the post-test condition after practice. The change in performance before and after practice may be due to different degrees of reliance on force sense.

Effects of kinesiotaping and athletic taping on ankle kinematics during walking in individuals with chronic ankle instability: A pilot study

BACKGROUND

Individuals with chronic ankle instability (CAI) tend to walk with an overly inverted foot, which increases the risk of ankle sprains during stance phase. Clinicians could perform ankle taping using kinesiotape (KT) or athletic tape (AT) to address this issue. Because KT is elastic while AT is not, the techniques and underlying mechanisms for applying these tapes are different, which may lead to different outcomes.

RESEARCH QUESTION

To compare the effects of KT and AT interventions on foot motion in the frontal plane and tibial motion in the transverse plane during stance phase of walking.

METHODS

Twenty subjects with CAI were assigned to either KT or AT group, and walked on a treadmill in no tape and taped conditions. Their foot and tibial motions were captured by 3D motion analysis system. The main component of KT application was two pieces of tape applied from the medial aspect of the hindfoot to the lateral to generate a pulling tension towards eversion. AT was applied to the ankle using the closed basket weave approach. AT was not stretchable and not able to generate the same pulling tension as KT.

RESULTS

KT increased foot eversion during early stance, but showed no effect during late stance. AT increased tibial internal rotation during late stance, but showed no effect during early stance.

SIGNIFICANCE

Compared to AT, KT better provides a flexible pulling force that facilitates foot eversion during early stance, while not restricting normal inversion in late stance during walking. KT may be a useful clinical tool in correcting aberrant motion while not limiting natural movement in sports.

Muscle activation pattern during self-propelled treadmill walking

[Purpose] To examine muscular demands during self-propelled treadmill walking to provide a potential option for fitness training. [Participants and Methods] Eleven healthy college students were recruited. Participants walked under three conditions: over-ground walking at a self-selected speed, treadmill walking at a self-selected speed, and treadmill walking at a speed comparable to that of over-ground walking. Step lengths and lower extremity muscle activations were recorded while participants walked under the three conditions. [Results] Step lengths were significantly shorter when participants walked on a self-propelled treadmill than when walking over-ground. The spatiotemporal and muscle activations of the gaits varied among the different walking conditions. Muscular demands at the moment of heel-strike were higher around the hip and knee when walking on the self-propelled treadmill than when walking over-ground. [Conclusion] During heel-strike, the lower extremity extensors were activated more on the self-propelled treadmill with an incline, especially at faster speeds, than during over-ground walking. A low-cost, self-propelled treadmill may be a modality for training specific muscles.

Hip-ankle coordination during gait in individuals with chronic ankle instability

Individuals with chronic ankle instability (CAI) may have sensorimotor impairments that affect control at the hip in addition to the ankle. The purpose of this study was to compare hip-ankle coordination and coordination variability between individuals with CAI and healthy individuals during walking. Ten healthy subjects and 10 subjects with CAI were recruited to walk on a treadmill. Hip-ankle coordination was quantified using vector coding, and coordination variability was quantified using coefficient of correspondence. We found significant between-group differences in hip-ankle coordination in the frontal plane around loading response (Control: 165.9±18.4°; CAI: 127.6±48.6°, p=0.04) and in the sagittal plane around the first half of mid stance (Control: 307.2±9.8°; CAI: 291.8±11.4°, p<0.01), terminal stance (Control: 301.1±13°; CAI: 313.4±10.9°, p=0.04), and pre-swing (Control: 243.9±35.2°; CAI: 329.9±57.8°, p<0.01). We also found significant between-group differences in hip-ankle coordination variability in the frontal plane around the second half of mid stance (Control: 0.54±0.06; CAI: 0.45±0.07, P<0.01). CAI is associated with alteration of hip-ankle coordination and coordination variability in stance phase during walking. Gait training is important in CAI rehabilitation, and the training should address altered hip-ankle coordination to reduce the risk of recurrent injuries.

An arm for a leg: Adapting a robotic arm for gait rehabilitation

The purpose of this study was to adapt a multipurpose robotic arm for gait rehabilitation. An advantage of this approach is versatility: a robotic arm can be attached to almost any point on the body to assist with lower- and upper-extremity rehabilitation. This may be more cost-effective than purchasing and training rehabilitation staff to use several specialized rehabilitation robots. Robotic arms also have a more human-like morphology, which may make them less intimidating or alien to patients. In this study a mechanical interface was developed that allows a fast, secure, and safe attachment between a robotic arm and a human limb. The effectiveness of this interface was assessed by having two healthy subjects walk on a treadmill with and without a robotic arm attached to their legs. The robot's ability to follow the subjects' swinging legs was evaluated at slow and fast walking speeds. Two different control schemes were evaluated: one using the standard manufacturer-provided control algorithm, and another using a custom algorithm that actively compensated for robot-human interaction forces. The results showed that both robot control schemes performed well for slow walking. There were negligible differences between subjects' gait kinematics with and without the robot. During fast walking with the robot, similar results were obtained for one subject; however, the second subject demonstrated noticeable gait modifications. Together, these results show the feasibility of adapting a multipurpose robotic arm for gait rehabilitation.

A reinforcement learning approach to gait training improves retention

Many gait training programs are based on supervised learning principles: an individual is guided towards a desired gait pattern with directional error feedback. While this results in rapid adaptation, improvements quickly disappear. This study tested the hypothesis that a reinforcement learning approach improves retention and transfer of a new gait pattern. The results of a pilot study and larger experiment are presented. Healthy subjects were randomly assigned to either a supervised group, who received explicit instructions and directional error feedback while they learned a new gait pattern on a treadmill, or a reinforcement group, who was only shown whether they were close to or far from the desired gait. Subjects practiced for 10 min, followed by immediate and overnight retention and over-ground transfer tests. The pilot study showed that subjects could learn a new gait pattern under a reinforcement learning paradigm. The larger experiment, which had twice as many subjects (16 in each group) showed that the reinforcement group had better overnight retention than the supervised group (a 32% vs. 120% error increase, respectively), but there were no differences for over-ground transfer. These results suggest that encouraging participants to find rewarding actions through self-guided exploration is beneficial for retention.

Using swing resistance and assistance to improve gait symmetry in individuals post-stroke

A major characteristic of hemiplegic gait observed in individuals post-stroke is spatial and temporal asymmetry, which may increase energy expenditure and the risk of falls. The purpose of this study was to examine the effects of swing resistance/assistance applied to the affected leg on gait symmetry in individuals post-stroke. We recruited 10 subjects with chronic stroke who demonstrated a shorter step length with their affected leg in comparison to the non-affected leg during walking. They participated in two test sessions for swing resistance and swing assistance, respectively. During the adaptation period, subjects counteracted the step length deviation caused by the applied swing resistance force, resulting in an aftereffect consisting of improved step length symmetry during the post-adaptation period. In contrast, subjects did not counteract step length deviation caused by swing assistance during adaptation period and produced no aftereffect during the post-adaptation period. Locomotor training with swing resistance applied to the affected leg may improve step length symmetry through error-based learning. Swing assistance reduces errors in step length during stepping; however, it is unclear whether this approach would improve step length symmetry. Results from this study may be used to develop training paradigms for improving gait symmetry of stroke survivors.

An exploratory examination of the association between altered lumbar motor control, joint mobility and low back pain in athletes

Background:

Low back pain (LBP) is a common cause of lost playing time and can be a challenging clinical condition in competitive athletes. LBP in athletes may be associated with joint and ligamentous hypermobility and impairments in activation and coordination of the trunk musculature, however there is limited research in this area.

Objectives:

To determine if there is an association between altered lumbar motor control, joint mobility and low back pain (LBP) in a sample of athletes.

Materials and Methods:

Fifteen athletes with LBP were matched by age, gender and body mass index (BMI) with controls without LBP. Athletes completed a questionnaire with questions pertaining to demographics, activity level, medical history, need to self-manipulate their spine, pain intensity and location. Flexibility and lumbar motor control were assessed using: active and passive straight leg raise, lumbar range of motion (ROM), hip internal rotation ROM (HIR), Beighton ligamentous laxity scale, prone instability test (PIT), observation of lumbar aberrant movements, double leg lowering and Trendelenburg tests. Descriptive statistics were compiled and the chi square test was used to analyze results.

Results:

Descriptive statistics showed that 40% of athletes with LBP exhibited aberrant movements (AM), compared to 6% without LBP. 66% of athletes with LBP reported frequently self-manipulating their spine compared to 40% without LBP. No significant differences in motor control tests were found between groups. Athletes with LBP tended to have less lumbar flexion (63 ± 11°) compared to those without LBP (66 ± 13°). Chi-Square tests revealed that the AM were more likely to be present in athletes with LBP than those without (X2 = 4.66, P = 0.03).

Conclusions:

The presence of aberrant movement patterns is a significant clinical finding and associated with LBP in athletes.

Test of a customized compliant ankle rehabilitation device in unpowered mode

Presented is the design, implementation, and initial gait testing of a lightweight, compliant robotic device for ankle rehabilitation. Many patients with neuromuscular disorders suffer deficits in sensorimotor control of the ankle joint, leading to an abnormal walking pattern. Robotic devices have been used to assist ankle rehabilitation. However, these devices are usually heavy and rigid, which can deviate a natural gait pattern. To address these issues, our team has developed a light weight, compliant ankle robotic device actuated by artificial pneumatic muscles. A total of 3 healthy subjects were recruited to test whether the mechanical structure of the device deviates gait. We used a 3-dimensional (3D) motion analysis system to record and analyze subjects' ankle kinematics during gait while walking barefoot and while wearing the device unpowered. The preliminary results suggest that the device caused some, but minimal changes in ankle kinematics during gait. The changes were mainly caused by the device's rigid footplate, used to support the foot and connect to the pneumatic muscles. The preliminary results will be used for future improvement of the device.

Size of kinematic error affects retention of locomotor adaptation in human spinal cord injury

Studies in arm motor adaptation suggest that introducing small errors during the adaptation period may lead to a longer retention of the aftereffect than introducing large errors. However, it is unclear whether this notion can be generalized to locomotor adaptation in patients with incomplete spinal cord injury (SCI). We hypothesized that a smaller error size may lead to longer retention of the aftereffect in patients with SCI. We recruited 12 subjects with incomplete SCI for this study. They were instructed to walk on a treadmill while light-, medium-, and heavy-resistance loads were applied to the right ankle to perturb leg swing. Each of the three resistance-load conditions were specific to the subject and determined by each subject's maximum voluntary contraction of the hip flexors. We observed that subjects tended to make larger errors when the resistance-load condition was greater. Following resistance load release, subjects showed an aftereffect consisting of an increase in stride length. Further, the aftereffect was retained longer in the medium-resistance load condition than in the heavy- and light-resistance load conditions. This finding suggests that a patient-specific resistance load may be needed to facilitate retention of locomotor adaptation in patients with incomplete SCI.

Robotic resistance/assistance training improves locomotor function in individuals poststroke: a randomized controlled study

OBJECTIVE

To determine whether providing a controlled resistance versus assistance to the paretic leg at the ankle during treadmill training will improve walking function in individuals poststroke.

DESIGN

Repeated assessment of the same patients with parallel design and randomized controlled study between 2 groups.

SETTING

Research units of rehabilitation hospitals.

PARTICIPANTS

Patients (N=30) with chronic stroke.

INTERVENTION

Subjects were stratified based on self-selected walking speed and were randomly assigned to the resistance or assistance training group. For the resistance group, a controlled resistance load was applied to the paretic leg at the ankle to resist leg swing during treadmill walking. For the assistance group, a load that assists swing was applied.

MAIN OUTCOME MEASURES

Primary outcome measures were walking speed and 6-minute walking distance. Secondary measures included clinical assessments of balance, muscle tone, and quality of life. Outcome measures were evaluated before and after 6 weeks of training and at 8 weeks' follow-up, and compared within group and between the 2 groups.

RESULTS

After 6 weeks of robotic training, walking speed significantly increased for both groups, with no significant differences in walking speed gains observed between the 2 groups. In addition, 6-minute walking distance and balance significantly improved for the assistance group but not for the resistance group.

CONCLUSIONS

Applying a controlled resistance or an assistance load to the paretic leg during treadmill training may induce improvements in walking speed in individuals poststroke. Resistance training was not superior to assistance training in improving locomotor function in individuals poststroke.

A novel cable-driven robotic training improves locomotor function in individuals post-stroke

A novel cable-driven robotic gait training system has been tested to improve the locomotor function in individuals post stroke. Seven subjects with chronic stroke were recruited to participate in this 6 weeks robot-assisted treadmill training paradigm. A controlled assistance force was applied to the paretic leg at the ankle through a cable-driven robotic system. The force was applied from late stance to mid-swing during treadmill training. Body weight support was provided as necessary to prevent knee buckling or toe drag. Subjects were trained 3 times a week for 6 weeks. Overground gait speed, 6 minute walking distance, and balance were evaluated at pre, post 6 weeks robotic training, and at 8 weeks follow up. Significant improvements in gait speed and 6 minute walking distance were obtained following robotic treadmill training through a cable-driven robotic system. Results from this study indicate that it is feasible to improve the locomotor function in individuals post stroke through a flexible cable-driven robot.

Temporal relationship between trunk and thigh contributes to balance control in load carriage walking

Load carriage walking (LCW) challenges a person's balance as the load increases their forward trunk inclination, shifting the center of mass (COM) forward with respect to the base of support (BOS). We examined LCW to understand whether and how healthy people adjust the temporal relationship (TR) between the trunk and leg for balance control. Ten subjects were recruited to perform unloaded walking and LCW. The TR between the trunk and leg was measured by the continuous relative phase. The maximum forward displacement of the COM with respective to the BOS (FDCOM(BOS)) was recorded during the stance phase. We found that the TR was shifted in LCW, and the shift was associated with a decrease in the maximum FDCOM(BOS). The findings suggest that the TR between the trunk and leg contributes to balance control, and it may be a variable that needs to be addressed in gait rehabilitation.

The stage-dependent inhibitory effect of porcine follicular cells on the development of preantral follicles

The objective of this study was to examine the effects of follicular cells on the in vitro development of porcine preantral follicles. In Experiment 1, one preantral follicle alone (Trt 1) was cocultured with a follicle of the same size with oocytes (Trt 2) or without oocytes (Trt 3). Preantral follicles cultured alone in vitro for 12 days had greater follicle diameters (1017 +/- 96 microm versus 706 +/- 69 or 793 +/- 72 microm, P < 0.05), growth rates (201 +/- 0.3 versus 103 +/- 0.2 or 128 +/- 0.2, P < 0.05) and oocyte survival rates (73% versus 48, or 25%, P < 0.05) than other groups. The inhibitory effects of follicle cells on the growth of preantral follicles and oocyte survival rates were not enhanced by the addition of oocytectomized preantral follicles (Experiment 2). Follicles were cocultured with different sources of follicular cells in other experiments. Coculture with cumulus cells enhanced oocyte survival compared to the control (without coculture) and mural follicular cell groups (Experiment 3). The growth and survival rates of oocytes collected from the group of follicles cocultured with cumulus cells from large antral follicles (>3 mm) were greater (P < 0.05) than those from small antral follicles (<3 mm), or than the control group (without cumulus cells, experiment 4). No significant differences in the follicular diameters (674 +/- 30 microm versus 638 +/- 33 and 655 +/- 28 microm) and growth rate (105% versus 94 and 105%) were observed among the preantral follicles of the different treatments (P > 0.05). Taken together, coculture with the cells from large antral follicles (>3 mm) exerted a significant positive effect on oocyte survival. The growth and oocyte survival of preantral follicle cocultured with the same size of follicles (with or without oocyte) were inhibited. Growth and survival rates of preantral follicles and oocytes are improved by coculturing them with the cumulus cells derived from larger antral follicles.

Combination of a new composite biocampatible skin graft on the neodermis of artificial skin in an animal model

INTRODUCTION

There have been very limited and inconsistent attempts at combining the cultured epidermal autograft (CEA) with the neodermis of artificial skin (Integra). The reasons for this remain unknown. The basement membrane proteins of conventional CEA sheets are easily damaged by the dispase treatment during the harvesting of the CEA from the culture flask. The damage of the basement membrane proteins may affect the anchorage of CEA onto the neodermis of Integra. A new Composite Biocompatible Skin Graft (CBSG) was recently developed.

METHODS

Composite biocompatible skin graft consists of autologous keratinocytes cultivated on a pliable hyaluronate-derived membrane (Laserskin)which has been pre-seeded with allogenic dermal fibroblasts. Basement membrane proteins of CBSG are protected from the dispase treatment because the keratinocytes are directly seeded onto Laserskin. The engraftment of CBSG was evaluated on 20 wounds of 10 rats. Integrawas grafted on two freshly excised full-thickness wounds (3cm in diameter) in the dorsum of each animal. A polypropylene ring was applied to each wound to prevent the migration of epithelium from the edges. Composite Biocompatible Skin Graft was used to cover the neodermis of Integra after the silicone membrane was removed 14-21 days postgrafting.

RESULTS

Fourteen (70%) of 20 skin biopsies taken at day 21 from the centre of the grafted wounds revealed regenerated epithelium.

CONCLUSION

A feasible delivery system of cultured keratinocytes onto theneodermis of Integra is demonstrated in this animal -experiment.

The efficacy of collagen dermis membrane and fibrin on cultured epidermal graft using an athymic mouse model

A human skin substitute consisting of human cultured keratinocytes, collagen dermis, and fibrin was evaluated in athymic mice. Eighty athymic mice were divided randomly into four groups. A 1.5x1.5-cm full-thickness wound defect was created on the back of each athymic mouse under anesthesia. These wounds were covered by sheets of cultured epidermal graft (group A), cultured epidermal graft with collagen dermis and fibrin (group B), cultured epidermal graft with collagen dermis (group C), or cultured epidermal graft with fibrin (group D). The grafts were secured and kept moist by specially designed saline gauze chambers. The take rates of the cultured graft with more than 50% of the wound covered were 65%, 15%, 50%, and 45% respectively. Group B had a significantly lower graft take rate, however the difference was not significant among groups A, C, and D. Light microscopy of biopsies of the grafted sites at 12 days showed complete epithelialization. The incidence of discharge from wound beds in groups A, B, C, and D was 0%, 15%, 15%, and 10% respectively. The results suggest that cultured cells are best grafted directly onto the wound bed or in combination with either a thin layer of collagen or fibrin but not both because the collagen dermal membrane and the fibrin together may impose too great a diffusion barrier for the cultured cell graft to become vascularized.

Development and evaluation of a new composite Laserskin graft

BACKGROUND

Tremendous effort has been made to improve the graft take rate of cultured epidermal autograph. The purpose of this study is to develop and evaluate a new composite Laserskin graft (CLSG) as a human skin substitute for wound resurfacing.

METHODS

The seeding efficacy of cultured keratinocytes on plain Laserskin was compared with the 3T3 cell-seeded Laserskin and allogenic fibroblast-populated Laserskin. Three different types of CLSG, 2 cm in diameter each, were prepared and tested in rats. Type A CLSG consisted of proliferative allogenic rat fibroblasts on both sides of the Laserskin with autologous keratinocytes also on the upper side. Fibroblasts and keratinocytes were seeded only on the upper side of the Laserskin in type B CLSG. Keratinocytes alone were seeded on plain Laserskin in type C CLSG. Type B CLSG consisting of autologous keratinocytes and autologous dermal fibroblasts was tested on five selected wounds (5x5 cm each) of a patient with full-thickness burn. In another burn patient, type B CLSG consisting of autologous keratinocytes and allogenic dermal fibroblasts was grafted onto three wounds (5x5 cm each).

RESULTS

The seeding efficacy of human keratinocytes on plain Laserskin increased from 75% to 95% when proliferative allogenic fibroblasts were grown as a feeder layer on the Laserskin. The seeding efficacy of rat keratinocytes increased from 36% to 88% in the presence of a proliferative allogenic fibroblast feeder layer, whereas human/rat keratinocytes had respective seeding efficacy of 98%/91% on Laserskin preseeded with mitomycin C-treated 3T3 cells. Skin biopsies of grafted type A CLSG on day 14 after grafting showed complete epithelialization without severe inflammation in 16 of 20 (80%) grafted surgical wounds in rats. There were eight (40%) and seven (35%) "takes" of the CLSG in types B and C, respectively. The infection rate in type B CLSG was two (10%). There was one (5%) infection in types A and C. The respective take rates on the two patients grafted with type B CLSG were 60% and 100%.

CONCLUSION

The animal experiment and the preliminary clinical data showed that the CSLGs consisting of autologous keratinocytes and of autologous/allogenic fibroblasts are good human skin substitutes in terms of durability, biocompatibility, high seeding efficacy for keratinocytes, high graft take rate, and low infection rate.

PAK promotes morphological changes by acting upstream of Rac

The serine/threonine kinase p21-activated kinase (PAK) has been implicated as a downstream effector of the small GTPases Rac and Cdc42. While these GTPases evidently induce a variety of morphological changes, the role(s) of PAK remains elusive. Here we report that overexpression of betaPAK in PC12 cells induces a Rac phenotype, including cell spreading/membrane ruffling, and increased lamellipodia formation at growth cones and shafts of nerve growth factor-induced neurites. These effects are still observed in cells expressing kinase-negative or Rac/Cdc42 binding-deficient PAK mutants, indicating that kinase- and p21-binding domains are not involved. Furthermore, lamellipodia formation in all cell lines, including those expressing Rac binding-deficient PAK, is inhibited significantly by dominant-negative RacN17. Equal inhibition is achieved by blocking PAK interaction with the guanine nucleotide exchange factor PIX using a specific N-terminal PAK fragment. We conclude that PAK, via its N-terminal non-catalytic domain, acts upstream of Rac mediating lamellipodia formation through interaction with PIX.

Extraction of perceptually salient contours by striate cortical networks

We present a cortical-based model for computing the perceptual salience of contours embedded in noisy images. It has been suggested that horizontal intra-cortical connections in primary visual cortex may modulate contrast detection thresholds and pre-attentive "pop-out". In our model, horizontal connections mediate context-dependent facilitatory and inhibitory interactions among oriented cells. Strongly facilitated cells undergo temporal synchronization; and perceptual salience is determined by the level of synchronized activity. The model accounts for a range of reported psychophysical and physiological effects of contour salience. In particular, the model proposes that intrinsic properties of synchronization account for the increased salience of smooth, closed contours. Application of the model to real images is demonstrated.

Coarse-grain parallel computing for very large scale neural simulations in the NEXUS simulation environment

We describe a neural simulator designed for simulating very large scale models of cortical architectures. This simulator, NEXUS, uses coarse-grain parallel computing by distributing computation and data onto multiple conventional workstations connected via a local area network. Coarse-grain parallel computing offers natural advantages in simulating functionally segregated neural processes. We partition a complete model into modules with locally dense connections--a module may represent a cortical area, column, layer, or functional entity. Asynchronous data communications among workstations are established through the Network File System, which, together with the implicit modularity, decreases communications overhead, and increases overall performance. Coarse-grain parallelism also benefits from the standardization of conventional workstations and LAN, including portability between generations and vendors.

Regulation of insulin-like growth factor binding protein-1 during the 24-hour metabolic clock and in response to hypoinsulinemia induced by fasting and Sandostatin in normal women

OBJECTIVE

To establish the relation of insulin-like growth factor-I (IGF-I) and IGF-binding protein-1 (IGFBP-1) with 24-hour metabolic excursions in normal healthy women and in response to acute interruption of metabolic homeostasis by hypoinsulinemia.

METHODS

Hourly blood samples during the 24-hour metabolic clock were obtained from seven normally cycling women. Uniform dietary composition (50% carbohydrate, 35% fat, and 15% protein) and timing of meals (8 AM, 12 PM, and 6 PM) were prescribed. Daytime hypoinsulinemia was induced by omitting meals and by Sandostatin (100 micrograms) administration. Changes in serum levels of glucose, insulin, cortisol, IGF-I, and IGFBP-1 were measured.

RESULTS

The diurnal pattern of serum IGFBP-1 levels during the 24-hour metabolic clock was characterized by a rapid fall during the feeding phase of the day and a progressive 3.5-fold rise during nocturnal fasting; IGF-I levels were unchanged. Changes in IGFBP-1 levels were in parallel to those of cortisol and were inversely related to increases in glucose (80%) and insulin (tenfold) levels after each meal and to their decline during nocturnal fasting. Daytime fasting and administration of Sandostatin were accompanied by rapid and sustained increases in IGFBP-1 when insulin levels declined to 54 +/- 20 pmol/L.

CONCLUSIONS

With constant levels of IGF-I, the diurnal rhythm of IGFBP-1 may subserve a physiologic function by coordinating insulin and IGF-I action with substrate availability. Fluctuations of insulin levels during the 24-hour metabolic clock in normal women appear to serve as a signal, with an inhibitory effect on IGFBP-1 production when levels are above 70 pmol/L and a stimulatory effect at levels below 70 pmol/L. These findings provide a basis for future investigations in women with nutritionally related reproductive disorders.

The premenstrual syndrome. Effects of "medical ovariectomy"

In a crossover study conducted over a six-month period in eight patients with well-characterized premenstrual syndrome, physical and behavioral symptoms were relieved by daily administration of an agonist of gonadotropin-releasing hormone. The reversible "medical ovariectomy" attained with this agonist suggests that it may be an effective and rational treatment for this distressing syndrome in the short term. Whether prolonged therapy would be safe and effective, or even necessary, remains to be determined.