Assimilation of socially assistive robots' by older adults: an interplay of uses, constraints and outcomes.

By supporting autonomy, aging in place, and wellbeing in later life, Socially Assistive Robots are expected to help humanity face the challenges posed by the rapid aging of the world's population. For the successful acceptance and assimilation of SARs by older adults, it is necessary to understand the factors affecting their Quality Evaluations Previous studies examining Human-Robot Interaction in later life indicated that three aspects shape older adults' overall QEs of robots: uses, constraints, and outcomes. However, studies were usually limited in duration, focused on acceptance rather than assimilation, and typically explored only one aspect of the interaction. In the present study, we examined uses, constraints, and outcomes simultaneously and over a long period. Nineteen community-dwelling older adults aged 75-97 were given a SAR for physical training for 6 weeks. Their experiences were documented via in-depth interviews conducted before and after the study period, short weekly telephone surveys, and reports produced by the robots. Analysis revealed two distinct groups: (A) The 'Fans' - participants who enjoyed using the SAR, attributed added value to it, and experienced a successful assimilation process; and (B) The 'Skeptics' - participants who did not like it, negatively evaluated its use, and experienced a disappointing assimilation process. Despite the vast differences between the groups, both reported more positive evaluations of SARs at the end of the study than before it began. Overall, the results indicated that the process of SARs' assimilation is not homogeneous and provided a profound understanding of the factors shaping older adults' QE of SARs following actual use. Additionally, the findings demonstrated the theoretical and practical usefulness of a holistic approach in researching older SARs users.

Providing Skin Stretch On The Lower Back - Design And Psychophysical Evaluation With A Stepping Task.

Haptic devices are becoming popular in many applications, including medical, gaming, and consumer devices. Yet, the majority of studies focus on the use of haptics for the upper limbs, with much less attention to the stimulation of other regions of the body such as the lower back. In this study, we designed three types of skin stretch stimulation devices that can be placed on a belt and apply tactile stimulation on the lower back. We present these devices that apply lateral, longitudinal, and rotational skin stretch stimulation on the lower back, and evaluate their effectiveness in providing haptic commands for the lower limbs of healthy participants. We designed psychophysical experiments that quantify the discrimination accuracy of participants with a stepping task. The results demonstrate the ability of participants to discriminate two out of three features of stimulation provided on the lower back. These results demonstrate that skin stretch on the lower back can effectively transmit haptic signals and elicit responses in the lower limb for various applications. Future studies are needed to optimize providing skin stretch on the lower back to benefit various applications such as training, rehabilitation, gaming, and assistive devices.

Older adults and stroke survivors are steadier when gazing down.

BACKGROUND: Advanced age and brain damage have been reported to increase the propensity to gaze down while walking, a behavior that is thought to enhance stability through anticipatory stepping control. Recently, downward gazing (DWG) has been shown to enhance postural steadiness in healthy adults, suggesting that it can also support stability through a feedback control mechanism. These results have been speculated to be the consequence of the altered visual flow when gazing down. The main objective of this cross-sectional, exploratory study was to investigate whether DWG also enhances postural control in older adults and stroke survivors, and whether such effect is altered with aging and brain damage. METHODS: Posturography of older adults and stroke survivors, performing a total of 500 trials, was tested under varying gaze conditions and compared with a cohort of healthy young adults (375 trials). To test the involvement of the visual system we performed spectral analysis and compared the changes in the relative power between gaze conditions. RESULTS: Reduction in postural sway was observed when participants gazed down 1 and 3 meters ahead whereas DWG towards the toes decreased steadiness. These effects were unmodulated by age but were modulated by stroke. The relative power in the spectral band associated with visual feedback was significantly reduced when visual input was unavailable (eyes-closed condition) but was unaffected by the different DWG conditions. CONCLUSIONS: Like young adults, older adults and stroke survivors better control their postural sway when gazing down a few steps ahead, but extreme DWG can impair this ability, especially in people with stroke.

Unilaterally Applied Resistance to Swing Leg Shows a Different Adaptation Pattern Compared to Split-Belt Treadmill in Patients with Stroke.

Persons with chronic stroke (PwCS) have a decreased ability to ambulate and walk independently. We aimed to investigate the differences between the motor adaptation process for two different perturbation methods: split-belt treadmill walking and unilaterally applied resistance to the swing leg during walking. Twenty-two PwCS undergo split-belt treadmill walking and unilaterally applied resistance to the swing leg during walking, each one week apart. The test included three phases: the baseline period, the early-adaptation period and the late-adaptation period, as well as the early-de-adaptation period and the late-de-adaptation period. The average step length, swing duration, double-limb support duration, and coefficient of variance (CV) of these parameters were measured. During the split-belt treadmill walking, PwCS showed an adaptation of double-limb support duration symmetry (p = 0.004), specifically a trend between baseline versus early-adaptation (p = 0.07) and an after-effect (late-adaptation compare to early-de-adaptation, p = 0.09). In unilaterally applied resistance to the swing leg during walking, PwCS showed lower swing phase duration CV, in the adaptation period (baseline compare to adaptation, p = 0.006), and a trend toward increased variability of gait in the de-adaptation period compare to the adaptation periods (p = 0.099). The rate of adaptation and de-adaptation were alike between the two perturbation methods. Our findings show that the learning process happening in the central nervous system of PwCS may be dependent on the nature of the perturbation (mechanical resistance vs. split-belt) and that PwCS are able to adapt to two types of errors.

Haemodynamics and oxygenation in the lower-limb muscles of young ambulatory adults with cerebral palsy.

AIM: To evaluate muscle haemodynamics and oxygen metabolism in adults with cerebral palsy (CP) at rest and during exercise. METHOD: This cross-sectional study included 12 adults with spastic CP (four females, eight males; mean age [SD] 29 years 6 months [7 years 10.8 months]) and 13 typically developing individuals (seven females, six males; mean age [SD] 26 years 6 months [1 year 1.9 months]). Near-infrared spectroscopy was used to assess changes in muscle blood flow (mBF), muscle oxygen consumption (mVO2 ), and muscle oxygen saturation in the vastus lateralis and rectus femoris muscles during three conditions: rest, low load at 20% maximum voluntary contraction (MVC), and high load at 80% MVC. RESULTS: MBF was lower in participants with CP than in typically developing participants at rest (p < 0.001) and at 20% MVC (p = 0.007) in both muscles. Increased load caused a reduction in mBF in typically developing participants and an increase in CP. MVO2 in typically developing participants increased from rest to 20% MVC and was reduced at 80% MVC compared with 20% MVC. In participants with CP, there was no change with load in the rectus femoris muscle; however, there was an increase in the vastus lateralis muscle from rest to 20% MVC, and 80% MVC had a similar value. Muscle saturation was higher in participants with CP across all conditions (vastus lateralis, p < 0.001; rectus femoris, p = 0.0518). INTERPRETATION: Oxidative metabolism in CP is not limited by oxygen delivery (mBF), because high muscle saturation suggests oxygen availability. Adults with CP demonstrate muscular responses to exercise that are inconsistent with typical high-workload activation, probably because of inefficient fibre recruitment and secondary anomalies.

The functional and structural neural correlates of dynamic balance impairment and recovery in persons with acquired brain injury.

Dynamic balance control is associated with the function of multiple brain networks and is impaired following Acquired Brain Injury (ABI). This study aims to characterize the functional and structural correlates of ABI-induced dynamic balance impairments and recovery following a rehabilitation treatment. Thirty-one chronic participants with ABI participated in a novel rehabilitation treatment composed of 22 sessions of a perturbation-based rehabilitation training. Dynamic balance was assessed using the Community Balance and Mobility scale (CB&M) and the 10-Meter Walking Test (10MWT). Brain function was estimated using resting-state fMRI imaging that was analysed using independent component analysis (ICA), and regions-of-interest analyses. Brain morphology was also assessed using structural MRI. ICA revealed a reduction in component-related activation within the sensorimotor and cerebellar networks post-intervention. Improvement in CB&M scale was associated with a reduction in FC within the cerebellar network and with baseline FC within the cerebellar-putamen and cerebellar-thalamic networks. Improvement in 10MWT was associated with baseline FC within the cerebellar-putamen and cerebellar-cortical networks. Brain volume analysis did not reveal structural correlates of dynamic balance, but dynamic balance was correlated with time since injury. Our results show that dynamic balance recovery is associated with FC reduction within and between the cerebellar and sensorimotor networks. The lack of global structural correlates of dynamic balance may point to the involvement of specific networks in balance control.

Vision, cognition, and walking stability in young adults.

Downward gazing is often observed when walking requires guidance. This gaze behavior is thought to promote walking stability through anticipatory stepping control. This study is part of an ongoing effort to investigate whether downward gazing also serves to enhance postural control, which can promote walking stability through a feedback/reactive mechanism. Since gaze behavior alone gives no indication as to what information is gathered and the functions it serves, we aimed to investigate the cognitive demands associated with downward gazing, as they are likely to differ between anticipatory and feedback use of visual input. To do so, we used a novel methodology to compromise walking stability in a manner that could not be resolved through modulation of stepping. Then, using interference methodology and neuroimaging, we tested for (1) interference related to dual tasking, and (2) changes in prefrontal activity. The novel methodology resulted in an increase in the time spent looking at the walking surface. Further, while some dual-task interference was observed, indicating that this gaze behavior is cognitively demanding, several gaze parameters pertaining to downward gazing and prefrontal activity correlated. These correlations revealed that a greater tendency to gaze onto the walking surface was associated with lower PFC activity, as is expected when sensory information is used through highly automatic, and useful, neural circuitry. These results, while not conclusive, do suggest that gazing onto the walking surface can be used for purposes other than anticipatory stepping control, bearing important motor-control and clinical implications.

Perceived barriers and facilitators for increasing the physical activity of adolescents and young adults with cerebral palsy: a focus group study.

PURPOSE: Identifying the factors impacting physical activity (PA) among adolescents and young adults with cerebral palsy (CP). METHODS: Four focus groups were conducted, with a total of 22 participants with CP, aged 14-24 years, Gross Motor Function Classification (GMFCS) I-III. Our qualitative analysis drew on grounded theory and used Atlas software. RESULTS: Findings revealed four categories of factors impacting PA: (1) Musculoskeletal-pain and additional impairments related to activity limitations; (2) knowledge and exercising skills, and life skills such as problem-solving, decision-making, planning and organizing; (3) availability: lack of transportation, professional guidance, adapted and community-based programs, especially enjoyable activities; (4) social support from professionals (mainly physiotherapists) and peer support with socializing opportunities. Many opposed parental involvement. Those who attended special education schools and had moderate to severe learning disabilities saw PA as an opportunity for social contacts, limited by lack of availability. Those in mainstream schools with mild to no learning disabilities used PA for relieving pain and preserving function, limited by difficulty balancing PA and life goals. CONCLUSIONS: Service providers should inculcate knowledge and active-living skills during the transition to adulthood. Professional guidance needed to ensure inclusion in communal PA and offer adapted programs for young people with CP.IMPLICATIONS FOR REHABILITATIONThere is a need for ongoing, accessible, adapted, community-based physical activity programs for young adults with CP guided by skilled professionals that can provide them with opportunities for enjoyable activities involving social interactions.When planning treatment interventions for children and young individuals with CP, healthcare providers should be aware of past therapeutic experiences and in collaboration with parents, are encouraged to be sensitive to possible tensions which may exist regarding their body care.Healthcare and educational professionals should provide young people with CP and their families with theoretical and practical knowledge about physical activity and its health benefits, as well as information about exercise options.Developing life skills in young adults with CP is important for helping them to effectively engage in physical activity and develop the competencies needed to achieve long term physical care.

Dynamic balance recovery in chronic acquired brain injury participants following a perturbation training.

Acquired brain injury (ABI) is defined as a damage to the brain that occurs after birth. Subjects post-ABI frequently suffer from dynamic balance impairments that persist years after the injury. This study aimed to investigate the effect of a perturbation method using mechatronic shoes that introduce unexpected balance perturbations on the recovery of dynamic balance and gait velocity in chronic ABI participants. In an intervention trial, 35 chronic ABI participants (stroke and traumatic brain injury) participated in 22 sessions of perturbation training, twice a week for 3 months. Dynamic balance was assessed pre- and post-training using Community Balance and Mobility Scale (CB&M). Gait velocity was also assessed in the stroke participants using the 10 Meter Walking Test (10MWT). Dynamic balance improved significantly post-training (P = 0.001). This improvement was greater than the improvement that was observed in a sub-group that was tested twice before training (P = 0.04). Sixteen participants (45.7%) out of 35 met or exceeded minimal detectable change (MDC) of the CB&M Scale. Self-paced velocity also improved significantly (P = 0.02) but only two participants (9.5%) out of 21 exceeded the MDC of 10MWT post-stroke. Our results suggest that unexpected balance perturbation training using mechatronic shoes leads to an improvement in dynamic balance and gait velocity in chronic ABI participants. The advantage of perturbation training using mechatronic shoes with respect to conventional balance training should be further examined.

Insights into motor performance deficits after stroke: an automated and refined analysis of the lower-extremity motor coordination test (LEMOCOT).

BACKGROUND: The lower-extremity motor coordination test (LEMOCOT) is a performance-based measure used to assess motor coordination deficits after stroke. We aimed to automatically quantify performance on the LEMOCOT and to extract additional performance parameters based on error analysis in persons with stroke (PwS) and healthy controls. We also aimed to explore whether these parameters provide additional information regarding motor control deficit that is not captured by the traditional LEMOCOT score. In addition, the associations between the LEMOCOT score, parameters of error and performance-based measures of lower-extremity impairment and gait were tested. METHODS: Twenty PwS (age: 62 ± 11.8 years, time after stroke onset: 84 ± 83 days; lower extremity Fugl-Meyer: 30.2 ± 3.7) and 20 healthy controls (age: 42 ± 15.8 years) participated in this cross-sectional exploratory study. Participants were instructed to move their big toe as fast and accurately as possible between targets marked on an electronic mat equipped with force sensors (Zebris FDM-T, 60 Hz). We extracted the contact surface area of each touch, from which the endpoint location, the center of pressure (COP), and the distance between them were computed. In addition, the absolute and variable error were calculated. RESULTS: PwS touched the targets with greater foot surface and demonstrated a greater distance between the endpoint location and the location of the COP. After controlling for the number of in-target touches, greater absolute and variable errors of the endpoint were observed in the paretic leg than in the non-paretic leg and the legs of controls. Also, the COP variable error differentiated between the paretic, non-paretic, and control legs and this parameter was independent of in-target counts. Negative correlations with moderate effect size were found between the Fugl Meyer assessment and the error parameters. CONCLUSIONS: PwS demonstrated lower performance in all outcome measures than did controls. Several parameters of error indicated differences between legs (paretic leg, non-paretic leg and controls) and were independent of in-target touch counts, suggesting they may reflect motor deficits that are not identified by the traditional LEMOCOT score.

Gazing down increases standing and walking postural steadiness.

When walking on an uneven surface or complex terrain, humans tend to gaze downward. This behaviour is usually interpreted as an attempt to acquire useful information to guide locomotion. Visual information, however, is not used exclusively for guiding locomotion; it is also useful for postural control. Both locomotive and postural control have been shown to be sensitive to the visual flow arising from the respective motion of the individual and the three-dimensional environment. This flow changes when a person gazes downward and may present information that is more appropriate for postural control. To investigate whether downward gazing can be used for postural control, rather than exclusively for guiding locomotion, we quantified the dynamics of standing and walking posture in healthy adults, under several visual conditions. Through these experiments we were able to demonstrate that gazing downward, just a few steps ahead, resulted in a steadier standing and walking posture. These experiments indicate that gazing downward may serve more than one purpose and provide sufficient evidence of the possible interplay between the visual information used for guiding locomotion and that used for postural control. These findings contribute to our understanding of the control mechanism/s underlying gait and posture and have possible clinical implications.

SIT LESS: A prototype home-based system for monitoring older adults sedentary behavior.

This paper presents the overall design of a prototype home-based system aimed to reduce sedentary behavior of older adults. Quantitative performance indicators were developed to measure the sedentary behavior and daily activities of an older adult. The sedentary behavior is monitored by identifying individual positions (standing, sitting, and lying) within the field of view of a Microsoft Kinect sensor, using a custom designed algorithm. The physical activity of the older adult when outside the field of view of the Microsoft Kinect sensor is monitored by counting the number of steps using a Fitbit Charge HR watch, which the older adult is equipped with. A user interface was developed on a PC platform to interact with the older adult. The user interface is automatically operated and includes several modules. It displays the activity level, and provides feedbacks, alerts, and reminders to reduce sedentary behavior. Evaluations using a mixed methods approach that included a focus group, interviews, and observations were conducted to examine the integrated system, evaluate the users' experience with the system, and compare different types of feedbacks and alerts. The analyses indicated the feasibility of the proposed SIT LESS system along with recommendations for improving the system in future research.

Effects of Exercise Interventions on Habitual Physical Activity and Sedentary Behavior in Adolescents With Cerebral Palsy.

PURPOSE: Exercise interventions have been shown to increase motor capacities in adolescents with cerebral palsy; however, how they affect habitual physical activity (HPA) and sedentary behavior is unclear. The main objective was to correlate changes in HPA with changes in mobility capacity following exercise interventions. METHODS: A total of 54 participants (aged 12-20 y) with bilateral spastic cerebral palsy at Gross Motor Function Classification System (GMFCS) levels II and III received 4 months of group progressive resistance training or treadmill training. Mobility measurements and HPA (averaged over 96 h) were made before and after interventions. RESULTS: Averaged baseline mobility and HPA measures and improvements in each after both interventions were positively correlated in all participants. Percentage of sedentary/awake time decreased 2%, with significant increases in HPA measures of step count (16%), walk time (14%), and upright time (9%). Mobility measures and HPA changes were quite similar between Gross Motor Function Classification System levels, but improvement in HPA after group progressive resistance training was greater than after treadmill training (12% vs 4%) and correlated with mobility improvement. CONCLUSIONS: Mobility capacity improved after these interventions and was clearly associated with improved HPA. The group progressive resistance training intervention seems preferable to improve HPA, perhaps related to greater social interaction and motivation provided by group training.

Treading on the unknown increases prefrontal activity: A pilot fNIRS study.

BACKGROUND: Complex walking conditions (e.g. dual tasking) have been associated with increased prefrontal (PFC) activity. However, most paradigms include a predictable environment, specifically, a predictable walking terrain. In the present study we investigate PFC activity under an unusual walking condition where each foot placement was on unexpected terrain, thus causing a mismatch between visuospatial perception and lower-extremity proprioception. RESEARCH OBJECTIVE: To assess whether PFC activity increases under unstable unpredictable conditions compared to unstable but predictable conditions. METHODS: This was a prospective study involving twenty healthy adults. Participants walked in two conditions: unstable but predictable, and unstable and unpredictable. To assess walking stability, both stride-time (ST) and stride-time variability (CV) were measured. To assess PFC activity, two wireless near-infrared spectroscopy devices were used. The group hemodynamic response (GHR) was calculated for each condition. For statistical analysis, a linear-mixed-effects model was used. RESULTS: Walking with unpredictable perturbations did not change the ST (t = 0.51, p = 0.61) but significantly increased the parameter CV (t = 11.74, p < 0.001). The GHR of both conditions indicated brief per-initiation PFC activity that was similar across conditions. However, when GHRs were calculated relative to normal walking (i.e., the participants' own shoes), continuous activity was evident. Compared to the predictable condition, the unpredictable condition significantly increased this activity during steady-state walking (t = 2.13, p = 0.033). SIGNIFICANCE: Observations from the present study suggest that at least two neural components are present in the measured signal-a brief one, occurring per-initiation, and a continuous one, sensitive to the predictability of the terrain. The second component was accompanied by a decrease in walking stability. These results may contribute to our understanding of the control mechanism underlying gait and future planning of rehabilitation protocols.

Comparison of Habitual Physical Activity and Sedentary Behavior in Adolescents and Young Adults With and Without Cerebral Palsy.

PURPOSE: The comparison of habitual physical activity and sedentary time in teenagers and young adults with cerebral palsy (CP) with typically developed (TD) peers can serve to quantify activity shortcomings. METHODS: Patterns of sedentary, upright, standing, and walking components of habitual physical activity were compared in age-matched (16.8 y) groups of 54 youths with bilateral spastic CP (38 who walk with limitations and 16 who require mobility devices) and 41 TD youths in the Middle East. Activity and sedentary behavior were measured over 96 hours by activPAL3 physical activity monitors. RESULTS: Participants with CP spent more time sedentary (8%) and sitting (37%) and less time standing (20%) and walking (40%) than TD (all Ps < .01). These trends were enhanced in the participants with CP requiring mobility devices. Shorter sedentary events (those <60-min duration) were similar for TD and CP groups, but CP had significantly more long sedentary events (>2 h) and significantly fewer upright events (taking <30, 30-60, and >60 min) and less total upright time than TD. CONCLUSION: Ambulant participants with CP, as well as TD youth must be encouraged to take more breaks from being sedentary and include more frequent and longer upright events.

Treading on the unknown-the feasibility of a novel approach to investigating the motor control of walking.

BACKGROUND AND OBJECTIVE: Walking is a complex human behavior, usually performed in a dynamic environment. Gait parameters are thought to reflect this complexity. Re-Step™ is a therapy system in the form of a computerized shoe, originally developed for the training and rehabilitation of individuals with brain damage. This system may be used as model for studying the complexity that underlies gait. As the first step, we present here the feasibility of the model, after establishing the validity and reliability of stride time and stride-time variability, observed in healthy adults. APPROACH: Fifteen healthy adults participated in this study. To establish concurrent validity, we had five participants walk with the Re-Step on a treadmill equipped with a force plate. To establish inter-rater reliability, we used data from ten participants who walked approximately 300 m with the system. Finally, the stride-time variability of perturbed and unperturbed walks was compared to establish the feasibility of the model. RESULTS: The correlation between the stride times observed with the treadmill and those observed with the Re-Step system was r = 0.971. The interclass correlation coefficient between left and right legs was 1.000 for stride time and 0.827 for its variability. A significant increase (mean difference 0.68%) in stride time variability was observed between unperturbed and perturbed walks. SIGNIFICANCE: The results of this study suggest that stride-time measurements and variability observed in the Re-Step system are valid and reliable and that the model increases the challenge to the control system, thereby making Re-Step useful in the investigation of gait.

Parameters and Measures in Assessment of Motor Learning in Neurorehabilitation; A Systematic Review of the Literature.

Upper limb function, essential for daily life, is often impaired in individuals after stroke and cerebral palsy (CP). For an improved upper limb function, learning should occur, and therefore training with motor learning principles is included in many rehabilitation interventions. Despite accurate measurement being an important aspect for examination and optimization of treatment outcomes, there are no standard algorithms for outcome measures selection. Moreover, the ability of the chosen measures to identify learning is not well established. We aimed to review and categorize the parameters and measures utilized for identification of motor learning in stroke and CP populations. PubMed, Pedro, and Web of Science databases were systematically searched between January 2000 and March 2016 for studies assessing a form of motor learning following upper extremity training using motor control measures. Thirty-two studies in persons after stroke and 10 studies in CP of any methodological quality were included. Identified outcome measures were sorted into two categories, "parameters," defined as identifying a form of learning, and "measures," as tools measuring the parameter. Review's results were organized as a narrative synthesis focusing on the outcome measures. The included studies were heterogeneous in their study designs, parameters and measures. Parameters included adaptation (n = 6), anticipatory control (n = 2), after-effects (n = 3), de-adaptation (n = 4), performance (n = 24), acquisition (n = 8), retention (n = 8), and transfer (n = 14). Despite motor learning theory's emphasis on long-lasting changes and generalization, the majority of studies did not assess the retention and transfer parameters. Underlying measures included kinematic analyses in terms of speed, geometry or both (n = 39), dynamic metrics, measures of accuracy, consistency, and coordination. There is no exclusivity of measures to a specific parameter. Many factors affect task performance and the ability to measure it-necessitating the use of several metrics to examine different features of movement and learning. Motor learning measures' applicability to clinical setting can benefit from a treatment-focused approach, currently lacking. The complexity of motor learning results in various metrics, utilized to assess its occurrence, making it difficult to synthesize findings across studies. Further research is desirable for development of an outcome measures selection algorithm, while considering the quality of such measurements.

Formation of Long-Term Locomotor Memories Is Associated with Functional Connectivity Changes in the Cerebellar-Thalamic-Cortical Network.

Although motor adaptation is typically rapid, accumulating evidence shows that it is also associated with long-lasting behavioral and neuronal changes. Two processes were suggested to explain the formation of long-term motor memories: recall, reflecting a retrieval of previous motor actions, and faster relearning, reflecting an increased sensitivity to errors. Although these manifestations of motor memories were initially demonstrated in the context of adaptation experiments in reaching, indications of long-term motor memories were also demonstrated recently in other kinds of adaptation such as in locomotor adaptation. Little is known about the neural processes that underlie these distinct aspects of memory. We hypothesize that recall and faster relearning reflect different learning processes that operate at the same time and depend on different neuronal networks. Seventeen subjects performed a multisession locomotor adaptation experiment in the laboratory, together with resting-state and localizer fMRI scans, after the baseline and the locomotor adaptation sessions. We report a modulation of the cerebellar-thalamic-cortical and cerebellar-basal ganglia networks after locomotor adaptation. Interestingly, whereas thalamic-cortical baseline connectivity was correlated with recall, cerebellar-thalamic baseline connectivity was correlated with faster relearning. Our results suggest that separate neuronal networks underlie error sensitivity and retrieval components. Individual differences in baseline resting-state connectivity can predict idiosyncratic combination of these components. SIGNIFICANCE STATEMENT: The ability to shape our motor behavior rapidly in everyday activity, such as when walking on sand, suggests the existence of long-term motor memories. It was suggested recently that this ability is achieved by the retrieval of previous motor actions and by enhanced relearning capacity. Little is known about the neural mechanisms that underlie these memory processes. We studied the modularity in long-term motor memories in the context of locomotor adaptation using resting-state fMRI. We show that retrieval and relearning effects are associated with separate locomotor control networks and that intersubject variability in learning and in the generation of motor memories could be predicted from baseline resting-state connectivity in locomotor-related networks.

Effects of a group circuit progressive resistance training program compared with a treadmill training program for adolescents with cerebral palsy.

OBJECTIVE: To determine whether goal-directed group circuit progressive resistance exercise training (GT) can improve motor function in adolescents with cerebral palsy (CP) and to compare outcomes with a treadmill training (TT) intervention. METHODS: In a multi-centered matched pairs study, 95 adolescents with spastic CP (GMFCS II-III) were allocated to GT or TT interventions for 30 bi-weekly one hour training. Outcome measures of GMFM-66, GMFM-D%, GMFM-E%, TUG, 10 meter walk test (10 MWT), and 6 minute walk test (6 MWT) were made at baseline (T1), after interventions (T2) and 6 months post training (T3). RESULTS: Both training programs induced significant improvement in all outcome measures (T2-T1) that were mostly retained at T3. At the end of the intervention, the GT group showed an advantage in all measured changes compared to the TT group and in percentage changes. Differences were significant (p < 0.02) for GMFM-66, GMFM-D%, GMFM-E% and TUG. The advantage trend for the GT group was less apparent at follow up (T3-T1). CONCLUSION: Both programs were effective in improving motor function in adolescents with cerebral palsy. The GT program had generally greater benefits based on the functional measures.

Increased Adaptation Rates and Reduction in Trial-by-Trial Variability in Subjects with Cerebral Palsy Following a Multi-session Locomotor Adaptation Training.

Cerebral Palsy (CP) results from an insult to the developing brain and is associated with deficits in locomotor and manual skills and in sensorimotor adaptation. We hypothesized that the poor sensorimotor adaptation in persons with CP is related to their high execution variability and does not reflect a general impairment in adaptation learning. We studied the interaction between performance variability and adaptation deficits using a multi-session locomotor adaptation design in persons with CP. Six adolescents with diplegic CP were exposed, during a period of 15 weeks, to a repeated split-belt treadmill perturbation spread over 30 sessions and were tested again 6 months after the end of training. Compared to age-matched healthy controls, subjects with CP showed poor adaptation and high execution variability in the first exposure to the perturbation. Following training they showed marked reduction in execution variability and an increase in learning rates. The reduction in variability and the improvement in adaptation were highly correlated in the CP group and were retained 6 months after training. Interestingly, despite reducing their variability in the washout phase, subjects with CP did not improve learning rates during washout phases that were introduced only four times during the experiment. Our results suggest that locomotor adaptation in subjects with CP is related to their execution variability. Nevertheless, while variability reduction is generalized to other locomotor contexts, the development of savings requires both reduction in execution variability and multiple exposures to the perturbation.