A Comparative Study of Time Frequency Representation Techniques for Freeze of Gait Detection and Prediction.

Freezing of Gait (FOG) is an impairment that affects the majority of patients in the advanced stages of Parkinson's Disease (PD). FOG can lead to sudden falls and injuries, negatively impacting the quality of life for the patients and their families. Rhythmic Auditory Stimulation (RAS) can be used to help patients recover from FOG and resume normal gait. RAS might be ineffective due to the latency between the start of a FOG event, its detection and initialization of RAS. We propose a system capable of both FOG prediction and detection using signals from tri-axial accelerometer sensors that will be useful in initializing RAS with minimal latency. We compared the performance of several time frequency analysis techniques, including moving windows extracted from the signals, handcrafted features, Recurrence Plots (RP), Short Time Fourier Transform (STFT), Discreet Wavelet Transform (DWT) and Pseudo Wigner Ville Distribution (PWVD) with Deep Learning (DL) based Long Short Term Memory (LSTM) and Convolutional Neural Networks (CNN). We also propose three Ensemble Network Architectures that combine all the time frequency representations and DL architectures. Experimental results show that our ensemble architectures significantly improve the performance compared with existing techniques. We also present the results of applying our method trained on a publicly available dataset to data collected from patients using wearable sensors in collaboration with A.T. Still University.

Aging-related decrements during specific phases of the dual-task Timed Up-and-Go test.

BACKGROUND: It is unclear how young and older adults modulate dual-task mobility under changing postural challenges. AIM: To examine age-related changes in dual-task processing during specific phases of dual-task Timed Up-and-Go (TUGdual-task). METHOD: Healthy young and older adults performed the Timed Up-and-Go (TUG) with the following dual-task conditions: (1) serial-three subtractions, (2) carrying cup of water, (3) combined subtraction and carrying water, and (4) dialing cell phone. The primary outcome was the dual-task cost on performance of TUG (percent change from single- to dual-task) based on duration and peak trunk velocity of each phase: (a) straight-walk, (b) sit-to-stand, (c) turn, (d) turn-to-sit. Mixed-design univariate analysis of variance was performed for each type of task. RESULTS: Older adults had more pronounced mobility decrements than young adults during straight-ahead walking and turns when the secondary task engaged both cognitive and manual modalities. Simple cognitive or manual tasks during TUGdual-task did not differentiate young from older participants. Subtraction performance during simple and complex cognitive conditions differed by phase of the TUG. Manual task performance of carrying water did not vary by phase or age. DISCUSSION: Our findings suggest that dual-task processing is dynamic across phases of TUGdual-task. Aging-related dual-task decrements are demonstrated during straight-ahead walking and turning, particularly when the secondary task is more complex. CONCLUSION: Older adults are susceptible to reduced dual-task mobility during straight-ahead walking and turning particularly when attentional loading was increased.

Allocation of attention and dual-task effects on upper and lower limb task performance in healthy young adults.

Many daily activities require separate tasks of the arms and legs to be performed together, as in driving where one foot controls the accelerator, one arm steers, and the other arm and foot shift gears and clutch. Strategies and underlying mechanisms for attention allocation and task prioritization have been explored in standing and walking while performing a manual or cognitive task. These studies reveal a task-related strategy that often, but not always, prioritizes the lower limb task of walking. However, in the absence of locomotion and gait-related postural control, as in sitting, multi-limb dual-task strategies are largely unexplored. Therefore, to characterize dual-task interference of arm and leg tasks during a driving-like activity, seated participants were assessed for the interference effect on hand velocity and movement time of a three-phase reach task and on the error in tracking of a foot-pedal ramp-tracking task. We found that the dual-task cost to reaching shown as decreases in reach performance differed among the three phases, that the cost to foot-pedal tracking also differed by phase, and that the between-task trade-off and prioritization strategy varied between the steep and gradual tracking ramps. Therefore, we propose that attention to concurrent reaching and foot-pedal tracking was flexibly allocated based on phase of the tasks.

Falls and spinal muscular atrophy: exploring cause and prevention.

INTRODUCTION: Falls can cause injury and may compromise function in spinal muscular atrophy (SMA) patients. Weakness and gait variability are associated with falls in other neurological disorders, and fatigue is well documented in SMA. The relationship of weakness, fatigue, and gait variability to falls has never been investigated. METHODS: Seven ambulatory patients with SMA completed a falls history questionnaire, 6MWT, gait analysis, and strength testing. Pearson correlation coefficients were used to examine associations between these variables. RESULTS: All 7 subjects reported falls in the previous year. Stride-length variability was significantly associated with falls, unlike strength, fatigue, or other gait variables. CONCLUSIONS: Stride-length variability was the key variable associated with falls. Preventive strategies to avoid falls should be incorporated into patient management plans. Gait analysis provides actionable information not revealed by standard assessments and should be included in clinical trials designed to address the prevention of falls in the SMA population.

Impact of a 7-day retreat for people with Parkinson's disease: a phenomenological study.

Aim: Early and ongoing access to rehabilitation and exercise may preserve functional mobility and quality of life for persons with Parkinson disease (PwP). The aim of the current study was to describe the experience of PwP who participated in a 7-day retreat. Materials & methods: A phenomenological approach was used to describe the lived experience of PwP. Results: Three themes emerged from interviews: a community of shared information where participants discussed exercising and learning with other PwP; improved control of Parkinson's disease symptoms, including performing physical tasks more easily and renewed motivation for their long-term plans for exercise because of the retreat. Conclusion: A 7-day retreat for PwP positively impacted perceived control of disease-related symptoms and intentions to continue exercise.

Configuration variability of the six-minute walk test among licensed physical therapists working with neurologic conditions: a pilot survey.

BACKGROUND: The six-minute walk test (6MWT) is considered reliable and valid for assessing walking capacity in people with neurologic conditions. However, the consistency in the test length and configuration used is unclear. PURPOSE: To determine how the 6MWT was configured by licensed physical therapists working with patients with neurologic conditions in clinical practice, identify their knowledge of the American Thoracic Society (ATS) and Academy of Neurologic Physical Therapy (ANPT) guidelines for the 6MWT and assess relationships between therapist demographic characteristics and knowledge of the 6MWT guidelines. METHODS: One hundred forty-six therapists completed a survey related to the configuration they used for the 6MWT. RESULTS: Configuration of the 6MWT varied widely. Space limitation was the most frequently selected reason for reported configurations. Over half had available the standardized 100-feet straight walkway but fewer than one-third used this configuration of the ATS guidelines. Fewer than half knew of the ATS guidelines and nearly three-fourths knew of the ANPT guidelines. American Physical Therapy Association membership and having a higher percentage of neurologic patients were associated with knowledge of both guidelines. CONCLUSION: The 6MWT must be completed within the constraints of the working environment, and this requirement is clinically relevant when comparing patient results to normative values and measurements across clinics. Our results suggest a need for updated norms that are more congruent with space constraints in current practice settings.

Within-trial modulation of multi-digit forces to friction.

Tactile signals from the fingertips play a crucial role in the planning and control of object manipulations. Specifically, subjects adapt their digit forces to the object physical properties, including the friction at the object surface, to perform object manipulation while preventing slipping or dropping. This study addressed the adaptation of multi-digit forces to friction that occurs within a trial (from contact to onset of object manipulation) and across trials. Ten healthy participants were instructed to grasp, lift, hold, and release a grip device with five digits under four texture conditions: (1) all digits on rayon (R-R), (2) all digits on sandpaper (S-S), (3) thumb on sandpaper and fingers on rayon (S-R), and (4) thumb on rayon and fingers on sandpaper (R-S). Changing the texture conditions elicited significant changes from object contact to lift onset on digit normal force and center of pressure, as well as on the safety margins and force sharing patterns, e.g., normal forces exerted by each finger expressed as percentage of thumb normal forces. Furthermore, these friction effects were found on the very first trial and were observed throughout the remainder of the trials, thus indicating that force adaptation occurred within the first manipulation. Finally, a highly linear relation between the safety margin at object lift onset and object hold confirmed that digit force adaptation to friction occurred before object lift onset. These findings are discussed in relation to the role of tactile input in force modulation during the early phase of multi-digit grasping.

Finger force coordination underlying object manipulation in the elderly - a mini-review.

BACKGROUND: A decline in manual dexterity is a common phenomenon in elderly individuals. Often, simple daily activities such as handling coins and preparing meals become challenging. A substantial decline in manual dexterity may impact one's ability to live independently. Thus, understanding the underlying causes of these impairments is essential. Considerable attention has been given to the regulation of fingertip forces during object grasp, lift and transport in the elderly. OBJECTIVE: Here we review studies on fingertip force coordination in the elderly, with an emphasis on the relationship between the degree of change in elderly grip force control and the nature of the tasks performed. METHODS: A literature search was performed using Medline, Pubmed, and Web of Science electronic databases covering studies from 1985 to 2009, inputting combinations of the following key words: grip force, grasp force, fingertip forces, precision grip, aging, elderly, and hand motor control. RESULTS: Studies show a consistent elevation in grip force magnitudes that may easily lead to fatigue. These force increases may represent a compensation for increased skin slipperiness or a reduction in tactile information. In contrast, anticipatory grip force control (planning) remains relatively intact. Age-related changes in anticipatory control seem to emerge only during more complex tasks. CONCLUSION: The relationship between task complexity and degree of age-related changes suggests that results from simple, laboratory-based tasks may only partially explain impairments observed during the performance of activities of daily living, since the latter ones are typically more complex. A better understanding of impaired manual dexterity experienced by elderly individuals could be achieved by expanding experimental paradigms so that they more closely resemble the complexities encountered in functional daily tasks. Subsequently, these findings could be used in clinical settings to develop treatment approaches that consider grasp control in the context of behaviorally meaningful tasks.

Coordination of grasping and walking in Parkinson's disease.

Studies on grasp control underlying manual dexterity in people with Parkinson disease (PD) suggest that anticipatory grasp control is mainly unaffected during discrete tasks using simple two-digit grasp. Nevertheless, impaired hand function during daily activities is one of the most disabling symptoms of PD. As many daily grasping activities occur during functional movements involving the whole body, impairments in anticipatory grasp control might emerge during a continuous dynamic task such as object transport during walking. In this case, grasp control must be coordinated along with multiple body segments. The present study investigated the effect of PD on anticipatory grasp control and intersegmental coordination during walking with a hand-held object. Nine individuals with idiopathic PD (tested OFF and ON medication) and nine healthy age-matched controls carried a grip instrument between their right thumb and index finger during self-paced and fast walking. Although the amplitude of grip forces was higher in standing and walking for subjects with PD, both subjects with PD and control subjects coupled grip and inertial force changes in an anticipatory fashion while walking. However, gait-induced motions of the object relative to that of the trunk (i.e., dampening) was reduced in subjects with PD. Medication increased the dampening in all subjects with PD. We suggest that these differences are associated with impairments in intersegmental coordination.

Task-specific modulation of multi-digit forces to object texture.

During multi-digit grasping both local and non-local digit force responses occur in response to changes in texture at selected digits depending on the grasp configuration. However, the extent to which the specific patterns of force distribution depend on the requirement to hold the object against gravity remains to be determined. In the present study, we examined whether grasp force sharing patterns are invariant when the constraint of maintaining the object orientation vertical against gravity is removed. We used changes in object texture to elicit force changes at single digits during two grasping tasks with different behavioral contexts. One task entailed holding an object against gravity (object hold [OH]). A second (force production [FP]) task consisted of generating lifting forces on an object clamped to the tabletop that were matched to those used during OH. Unlike OH, the FP task lacks the behavioral consequences associated with erroneous sharing of normal and tangential digit forces, e.g., object tilt. Ten subjects lifted and simulated lifting an instrumented object measuring grasping normal and vertical tangential forces at all five digits when the textures were uniformly high-friction sandpaper or low-friction rayon and when one digit contacted a different frictional texture than the other four digits. We found that in both tasks texture changes at individual digits elicited force changes at that digit as well as other digits. However, the specific pattern of force distribution changes differed during OH compared to FP. While subjects modulate the normal and tangential digit forces to different degrees depending on object texture and the grasping task, they ignore the requirement of moment equilibrium when this has no consequences on object orientation (FP task). These findings indicate that multi-digit force responses to texture revealed by previous studies are not obligatory and suggest that the behavioral context of a task should be considered when inferring general principles of multi-digit force coordination.

A physical therapy decision-making tool for stratifying persons with Parkinson's disease into community exercise classes.

Aim: Physical therapy and exercise are considered essential components in the management of Parkinson's disease (PD). Using our retrospective data and years of experience in assigning persons with PD to multilevel group classes we propose a two-part physical therapy decision-making tool consisting of participant and exercise program considerations. Methods: Retrospective medical record review and therapist consensus identified evaluation considerations determined to aide clinical decision making. The ability of these variables (i.e., demographics, clinical characteristics, clinical measures cut-offs) to predict the class assignment decision of PD-specialized physical therapists was evaluated using discriminant function analysis. Results: Therapist-assigned groups differed significantly on all clinical measures (p < 0.001) which provided the categorical data required for discriminant analysis. Using all variables, the discriminant function analysis predicted class assignment of the therapists with 79% agreement. Conclusion: This proposed tool provides a framework that may guide the process for increasing access to multilevel group classes.

Common synaptic input across motor nuclei supplying intrinsic muscles involved in the precision grip.

To gain insight into the mechanism by which the nervous system orchestrates the activities of multiple muscles during voluntary motor behaviors, we measured the degree of synchrony in the discharge times across pairs of motor units recorded from two intrinsic hand muscles, the adductor pollicis (AdP) and first dorsal interosseous (FDI), in human subjects performing a precision grip. The magnitude of synchrony measured across muscles is thought to reflect the extent of divergent synaptic input delivered in common to the motor nuclei supplying the two muscles. Unlike the pronounced motor-unit synchrony observed across comparable extrinsic hand muscles during the precision grip, little synchrony was detected across these two intrinsic muscles. These results suggest that extrinsic and intrinsic muscles of the hand are controlled by descending pathways with distinctly different patterns of spinal connectivity--more widespread terminations across motor nuclei supplying extrinsic muscles whereas more focal input to individual motor nuclei innervating intrinsic muscles.

Impaired anticipatory control of force sharing patterns during whole-hand grasping in Parkinson's disease.

We examined the coordination of multi-digit grasping forces as they developed during object grasping and lifting. Ten subjects with Parkinson's disease (PD; OFF and ON medication) and ten healthy age-matched control subjects lifted a manipulandum that measured normal forces at each digit and the manipulandum's position. The center of mass (CM) was changed from trial to trial in either a predictable (blocked) or unpredictable (random) order. All subjects modulated individual fingertip forces to counterbalance forces exerted by the thumb and minimize object tilt after lift-off. However, subjects with PD OFF exhibited an impaired ability to use anticipatory mechanisms resulting in less differentiated scaling of individual finger forces to the object CM location. Remarkably, these between-group differences in force modulation dissipated as subjects reached peak grip forces during object lift, although these occurred significantly later in subjects with PD OFF than controls and PD ON. Analysis of the tilt of the object during lift revealed all subjects had similar deviations of the object from the vertical, the direction of which depended on CM location. Thus these findings in subjects with PD indicate that: (a) PD-induced impairments in anticipatory force mechanisms appear to be greatly increased in multi-digit grasping as opposed to previous reports from two-digit grasping; (b) inaccurate scaling of fingertip force amplitude and sharing patterns before object lift is recovered during object lift; (c) the implementation of appropriate force amplitude and sharing among the digits during the lift occurs significantly later than for controls; (d) medication improves the temporal recovery of multi-digit force coordination. These results are discussed within the framework of PD-related deficits in sensorimotor integration and control of multi-degrees of freedom movement.

Cognitive-Motor Interference in Neurodegenerative Disease: A Narrative Review and Implications for Clinical Management.

This paper provides a narrative review of cognitive motor interference in neurodegeneration, including brain imaging findings specific to interference effects in neurodegenerative disease, and dual task assessment and intervention in Parkinson's disease (PD), multiple sclerosis (MS), and Huntington's disease (HD). In a healthy central nervous system the ability to process information is limited. Limitations in capacity to select and attend to inputs influence the ability to prepare and perform multiple tasks. As a result, the system balances demands, switching attention to the most task-relevant information as it becomes available. Limitations may become more apparent in persons with neurodegenerative diseases (ND) with system-specific impairments in PD, MS, and HD. These ND affect both cognitive and motor function and are thus particularly susceptible to dual task interference. Issues related to performer and task characteristics and implications of these findings for both the standard assessment of dual task abilities as well as development and evaluation of interventions aimed at improving dual task ability are discussed. In addition, we address the need for optimizing individualized assessment, intervention and evaluation of dual task function by choosing cognitive and motor tasks and measures that are sensitive to and appropriate for the individual's level of function. Finally, we use current evidence to outline a 5-step process of clinical decision making that uses the dual task taxonomy as a framework for assessment and intervention.

Motor imagery modality in expert dancers: an investigation of hip and pelvis kinematics in demi-plié and sauté.

Elite dancers often engage in mental practice during training, but little is known about the effects of discrete, repetitive motor imagery on dance movement performance. This study compared the effects of two motor imagery modalities, third-person visual imagery and kinesthetic imagery, on hip and pelvis kinematics during two technical dance movements, plié and sauté. Twenty-four female dancers (mean age: 26.04; mean years of training: 19.63) were randomly assigned to a type of imagery practice: visual imagery (VI), kinesthetic imagery (KI), or a mental arithmetic task control condition (MAT). No statistically significant effects of imagery group or task type were found for external hip rotation, sagittal pelvic excursion, or a ratio relating hip to pelvic movement, suggesting that imagery practice did not affect either temporal or kinematic characteristics of the plié or sauté.

Building a framework for a dual task taxonomy.

The study of dual task interference has gained increasing attention in the literature for the past 35 years, with six MEDLINE citations in 1979 growing to 351 citations indexed in 2014 and a peak of 454 cited papers in 2013. Increasingly, researchers are examining dual task cost in individuals with pathology, including those with neurodegenerative diseases. While the influence of these papers has extended from the laboratory to the clinic, the field has evolved without clear definitions of commonly used terms and with extreme variations in experimental procedures. As a result, it is difficult to examine the interference literature as a single body of work. In this paper we present a new taxonomy for classifying cognitive-motor and motor-motor interference within the study of dual task behaviors that connects traditional concepts of learning and principles of motor control with current issues of multitasking analysis. As a first step in the process we provide an operational definition of dual task, distinguishing it from a complex single task. We present this new taxonomy, inclusive of both cognitive and motor modalities, as a working model; one that we hope will generate discussion and create a framework from which one can view previous studies and develop questions of interest.

Walking economy during cued versus non-cued self-selected treadmill walking in persons with Parkinson's disease.

BACKGROUND: Gait impairments related to Parkinson's disease (PD) include variable step length and decreased walking velocity, which may result in poorer walking economy. Auditory cueing is a common method used to improve gait mechanics in PD that has been shown to worsen walking economy at set treadmill walking speeds. It is unknown if auditory cueing has the same effects on walking economy at self-selected treadmill walking speeds. OBJECTIVES: To determine if auditory cueing will affect walking economy at self-selected treadmill walking speeds and at speeds slightly faster and slower than self-selected. METHODS: Twenty-two participants with moderate PD performed three, 6-minute bouts of treadmill walking at three speeds (self-selected and ± 0.22 m·sec-1). One session used cueing and the other without cueing. Energy expenditure was measured and walking economy was calculated (energy expenditure/power). RESULTS: Poorer walking economy and higher energy expenditure occurred during cued walking at a self-selected and a slightly faster walking speed, but there was no apparent difference at the slightly slower speed. CONCLUSION: These results suggest that potential gait benefits of auditory cueing may come at an energy cost and poorer walking economy for persons with PD at least at some treadmill walking speeds.

Walking economy during cued versus non-cued treadmill walking in persons with Parkinson's disease.

BACKGROUND: Gait impairment is common in Parkinson's disease (PD) and may result in greater energy expenditure, poorer walking economy, and fatigue during activities of daily living. Auditory cueing is an effective technique to improve gait; but the effects on energy expenditure are unknown. OBJECTIVE: To determine whether energy expenditure differs in individuals with PD compared with healthy controls and if auditory cueing improves walking economy in PD. METHODS: Twenty participants (10 PD and 10 controls) came to the laboratory for three sessions. Participants performed two, 6-minute bouts of treadmill walking at two speeds (1.12 m·sec-1 and 0.67 m·sec-1). One session used cueing and the other without cueing. A metabolic cart measured energy expenditure and walking economy was calculated (energy expenditure/power). RESULTS: PD had worse walking economy and higher energy expenditure than control participants during cued and non-cued walking at the 0.67 m·sec-1 speed and during non-cued walking at the 1.12 m·sec-1. With auditory cueing, energy expenditure and walking economy worsened in both participant groups. CONCLUSIONS: People with PD use more energy and have worse walking economy than adults without PD. Walking economy declines further with auditory cuing in persons with PD.

Impaired anticipatory control of grasp during obstacle crossing in Parkinson's disease.

During self-paced walking, people with Parkinson's disease maintain anticipatory control during object grasping. However, common functional tasks often include carrying an object while changing step patterns mid-path and maneuvering over obstacles, increasing task complexity and attentional demands. Thus, the present study investigated the effect of Parkinson's disease on the modulation of grasping force changes as a function of gait-related inertial forces. Subjects with Parkinson's disease maintained the ability to scale and to couple over time their grip and inertial forces while walking at irregular step lengths, but were unable to maintain the temporal coupling of grasping forces compared to controls during obstacle crossing. We suggest that this deterioration in anticipatory control is associated with the increased demands of task complexity and attention during obstacle crossing.

Aging effects on object transport during gait.

The ability to manipulate objects deteriorates with increasing age. In the coordination of fingertip forces underlying object manipulation, older adults use excessive grip (normal) forces but maintain anticipatory force control during simple manipulations. Daily activities are often more complex and involve grasp manipulations while simultaneously performing other activities. When walking while carrying an object, young adults couple grip forces to gait-induced inertial force changes (anticipatory control). It is unclear if anticipatory control is preserved in older adults during demanding tasks. The purpose of this study was therefore to investigate aging effects on grasp control when walking and transporting an object. We included gait perturbations to vary task difficulty and step regularity associated with walking. Twelve healthy older (65-84 years) and young (20-30 years) adults transported a hand-held object during unperturbed walking, obstacle crossing and step-length changes. While older subjects employed higher grip-inertial force ratios, they showed a strong force coupling comparable to that of the young during unperturbed walking and step-length changes. During obstacle crossing the forces in the older group were less tightly coupled (grip force delays). Gait patterns were similar between groups. Our findings indicate that older adults maintain anticipatory control during regular and irregular walking. Grasp control changes in older adults only during obstacle crossing suggest that overall task demands (balance requirements, attention demands) may contribute to declines of manual dexterity in functional tasks. This highlights the need to investigate grasp control within complex tasks when aiming to understand impairments of older adults encountered in daily life.