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• Total brainstem, pons, and midbrain volumes are decreased in people with cerebral palsy (CP). • The reduced brainstem volumes are associated with reduced gait velocity and step length. • Structural changes within the brainstem may contribute to clinical mobility impairments in people with CP. Persons with cerebral palsy (CP) have impaired mobility that has been attributed to changes in structure and function within the nervous system. The brainstem is a region that plays a critical role in mobility by connecting the cortex and cerebellum to the spinal cord, yet this region has been largely unstudied in persons with CP. We used high-resolution structural MRI and biomechanical analyses to examine whether the volume of the whole brainstem and its constituent elements are altered in CP and if these alterations relate to the mobility impairments within this population. A cohort study was conducted to assess the volume of the whole brainstem, pons, midbrain, medulla, and superior cerebellar peduncle in a cohort of persons with CP (N = 26; Age = 16.3 ± 1.0 years; GMFCS levels I-IV, Females = 12) and a cohort of neurotypical (NT) controls (N = 38; Age = 14.3 ± 0.4 years, Females = 14) using structural MR imaging of the brainstem. Outside the scanner, a digital mat was used to quantify the spatiotemporal gait biomechanics of these individuals. We found a significant decrease in volume of the total brainstem, midbrain, and pons in persons with CP in comparison to the NT controls. Furthermore, we found that the altered volumes were related to reduced gait velocity and step length. The structural changes in the brainstems of persons with CP may contribute to the mobility impairments that are ubiquitous within this population. [ABSTRACT FROM AUTHOR]

To compare the prefrontal cortex (PFC) activation and task performance during single- and dual-task conditions between typically developing (TD) children and children with hemiplegic cerebral palsy (HCP). A prospective, comparative design. Research laboratory. Participants (N=21) included 12 TD children (age, 6.0±1.1y) and 9 children with HCP (age, 7.2±3.1). Not applicable. PFC activation was assessed by measuring the concentration of oxygenated hemoglobin while the children performed a shape-matching task with their more affected arm while sitting on a stable (single task) vs dynamic surface (dual task). The task performance was assessed with the total number of shapes matched, dual-task cost, and reaction time (RT). For both conditions, the children with HCP exhibited greater PFC activation, matched a fewer shapes, and had slower RT than the TD children. These differences were accentuated during the dual-task condition and the dual-task cost was greater. An increase in the PFC activation during the dual-task condition was tightly correlated with a higher dual-task cost in children with HCP (r =0.77, P =.01). Children with HCP appear to have a heightened amount of PFC activity while performing a dual task. The greater cortical activity may be a result of the finite attentional resources that are shared between both the motor as well as cognitive demands of the task. The cognitive-motor interference is likely exacerbated in children with HCP because of the structural and functional brain changes as a result of an insult to the developing brain. • This is the first study that assessed the neural substrate of cognitive-motor interference during goal-directed upper extremity dual-task in children with hemiplegic cerebral palsy (HCP). • Children with HCP have greater activation within the prefrontal cortex while performing goal-directed dual task with the affected upper extremity, which indicates a greater degree of burden imposed on the prefrontal cortex for simultaneously processing the cognitive-motor demands of dual task. • Cognitive-motor interference deteriorates task performance, such as resulting increase in reaction time and reduced number of shapes matched in children with HCP. [ABSTRACT FROM AUTHOR]

Objective To evaluate the mobility and postural balance improvements that could be achieved in a cohort of persons with multiple sclerosis (MS) who participated in a motor adaptation protocol and a cohort of persons with MS who participated in a therapeutic exercise protocol. Design A cohort design, where subjects were evaluated before and after a 6-week intervention period. Setting Clinical laboratory setting. Participants Individuals (N=42) with relapsing-remitting or secondary progressive MS (Expanded Disability Status Scale [EDSS] scores, 3.0–6.5) were initially screened for eligibility for participation in the study, from which those who fit the inclusion criteria (n=32) were enrolled in the study. Subjects were pseudorandomly assigned to a treatment group and matched based on EDSS scores. Fourteen individuals in the motor adaptation cohort (MAC) (mean age ± SD, 52.6±9y; mean EDSS score ± SD, 5.5±0.9) and 13 individuals in the therapeutic exercise cohort (TEC) (mean age ± SD, 54.0±9y; mean EDSS score ± SD, 5.3±0.9) completed the entire duration of their respective programs. Interventions Both cohorts completed their therapy twice a day, 5 days each week, for 6 weeks. Each session of the MAC program consisted of balance and gait training that encouraged new ways to adapt to challenging task demands. The TEC program was similar to a traditional exercise program. Main Outcome Measures The Sensory Organization Test, 6-minute walk test, and gait spatiotemporal kinematics. Results Collectively, both treatment groups had improvements in postural balance ( P =.001), walking endurance ( P =.002), walking speed ( P =.004), and step length ( P <.001) after therapy. However, there were no statistical differences between the 2 treatment groups for any of the outcome variables ( P values >.01). Conclusions Our exploratory results suggest that a high frequency of physical therapy rather than a specific activity focus might be an important parameter for persons with MS. [ABSTRACT FROM AUTHOR]

Objective: The primary aim of this exploratory investigation was to determine if there are differences in cortical activation of children with spastic diplegic cerebral palsy (CP) and typically developing children during gait. Methods: Functional near-infrared spectroscopy was used to measure the concentration of oxygenated hemoglobin that was present in the supplementary motor area, pre-central gyrus, post-central gyrus and superior parietal lobule as the children walked on a treadmill. A sagittal plane video was concurrently collected and later digitized to quantify the temporal gait variations. Results: (1) The children with CP had an increased amount of activation in the sensorimotor cortices and superior parietal lobule during gait, (2) the children with CP had a greater amount of variability or error in their stride time intervals, and (3) an increased amount of error in the temporal gait kinematics was associated with an increased amount of activity across the cortical network. Conclusion: Our results suggest that the perinatal damage and subsequent neural reorganization that occurs with spastic diplegic CP may impact the functional cortical activity for controlling gait. Furthermore, our results imply the increased cortical activity of the somatosensory cortices and superior parietal cortices may underlie the greater amount of error in the temporal gait kinematics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Langevin equation methodology was used to quantify the nature of the gait variability. [•] Children with CP had a more variable stepping kinematics. [•] Children with CP and TD children had similar deterministic features. [•] Children with CP had more stochastic features in their gait patterns. [•] More variable stepping kinematics were related to greater stochastic features. [Copyright &y& Elsevier]

Abstract: Children with cerebral palsy (CP) have altered tactile, proprioceptive and kinesthetic awareness. These sensory impairments appear to be related to an aberrant organization of the somatosensory cortex. To date, the neuromagnetic responses of somatosensory cortices representing the foot have not been investigated in children with spastic diplegic CP. In this investigation, we used magnetoencephalography (MEG) to evaluate cortical differences in the earliest somatosensory responses elicited by foot stimulation in typically developing children and those with spastic diplegic CP who have a Gross Motor Function Classification Score of III–IV. All participants underwent unilateral tibial nerve stimulation of each foot as whole brain MEG data were acquired. Primary somatosensory cortical responses were modeled using an equivalent current dipole for each foot. The results presented in this study are the first to show that activation of the somatosensory cortices representing the foot in children with spastic diplegic CP is diminished, but not latent. [ABSTRACT FROM AUTHOR]

Abstract: There is a growing body of evidence that the step-to-step variations present in human walking are related to the biomechanics of the locomotive system. However, we still have limited understanding of what biomechanical variables influence the observed nonlinear gait variations. It is necessary to develop reliable models that closely resemble the nonlinear gait dynamics in order to advance our knowledge in this scientific field. Previously, Goswami et al. [1998. A study of the passive gait of a compass-like biped robot: symmetry and chaos. International Journal of Robotic Research 17(12)] and Garcia et al. [1998. The simplest walking model: stability, complexity, and scaling. Journal of Biomechanical Engineering 120(2), 281–288] have demonstrated that passive dynamic walking computer models can exhibit a cascade of bifurcations in their gait pattern that lead to a deterministic nonlinear gait pattern. These computer models suggest that the intrinsic mechanical dynamics may be at least partially responsible for the deterministic nonlinear gait pattern; however, this has not been shown for a physical walking robot. Here we use the largest Laypunov exponent and a surrogation analysis method to confirm and extend Garcia et al.''s and Goswami et al.''s original results to a physical passive dynamic walking robot. Experimental outcomes from our walking robot further support the notion that the deterministic nonlinear step-to-step variations present in gait may be partly governed by the intrinsic mechanical dynamics of the locomotive system. Furthermore the nonlinear analysis techniques used in this investigation offer novel methods for quantifying the nature of the step-to-step variations found in human and robotic gait. [Copyright &y& Elsevier]

Abstract: The purpose of this investigation was to determine if a chronic Parkinson''s disease mouse model will display less certainty in its gait pattern due to basal ganglia dysfunction. A chronic Parkinson''s disease mouse model was induced by injecting male C57/BL mice with 10 doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (25mg/kg) (MPTP) and probenecid (250mg/kg) (P) over 5 weeks. This chronic model produces a severe and persistent loss of nigrostriatal neurons resulting in dopamine depletion and locomotor impairment. The control mice were treated with probenecid alone. Fifteen weeks after the last MPTP/P treatment, the mice were videotaped in the sagittal plane with a digital camera (60Hz) as they ran on a motorized treadmill at a speed of 10m/min. The indices of gait and gait variability were calculated. Stride length was significantly (p =0.016) more variable in the chronic MPTP/P mice. Additionally, the chronic MPTP/P mice had a statistically less certain gait pattern when compared to the control mice (p =0.02). These results suggest that variability in the gait pattern can be used to evaluate changes in neural function. Additionally, our results imply that disorder of the basal ganglia results in less certainty in modulating the descending motor command that controls the gait pattern. [Copyright &y& Elsevier]

This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result in less certainty of the neuromuscular system in selecting a stable gait. [Copyright &y& Elsevier]

The purpose of this investigation was to determine if phase plot normalization and phase angle definitions would have an affect on continuous relative phase calculations. A subject ran on a treadmill while sagittal plane kinematic data were collected with a high-speed (180 Hz) camera. Segmental angular displacements and velocities were used to create phase plots, and examine the coordination between the leg and thigh. Continuous relative phase was calculated with a combination of two different amplitude normalization techniques, and two different phase angle definitions. Differences between the techniques were noted with a root mean square (RMS) calculation. RMS values indicated that there were differences in the configuration of the non-normalized and normalized continuous relative phase curves. Graphically and numerically, it was noted that normalization tended to modify the continuous relative phase curve configuration. Differences in continuous relative phase curves were due to a loss in the aspect ratio of the phase plot during normalization. Normalization tended to neglect the nonlinear forces acting on the system since it did not maintain the aspect ratio of the phase plot. Normalization is not necessary because the arc tangent function accounts for differences in amplitudes between the segments. RMS values indicated that there were profound differences in the continuous relative phase curve when the phase angle was normalized and a phase angle was calculated relative to the right horizontal axis. [Copyright &y& Elsevier]

[Display omitted] • Persons with CP underwent MEG during an arrow-based Flanker task. • Reaction time was used to assess motor performance. • Cognitive interference of cortical oscillations moderated the reaction time. • Changes in cortical oscillations reflects top-down control over motor system in CP. Emerging evidence indicates that aberrations in sensorimotor cortical oscillations likely play a key role in uncharacteristic motor actions seen in cerebral palsy. This interpretation is largely centered on the assumption that the aberrant cortical oscillations primarily reflect the motor aspects, with less consideration of possible higher-order cognitive connections. To directly probe this view, we examined the impact of cognitive interference on the sensorimotor cortical oscillations seen in persons with cerebral palsy using magnetoencephalography. Persons with cerebral palsy (N = 26, 9–47 years old) and controls (N = 46, 11–49 years) underwent magnetoencephalographic imaging while completing an arrow-based version of the Eriksen flanker task. Structural equation modeling was used to evaluate the relationship between the extent of interference generated by the flanker task and the strength of the sensorimotor cortical oscillations and motor performance. Our results indicated that the impact of cognitive interference on beta and gamma oscillations moderated the interference effect on reaction times in persons with cerebral palsy, above and beyond that seen in controls. Overall, these findings suggest that alterations in sensorimotor oscillatory activity in those with cerebral palsy at least partly reflects top-down control influences on the motor system. Thus, suppression of distracting stimuli should be a consideration when evaluating altered motor actions in cerebral palsy. [ABSTRACT FROM AUTHOR]

Abstract Cerebral palsy (CP) is a neurological disorder that results in life-long mobility impairments. Musculoskeletal models used to investigate mobility deficits for children with CP often lack subject-specific characteristics such as altered muscle strength, despite a high prevalence of muscle weakness in this population. We hypothesized that incorporating subject-specific strength scaling within musculoskeletal models of children with CP would improve accuracy of muscle excitation predictions in walking simulations. Ten children (13.5 ± 3.3 years; GMFCS level II) with spastic CP participated in a gait analysis session where lower-limb kinematics, ground reaction forces, and bilateral electromyography (EMG) of five lower-limb muscles were collected. Isometric strength was measured for each child using handheld dynamometry. Three musculoskeletal models were generated for each child including a 'Default' model with the generic musculoskeletal model's muscle strength, a 'Uniform' model with muscle strength scaled allometrically, and a 'Custom' model with muscle strength scaled based on handheld dynamometry strength measures. Muscle-driven gait simulations were generated using each model for each child. Simulation accuracy was evaluated by comparing predicted muscle excitations and measured EMG signals, both in the duration of muscle activity and the root-mean-square difference (RMSD) between signals. Improved agreement with EMG were found in both the 'Custom' and 'Uniform' models compared to the 'Default' model indicated by improvement in RMSD summed across all muscles, as well as RMSD and duration of activity for individual muscles. Incorporating strength scaling into musculoskeletal models can improve the accuracy of walking simulations for children with CP. [ABSTRACT FROM AUTHOR]

• Individuals with cerebral palsy have reduced somatosensory cortical activity during movement. • The reduced somatosensory cortical activity during movement is related to reduced somatosensory cortical activity during rest. • The reduced somatosensory cortical activity during movement may contribute to clinical deficits in motor actions. There are numerous clinical reports that youth with cerebral palsy (CP) have proprioceptive, stereognosis and tactile discrimination deficits. The growing consensus is that the altered perceptions in this population are attributable to aberrant somatosensory cortical activity seen during stimulus processing. It has been inferred from these results that youth with CP likely do not adequately process ongoing sensory feedback during motor performance. However, this conjecture has not been tested. Herein, we address this knowledge gap using magnetoencephalographic (MEG) brain imaging by applying electrical stimulation to the median nerve of youth with CP (N = 15, Age = 15.8 ± 0.83 yrs, Males = 12, MACS levels I-III) and neurotypical (NT) controls (N = 18, Age = 14.1 ± 2.4 yrs, Males = 9) while at rest (i.e., passive) and during a haptic exploration task. The results illustrated that the somatosensory cortical activity was reduced in the group with CP compared to controls during the passive and haptic conditions. Furthermore, the strength of the somatosensory cortical responses during the passive condition were positively associated with the strength of somatosensory cortical responses during the haptic condition (r = 0.75, P = 0.004). This indicates that the aberrant somatosensory cortical responses seen in youth with CP during rest are a good predictor of the extent of somatosensory cortical dysfunction during the performance of motor actions. These data provide novel evidence that aberrations in somatosensory cortical function in youth with CP likely contribute to the difficulties in sensorimotor integration and the ability to effectively plan and execute motor actions. [ABSTRACT FROM AUTHOR]

Abstract: It has been suggested that the intercycle variability present in the time series of biomechanical gait data is of chaotic nature. However, the proper methodology for the correct determination of whether intercycle fluctuations in the data are deterministic chaos or random noise has not been identified. Our goal was to evaluate the pseudoperiodic surrogation (PPS) [Small et al., 2001. Surrogate test for pseudoperiodic time series data. Physical Review Letters 87(18), 188,101–188,104], and the surrogation algorithms of Theiler et al. [1992. Testing for nonlinearity in time series: the method of surrogate data. Physica D 58(1–4), 77–94] and of Theiler and Rapp [1996. Re-examination of the evidence for low-dimensional, nonlinear structure in the human electroencephalogram. Electroencephalography and Clinical Neurophysiology 98, 213–222], to determine which is the more robust procedure for the verification of the presence of chaos in gait time series. The knee angle kinematic time series from six healthy subjects, generated from a 2-min walk, were processed with both algorithms. The Lyapunov exponent (LyE) and the approximate entropy (ApEn) were calculated from the original data and both surrogates. Paired t-tests that compared the LyE and the ApEn values revealed significant differences between both surrogated time series and the original data, indicating the presence of deterministic chaos in the original data. However, the Theiler algorithm affected the intracycle dynamics of the gait time series by changing their overall shape. This resulted in significantly higher LyE and ApEn values for the Theiler-surrogated data when compared with both the original and the PPS-generated data. Thus, the discovery of significant differences was a false positive because it was not based on differences in the intercycle dynamics but rather on the fact that the time series was of a completely different shape. The PPS algorithm, on the other hand, preserved the intracycle dynamics of the original time series, making it more suitable for the investigation of the intercycle dynamics and the identification of the presence of chaos in the gait time series. [Copyright &y& Elsevier]

Objective. To investigate the nature of variability present in time series generated from gait parameters of two different age groups via a nonlinear analysis.Design. Measures of nonlinear dynamics were used to compare kinematic parameters between elderly and young females.Background. Aging may lead to changes in motor variability during walking, which may explain the large incidence of falls in the elderly.Methods. Twenty females, 10 younger (20–37 yr) and 10 older (71–79 yr) walked on a treadmill for 30 consecutive gait cycles. Time series from selected kinematic parameters of the right lower extremity were analyzed using nonlinear dynamics. The largest Lyapunov exponent and the correlation dimension of all time series, and the largest Lyapunov exponent of the original time series surrogated were calculated. Standard deviations and coefficient of variations were also calculated for selected discrete points from each gait cycle. Independent t-tests were used for statistical comparisons.Results. The Lyapunov exponents were found to be significantly different from their surrogate counterparts. This indicates that the fluctuations observed in the time series may reflect deterministic processes by the neuromuscular system. The elderly exhibited significantly larger Lyapunov exponents and correlation dimensions for all parameters evaluated indicating local instability. The linear measures indicated that the elderly demonstrated significantly higher variability.Conclusions. The nonlinear analysis revealed that fluctuations in the time series of certain gait parameters are not random but display a deterministic behavior. This behavior may degrade with physiologic aging resulting in local instability.RelevanceElderly show increased local instability or inability to compensate to the natural stride-to-stride variations present during locomotion. We hypothesized that this may be the one of the reasons for the increases in falling due to aging. Future efforts should attempt to evaluate this hypothesis by making comparisons to pathological subjects (i.e. elderly fallers), and examine the sensitivity and specificity of the nonlinear methods used in this study to aid clinical assessment. [Copyright &y& Elsevier]

Background: Action-planning and execution deficits in children with hemiplegic cerebral palsy (HCP) are potentially due to deficits in the integration of sensory information, such as vision, with motor output.Aims: To determine differences in anticipatory visual patterns in children with HCP compared to typically developing (TD) children, and to assess visuomotor coordination in children with HCP.Methods and Procedures: We included 13 children with HCP (Age = 6.8 + 2.9 yrs) and 15 TD children (Age = 5.8 + 1.1 yrs). The experimental task used in this study is a valid action-planning task, which consisted of initially reaching and grasping an object placed at a fixed position, followed by placing the object in a random target position. Visual patterns were recorded using a head-mounted eye-tracker system and arm movements were recorded using motion capture (120 Hz).Outcomes and Results: Children with HCP had delayed anticipatory gaze time and longer latency than TD children during the planning and execution phases. Children with HCP also had a higher frequency of gaze shifts, longer reaction times (RT) and movement times (MT) than TD children.Conclusions and Implications: Children with HCP may have deficits in anticipatory vision, which potentially affected planning and executing a goal-directed action. Therapeutic interventions focusing on improving visuomotor coordination may improve the motor performance in children with HCP. [ABSTRACT FROM AUTHOR]

Background: Cerebral palsy (CP) has a high probability of resulting in lower extremity strength and walking deficits. Numerous studies have shown that gait training has the potential to improve the walking abilities of these children; however, the factors governing these improvements are unknown.Aims: This study aimed to evaluate the relationship between change in lower extremity strength, walking speed and endurance of children with CP following gait training.Methods and Procedures: Eleven children with CP (GMFCS levels=II-III) completed a gait training protocol three days a week for six weeks. Outcome measures included a 10m fast-as-possible walk test, 6min walking endurance test and lower extremity strength.Outcomes and Results: The group results indicated there were improvements in walking speed, walking endurance and lower extremity strength. In addition, there was a positive correlation between percent change in lower extremity strength and walking speed and a negative correlation between the percent change in lower extremity strength and the child's age.Conclusions: Our results imply that changes in lower extremity strength might be related to the degree of the walking speed changes seen after gait training. Younger children may be more likely to show improvements in lower extremity strength after gait training. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to quantify the differences in torque steadiness and variability of the muscular control in children with cerebral palsy (CP) and typically developing (TD) children. Fifteen children with CP (age=14.2±0.7 years) that had a Gross Motor Function Classification System (GMFCS) score of I-III and 15 age and gender matched TD children (age=14.1±0.7 years) participated in this investigation. The participants performed submaximal steady-state isometric contractions with the ankle, knee, and hip while surface electromyography (sEMG) was recorded. An isokinetic dynamometer was used to measure the steady-state isometric torques while the participants matched a target torque of 20% of the subject''s maximum voluntary torque value. The coefficient of variation was used to assess the amount of variability in the steady-state torque, while approximate entropy was used to assess the regularity of the steady-state torque over time. Lastly, the distribution of the power spectrum of the respective sEMG was evaluated. The results of this investigation were: 1) children with CP had a greater amount of variability in their torque steadiness at the ankle than TD children, 2) children with CP had a greater amount of variability at the ankle joint than at the knee and hip joint, 3) the children with CP had a more regular steady-state torque pattern than TD children for all the joints, 4) the ankle sEMG of children with CP was composed of higher harmonics than that of the TD children. [Copyright &y& Elsevier]

Abstract: With human exploration of the Moon and Mars on the horizon, research considerations for space suit redesign have surfaced. Review of Apollo mission videos revealed repeated instance of falling during extravehicular activities. A better understanding of how suit weight influences the sagittal dynamic stability of the gait pattern may provide insight for new suit design such that space missions may have more productive extravehicular activities and smaller risk of falls that may cause injuries and damage equipment. Participants walked for 4min in simulated Martian gravity with additional loads of 0%, 15%, 30% and 45% of their body weight. Floquet and Lyapunov analysis techniques were used to quantify the dynamic stability of the sagittal plane gait pattern. Additionally, sagittal plane joint kinematics were evaluated to determine if any modification occurred. Results indicated that weight (i.e., added load) had little effect on the sagittal dynamic stability or joint kinematics while in simulated Martian gravity. Potentially, suit weight may not be a priority for space suit redesign. [Copyright &y& Elsevier]