ASSESSING THE ATTENTIONAL DEMANDS OF ADDING HAPTIC INPUT DURING OVERGROUND WALKING

Poor performance of two or more tasks have been linked to recurrent falls, lower attentional capacity and inability to allocate attention appropriately in older adults (Beauchet et al. 2008). Increasing attentional demands during walking through the addition of other tasks (i.e., modality use, cognitive tasks) can increase fall-risk in older adults, as the ability to achieve successful performance of two or more tasks is affected (Woollacott & Shumway-Cook, 2002). The addition of sensory input in the form of haptic modalities, such as light touch (LT) of a rigid railing with less than 1 newton of force (Holden, Ventura, & Lackner, 1994), or haptic anchors (Mauerberg-deCastro et al., 2014), which involves pulling a light weight (~ 125 grams) attached to a string in each hand have been observed to improve dynamic stability, while not providing mechanical support. Determining the attentional demands of haptic modalities and the effect on dynamic stability will assist in better understanding their impact on fall-risk. The primary objective of this thesis was to assess the attentional demands of haptic modalities during walking using a verbal reaction time (VRT) task in healthy, young adults. The secondary objective of this thesis was to assess the effect of haptic modalities during walking with an added VRT task on dynamic stability. Twenty-two (12 male) healthy, young adults completed the testing protocol. Participants performed walking without haptic modalities (baseline), with LT of a rigid railing, and use of haptic anchors, with and without a VRT task that involved responding to a low or high frequency tone with the word “low” or “high”, respectively. A one-way RM ANOVA [condition (Baseline/LT/Anchors)] was performed on VRTs to assess attentional demands. A 2 × 2 RM ANOVA [condition (baseline walking/haptic modality) × presence of VRT task (no VRT task/VRT task)] on all calculated kinematic variables for each haptic modality separately to measure dynamic stability and walking performance with the addition of the haptic modality and the VRT task. No significant differences were observed (p = 0.506) between VRTs during walking conditions suggesting haptic modalities require similar attentional demands compared to baseline walking. It was observed that ML MOS was significantly decreased with LT (p < 0.001) and anchors (p = 0.010) suggesting using haptic modalities affects dynamic stability. There was little effect on dynamic stability measures with the added presence of a VRT task. The effect on dynamic stability observed when using haptic modalities may be associated with the arm position and the lack of arm swing. Overall, these findings suggest haptic modalities may require similar attentional demands to baseline walking and that adding a VRT when using a haptic modality does not affect walking behaviour. Dynamic stability might be affected with modality use as indicated by changes in outcome measures related to stability and walking when the haptic modalities were used during walking

BIOMECHANICAL MARKERS AS INDICATORS OF POSTURAL INSTABILITY PROGRESSION IN PARKINSON'S DISEASE

The long term objective of this research is to identify quantitative biomechanical parameters of postural instability in patients with Parkinson’s disease (PD) that can in turn be used to assess fall risk. Currently, clinical assessments in PD are not sufficiently sensitive to predict fall risk, making a history of falls to be the best predictor of a future fall. Identifying biomechanical measures to predict risk of falls in PD would provide a quantitative justification to implement fall-reducing therapies prior to a first fall and help prevent the associated debilitating fractures or even morbidity. While past biomechanical studies have shown the presence of balance deficits in PD patients, which often include a broad spectrum of disease stages, compared to healthy controls (HC), no studies have assessed whether such parameters can distinguish the onset of postural instability prior to clinical presentation, and if such parameters persist following clinical presentation of postural instability. Toward this end this study had three goals: • Determine if biomechanical assessment of a quasi-static task, postural sway, could provide preclinical indication of postural instability in PD. • Define a mathematical model (based on principal component analysis, PCA) with biomechanical and clinical measures as inputs to quantitatively score earlier postural instability presence and progression in PD. • Investigate if biomechanical assessment of a dynamic task, gait initiation, could provide preclinical indication of postural instability in PD. Specific Aim 1 determined that some biomechanical postural sway variables showed evidence of preclinical postural instability and increased with PD progression. This aim distinguished mild PD (Hoehn and Yahr stage (H&Y) 2, without postural deficits) compared to HC suggesting preclinical indication of postural instability, and confirmed these parameters persisted in moderate PD (H&Y 3, with postural deficits). Specifically, trajectory, variation, and peak measures of the center of pressure (COP) during postural sway showed significant differences (p < .05) in mild PD compared to healthy controls, and these differences persisted in moderate PD. Schwab and England clinical score best correlated with the COP biomechanical measures. These results suggest that postural sway COP measures may provide preclinical indication of balance deficits in PD and increase with clinical PD progression. Specific Aim 2 defined a PCA model based on biomechanical measures of postural sway and clinical measures in mild PD, moderate PD, and HC. PCA modeling based on a correlation matrix structure identified both biomechanical and clinical measures as the primary drivers of variation in the data set. Further, a PCA model based on these selected parameters was able to significantly differentiate (p < .05) all 3 groups, suggesting PCA scores may help with preclinical indication of postural instability (mild PD versus HC) and could be sensitive to clinical disease progression (mild PD versus moderate PD and moderate PD versus HC). AP sway path length and a velocity parameter were the 2 primary measures that explained the variability in the data set, suggesting further investigation of these parameters and mathematical models for scoring postural instability progression is warranted. Specific Aim 3 determined that a velocity measure from biomechanical assessment of gait initiation (peak COP velocity towards the swing foot during locomotion) showed evidence of preclinical postural instability in PD. Because balance is a complex task, having a better understanding of both quasi-static (postural sway) and dynamic (gait initiation) tasks can provide further insight about balance deficits resulting from PD. Several temporal and kinematic parameters changed with increasing disease progression, with significant difference in moderate PD versus HC, but missed significance in mild PD compared to HC. Total Unified Parkinson’s Disease Rating Scale (UPDRS) and Pull Test clinical scores best correlated with the biomechanical measures of the gait initiation response. These results suggest dynamic biomechanical assessment may provide additional information in quantifying preclinical postural instability and progression in PD. In summary, reducing fall risk in PD is a high priority effort to maintain quality of life by allowing continued independence and safe mobility. Since no effective screening method exists to measure fall risk, our team is developing a multi-factorial method to detect postural instability through clinical balance assessment, and in doing so, provide the justification for implementing fall reducing therapies before potentially debilitating falls begin

History of Concussion and Current Functional Movement Screen Scores in a Collegiate Recreational Population

Introduction: 1.6-3.8 million concussions occur annually related to sport.1 Although neurometabolic alterations in the brain last 7-10 days following a concussion, an increased Cortical Silent Period (CSP) has been found to persist after 19 months.2,3 Further, movement impairments have been noted years after injury.4 The Functional Movement Screen (FMS) assesses mobility and stability in the body.5 The purpose of this study was to assess if FMS scores correlate to history of a concussion in healthy college club sport participants. Methods: Health history and FMS score were collected on 55 participants (38 male, 17 female). Correlation between history of concussion and FMS score was assessed in SPSS. Results: Past history of concussion did not correlate to composite FMS score (R=.076). Conclusion: Past history of concussion does not affect FMS score

Image-based Stability Quantification

Quantitative evaluation of human stability using foot pressure/force measurement hardware and motion capture (mocap) technology is expensive, time consuming, and restricted to the laboratory. We propose a novel image-based method to estimate three key components for stability computation: Center of Mass (CoM), Base of Support (BoS), and Center of Pressure (CoP). Furthermore, we quantitatively validate our image-based methods for computing two classic stability measures, CoMtoCoP and CoMtoBoS distances, against values generated directly from laboratory-based sensor output (ground truth) using a publicly available, multi-modality (mocap, foot pressure, two-view videos), ten-subject human motion dataset. Using Leave One Subject Out (LOSO) cross-validation, experimental results show: 1) our image-based CoM estimation method (CoMNet) consistently outperforms state-of-the-art inertial sensor-based CoM estimation techniques; 2) stability computed by our image-based method combined with insole foot pressure sensor data produces consistent, strong, and statistically significant correlation with ground truth stability measures (CoMtoCoP r = 0.79 p < 0.001, CoMtoBoS r = 0.75 p < 0.001); 3) our fully image-based estimation of stability produces consistent, positive, and statistically significant correlation on the two stability metrics (CoMtoCoP r = 0.31 p < 0.001, CoMtoBoS r = 0.22 p < 0.043). Our study provides promising quantitative evidence for the feasibility of image-based stability evaluation in natural environments

From cellular vulnerability to altered circuit activity:a systems biology approach to study amyotrophic lateral sclerosis

The devastating effects of the brain losing its ability to control voluntary body movement are illustrated by diseases such as amyotrophic lateral sclerosis (ALS) - where the nerve cells that allow the brain to effectively communicate with muscles are progressively lost. Most of the ALS research traditionally revolves around the affected nerve cells, known as motoneurons, and aims to rescue their decline in function. Motoneurons are however part of larger networks in the nervous system and constantly receive, process and transmit signals. Therefore, even the smallest alteration of a single motoneuron will likely leave a mark on its connecting neurons and vice versa. Could it be that solely targeting the function of diseased neurons has unexpected effects in an already (mal)adapted network? To mimic ALS, we used the worm Caenorhabditis elegans engineered to express the human gene TDP-43. Dysregulated TDP-43 is considered a uniform hallmark of ALS and its expression in C. elegans causes severe paralysis. By developing and combining numerous technology-driven, mostly unbiased screening approaches we show that TDP-43 impedes neuronal function and causes an imbalance between stimulatory and inhibitory signals in the motor circuit. While functional output of repressed motoneurons could be restored via modulation of their activity, these interventions did not result in improved locomotion. Rebalancing the derailed motor circuit dynamics by combining multiple treatments, however, effectively restored movement. Because of the high degree of similarity in genetic alterations and pathology between ALS worms and patients, similar therapeutic strategies may eventually be valuable for ALS patients

Determining the False Positive Rate of a Concussion Battery in Healthy Division I Collegiate Athletes

Context: Athletic participation accounts for 1.6-3.8 million concussions, or mild traumatic brain injuries (mTBI) every year in the United States. Accurate assessment and diagnosis of concussions is critical to protect athletes from further injury. The Fourth International Conference on Concussion in Sport Consensus Statement recommends a multifaceted concussion assessment which includes symptom inventories, postural stability assessment, and neurocognitive testing. The accuracy of each test is vital in correctly diagnosing concussions. The Balance Error Scoring System (BESS), Standardized Assessment of Concussion (SAC), and Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) are among the most commonly used assessment tools by NCAA athletic trainers. Objectives: (1) evaluate the false positive rate of a clinical concussion assessment battery (BESS, SAC, ImPACT) in a healthy Division I collegiate athlete population and (2) identify trends in pass/fail rates based on months elapsed from baseline testing. Design: Prospective longitudinal study. Setting: A large university in southeast Georgia. Participants: Fifty Division I collegiate athletes were recruited as participants. Forty-eight participants fulfilled the study requirements. Main Outcome Measure(s): Descriptive statistics were run for all demographic variables, along with scores on the various dependent variables. Failure rates for each test were then determined. Any increase in BESS score, decrease in SAC score, or change in an ImPACT composite score exceeding the reliable change index was classified as a false positive for the concussion battery. A one-way repeated measures ANOVA was run to determine changes in scores by testing time (baseline vs. current) and time elapsed from baseline. Tukey post-hoc testing and planned simple contrasts were evaluated as needed. Results: The concussion battery produced an 81% false positive rate. BESS produced the most false positives (62.5%), followed by ImPACT (33.3%), and SAC (27.1%). No significant interactions were found between the time from baseline testing and differences in scores from baseline to current testing. There was a significant main effect across time between BESS baseline scores and testing scores. Conclusions: Eighty-one percent of participants demonstrated a deficit from their baseline scores on one or more of the assessments, thus failing the concussion battery and giving objective evidence of a possible concussion. When a patient fails an objective assessment used to identify and diagnose a concussion, they are at risk of being removed from all participation. To return to participation, the current recommendation is a symptom free graduated return to play protocol taking about seven days to complete. This may result in significant playing time lost for the athlete

The Development of a Novel Pitching Assessment Tool

Posture based ergonomic assessment tools are widely used to evaluate posture and injury risk for many workplace/occupational tasks. To date, there is no validated equivalent that can be used to assess the posture of a pitcher during baseball pitching. Therefore, the purpose of this study was to develop an inexpensive tool which can allow for the rapid assessment of a pitcher’s posture at lead foot strike, and establish the inter- and intra- rater reliability of the tool. For this study, 11 participants threw 30 pitches (15 fastballs, 15 curveballs) off an indoor pitching. Full body 3D kinematics were measured using reflective markers attached to anatomical landmarks and rigid bodies attached to body segments using a 10-camera Vicon Motion Capture system along with two high-speed video cameras (rear and side view) to record each pitch during the experimental trials. The kinematic data was analyzed, after which the highest velocity fastball of each of the 11 pitchers was selected for further analysis. A Pitching Mechanics Tool was designed to evaluate 16 different parameters at lead foot strike. Each of the 16 parameters had posture ranges or categories established based on scientific literature. Six evaluators with at least five years of experience working with adult pitchers completed the Pitching Mechanics Tool. Findings showed moderate to good levels of repeatability across multiple sessions as well as across multiple evaluators. Additionally, PMT results suggested that 2D qualitative analysis is a viable alternative to 3D motion capture

Consensus Paper: Neurophysiological Assessments of Ataxias in Daily Practice

The purpose of this consensus paper is to review electrophysiological abnormalities and to provide a guideline of neurophysiological assessments in cerebellar ataxias. All authors agree that standard electrophysiological methods should be systematically applied in all cases of ataxia to reveal accompanying peripheral neuropathy, the involvement of the dorsal columns, pyramidal tracts and the brainstem. Electroencephalography should also be considered, although findings are frequently non-specific. Electrophysiology helps define the neuronal systems affected by the disease in an individual patient and to understand the phenotypes of the different types of ataxia on a more general level. As yet, there is no established electrophysiological measure which is sensitive and specific of cerebellar dysfunction in ataxias. The authors agree that cerebellar brain inhibition (CBI), which is based on a paired-pulse transcranial magnetic stimulation (TMS) paradigm assessing cerebellar-cortical connectivity, is likely a useful measure of cerebellar function. Although its role in the investigation and diagnoses of different types of ataxias is unclear, it will be of interest to study its utility in this type of conditions. The authors agree that detailed clinical examination reveals core features of ataxia (i.e., dysarthria, truncal, gait and limb ataxia, oculomotor dysfunction) and is sufficient for formulating a differential diagnosis. Clinical assessment of oculomotor function, especially saccades and the vestibulo-ocular reflex (VOR) which are most easily examined both at the bedside and with quantitative testing techniques, is of particular help for differential diagnosis in many cases. Pure clinical measures, however, are not sensitive enough to reveal minute fluctuations or early treatment response as most relevant for pre-clinical stages of disease which might be amenable to study in future intervention trials. The authors agree that quantitative measures of ataxia are desirable as biomarkers. Methods are discussed that allow quantification of ataxia in laboratory as well as in clinical and real-life settings, for instance at the patients' home. Future studies are needed to demonstrate their usefulness as biomarkers in pharmaceutical or rehabilitation trials