Distinctive visual tasks for characterizing mild cognitive impairment and dementia using oculomotor behavior.

Introduction: One's eye movement (in response to visual tasks) provides a unique window into the cognitive processes and higher-order cognitive functions that become adversely affected in cases with cognitive decline, such as those mild cognitive impairment (MCI) and dementia. MCI is a transitional stage between normal aging and dementia. Methods: In the current work, we have focused on identifying visual tasks (such as horizontal and vertical Pro-saccade, Anti-saccade and Memory Guided Fixation tasks) that can differentiate individuals with MCI and dementia from their cognitively unimpaired healthy aging counterparts based on oculomotor Performance indices. In an attempt to identify the optimal combination of visual tasks that can be used to differentiate the participant groups, clustering was performed using the oculomotor Performance indices. Results: Results of our study with a group of 60 cognitively unimpaired healthy aging individuals, a group with 60 individuals with MCI and a group with 60 individuals with dementia indicate that the horizontal and vertical Anti-saccade tasks provided the optimal combination that could differentiate individuals with MCI and dementia from their cognitively unimpaired healthy aging counterparts with clustering accuracy of ∼92% based on the saccade latencies. Also, the saccade latencies during both of these Anti-saccade tasks were found to strongly correlate with the Neuropsychological test scores. Discussion: This suggests that the Anti-saccade tasks can hold promise in clinical practice for professionals working with individuals with MCI and dementia.

Virtual Reality based Gaze-sensitive Aiming Task Platform: Role of Attention Allocation in Task Performance for Individuals with Autism and Typically Developing Individuals.

Individuals with Autism Spectrum Disorder (ASD) often exhibit difficulty in movement preparation and allocating attention towards different Regions of Interest (ROIs) of a visual stimulus. Though research has alluded to differences in movement preparation for aiming tasks between individuals with ASD and typically developing (TD) individuals, there is limited evidence (true for near-aiming tasks) on the contribution of the window (i.e., time duration) of movement preparation (i.e., the planning window preceding movement initiation) on one's aiming performance. However, investigation of the contribution of this planning window on one's performance in far-aiming task remains as majorly unexplored. Again, often one's eye movement leads the initiation of hand movement (for task execution) indicating the importance of monitoring one's eye movement in the planning stage, critical for far-aiming task. Most of the studies (in conventional settings) examining the role of gaze behavior on aiming performance have involved TD individuals and only a few involving individuals with ASD. Here, we have designed Virtual Reality (VR)-based Gaze-sensitive far-aiming (dart throw) task and monitored the looking pattern of participants while they interacted with the task environment. We carried out a study with 40 participants (20 in each of ASD and TD groups) to understand how the participant groups differed in task performance and gaze fixation within the movement planning window. We observed difference in the scan path and last fixation within the movement planning window before triggering the release of the dart with relevance to task performance.

Design of SmartWalk for Estimating Implication of Pathway With Turn and Task Condition on Postural and Gait Indices: Relevance to Fear of Fall.

Fear of Fall (FoF) is often associated with postural and gait abnormalities leading to decreased mobility in individuals with Parkinson's Disease (PD). The variability in knee flexion (postural index) during heel-strike and toe-off events while walking can be related to one's FoF. Depending on the progression of the disease, gait abnormality can be manifested as start/turn/stop hesitation, etc. adversely affecting one's cadence along with an inability to transfer weight from one leg to the other. Also, task demands can have implications on one's gait and posture. Given that individuals with PD often suffer from FoF and their dynamic balance is affected by task conditions and pathways, in- depth investigation is warranted to understand the implications of task condition and pathways on one's gait and posture. This necessitates use of portable, wearable device that can capture one's gait-related indices and knee flexion in free-living conditions. Here, we have designed a portable, wearable and cost-effective device (SmartWalk) comprising of instrumented Shoes integrated with knee flexion recorder units. Results of our study with age-matched groups of healthy individuals (GrpH) and those with PD (GrpPD) showed the potential of SmartWalk to estimate the implication of task condition, pathways (with and without turn) and pathway segments (straight and turn) on one's knee flexion and gait with relevance to FoF. The knee flexion and gait-related indices were found to strongly corroborate with clinical measure related to FoF, particularly for GrpPD, serving as pre-clinical inputs for clinicians.

Portable Electromyogram-sensitive System for Assessment of Fear of Fall: Relevance of Gait Phases for Post-Stroke Patients.

Post-stroke patients often suffer from gait deficits along with Fear of Fall (FoF) that adversely affect their ambulation. The FoF has been reported to be negatively correlated with one's performance in daily life. Clinical scales, e.g., Falls Efficacy Scale are often used to assess one's FoF. Though powerful, it can suffer from subjectivity. Thus, it is important to have reliable assessment of FoF. Motivated by this, we used one's lower limb muscle activation during specific gait phases to assess one's FoF. For this, we developed a portable electromyogram-sensitive system that can synchronously measure one's muscle activation along with gait phases. We conducted an experimental study with post-stroke patients and age-matched healthy controls who walked under Dual-Task condition. We investigated the lower limb muscle (Gastrocnemius Lateralis (GM) and Tibialis Anterior (TA)) activation during Loading Response, Terminal Stance and Initial Swing phases of gait, associated with slips contributing to FoF. Results show that our system could quantify the disparity (∆) in muscle activation between the affected and unaffected sides of patients (∆ =  âˆ¼ 84% during Loading response for both GM and TA, ~32%for GM during Terminal Stance and TA during Initial Swing) which was considerably higher than that between dominant and non-dominant sides of healthy controls. This might infer reduced dynamic stability of patients leading to their FoF. Also, muscle activation could classify patients from healthy controls with 90% accuracy during Loading Response and Initial Swing phases with clinical relevance in diagnostics and monitoring rehabilitation outcomes. Clinical Relevance- This study indicated that our system has potential to be utilized as a tool for diagnostic and monitoring rehabilitation outcomes as it can quantify the residual muscle ability of the post-stroke patients during gait.

Smart Wearable Device for Quantification of Risk of Fall: Exploring Role of Gait Phases and Knee Bending Angle for Parkinson's Patients.

Gait disturbances with falls are common among patients with Parkinson's disease. Falls commonly occur from slips while walking on pathways with turns. Gait phases namely Loading Response and Terminal Stance are linked with forward and backward slips. Also, postural deformities (connected with knee joint angles) are debilitating symptoms of Parkinson's patients and are related with falls. Here, we have focused on exploring the contribution of Loading Response and Terminal Stance to risk of fall along with the relevance of postural deformity (e.g., knee bending) while an individual walked overground on pathways (with 0° and 180° turn) under dual task condition. For this, we have used a wearable device consisting of a pair of Sensored shoes and Knee Bending Angle Recorder Units. The device was used to compute Coefficient of Variation of knee bending angle during different gait phases as an indicator of one's risk of fall that corroborated with clinical measure. Clinical Relevance- A study with age and gender matched healthy and Parkinson's individuals indicated the importance of Loading Response and pathway turn while assessing risk of fall. This can serve as important pre-clinical input while designing intervention paradigms.

The Implication of Pathway Turn and Task Condition on Gait Quantified Using SmartWalk: Changes With Age and Parkinson's Disease With Relevance to Postural Strategy and Risk of Fall.

One's gait can be affected by aging, pathway with turns, task demands, etc., causing changes in gait-related indices and knee flexion (influencing posture). Walking on pathways with turns threatens stability, affecting one's gait-related indices and posture. The ability to overcome such deficits is compromised with age and neurological disorders, e.g., Parkinson's Disease (PD) leading to falls. Also, task demands imposed by single and dual-task (e.g., counting backward while walking) conditions affect the gait of individuals using different postural strategies varying with age and neurological disorder. Existing research has investigated either the effect of the pathway with turn or task condition on one's gait. However, none (to our knowledge) have explored the differentiated implications of the pathway with turn and task conditions on one's gait-related indices and knee flexion while walking. Our study had two phases with 30 participants. Phase 1 had healthy adults (young and old) and Phase 2 had age and gender-matched healthy elderly and individuals with Parkinson's disease (PD) who walked on pathways having turns under single and dual-task conditions. We analysed gait in terms of (i) gait-related indices (Phases 1 and 2) and (ii) knee flexion (Phase 2). Also, we analysed one's counting performance during dual task. One's gait-related indices and knee flexion were measured using a portable gait quantifier. The aim was to (i)understand whether both pathways with turn and task conditions are equally effective in affecting the gait of (a)individuals of varying ages and (b) gender-matched healthy older adults and individuals with PD, (ii)study variations of knee joint angles while walking on pathways having turns (under different task conditions) in terms of its clinical relevance, and (iii) explore the implication of pathway with turn on counting performance (with relevance to postural strategy) with varying age and PD. Results indicated that for the younger group, the task condition caused statistical variations in gait-related indices. For the older group, both pathways with turn and task conditions had statistical implications on gait-related indices. Additionally, individuals with PD demonstrated a higher variation in knee flexion than their healthy counterparts. Again, pathways with varying turns elicited variations in counting performance indicating different postural strategies being employed by the three groups.

Wearable Technology for Evaluation of Risk of Falls.

One's risk of fall can be quantified in terms of variability in one's gait, reflecting a loss of automatic rhythm of one's gait. In gait analysis, variability is commonly understood in terms of the fluctuation in the kinematic, kinetic, spatio-temporal, or physiological information. Here, we have focused on the estimation of knee joint angle (kinematic variable) synchronized with some of the kinetic and spatio-temporal gait parameters while an individual walked overground. Our system consisted of a pair of shoes with instrumented insoles and knee flexion/extension recorder unit having bend sensors. In addition, we have used the Coefficient of Variation for estimating the variability in the knee flexion/extension angle while walking overground as an indicator of the risk of fall. A study with healthy individuals (young and old) walking overground on pathways having 00 and 1800 turning angles indicated the feasibility of our wearable system to compute the variability in knee flexion/extension angle as an indicator of the risk of fall.

Feasibility of Cerebellar Transcranial Direct Current Stimulation to Facilitate Goal-Directed Weight Shifting in Chronic Post-Stroke Hemiplegics.

Neurological disorder such as stroke can adversely affect one's weight-bearing symmetry leading to dysfunctional postural control. Recovery after stroke is facilitated through functionally-relevant neuroplastic modulation. Functionally-relevant cerebellum coordinates voluntary movements. Specifically, the dentate nuclei and lower limb representations (lobules VII-IX) of the cerebellum are involved in error-correction, crucial for postural control. It is postulated that cerebellar transcranial direct current stimulation (ctDCS) of the dentate nuclei and lobules VII-IX can modulate postural control in chronic stroke survivors. The objectives of this work were to (1) present a refined Virtual Reality (VR)-based balance training platform (VBaT) that can measure Center of Pressure (CoP) and (2) carry out a study to understand the implication of ctDCS stimulating the dentate nuclei (PhaseD) and lobules VII-IX (PhaseL) on the postural control of chronic stroke patients when they interacted with VBaT. Also, we investigated whether hemiplegic patients (with intact cerebellum) having Basal Ganglia (BG) infarction had any differential abilities to correct postural sway from those with no BG infarction (while shifting weight to the Affected side). Results of a single-session single-blind crossover study on randomized PhaseD and PhaseL stimulation (with an intermediate resting state bipolar bilateral ctDCS) on 12 chronic hemiplegic patients on separate days indicated differentiated findings (post stimulation) on CoP-related indices. We observed an incremental effect on one's postural control during PhaseD and inhibitory effect on the dentate nuclei during PhaseL. Clustering analysis showed that those with BG infarction demonstrated poor postural control and deficit in error correction ability irrespective of the ctDCS Phase.

Feasibility of combining functional near-infrared spectroscopy with electroencephalography to identify chronic stroke responders to cerebellar transcranial direct current stimulation-a computational modeling and portable neuroimaging methodological study.

Feasibility of portable neuroimaging of cerebellar transcranial direct current stimulation (ctDCS) effects on the cerebral cortex has not been investigated vis-à-vis cerebellar lobular electric field strength. We studied functional near-infrared spectroscopy (fNIRS) in conjunction with electroencephalography (EEG) to measure changes in the brain activation at the prefrontal cortex (PFC) and the sensorimotor cortex (SMC) following ctDCS as well as virtual reality-based balance training (VBaT) before and after ctDCS treatment in 12 hemiparetic chronic stroke survivors. We performed general linear modeling (GLM) that putatively associated the lobular electric field strength with the changes in the fNIRS-EEG measures at the ipsilesional and contra-lesional PFC and SMC. Here, fNIRS-EEG measures were found in the latent space from canonical correlation analysis (CCA) between the changes in total hemoglobin (tHb) concentrations (0.01-0.07Hz and 0.07-0.13Hz bands) and log10-transformed EEG bandpower within 1-45 Hz where significant (Wilks' lambda>0.95) canonical correlations were found only for the 0.07-0.13-Hz band. Also, the first principal component (97.5% variance accounted for) of the mean lobular electric field strength was a good predictor of the latent variables of oxy-hemoglobin (O2Hb) concentrations and log10-transformed EEG bandpower. GLM also provided insights into non-responders to ctDCS who also performed poorly in the VBaT due to ideomotor apraxia. Future studies should investigate fNIRS-EEG joint-imaging in a larger cohort to identify non-responders based on GLM fitting to the fNIRS-EEG data.

Investigating the feasibility of cerebellar transcranial direct current stimulation to facilitate post-stroke overground gait performance in chronic stroke: a partial least-squares regression approach.

BACKGROUND: Investigation of lobule-specific electric field effects of cerebellar transcranial direct current stimulation (ctDCS) on overground gait performance has not been performed, so this study aimed to investigate the feasibility of two lobule-specific bilateral ctDCS montages to facilitate overground walking in chronic stroke. METHODS: Ten chronic post-stroke male subjects participated in this repeated-measure single-blind crossover study, where we evaluated the single-session effects of two bilateral ctDCS montages that applied 2 mA via 3.14 cm2 disc electrodes for 15 min targeting (a) dentate nuclei (also, anterior and posterior lobes), and (b) lower-limb representations (lobules VIIb-IX). A two-sided Wilcoxon rank-sum test was performed at a 5% significance level on the percent normalized change measures in the overground gait performance. Partial least squares regression (PLSR) analysis was performed on the quantitative gait parameters as response variables to the mean lobular electric field strength as the predictors. Clinical assessments were performed with the Ten-Meter walk test (TMWT), Timed Up & Go (TUG), and the Berg Balance Scale based on minimal clinically important differences (MCID). RESULTS: The ctDCS montage specific effect was found significant using a two-sided Wilcoxon rank-sum test at a 5% significance level for 'Step Time Affected Leg' (p = 0.0257) and '%Stance Time Unaffected Leg' (p = 0.0376). The changes in the quantitative gait parameters were found to be correlated to the mean electric field strength in the lobules based on PLSR analysis (R2 statistic = 0.6574). Here, the mean electric field strength at the cerebellar lobules, Vermis VIIIb, Ipsi-lesional IX, Vermis IX, Ipsi-lesional X, had the most loading and were positively related to the 'Step Time Affected Leg' and '%Stance Time Unaffected Leg,' and negatively related to the '%Swing Time Unaffected Leg,' '%Single Support Time Affected Leg.' Clinical assessments found similar improvement in the TMWT (MCID: 0.10 m/s), TUG (MCID: 8 s), and BBS score (MCID: 12.5 points) for both the ctDCS montages. CONCLUSION: Our feasibility study found an association between the lobular mean electric field strength and the changes in the quantitative gait parameters following a single ctDCS session in chronic stroke. Both the ctDCS montages improved the clinical outcome measures that should be investigated with a larger sample size for clinical validation. TRIAL REGISTRATION: Being retrospectively registered.

Multiplayer Interaction Platform With Gaze Tracking for Individuals With Autism.

Deficits in interpersonal communication along with difficulty in putting oneself into the shoes of others characterizes individuals with Autism Spectrum Disorder (ASD). Additionally, they exhibit atypical looking pattern causing them to miss aspects related to understanding other's preference for a context that is crucial for effective social communication. Prior research studies show the use of multiplayer platforms can improve interaction among these individuals. However, these multiplayer platforms do not demand players to understand each other's preference, important for effective social interaction. In this work, we have developed a multiplayer interaction platform using virtual reality augmented with eye-tracking technology. Thirty-six participants comprising of individuals with ASD (n = 18; GroupASD) and typically developing (TD) individuals (n = 18; GroupTD) interacted in pairs within each participant group using our platform. Results indicate that both GroupASD and GroupTD showed improvement in performance across the tasks with the GroupTD performing better than the GroupASD. Additionally, the eye-gaze data indicated an underlying relationship between one's looking pattern and task performance that was differentiated between the GroupASD and GroupTD. The current results indicate a potential of our multiplayer interaction platform to serve as a complementary tool in the hands of the interventionist promoting social reciprocity and interaction among individuals with ASD.

Implications of Physiology-Sensitive Gait Exercise on the Lower Limb Electromyographic Activity of Hemiplegic Post-Stroke Patients: A Feasibility Study in Low Resource Settings.

Background: Stroke is one of the leading causes of disability with ~80% of post-stroke survivors suffering from gait-related deficits. Conventional gait rehabilitation settings are labor-intensive and need rigorous involvement of clinicians (who use their expertise to decide the dosage of exercise intensity based on patient's capability). This demands a technology-assisted individualized exercise platform that can offer varying dosage of exercise intensity based on one's capability. Here, we have used an individualized physiology-sensitive treadmill-assisted gait exercise platform. We wanted to investigate the implications of this platform on one's lower limb muscle strength and muscle fatigue by analyzing surface Electromyogram (sEMG)-related indices and standard gait-related clinical measures. METHODS: We designed a feasibility study involving post-stroke patients (n=9; 44.4(±15)years; post-stroke period=3.1(±3)years) and gave them multiple exposures to this exercise platform. We investigated the Gastrocnemius Lateralis and Tibialis Anterior muscle activation prior to and post multiple exposures to our exercise platform while they walked overground. The feasibility study ended with collecting feedback on the patients' perception on the implications of having gait exercise using such a platform on their ambulation capability. RESULTS: The results showed that repeated exposures to this gait exercise platform can contribute towards gait rehabilitation of post-stroke patients with rehabilitation outcomes measured in terms of group average improvement of (i)~14% in muscle strength and (ii)marginal (~6%) in functional mobility (as in our case). CONCLUSION: Such a physiology-sensitive treadmill-assisted gait exercise platform can hold promise towards contributing to post-stroke gait rehabilitation in low-resource settings with the rehabilitation outcomes being measured in terms of sEMG-based observations.

Deep Cerebellar Transcranial Direct Current Stimulation of the Dentate Nucleus to Facilitate Standing Balance in Chronic Stroke Survivors-A Pilot Study.

OBJECTIVE: Cerebrovascular accidents are the second leading cause of death and the third leading cause of disability worldwide. We hypothesized that cerebellar transcranial direct current stimulation (ctDCS) of the dentate nuclei and the lower-limb representations in the cerebellum can improve functional reach during standing balance in chronic (>6 months' post-stroke) stroke survivors. MATERIALS AND METHODS: Magnetic resonance imaging (MRI) based subject-specific electric field was computed across a convenience sample of 10 male chronic (>6 months) stroke survivors and one healthy MRI template to find an optimal bipolar bilateral ctDCS montage to target dentate nuclei and lower-limb representations (lobules VII-IX). Then, in a repeated-measure crossover study on a subset of 5 stroke survivors, we compared 15minutes of 2mA ctDCS based on the effects on successful functional reach (%) during standing balance task. Three-way ANOVA investigated the factors of interest- brain regions, montages, stroke participants, and their interactions. RESULTS: "One-size-fits-all" bipolar ctDCS montage for the clinical study was found to be PO9h-PO10h for dentate nuclei and Exx7-Exx8 for lobules VII-IX with the contralesional anode. PO9h-PO10h ctDCS performed significantly (alpha = 0.05) better in facilitating successful functional reach (%) when compared to Exx7-Exx8 ctDCS. Furthermore, a linear relationship between successful functional reach (%) and electric field strength was found where PO9h-PO10h montage resulted in a significantly (alpha = 0.05) higher electric field strength when compared to Exx7-Exx8 montage for the same 2mA current. CONCLUSION: We presented a rational neuroimaging based approach to optimize deep ctDCS of the dentate nuclei and lower limb representations in the cerebellum for post-stroke balance rehabilitation. However, this promising pilot study was limited by "one-size-fits-all" bipolar ctDCS montage as well as a small sample size.

Design of Virtual Reality-Enabled Surface Electromyogram-Triggered Grip Exercise Platform.

Adequate grip ability is important for effective execution of daily living activities. Neurological disorders like stroke that result in muscle weakness, limited strength and poor control often lead to reduced grip ability in the affected limb. Conventional rehabilitation for grip training is often monotonous and subjective. Technology-assisted Virtual Reality (VR)-based rehabilitation offers a motivating environment to the participants for rehabilitation. However, the existing systems need specialized set-up architecture, thereby limiting their accessibility. Furthermore, these systems quantify the functional grip ability based on task performance, and do not explore physiological basis of grip ability. In this work, we develop a VR-based rehabilitation platform integrated with physiology-sensitive biofeedback. The developed platform, Gripx makes use of features extracted from sEMG data collected from upper limb muscles to adaptively provide audio-visual biofeedback through a VR environment. We compare task based performance, physiological indices and clinical measures to evaluate the potential of Gripx. The results of our study with 8 healthy and 12 post-stroke participants show the potential of Gripx to contribute to grip rehabilitation over multiple exposures. This approach of integrating VR-based task design with physiology-sensitive biofeedback helps patients to better assess their physiological responses and enhance the efficacy of rehabilitation.

Virtual reality-based balance training system augmented with operant conditioning paradigm.

BACKGROUND: Stroke-related sensory and motor deficits often steal away the independent mobility and balance from stroke survivors. Often, this compels the stroke survivors to rely heavily on their non-paretic leg during weight shifting to execute activities of daily living (ADL), with reduced usage of the paretic leg. Increased reliance on non-paretic leg often leads to learned nonuse of the paretic leg. Therefore, it is necessary to measure the contribution of individual legs toward one's overall balance. In turn, techniques can be developed to condition the usage of both the legs during one's balance training, thereby encouraging the hemiplegic patients for increased use of their paretic leg. The aim of this study is to (1) develop a virtual reality (VR)-based balance training platform that can estimate the contribution of each leg during VR-based weight-shifting tasks in an individualized manner and (2) understand the implication of operant conditioning paradigm during balance training on the overall balance of hemiplegic stroke patients. RESULT: Twenty-nine hemiplegic patients participated in a single session of VR-based balance training. The participants maneuvered virtual objects in the virtual environment using two Wii Balance Boards that measured displacement in the center of pressure (CoP) due to each leg when one performed weight-shifting tasks. For operant conditioning, the weight distribution across both the legs was conditioned (during normal trial) to reward participants for increased usage of the paretic leg during the weight-shifting task. The participants were offered multiple levels of normal trials with intermediate catch trial (with equal weight distribution between both legs) in an individualized manner. The effect of operant conditioning during the normal trials was measured in the following catch trials. The participants showed significantly improved performance in the final catch trial compared to their initial catch trial task. Also, the enhancement in CoP displacement of the paretic leg was significant in the final catch trial compared to the initial catch trial. CONCLUSION: The developed system was able to encourage participants for improved usage of their paretic leg during weight-shifting tasks. Such an approach has the potential to address the issue of learned nonuse of the paretic leg in stroke patients.

Quantification of grip strength with complexity analysis of surface electromyogram for hemiplegic post-stroke patients.

BACKGROUND: Reduction in grip-strength due to spasticity is a common cause of impairment after stroke. OBJECTIVE: To find an objective measure of post-stroke spasticity affecting grip-strength through quantification of interaction between antagonist and agonist muscles using complexity analysis of surface electromyogrm (sEMG) signals during isometric grip in healthy and post-stroke participants. METHODS: The interaction between sEMG signals from antagonist and agonist muscles is quantified through Multiscale-Multivariate-Sample-Entropy (MMSE). This is used to quantify dissimilarity between hands of 12 healthy and 8 post-stroke participants during isometric grip. The clinical relevance of MMSE is explored by examining its correlation with spasticity score i.e. Modified-Ashworth-Scale (MAS). Further, potential of sEMG-based approach to quantify muscle-specific dissimilarity in sEMG activation across hands is investigated in terms of Cepstral-coefficients and power content of sEMG during grip tasks. RESULTS: Mean MMSE scores of sEMG signals were significantly different (p < 0.05) between paretic and non-paretic hands of Post-stroke participants. High negative correlation was observed between spasticity and complexity scores of paretic hand for post-stroke participants. CONCLUSIONS: A negative correlation between MAS and MMSE shows higher spasticity can lead to reduced complexity in sEMG. Thus, MMSE based complexity analysis can be used as an indicator of spasticity, affecting grip function.

Kinect-Assisted Performance-Sensitive Upper Limb Exercise Platform for Post-stroke Survivors.

One's ability to use upper limbs is critical for performing activities of daily living necessary for enjoying quality community life. However, after stroke, such abilities becomes adversely affected and it often deprives one of their capability to perform tasks that need coordinated movement in the upper limbs. To address issues with upper limb dysfunction, patients typically undergo rehabilitative exercises. Given the high patient to doctor ratio particularly in developing countries like India, conventional rehabilitation with patients undergoing exercises under one-on-one therapist's supervision often becomes a challenge. Thus, investigators are exploring technology such as computer-based platforms coupled with cameras that can alleviate the need for the continuous presence of a therapist and can offer a powerful complementary tool in the hands of the clinicians. Such marker-based imaging systems used for rehabilitation can offer real-time processing and high accuracy of data. However, these systems often require dedicated lab space and high set-up time. Often this is very expensive and suffers from portability issues. Investigators have been exploring marker-less imaging techniques e.g., Kinect integrated computer-based graphical user interfaces in stroke-rehabilitation such as tracking one's limb movement during rehabilitation. In our present study, we have developed a Kinect-assisted computer-based system that offered Human Computer Interaction (HCI) tasks of varying challenge levels. Execution of the tasks required one to use reaching and coordination skills of the upper limbs. Also, the system was Performance-sensitive i.e., adaptive to the individualized residual movement ability of one's upper limb quantified in terms of task performance score. We tested for the usability of our system by exposing 15 healthy participants to our system. Subsequently, seven post-stroke patients interacted with our system over a few sessions spread over 2 weeks. Also, we studied patient's mean tonic activity corresponding to the HCI tasks as a possible indicator of one's post-stroke functional recovery suggesting its potential of our system to serve as a rehabilitation platform. Our results indicate the potential of such systems toward the improvement of task performance capability of post-stroke patients with possibilities of upper limb movement rehabilitation.

Evaluating Age-Related Variations of Gaze Behavior for a Novel Digitized-Digit Symbol Substitution Test.

Analysis of cognitive functioning from gaze behavior might serve as an early indicator of age related decline of cognitive functions. Standard psychological tests like the digit-symbol substitution test or the symbol-digit modalities test is used exclusively in this regard. In this paper, we have designed and developed a digitized version of the digit symbol substitution test. Three different versions have been designed in order to derive deeper insights of the user behavior. The test-retest validation of the versions reveals good correlation across sessions. Further, the difference in gaze behavior which might be used as an indicator of cognitive functions is tested for two different age groups (13 participants <30 years and 11 participants >40 years). It is seen that the designed digitized version along with the usage of physiological markers like eye tracking bestows additional information and is sensitive to age related factors which might be used for the assessment as well as for the training purpose in rehabilitation systems. Results show that the performance can be analyzed using gaze and pupillometric features in addition to the conventional test performance metrics. We derived an index to measure the performance related to visuo-spatial functioning on one of the designed versions of the test. Results of this index on the number of fixations for two age groups are found to be separated in a statistically significant (p<0.05) manner. The age related difference (p<0.05) is also evident in the pupillometric responses obtained.

Eye movements - an early marker of cognitive dysfunctions.

Cognitive impairments or dysfunctions are one of the major issues of aging population and medical conditions like brain damage, stroke etc. Assessment of cognitive functioning is usually done by medical practitioners using various standard psychological tests which require expert interventions. In the present study we have tried to use eye tracking as a possible option for assessment of cognitive functions while executing a digitized digit symbol substitution task. The standard task has been modified so that more detail insights of one's cognitive state can be obtained without any manual intervention. Results show that it is possible to get more information like attention, perception etc. It also gives insight about the performance of an individual and can be used for analyzing the executive functions like processing speed, memory etc.

Design of Instrumented Shoes for Gait Characterization: A Usability Study With Healthy and Post-stroke Hemiplegic Individuals.

Ambulation is a fundamental requirement of human beings for enjoying healthy community life. A neurological disorder such as stroke can significantly affect one's gait thereby restricting one's active community participation. To quantify one's gait, spatiotemporal gait parameters are widely used in clinical context with different tests such as 10 meter walk test, 6 min walk test, etc. Though these conventional observation-based methods are powerful, yet they often suffer from subjectivity, a scarcity of adequately trained therapists and frequent clinical visits for assessment. Researchers have been exploring the technology-assisted solutions for gait characterization. There are laboratory-based stereophotogrammetric methods and walk mats that are powerful tools as far as gait characterization is concerned. However, these suffer from issues with portability, accessibility due to high cost, labor-intensiveness, etc. Faced with these issues, our present research tries to investigate and quantify the gait abnormalities in individuals with neurological disorder by using a portable and cost-effective instrumented shoes (ShoesFSRhenceforth). The in-house developed ShoesFSR comprised of a pair of shoes instrumented with Force Sensing Resistors (FSR) and a wireless data acquisition unit. The real-time FSR data was acquired wirelessly and analyzed by a central console to offer quantitative indices of one's gait. Studies were conducted with 15 healthy participants and 9 post-stroke survivors. The spatiotemporal gait parameters of healthy participants measured using ShoesFSR were validated with standard methods such as stereophotogrammetric system and paper-based setup. Statistical analysis showed good agreement between the gait parameters measured using ShoesFSR and the standard methods. Specifically, the mean absolute error of the spatial parameters measured by the ShoesFSR , in the worst case, was 1.24% and that for the temporal parameters was 1.12% with that measured by standard methods for healthy gait. This research shows the potential of the ShoesFSR to quantify gait abnormality of post-stroke hemiplegic patients. In turn, the results show a promise for the future clinical use of the ShoesFSR .