A unicellular walker controlled by a microtubule-based finite-state machine

Cells are complex biochemical systems whose behaviors emerge from interactions among myriad molecular components. Computation is often invoked as a general framework for navigating this cellular complexity. However, it is unclear how cells might embody computational processes such that the theories of computation, including finite-state machine models, could be productively applied. Here, we demonstrate finite-state-machine-like processing embodied in cells using the walking behavior of Euplotes eurystomus, a ciliate that walks across surfaces using fourteen motile appendages (cirri). We found that cellular walking entails regulated transitions among a discrete set of gait states. The set of observed transitions decomposes into a small group of high-probability, temporally irreversible transitions and a large group of low-probability, time-symmetric transitions, thus revealing stereotypy in the sequential patterns of state transitions. Simulations and experiments suggest that the sequential logic of the gait is functionally important. Taken together, these findings implicate a finite-state-machine-like process. Cirri are connected by microtubule bundles (fibers), and we found that the dynamics of cirri involved in different state transitions are associated with the structure of the fiber system. Perturbative experiments revealed that the fibers mediate gait coordination, suggesting a mechanical basis of gait control.

Walking Speed Alters Barefoot Gait Coordination and Variability

Using the dynamic system approach, we examined the pattern and variability of inter-joint coordination in barefoot and shod walking in 20 women at three speeds: SLOW, FAST, and comfortable walking speed (CWS). We found that barefoot and shod walking used different coordination strategies to cope with increasing walking speed. As walking speed increased, ankle-knee coordination patterns between shod and barefoot became less different (p < 0.00001), and ankle-hip coordination patterns became more different (p < 0.001). Compared to shod, barefoot walking had significantly lower coordination variability in mid stance of knee-hip at CWS and FAST and late swing of ankle-hip at SLOW and CWS with medium effect (effect size 0.61-0.74). Future research should investigate the connection between the decreased coordination variability and joint tissue stress to understand the impact of barefoot walking on the lower extremity joints.

Does Subthalamic Deep Brain Stimulation Impact Asymmetry and Dyscoordination of Gait in Parkinson's Disease?

Background. Subthalamic deep brain stimulation (STN-DBS) is an effective treatment for selected Parkinson's disease (PD) patients. Gait characteristics are often altered after surgery, but quantitative therapeutic effects are poorly described. Objective. The goal of this study was to systematically investigate modifications in asymmetry and dyscoordination of gait 6 months postoperatively in patients with PD and compare the outcomes with preoperative baseline and to asymptomatic controls without PD. Methods. A convenience sample of thirty-two patients with PD (19 with postural instability and gait disorder (PIGD) type and 13 with tremor dominant disease) and 51 asymptomatic controls participated. Parkinson patients were tested prior to the surgery in both OFF and ON medication states, and 6-months postoperatively in the ON stimulation condition. Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) I to IV and medication were compared to preoperative conditions. Asymmetry ratios, phase coordination index, and walking speed were assessed. Results. MDS-UPDRS I to IV at 6 months improved significantly, and levodopa equivalent daily dosages significantly decreased. STN-DBS increased step time asymmetry (hedges' g effect sizes [95% confidence interval] between pre- and post-surgery: .27 [-.13, .73]) and phase coordination index (.29 [-.08, .67]). These effects were higher in the PIGD subgroup than the tremor dominant (step time asymmetry: .38 [-.06, .90] vs .09 [-.83, 1.0] and phase coordination index: .39 [-.04, .84] vs .13 [-.76, .96]). Conclusions. This study provides objective evidence of how STN-DBS increases asymmetry and dyscoordination of gait in patients with PD and suggests motor subtypes-associated differences in the treatment response.

Footwear Alters Lower Extremity Coordination Variability

Footwear has been shown to have a significant effect on numerous kinematic and kinetic variables during walking and running. While footwear mass is an indisputably important influence on gait patterns, we suspected that the amount of outsole material on most footwear would likely diminish or delay the integration of tactile feedback in motor control strategies during gait. Thus, we designed this study to investigate the influence of footwear and augmented tactile feedback on lower extremity coordination patterns during walking. A secondary purpose of the study was to examine gender differences in response to altered footwear conditions. Forty-eight participants (24 male and 24 females) walked during four standardized footwear conditions (barefoot, shod, barefoot with augmented tactile feedback, and shod with augmented tactile feedback), and we collected three-dimensional kinematic data and calculated continuous relative phase values for two adjacent lower extremity joints to determine interjoint coordination patterns. We used deviation phase and the mean of the continuous relative phase to compare motor coordination patterns across conditions. We found significant footwear and gender effects for spatiotemporal variables but only significant footwear effects for motor coordination patterns. Females displayed a significantly higher cadence and shorter height-normalized stride length as compared to males. Participants displayed significantly greater thigh-shank coordination variability in the shod, as compared to the unshod, conditions. Thus, footwear results in a diminished or delayed tactile feedback that alters neuromuscular control strategies during walking.

Weighted Walking Influences Lower Extremity Coordination in Children on the Autism Spectrum

There is sparse quantitative research regarding gait coordination patterns of children on the autism spectrum, though previous studies, relying only upon observational data, have alluded to characteristically poor movement coordination. This study compared walking with a weighted vest, a backpack carriage, and an unloaded walking condition on lower extremity coordination among 10 male children (aged 8-17 years) on the autism spectrum. All participants completed 15 gait trials in the following three conditions: (a) unloaded, (b) wearing a backpack weighted with 15% body mass, and (c) wearing a vest weighted with 15% body mass. We used continuous relative phase analysis to quantify lower extremity coordination and analyzed data through both group and single-subject comparisons. We used the Model Statistic to test for statistical significance at each of the normalized data points for each segment couple (thigh-leg, leg-foot, and thigh-foot). The first 10 and last 10 stride blocks were tested for possible accommodation strategies. Group comparisons revealed no coordination changes among the three conditions (likely due to insufficient statistical power), while single-subject comparisons exposed significant decreased variability in gait coordination patterns ( p < .05) in both loaded conditions, relative to the unloaded condition. These participants exhibited variable coordination patterns during the unloaded gait. When walking with loads, coordination pattern variability of the lower extremities was decreased. This finding suggests that walking while carrying or wearing heavy objects may reduce the number of potential motor pattern choices and thus decrease the overall variability of lower extremity movement patterns. Additional research with a larger and more diverse participant sample is required to confirm this conclusion.

Reshaping of Bilateral Gait Coordination in Hemiparetic Stroke Patients After Early Robotic Intervention

Hemiparetic gait is a common condition after stroke which alters importantly the quality of life of stroke survivors. In recent years, several robotic interventions have been developed to support and enhance rehabilitation strategies for such population. The Hybrid Assistive Limb^® (HAL) robot suit is a unique device able to collect in real time bioelectric signals from the patient to support and enhance voluntary gait. HAL has been used before in early stages of stroke showing gait improvement after the intervention. However, evaluation of the coordination of gait has not been done yet. Coordination is a key factor for an adequate gait performance; consequently, its changes may be closely related to gait recovery. In this study, we used planar covariation to evaluate coordination changes in hemiparetic stroke patients after early HAL intervention. Before starting, impaired intersegmental coordination for the paretic and non-paretic side was evident. HAL intervention was able to induce recovery of the covariation loop shape and deviation from the covariation plane improving intersegmental coordination. Also, there was a tendency of recovery for movement range evidenced by comparison of peak elevation angles of each limb segment of the patients before and after HAL intervention, and also when compared to healthy volunteers. Our results suggest that early HAL intervention contributed to the improvement of gait coordination in hemiparetic stroke patients by reinforcing central pattern generators and therefore reshaping their gait pattern. Trial registration: UMIN000022410 2016/05/23.

Reshaping of Gait Coordination by Robotic Intervention in Myelopathy Patients After Surgery

The Ossification of the Posterior Longitudinal Ligament (OPLL) is an idiopathic degenerative spinal disease which may cause motor deficit. For patients presenting myelopathy or severe stenosis, surgical decompression is the treatment of choice; however, despite adequate decompression residual motor impairment is found in some cases. After surgery, there is no therapeutic approach available for this population. The Hybrid Assistive Limb® (HAL) robot suit is a unique powered exoskeleton designed to predict, support, and enhance the lower extremities performance of patients using their own bioelectric signals. This approach has been used for spinal cord injury and stroke patients where the walking performance improved. However, there is no available data about gait kinematics evaluation after HAL therapy. Here we analyze the effect of HAL therapy in OPLL patients in acute and chronic stages after decompression surgery. We found that HAL therapy improved the walking performance for both groups. Interestingly, kinematics evaluation by the analysis of the elevation angles of the thigh, shank, and foot by using a principal component analysis showed that planar covariation, plane orientation, and movement range evaluation improved for acute patients suggesting an improvement in gait coordination. Being the first study performing kinematics analysis after HAL therapy, our results suggest that HAL improved the gait coordination of acute patients by supporting the relearning process and therefore reshaping their gait pattern.

Motor Planning and Gait Coordination Assessments for Children with Developmental Coordination Disorder

AIMS

The purposes were to examine construct validity of the Motor Planning Maze Assessment (Maze) and three items from the Functional Gait Assessment (FGA) that were modified for children (pediatric modified FGA, pmFGA), by comparing performance of children with DCD and age matched peers with typical development (TD); the construct validity of total scores of the Dynamic Gait Index (DGI) and the FGA.

METHODS

Twenty pairs of children with DCD and TD, age from 5 to 12 years, participated in this study. Children in both groups were tested on the Maze, pmFGA, DGI, and FGA. Paired t-tests and agreement tables were used to compare the motor performances between two groups.

RESULTS

The DCD group showed higher summary scores in the Maze (p < 0.001) and demonstrated significantly fewer steps (p ≤ 0.001) while doing the pmFGA items than the TD group. However, the FGA quality scores demonstrated minimal differences between the two groups on all three items. Children with DCD showed significantly lower DGI and FGA total scores (p < 0.001) than the TD group.

CONCLUSION

The Maze, DGI, and FGA tests are easily applied in clinical settings and can differentiate motor planning and gait coordination between children with DCD and with TD.