Age-Related Differences in Motor Skill Transfer with Brief Memory Reactivation

Motor memories can be strengthened through online practice and offline consolidation. Offline consolidation involves the stabilization of memory traces in post-practice periods. Following initial consolidation of a motor memory, subsequent practice of the motor skill can lead to reactivation and reconsolidation of the memory trace. The length of motor memory reactivation may influence motor learning outcomes; for example, brief, as opposed to long, practice of a previously learned motor skill appears to optimize intermanual transfer in healthy young adults. However, the influence of aging on reactivation-based motor learning has been scarcely explored. Here, the effects of brief and long motor memory reactivation schedules on the retention and intermanual transfer of a visuomotor tracing task are explored in healthy older adults. Forty older adults practiced a virtual star-tracing task either three ("brief reactivation") or ten ("long reactivation") times per session over a two-week period. Comparison with a previously reported group of younger adults revealed significant age-related differences in the effect of the motor memory reactivation schedule on the intermanual transfer of the motor task. In older adults, unlike younger adults, no significant between-group differences were found by practice condition in the speed, accuracy, or skill of intermanual task transfer. That is, motor task transfer in healthy younger, but not older, adults appears to benefit from brief memory reactivation. These results support the use of age-specific motor training approaches and may inform motor practice scheduling, with possible implications for physical rehabilitation, sport, and music.

Beyond pain in the brain: A clinician's guide to interpreting the spinal cord's role in the pain experience

INTRODUCTION

Physical therapy practice has greatly improved in providing a biopsychosocial approach when considering persistent pain. However, the spinal cord is often overlooked as a structure with an important role in modulating nociceptive information.

PURPOSE

This article highlights the role of the dorsal horn (DH) in nociceptive processing and its impact on persistent pain conditions as they appear clinically. Key processes occurring in the spinal cord are described, including cellular changes and local spinal network responses to nociceptive stimuli. Additionally, associated clinical symptoms are discussed and some aspects of physical therapy evaluation are challenged based on the mechanisms of nociceptive processing presented in this commentary.

IMPLICATIONS

The spinal cord is an active participant in nociceptive processing, directly impacting the intensity, spread, and recurrence of pain, including within the context of central sensitization. Changes in the behavior of DH neurons are possible with sufficient stimulation and may occur after injury. Additionally, spinal cord activation patterns may lead to bilateral symptoms given adequate strength and duration despite a single peripheral driver. Viewing the spinal cord as a dynamic structure capable of up or down regulating its response to stimuli gives the clinician a better understanding of the nervous system's complex response to prolonged nociceptive input.

Neuromechanical control of impact absorption during induced lower limb loading in individuals post-stroke

Decreased loading of the paretic lower limb and impaired weight transfer between limbs negatively impact balance control and forward progression during gait in individuals post-stroke. However, the biomechanical and neuromuscular control mechanisms underlying such impaired limb loading remain unclear, partly due to their tendency of avoiding bearing weight on the paretic limb during voluntary movement. Thus, an approach that forces individuals to more fully and rapidly load the paretic limb has been developed. The primary purpose of this study was to compare the neuromechanical responses at the ankle and knee during externally induced limb loading in people with chronic stroke versus able-bodied controls, and determine whether energy absorption capacity, measured during induced limb loading of the paretic limb, was associated with walking characteristics in individuals post-stroke. Results revealed reduced rate of energy absorption and dorsiflexion velocity at the ankle joint during induced limb loading in both the paretic and non-paretic side in individuals post-stroke compared to healthy controls. The co-contraction index was higher in the paretic ankle and knee joints compared to the non-paretic side. In addition, the rate of energy absorption at the paretic ankle joint during the induced limb loading was positively correlated with maximum walking speed and negatively correlated with double limb support duration. These findings demonstrated that deficits in ankle dorsiflexion velocity may limit the mechanical energy absorption capacity of the joint and thereby affect the lower limb loading process during gait following stroke.

Perturbation-Induced Protective Arm Responses: Effect of Age, Perturbation-Intensity, and Relationship with Stepping Stability: A Pilot Study

During balance recovery from slip perturbations, forward flexion (elevation) of the arms serves to counterbalance the posteriorly displaced center of mass (CoM). We aimed to investigate whether aging affects modulation of arm responses to various intensities of unpredictable slip perturbations and whether arm responses are related to compensatory stepping stability. Ten healthy young adults and ten healthy older adults participated. Participants were asked to react naturally to three randomly administered levels of slip-like surface perturbations (intensity 1 (7.75 m/s2), intensity 2 (12.00 m/s2) and intensity 3 (16.75 m/s2), which occurred by means of forward acceleration of the treadmill belt while standing. Kinematic data were collected using a motion capture system. Outcomes included arm elevation displacement, velocity, and margin of stability (MoS) of compensatory stepping. The results reveal no modulation of arm elevation velocity in older adults from perturbation intensity 1 to 2, whereas younger adults demonstrated progressive increases from intensity 1 to 2 to 3. At intensity 3, older adults demonstrated reduced maximal arm elevation velocity compared to younger adults (p = 0.02). The results in both groups combined reveal a positive correlation between maximal arm elevation velocity and first compensatory step MoS at intensity 3 (p = 0.01). Together, these findings indicate age-related decreases in arm response modulation and the association of arm elevation response with protective stepping stability, suggesting that fall prevention interventions may benefit from an emphasis on arm elevation velocity control in response to greater perturbation intensities.

Development and Psychometric Testing of the Bimanual Assessment Measure for People With Chronic Stroke

IMPORTANCE

Few tools are available to assess bimanual deficits after stroke.

OBJECTIVE

To develop the Bimanual Assessment Measure (BAM), which assesses a person's hand coordination in both preferred and prestroke roles (i.e., stabilizer or manipulator).

DESIGN

Development and psychometric testing of the BAM.

SETTING

Research laboratory.

PARTICIPANTS

People with chronic stroke (n = 24), age-matched controls (n = 23), and occupational therapists (n = 40).

OUTCOMES AND MEASURES

We assessed the BAM's internal consistency, reliability, and face and known-groups validity.

RESULTS

Items were selected as meaningful tasks that represented a range of bimanual coordination requirements (e.g., symmetrical forces and timing, asymmetrical forces and timing, time-limited reactive movement). Focus groups of people with stroke and occupational therapists provided input into BAM development. The BAM was found to have excellent reliability and internal consistency and face and known-groups validity.

CONCLUSIONS AND RELEVANCE

The BAM is a valid, reliable measure for people with chronic stroke that identifies bimanual coordination deficits beyond unimanual impairments and the potential capacity for people to return to prestroke hand roles (i.e., as a manipulator). What This Article Adds: This article introduces the BAM as a new assessment measure of bimanual functioning with the potential capacity to restore prestroke hand roles as either a manipulator or a stabilizer among people with chronic stroke.

Enhancing motor learning in people with stroke via memory reactivation during sleep

PURPOSE

Investigate the use of repetitive delivery of task-related auditory cues, known as targeted memory reactivation (TMR), throughout a 1-hour daytime nap to enhance motor learning in individuals with chronic stroke.

RESEARCH METHOD

Participants with a history of stroke at least 6 months prior were recruited to perform a novel overhand throwing task to randomly appearing target locations using the nonparetic upper extremity immediately before and after a 1-hour daytime nap. Half of the participants received TMR during the nap.

RESULTS

Participants who received TMR demonstrated a greater overall reduction in absolute and variable spatial errors relative to the NoTMR control group. Both groups demonstrated similar generalization of skill to 2 untrained variants of the trained task, but not to a novel untrained task.

CONCLUSIONS

This study suggests that TMR may enhance motor learning after stroke. Future studies should investigate whether TMR can lead to improvements of the paretic upper extremity during clinically based rehabilitation interventions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Examining the influence of mental stress on balance perturbation responses in older adults

BACKGROUND

Reach-to-grasp responses following balance perturbations are important to fall prevention but are often ineffective in older adults. The ability to shift attention from an ongoing cognitive task to balance related processes has been shown to influence reach-to-grasp effectiveness in older adults. However, the added influence of stress and anxiety - known to negatively affect attention shifting ability - has not yet been explored in relation to recovery from balance perturbations. Given that fear and anxiety over falling is a key fall risk factor, an understanding of how such a negative mental state may affect postural reactions is important. This study aimed to investigate the effect of varied induced emotional states on reach-to-grasp balance responses in older adults.

METHODS

Healthy older adults (mean age 70.5 ± 5.38 years) stood laterally between 2 handrails with contact sensors. A safety harness with an integrated loadcell was worn to prevent falls and measure the amount of harness assistance (expressed as percent body weight). With instructions to grasp one rail to restore balance, participants' balance was laterally disturbed using surface translations under three randomized conditions: no cognitive task, neutral (verb generation) task, and mental stress task with negative prompts (paced auditory serial addition). The primary outcome was frequency of protective grasps. Secondary outcomes included frequency of harness assistance during trials with grasp errors as well as wrist movement time, trajectory distance, and peak velocity.

RESULTS

Perceived level of distress was highest for the mental stress task compared to no task (p < 0.001) and neutral task conditions (p = 0.008). The mental stress task resulted in the lowest percentage of protective grasps (p < 0.001) in response to balance perturbations. Closer examination of trials that resulted in grasp errors (i.e., collisions or overshoots), revealed increased harness assistance and reduced peak velocity of wrist movement (p < 0.001) under the mental stress condition compared to grasp errors that occurred under the no task or neutral task condition.

DISCUSSION AND CONCLUSION

Distressing mental thoughts immediately prior to a balance perturbation lead to reduced effectiveness in reach-to-grasp balance responses compared to no or neutral cognitive tasks and should be considered as a possible fall risk factor.

Trunk kinematics and muscle activation patterns during stand-to-sit movement and the relationship with postural stability in aging

BACKGROUND

Stand-to-sit (StandTS) movement is an important functional activity that can be challenging for older adults due to age-related changes in neuromotor control. Although trunk flexion, eccentric contraction of the rectus femoris (RF), and coordination of RF and biceps femoris (BF) muscles are important to the StandTS task, the effects of aging on these and related outcomes are not well studied.

RESEARCH QUESTION

What are the age-related differences in trunk flexion, lower extremity muscle activation patterns, and postural stability during a StandTS task and what is the relationship between these variables?

METHODS

Ten younger and ten older healthy adults performed three StandTS trials at self-selected speeds. Outcomes included peak amplitude, peak timing, burst duration, and onset latency of electromyography (EMG) activity of the RF and BF muscles, trunk flexion angle and angular velocity, whole body center of mass (CoM) displacement, center of pressure (CoP) velocity, and ground reaction force (GRF).

RESULTS

There were no age-related differences in weight-bearing symmetry, StandTS and trunk flexion angular velocity, or BF activity. In both groups, EMG peak timing of RF was preceded by BF. Compared to younger adults, older adults demonstrated shorter RF EMG burst duration, reduced trunk flexion, and reduced stability as indicated by the longer duration in which CoM was maintained beyond the posterior limit of base of support (BoS), greater mean anterior-posterior CoP velocity and larger standard deviation of CoM vertical acceleration during StandTS with smaller vertical GRF immediately prior to StandTS termination. Trunk flexion angle and RF EMG burst duration correlated with stability as measured by the duration in which the CoM stayed within the BoS.

SIGNIFICANCE

Decreased trunk flexion and impaired eccentric control of the RF are associated with StandTS instability in aging and suggest the importance of including StandTS training as a part of a comprehensive balance intervention.

Aging, Vestibular Function, and Balance: Proceedings of a National Institute on Aging/National Institute on Deafness and Other Communication Disorders Workshop

Balance impairment and falls are among the most prevalent and morbid conditions affecting older adults. A critical contributor to balance and gait function is the vestibular system; however, there remain substantial knowledge gaps regarding age-related vestibular loss and its contribution to balance impairment and falls in older adults. Given these knowledge gaps, the National Institute on Aging and the National Institute on Deafness and Other Communication Disorders convened a multidisciplinary workshop in April 2019 that brought together experts from a wide array of disciplines, such as vestibular physiology, neuroscience, movement science, rehabilitation, and geriatrics. The goal of the workshop was to identify key knowledge gaps on vestibular function and balance control in older adults and develop a research agenda to make substantial advancements in the field. This article provides a report of the proceedings of this workshop. Three key questions emerged from the workshop, specifically: (i) How does aging impact vestibular function?; (ii) How do we know what is the contribution of age-related vestibular impairment to an older adult's balance problem?; and more broadly, (iii) Can we develop a nosology of balance impairments in older adults that can guide clinical practice? For each of these key questions, the current knowledge is reviewed, and the critical knowledge gaps and research strategies to address them are discussed. This document outlines an ambitious 5- to 10-year research agenda for increasing knowledge related to vestibular impairment and balance control in older adults, with the ultimate goal of linking this knowledge to more effective treatment.

A systematic review of upper extremity responses during reactive balance perturbations in aging

BACKGROUND

Balance responses to perturbations often involve the arms in an attempt to either restore balance or protect against impact. Although a majority of research has been dedicated to understanding age-related changes in lower limb balance responses, there is a growing body of evidence supporting age-related changes in arm responses. This systematic review aimed to summarize differences in arm responses between older and younger adults under conditions requiring counterbalancing, reaching to grasping, and protection against impact.

METHODS

Following a systematic review and critical appraisal of the literature, data regarding the arm response in studies comparing young and older adults was extracted. The resulting articles were also assessed for quality to determine risk of bias.

RESULTS

Fifteen high quality studies were identified. The majority of these studies reported delayed onsets in muscle activation, differences in arm movement strategies, delayed movement timing, increased impact forces, and greater grasp errors in older compared to young adults. These differences were also identified under varied visual and cognitive conditions.

CONCLUSIONS

The studies included in this review demonstrate age-related differences in arm responses regardless of the direction and nature of the perturbation. These differences could provide insight into developing more targeted rehabilitation and fall prevention strategies. More research is needed to assess whether the identified age-related differences are a necessary compensation or a contributory factor to balance impairments and fall risk in older adults.

Competition for limited neural resources in older adults leads to greater asymmetry of bilateral movements than in young adults

We previously demonstrated that lateralization in the neural control of predictive and impedance mechanisms is reflected by interlimb differences in control of bilateral tasks. Aging has been shown to reduce lateralization during unilateral performance, presumably due to greater recruitment of the ipsilateral hemisphere. We now hypothesize that aging-related reduction in the efficiency of neural resources should produce greater behavioral asymmetry during bilateral actions that require hemispheric specialization for each arm. This is because simultaneous control of dominant and nondominant arm function should induce competition for hemisphere-specific resources. To test this hypothesis, we now examine the effect of aging (young, n = 20; old, n = 20) on performance of a mechanically coupled task, in which one arm reaches toward targets while the other arm stabilizes against a spring that connects the two arms. Results indicate better dominant arm reaching performance and better nondominant arm stabilizing performance for both groups. Most notably, limb and joint compliance was lower in the dominant arm, leading to dominant arm deficits in stabilizing performance. Group analysis indicated that older adults showed substantially greater asymmetry in stabilizing against the spring load than did the younger adults. We propose that competition for limited neural resources in older adults is associated with reduced contributions of right hemisphere mechanisms to right-dominant arm stabilizing performance, and thus to greater asymmetry of performance.NEW & NOTEWORTHY We provide evidence for greater asymmetry of interlimb differences in bilateral coordination for stabilizing and preserved asymmetry of reaching with aging. These results provide the first evidence for increased lateralization with aging within the context of a complementary bilateral task.

Systematic Review Investigating the Effects of Nonpharmacological Interventions During Sleep to Enhance Physical Rehabilitation Outcomes in People With Neurological Diagnoses

OBJECTIVE

Conduct a systematic review of nonpharmacological interventions applied during sleep to enhance physical rehabilitation outcomes of individuals with a neurological diagnosis.

DATA SOURCES

Three online databases were searched for original research.

STUDY SELECTION

Intervention studies were included that used outcome measures of impairment, activity, and/or participation.

DATA EXTRACTION

Two reviewers independently screened 2287 titles and abstracts, reviewed 101 full texts, extracted data, and assessed study quality and risk of bias for 9 included studies.

DATA SYNTHESIS

All included studies were randomized controlled trials involving continuous positive airway pressure (CPAP) with inpatient individuals with stroke and sleep apnea. Several studies also included long-term outpatient follow-ups. Results in terms of outcomes based on impairment, activity, and participation were mixed. However, several studies found that the use of CPAP following stroke and sleep apnea during early stroke recovery had benefits relative to no CPAP.

CONCLUSIONS

The only nonpharmacological intervention to be administered during sleep in a neurological population to improve physical rehabilitation outcomes was found to be CPAP. This review was complicated by the variety of outcome measures used, lack of physical rehabilitation description, and CPAP compliance. In general, participants who had acceptable to good CPAP compliance saw the largest improvements in physical rehabilitation outcomes. Several other promising methods of brain stimulation during sleep are discussed.

Use of targeted memory reactivation enhances skill performance during a nap and enhances declarative memory during wake in healthy young adults

Sleep is an important component of motor memory consolidation and learning, providing a critical tool to enhance training and rehabilitation. Following initial skill acquisition, memory consolidation is largely a result of non-rapid eye movement sleep over either a full night or a nap. Targeted memory reactivation is one method used to enhance this critical process, which involves the pairing of an external cue with task performance at the time of initial motor skill acquisition, followed by replay of the same cue during sleep. Application of targeted memory reactivation during sleep leads to increased functional connectivity within task-related brain networks and improved behavioural performance in healthy young adults. We have previously used targeted memory reactivation throughout the first two slow-wave sleep cycles of a full night of sleep to enhance non-dominant arm throwing accuracy in healthy young adults. Here, we aimed to determine whether application of targeted memory reactivation throughout a 1-hr daytime nap was sufficient to enhance performance on the same non-dominant arm throwing task in healthy young adults. Participants were allocated to either nap or no nap, and within those groups half received targeted memory reactivation throughout a 1-hr between-session period, leading to four groups. Only participants who slept between sessions while receiving targeted memory reactivation enhanced their throwing accuracy upon beginning the second session. Future studies will aim to use this technique as an adjunct to traditional physical rehabilitation with individuals with neurologic diagnoses such as stroke.

Handedness results from complementary hemispheric dominance, not global hemispheric dominance: evidence from mechanically coupled bilateral movements

Two contrasting views of handedness can be described as 1) complementary dominance, in which each hemisphere is specialized for different aspects of motor control, and 2) global dominance, in which the hemisphere contralateral to the dominant arm is specialized for all aspects of motor control. The present study sought to determine which motor lateralization hypothesis best predicts motor performance during common bilateral task of stabilizing an object (e.g., bread) with one hand while applying forces to the object (e.g., slicing) using the other hand. We designed an experimental equivalent of this task, performed in a virtual environment with the unseen arms supported by frictionless air-sleds. The hands were connected by a spring, and the task was to maintain the position of one hand while moving the other hand to a target. Thus the reaching hand was required to take account of the spring load to make smooth and accurate trajectories, while the stabilizer hand was required to impede the spring load to keep a constant position. Right-handed subjects performed two task sessions (right-hand reach and left-hand stabilize; left-hand reach and right-hand stabilize) with the order of the sessions counterbalanced between groups. Our results indicate a hand by task-component interaction such that the right hand showed straighter reaching performance whereas the left hand showed more stable holding performance. These findings provide support for the complementary dominance hypothesis and suggest that the specializations of each cerebral hemisphere for impedance and dynamic control mechanisms are expressed during bilateral interactive tasks. NEW & NOTEWORTHY We provide evidence for interlimb differences in bilateral coordination of reaching and stabilizing functions, demonstrating an advantage for the dominant and nondominant arms for distinct features of control. These results provide the first evidence for complementary specializations of each limb-hemisphere system for different aspects of control within the context of a complementary bilateral task.

Modulation of working memory load distinguishes individuals with and without balance impairments following mild traumatic brain injury

OBJECTIVES

Balance and gait deficits can persist after mild traumatic brain injury (TBI), yet an understanding of the underlying neural mechanism remains limited. The purpose of this study was to investigate differences in attention network modulation in patients with and without balance impairments 2-8 weeks following mild TBI.

METHODS

Using functional magnetic resonance imaging, we compared activity and functional connectivity of cognitive brain regions of the default mode, central-executive and salience networks during a 2-back working memory task in participants with mild TBI and balance impairments (n = 7, age 47 ± 15 years) or no balance impairments (n = 7, age 47 ± 15 years).

RESULTS

We first identified greater activation in the lateral occipital cortex in the balance impaired group. Second, we observed stronger connectivity of left pre-supplementary motor cortex in the balance impaired group during the working memory task, which was related to decreased activation of regions within the salience and central executive networks and greater suppression of the default mode network.

CONCLUSIONS

Results suggest a link between impaired balance and modulation of cognitive resources in patients in mTBI. Findings also highlight the potential importance of moving beyond traditional balance assessments towards an integrative assessment of cognition and balance in this population.

Link Between Parkinson Disease and Rapid Eye Movement Sleep Behavior Disorder With Dream Enactment: Possible Implications for Early Rehabilitation

The purpose of this article is 2-fold: first, to inform readers of the link between the loss of motor inhibition during rapid eye movement (REM) sleep dreaming, diagnosed as REM sleep behavior disorder, and the future onset of neurodegenerative disorders, such as Parkinson disease and dementia with Lewy bodies; it has been reported that motor disinhibition during REM sleep often precedes the onset of these disorders by years or even decades; second, to consider that the identification of REM sleep behavior disorder and the early involvement of rehabilitation and/or development of home exercise plans may aid in prolonging and even increasing function, independence, and quality of life, should such neurodegenerative disorders develop later in life.

Targeted Memory Reactivation During Sleep, But Not Wake, Enhances Sensorimotor Skill Performance: A Pilot Study

The benefits of sleep on memory consolidation have been enhanced for declarative and motor sequence learning through replaying classically conditioned auditory stimuli during sleep, known as targeted memory reactivation (TMR). However, it is unknown if TMR can influence performance of a sensorimotor skill, in the absence of the cognitive requirements of sequence learning. Here, young adults performed a nondominant arm throwing task separated by a full night of sleep or a full day of wake, with half of all participants receiving TMR between sessions. Participants who received TMR during sleep demonstrated enhanced sensorimotor performance relative to all other groups. In conclusion, this pilot study indicates that it is feasible to influence sensorimotor skill performance through TMR during sleep and may serve as a future adjunct to physical rehabilitation. Future studies will aim to confirm the present results with a larger sample size as well as investigate the effects of TMR during sleep on older adults both with and without a history of stroke.

Influence of non-spatial working memory demands on reach-grasp responses to loss of balance: Effects of age and fall risk

Reactive balance recovery strategies following an unexpected loss of balance are crucial to the prevention of falls, head trauma and other major injuries in older adults. While a longstanding focus has been on understanding lower limb recovery responses, the upper limbs also play a critical role. However, when a fall occurs, little is known about the role of memory and attention shifting on the reach to grasp recovery strategy and what factors determine the speed and precision of this response beyond simple reaction time. The objective of this study was to compare response time and accuracy of a stabilizing grasp following a balance perturbation in older adult fallers compared to non-fallers and younger adults while loading the processing demands of non-spatial, verbal working memory. Working memory was engaged with a progressively challenging verb-generation task that was interrupted by an unexpected sideways platform perturbation and a pre-instructed reach to grasp response. Results revealed that the older adults, particularly those at high fall risk, demonstrated significantly increased movement time to handrail contact and grasping errors during conditions in which non-spatial memory was actively engaged. These findings provide preliminary evidence of the cognitive deficit in attention shifting away from an ongoing working memory task that underlies delayed and inaccurate protective reach to grasp responses in older adult fallers.

Capturing subject variability in fMRI data: A graph-theoretical analysis of GICA vs. IVA

BACKGROUND

Recent studies using simulated functional magnetic resonance imaging (fMRI) data show that independent vector analysis (IVA) is a superior solution for capturing spatial subject variability when compared with the widely used group independent component analysis (GICA). Retaining such variability is of fundamental importance for identifying spatially localized group differences in intrinsic brain networks.

NEW METHODS

Few studies on capturing subject variability and order selection have evaluated real fMRI data. Comparison of multivariate components generated by multiple algorithms is not straightforward. The main difficulties are finding concise methods to extract meaningful features and comparing multiple components despite lack of a ground truth. In this paper, we present a graph-theoretical (GT) approach to effectively compare the ability of multiple multivariate algorithms to capture subject variability for real fMRI data for effective group comparisons. The GT approach is applied to components generated from fMRI data, collected from individuals with stroke, before and after a rehabilitation intervention.

COMPARISON WITH EXISTING METHOD

IVA is compared with widely used GICA for the purpose of group discrimination in terms of GT features. In addition, masks are applied for motor related components generated by both algorithms.

CONCLUSIONS

Results show that IVA better captures subject variability producing more activated voxels and generating components with less mutual information in the spatial domain than Group ICA. IVA-generated components result in smaller p-values and clearer trends in GT features.

Neural plasticity and implications for hand rehabilitation after neurological insult

Experience dependent plasticity refers to ability of the brain to adapt to new experiences by changing its structure and function. The purpose of this paper is to provide a brief review the neurophysiological and structural correlates of neural plasticity that occur during and following motor learning. We also consider that the extent of plastic reorganization is dependent upon several key principals and that the resulting behavioral consequences can be adaptive or maladaptive. In light of this research, we conclude that an increased understanding of the complexities of brain plasticity will translate into enhanced treatment opportunities for the clinician to optimize hand function.

Complex-value coherence mapping reveals novel abnormal resting-state functional connectivity networks in task-specific focal hand dystonia

Resting-state imaging designs are powerful in modeling functional networks in movement disorders because they eliminate task performance related confounds. However, the most common metric for quantifying functional connectivity, i.e., bivariate magnitude coherence (Coh), can sometimes be contaminated by spurious correlations in blood-oxygen level dependent (BOLD) signal due to smoothing and seed blur, thereby limiting the identification of true interactions between neighboring neural populations. Here, we apply a novel functional connectivity metric., i.e., imaginary coherence (ICoh), to BOLD fMRI data in healthy individuals and patients with task-specific focal hand dystonia (tspFHD), in addition to the traditional magnitude Coh metric. We reconstructed resting-state sensorimotor, basal ganglia, and default-mode networks using both Coh and ICoh. We demonstrate that indeed the ICoh metric eliminates spatial blur around seed placement and reflects slightly different networks from Coh. We then identified significant reductions in resting-state connectivity within both the sensorimotor and basal ganglia networks in patients with tspFHD, primarily in the hemisphere contralateral to the affected hand. Collectively, these findings direct our attention to the fact that multiple networks are decoupled in tspFHD that can be unraveled by different functional connectivity metrics, and that this aberrant communication contributes to clinical deficits in the disorder.

Functional connectivity in relation to motor performance and recovery after stroke

Plasticity after stroke has traditionally been studied by observing changes only in the spatial distribution and laterality of focal brain activation during affected limb movement. However, neural reorganization is multifaceted and our understanding may be enhanced by examining dynamics of activity within large-scale networks involved in sensorimotor control of the limbs. Here, we review functional connectivity as a promising means of assessing the consequences of a stroke lesion on the transfer of activity within large-scale neural networks. We first provide a brief overview of techniques used to assess functional connectivity in subjects with stroke. Next, we review task-related and resting-state functional connectivity studies that demonstrate a lesion-induced disruption of neural networks, the relationship of the extent of this disruption with motor performance, and the potential for network reorganization in the presence of a stroke lesion. We conclude with suggestions for future research and theories that may enhance the interpretation of changing functional connectivity. Overall findings suggest that a network level assessment provides a useful framework to examine brain reorganization and to potentially better predict behavioral outcomes following stroke.

Friendships of Adolescents with Physical Disabilities Attending Inclusive High Schools

Background

Adolescents with physical disabilities (PD) report difficulties making friends. Education in inclusive high schools may help to minimize these challenges.

Purpose

This paper begins to answer the question: What is the nature of the friendships of adolescents with PD attending inclusive high schools?

Methods

Standard qualitative methods were used to analyze the data of three multi-perspective case studies that included interviews of three adolescents with PD and their nominated friends, parents, and teachers. Based on these analyses, we describe the activities and the quality of the adolescents’ interactions and relationships.

Findings

Three unique patterns of friendship were identified: an extensive network of friendships, a core group of friends with an avid interest, and few friendships in or out of school.

Implications

Successful development of friendships among adolescents with and without PD is complex and influenced by personal, environmental, interactional, and relationship factors.

Pilot study of Lokomat versus manual-assisted treadmill training for locomotor recovery post-stroke

BACKGROUND

While manually-assisted body-weight supported treadmill training (BWSTT) has revealed improved locomotor function in persons with post-stroke hemiparesis, outcomes are inconsistent and it is very labor intensive. Thus an alternate treatment approach is desirable. Objectives of this pilot study were to: 1) compare the efficacy of body-weight supported treadmill training (BWSTT) combined with the Lokomat robotic gait orthosis versus manually-assisted BWSTT for locomotor training post-stroke, and 2) assess effects of fast versus slow treadmill training speed.

METHODS

Sixteen volunteers with chronic hemiparetic gait (0.62 +/- 0.30 m/s) post-stroke were randomly allocated to Lokomat (n = 8) or manual-BWSTT (n = 8) 3x/wk for 4 weeks. Groups were also stratified by fast (mean 0.92 +/- 0.15 m/s) or slow (0.58 +/- 0.12 m/s) training speeds. The primary outcomes were self-selected overground walking speed and paretic step length ratio. Secondary outcomes included: fast overground walking speed, 6-minute walk test, and a battery of clinical measures.

RESULTS

No significant differences in primary outcomes were revealed between Lokomat and manual groups as a result of training. However, within the Lokomat group, self-selected walk speed, paretic step length ratio, and four of the six secondary measures improved (p = 0.04-0.05, effect sizes = 0.19-0.60). Within the manual group, only balance scores improved (p = 0.02, effect size = 0.57). Group differences between fast and slow training groups were not revealed (p > or = 0.28).

CONCLUSION

Results suggest that Lokomat training may have advantages over manual-BWSTT following a modest intervention dose in chronic hemiparetic persons and further, that our training speeds produce similar gait improvements. Suggestions for a larger randomized controlled trial with optimal study parameters are provided.

Sensory-specific balance training in older adults: effect on proprioceptive reintegration and cognitive demands

BACKGROUND AND PURPOSE

Age-related changes in the ability to adjust to alterations in sensory information contribute to impaired postural stability. The purpose of this randomized controlled trial was to investigate the effect of sensory-specific balance training on proprioceptive reintegration.

SUBJECTS

The subjects of this study were 36 older participants who were healthy.

METHODS

Participants were randomly assigned to a balance exercise group (n=17) or a falls prevention education group (n=19). The primary outcome measure was the center-of-pressure (COP) velocity change score. This score represented the difference between COP velocity over 45 seconds of quiet standing and each of six 5-second intervals following proprioceptive perturbation through vibration with or without a secondary cognitive task. Clinical outcome measures included the Fullerton Advanced Balance (FAB) Scale and the Activities-specific Balance Confidence (ABC) Scale. Assessments were conducted at baseline, postintervention, and at an 8-week follow-up.

RESULTS

Following the exercise intervention, there was less destabilization within the first 5 seconds following vibration with or without a secondary task than there was at baseline or in the falls prevention education group. These training effects were not maintained at the 8-week follow-up. Postintervention improvements also were seen on the FAB Scale and were maintained at follow-up. No changes in ABC Scale scores were identified in the balance exercise group, but ABC Scale scores indicated reduced balance confidence in the falls prevention education group postintervention.

DISCUSSION AND CONCLUSION

The results of this study support short-term enhanced postural responses to proprioceptive reintegration following a sensory-specific balance exercise program.

Velocity discrimination: Reliability and construct validity in older adults

The aim of this study was to determine whether a test of velocity discrimination is a reliable and valid measure of proprioception in healthy older adults. Results revealed excellent test-retest reliability over a 2-week period. Velocity discrimination also indicated good construct validity with modest correlations with center of pressure sway outcomes in eyes open and closed conditions as well as stair climbing time. Good construct validity was identified by velocity discrimination sensitivity to age with a higher mean value for the older participants than for the younger participants. These findings suggest velocity discrimination is a valid and reliable measure of velocity sense, which may be included with measures of position and movement sense to enhance the proprioceptive testing repertoire among researchers. Implications of these results are discussed in terms of evaluation of proprioceptive training programs aimed to enhance postural control.

Sensory-specific balance training in older adults: effect on position, movement, and velocity sense at the ankle

BACKGROUND AND PURPOSE

Age-related changes in proprioception contribute to impairments in postural control and increased fall risk in older adults. The purpose of this randomized controlled trial was to examine the effects of balance exercises on proprioception.

SUBJECTS

The participants were 36 older people and 24 younger people who were healthy.

METHODS

Older participants were randomly assigned to a balance exercise group (n=17) or a falls prevention education group (n=19). Baseline, postintervention, and 8-week follow-up measurements of 3 proprioceptive measures (threshold to perception of passive movement, passive joint position sense, and velocity discrimination) were obtained at the ankle. For comparative purposes, younger participants underwent a one-time assessment of the 3 proprioceptive measures.

RESULTS

Postintervention improvements in velocity discrimination were found in the balance exercise group when compared with values at baseline and in the falls prevention education group. Age-related differences found at baseline were reduced in the balance exercise group after intervention. Improvements were not maintained at the 8-week follow-up. Threshold to perception of passive movement and passive joint position sense did not change as a function of the exercise intervention.

DISCUSSION AND CONCLUSION

The results suggest that short-term improvements in velocity sense, but not movement and position sense, may be achieved following a balance exercise intervention.