Parkinson's disease (PD) is associated with reduced coordination abilities. These can result either in random or rigid patterns of movement. The latter, described here as coordination rigidity (CR), have been studied les...Parkinson's disease (PD) is associated with reduced coordination abilities. These can result either in random or rigid patterns of movement. The latter, described here as coordination rigidity (CR), have been studied less often. We explored whether CR was present in gait, quiet stance, and speech-tasks involving coordination among multiple joints and muscles. Kinematic and voice recordings were used to compute measures describing the dynamics of systems with multiple degrees of freedom and nonlinear interactions. After clinical evaluation, patients with moderate stage PD were compared against matched healthy participants. In the PD group, gait dynamics was associated with decreased dynamic divergence-lower instability-in the vertical axis. Postural fluctuations were associated with increased regularity in the anterior-posterior axis, and voice dynamics with increased predictability, all consistent with CR. The clinical relevance of CR was confirmed by showing that some of those features contribute to disease classification with supervised machine learning (82/81/85% accuracy/sensitivity/specificity).
Historically, research aimed at improving motor performance has largely focused on the neural processes involved in motor execution due to their role in muscle activation. However, accompanying somatosensory and proprioc...Historically, research aimed at improving motor performance has largely focused on the neural processes involved in motor execution due to their role in muscle activation. However, accompanying somatosensory and proprioceptive sensory information is also vitally involved in performing motor skills. Here we review research from interdisciplinary fields to provide a description for how somatosensation informs the successful performance of motor skills as well as emphasize the need for careful selection of study methods to isolate the neural processes involved in somatosensory perception. We also discuss upcoming strategies of intervention that have been used to improve performance somatosensory targets. We believe that a greater appreciation for somatosensation's role in motor learning and control will enable researchers and practitioners to develop and apply methods for the enhancement of human performance that will benefit clinical, healthy, and elite populations alike.
Postural instability affects motor tasks after a stroke. We investigated the strategies used to maintain balance during quiet standing posture and dynamic tasks in a video game. Sixteen stroke volunteers (12 males, 56 ± ...Postural instability affects motor tasks after a stroke. We investigated the strategies used to maintain balance during quiet standing posture and dynamic tasks in a video game. Sixteen stroke volunteers (12 males, 56 ± 9 years, post-stroke time 35 ± 10 months) and sixteen matched healthy volunteers had their biomechanical data collected to obtain the variables: center of mass, base of support, margin of stability, and weight symmetry. Healthy individuals and stroke patients showed similar dynamic stability. However, they adopted different motor strategies to achieve this: healthy individuals increased their base of support as they progressed to more challenging tasks, and stroke volunteers maintained the same base. The margin of stability of stroke volunteers was correlated with the MiniBEST scale.
The present study adopted a primed target grasping-categorization task and selected pictures of animals as target stimuli to investigate whether motor inhibition influences the motor interference effect of dangerous anim...The present study adopted a primed target grasping-categorization task and selected pictures of animals as target stimuli to investigate whether motor inhibition influences the motor interference effect of dangerous animals. The results identified more positive P2 and P3 amplitudes accompanied by larger delta event-related synchronization in the dangerous condition than in the neutral condition, suggesting that compared to neutral animal targets, dangerous animal targets attracted increased attentional resources in early processing and that subjects recruited more cognitive resources to process dangerous animal targets than neutral animal targets. Moreover, the results identified larger theta event-related synchronization (reflecting motor inhibition) in the dangerous condition than in the neutral condition. Thus, the results suggested that prepared motor responses were inhibited to avoid touching dangerous animal targets in the current task, supporting that motor inhibition influences the motor interference effect of dangerous animals based on a primed target grasping-categorization task.
Saccadic eye movements are one of the sensitive and noninvasive methods to help monitor the cognitive course of mild cognitive impairment (MCI). The study aimed to evaluate both pro and anti-saccade longitudinally and th...Saccadic eye movements are one of the sensitive and noninvasive methods to help monitor the cognitive course of mild cognitive impairment (MCI). The study aimed to evaluate both pro and anti-saccade longitudinally and the relationship between cognitive functions and eye movements in MCI subgroups and healthy controls (HCs) at a two-year follow-up. This study revealed that the anti-saccade anticipatory responses decreased in amnestic MCI (aMCI). Correct vertical pro-saccades increased in non-amnestic MCI (naMCI), while the express saccades decreased. Our study demonstrated that longer than two years of follow-up is necessary to monitor the course of MCI. Findings of the relationships between longitudinal changes of saccades and cognitive measurements demonstrated the usability of eye movements in evaluating the process of MCI.
This study explored the effect of dual task (DT) training compared to single task (ST) training on postural and cognitive performances in DT conditions in individuals with intellectual disability (ID). Postural sways and...This study explored the effect of dual task (DT) training compared to single task (ST) training on postural and cognitive performances in DT conditions in individuals with intellectual disability (ID). Postural sways and cognitive performances were measured separately and simultaneously before and after 8 weeks in the ST training group (STTG), the DT training group (DTTG) and the control group (CG) that did not received any training. Before training, postural sways and cognitive performances were higher in the DT condition compared to ST one in all groups. After training, postural sways were higher in the DT condition compared to the ST only in the STTG and the CG. The cognitive performance increased after training only in the DTTG.
In this study, the relationship between behavioral complexity (sample entropy, SEn) during steady walking and the quickness of subsequent turning performance in older adults. Herein, healthy older and younger adults (n =...In this study, the relationship between behavioral complexity (sample entropy, SEn) during steady walking and the quickness of subsequent turning performance in older adults. Herein, healthy older and younger adults (n = 12 each) were instructed to walk straight and then turn into an intersection surrounded by four pylons. This walking task was performed under two turning conditions: reactive and pre-planned turning, where the direction of turning was unknown until immediately before turning or was informed beforehand, respectively. For older adults, behavioral complexity was comparable under both conditions, but was higher under reactive than pre-planned turning condition for younger adults. This suggests that older adults cannot adapt their walking patterns in response to turning conditions. Correlation analysis showed that older adults with lower SEn had more difficulty in turning rapidly under reactive turning condition, indicating a relationship between the two variables. Thus, deterioration of the reactive turning performance in older adults is related to stereotyped movements during steady walking.
Underdevelopment of cognitive abilities in children, such as memory and attention, may make the use of verbal instructions difficult for learning new motor skills. The objective of this study was to evaluate whether visu...Underdevelopment of cognitive abilities in children, such as memory and attention, may make the use of verbal instructions difficult for learning new motor skills. The objective of this study was to evaluate whether visual and haptic cues which emphasize certain instructions facilitate skill acquisition in young tennis players. Twenty children were distributed in 2 groups: experimental (EXP) and control (CON). EXP received a racket with visual and haptic cues while CON trained with a classic racket. The task consisted of playing 30 consecutive forehands during a pretest and 16 weeks post-intervention. EXP displayed a larger improvement both in their technique (better ready position, more balls hit in front and to the side of the body) and in their performance (more points scored), highlighting the positive impact of visual and haptic cues during the early stage of motor learning.
Traumatic brain injuries can result in short-lived and long-lasting neurological impairment. Identifying the correct recovery timeframe is challenging, as balance-based metrics may be negatively impacted if testing is pe...Traumatic brain injuries can result in short-lived and long-lasting neurological impairment. Identifying the correct recovery timeframe is challenging, as balance-based metrics may be negatively impacted if testing is performed soon after exercise. Thirty-two healthy controls and seventeen concussed individuals performed a series of balance challenges, including virtual reality optical flow perturbation. The control group completed a backpacking protocol to induce moderate fatigue. Concussed participants had lower spectral power in the motor cortex and central sulcus when compared to fatigued controls. Moreover, concussed participants experienced a decrease in overall theta band spectral power while fatigued controls showed an increase in theta band spectral power. This neural signature may be useful to distinguish between concussed and non-concussed fatigued participants in future assessments.
Using the non-affected leg as stable frame of reference for the affected leg in gait assessment in knee osteoarthritis (KO) fails due to compensatory mechanisms. Assessing the cyclical movements of the upper extremities...Using the non-affected leg as stable frame of reference for the affected leg in gait assessment in knee osteoarthritis (KO) fails due to compensatory mechanisms. Assessing the cyclical movements of the upper extremities in a frequency-controlled repetitive punching task may provide an alternative frame of reference in gait assessment in patients with KO. Eleven participants with unilateral KO and eleven healthy controls were asked to perform treadmill walking and repetitive punching. The KO group showed more predictable ( = 0.020) and less automatized ( = 0.007) movement behavior than controls during treadmill walking. During repetitive punching, the KO group showed a similar degree of predictability ( = 0.784) but relative more automatized movement behavior ( = 0.013). Thus, the predictability of the movement behavior of the upper extremities during repetitive punching seems unaffected by KO and could provide an alternative frame of reference in gait assessment in patients with KO.
Most actions of daily life engage the two upper extremities (UEs) in a highly coordinated manner. While it is recognized that bimanual movements are impaired post-stroke, understanding how the paretic and non-paretic UE...Most actions of daily life engage the two upper extremities (UEs) in a highly coordinated manner. While it is recognized that bimanual movements are impaired post-stroke, understanding how the paretic and non-paretic UE contributes to this impairment is important for future interventions. We investigated kinetic and kinematics at the shoulder, elbow, and wrist joints in the paretic and non-paretic UE in 8 individuals with chronic stroke and non-dominant UE in 8 healthy controls during unimanual and bimanual tasks. Kinematic analysis revealed little effect of stroke. However, kinetic analysis revealed that during unimanual movements, joint control was impaired during unimanual and bimanual movements in both UEs, although to a lesser extent in the non-paretic than paretic UE. During bimanual movements, joint control did not change in the paretic UE, and it further deteriorated in the non-paretic UE compared with the unimanual movements. Our findings suggest that a single session of bimanual task performance does not improve joint control of the paretic UE and it impairs control of the non-paretic UE, making it more like that of the paretic UE.
We investigated postural stability during simulated archery shooting. The experiment consisted of two force release conditions: self-triggered (time-set in a feedforward fashion) and external cue-triggered (time-set by r...We investigated postural stability during simulated archery shooting. The experiment consisted of two force release conditions: self-triggered (time-set in a feedforward fashion) and external cue-triggered (time-set by reacting to external cue) conditions while standing on the force platform. The electromyography of leg muscles and the center of pressure (COP) were recorded. The notions of muscle-modes (M-modes) and multi-muscle synergies were employed to quantify the postural stability, which described covariation patterns of the M-modes to stabilize the COP. The result showed relatively strong postural stability in a self-triggered condition associated with consistent shooting performance. The current findings suggested that initiating force release in a feedforward fashion would be a beneficial strategy to ensure the consistency in shooting performance.
Motor evoked potential amplitude (MEP) is frequently measured in transcranial direct current stimulation (tDCS) studies that target the primary motor cortex (M1), and a subset of these studies involve motor behavior. Thi...Motor evoked potential amplitude (MEP) is frequently measured in transcranial direct current stimulation (tDCS) studies that target the primary motor cortex (M1), and a subset of these studies involve motor behavior. This systematic review explored the role of MEP as an indicator of neural change in M1-targeted tDCS studies involving motor behavior (i.e., motor practice and/or evaluation of motor performance) in healthy individuals, and examined the association between changes in motor performance and MEP. We executed our search strategy across four bibliographic databases. Twenty-two manuscripts met eligibility criteria. While anodal tDCS combined with motor practice frequently increased MEP, MEP outcomes did not necessarily align with changes in motor performance. Thus, MEP may not be the most appropriate indicator of neural change in tDCS studies that aim to improve motor performance.
Interlimb coordination is required for adequate execution of most daily life activities. Yet, aging negatively affects interlimb coordination, impacting the quality of life in older people. Therefore, disentangling the u...Interlimb coordination is required for adequate execution of most daily life activities. Yet, aging negatively affects interlimb coordination, impacting the quality of life in older people. Therefore, disentangling the underlying age-related neural mechanisms is of utmost importance. Here, we investigated neurophysiological processes of an interlimb reaction time task, including both simple and complex coordination modes. Midfrontal theta power, measured using electroencephalography (EEG), was analyzed as a marker for cognitive control. In total, 82 healthy adults participated, with 27 younger, 26 middle-aged, and 29 older adults. On a behavioral level, reaction time increased across the adult lifespan, and error rate was higher in older adults. Notably, aging disproportionately affected reaction times in the complex coordination modes, with larger reaction time increases from simple to complex movements than in younger adults, starting already at middle age. On the neurophysiological level, EEG showed that only younger adults had significantly increased levels of midfrontal theta power during complex relative to simple coordination modes, while no significant differences were found between simple and complex movements in middle-aged and older adults. The absence of this theta power upregulation with regard to movement complexity with increasing age might reflect a premature saturation of the available mental resources.
The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction...The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction. Ten young participants received perturbations applied to the upper body while sitting on a stool with an anterior or posterior leg support and when using a footrest. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Anticipatory activities were observed in the tibialis anterior, biceps femoris, and erector spinae muscles in the anterior leg support condition. Early onset of muscle activity was observed in the tibialis anterior, biceps femoris, rectus femoris, and erector spinae muscles in the posterior leg support condition compared to the feet support condition. Moreover, to maintain balance participants utilized co-contraction of muscles as the main mechanism of balance control in sitting regardless of the availability of the anterior or posterior leg support. There was no effect of a leg support on center of pressure displacements. The outcome of the study provides a background for future investigations of the effect of leg supports on control of balance in sitting when perturbed.
The objective of the present study was to examine the effects of gender stereotype on the performance and learning of a classical ballet pirouette in 11-year-old boys. Participants in the stereotype threat (ST) group wer...The objective of the present study was to examine the effects of gender stereotype on the performance and learning of a classical ballet pirouette in 11-year-old boys. Participants in the stereotype threat (ST) group were informed that, in general, boys tend to show worse results when completing the pirouette task in comparison to girls. Participants in the stereotype lift (SL) group were told that girls tend to show worse results in comparison to boys. The control group did not receive stereotype instructions. The results demonstrated worse performance during practice and retention (next day) for the ST group relative to the SL and control groups; the SL and control groups did not differ. The findings indicate that gender stereotype threat can undermine motor performance and learning in boys.
the effect of acute exercise on cognition covers almost all stages of information processing, but few studies have focused on visual awareness. Reports on the appearance of faint speed-changes in the perception of stimul...the effect of acute exercise on cognition covers almost all stages of information processing, but few studies have focused on visual awareness. Reports on the appearance of faint speed-changes in the perception of stimuli were used as an index for visual awareness. Visual awareness was assessed after exercise or rest. Aside from the detection of speed-changes, speed-change discrimination was added as an index of perception. the results showed that reports on the appearance of faint speed-changes were affected by acute aerobic exercise. The d' index was higher after exercise. The hit rate for speed-change detection was marginally significantly higher after exercise than after the sedentary test condition. Analysis of the results obtained for the discrimination task showed that discrimination speed was boosted only when subjects were aware of the speed-change. Importantly, neither false alarm rate nor response bias was affected by exercise. acute moderate- to vigorous-intensity aerobic exercise improved subjects' awareness of speed changes. In addition, there was a perceptual advantage due to exercise.
The practice of early sport specialization, defined as intense year-round training in a single sport at the exclusion of others, is increasing in youth athletics. Despite potential benefits, sport specialization may be d...The practice of early sport specialization, defined as intense year-round training in a single sport at the exclusion of others, is increasing in youth athletics. Despite potential benefits, sport specialization may be detrimental to the health of young athletes, as specialization may increase the risk of musculoskeletal injuries-particularly overuse injuries. However, there remains limited knowledge about how sports specialization uniquely alters underlying sports-related motor behavior. The purpose of this study was to compare the variability of movement patterns exhibited by highly sports specialized youth athletes to that of nonspecialized athletes during performance of a sport-specific, virtual reality based cutting task. It was hypothesized that highly specialized athletes would display different patterns of movement coordination compared to nonspecialized athletes during both the run-up phase and cut-and-decelerate phase. In support of the hypothesis, specialized athletes exhibited both intra- and inter-limb coordination that were significantly different than unspecialized athletes. Overall, the results indicate that the highly specialized athletes tended to exhibit greater degrees of coordination but also the ability to break the coordinated patterns of joint angle changes to execute a cutting maneuver, which requires asymmetric demands on the lower extremities while planting on one leg and changing direction.
Tool-embodiment is said to occur when the representation of the body extends to incorporate the representation of a tool following goal-directed tool-use. The present study was designed to determine if tool-embodiment-li...Tool-embodiment is said to occur when the representation of the body extends to incorporate the representation of a tool following goal-directed tool-use. The present study was designed to determine if tool-embodiment-like phenomenon emerges following different interventions. Participants completed body-part compatibility task in which they responded with foot or hand presses to colored targets presented on the foot or hand of a model, or on a rake held by the model. This response time (RT) task was performed before and after one of four interventions. In the Virtual-Tangible and the Virtual-Keyboard interventions, participants used customized controllers or keyboards, respectively, to move a virtual rake and ball around a course. Participants in the Tool-Perception intervention manually pointed to targets presented on static images of the virtual tool-use task. Participants in the Tool-Absent group completed math problems and were not exposed to a tool task. Results revealed that all four interventions lead to a pattern of pre-/post-intervention changes in RT thought to indicate the emergence of tool-embodiment. Overall, the study indicated that tool-embodiment can occur through repeated exposure to the body-part compatibility paradigm in the absence of any active tool-use, and that the paradigm may tap into more than just body schema.
This study aimed to identify the kinematic measures determining balance outcome following an over-ground trip perturbation. 117 healthy older adults who experienced laboratory-induced trips were divided into loss of bala...This study aimed to identify the kinematic measures determining balance outcome following an over-ground trip perturbation. 117 healthy older adults who experienced laboratory-induced trips were divided into loss of balance (LOB) and no LOB groups. The LOB group contained 27 fallers and 34 non-fallers, and the no LOB group contained 21 participants using cross-over strategy and 35 participants using obstacle-hit strategy. A 2-class hierarchical regression model for balance loss showed that margin of stabilty could determine the balance outcomes (LOB or not) with an overall accuracy of 92.7%. The 4-class model for recovery strategies showed that the combination of margin of stability, trunk angle, and COM velocity could determine 81.9% of strategies. Our findings would enhance intervention development for populations at risk of trip-induced falls.