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Abstract Parkinson’s disease targets patients’ cognitive and motor abilities, including postural control. Many studies have been carried out to introduce mathematical models for a better understanding of postural control in such patients and the relation between the model parameters and the clinical assessments. So far, these studies have addressed this connection merely in static tests, such as quiet stance. The aim of this study is to develop a model for voluntary lean, and as such, identify the model parameters for both PD patients and healthy subjects from experimental data. The proposed model comprises planning and control sections. The model parameters for the planning section were extracted from the time response characteristics. Parameters for the control section were identified based on the spatial characteristics of the center-of-pressure (COP) response using an optimization process. 24 PD patients along with 24 matched healthy subjects participated in the study. The results showed a significant difference between the two groups in terms of temporal parameters for the planning section. This difference emphasizes bradykinesia as an essential symptom of PD. Also, differences were found for the postural control section. In all directions, the proportional gain of the feedback controller was significantly larger in PD patients; however, the gain of the feedforward controller was significantly smaller in PD patients. Furthermore, the control gains were strongly correlated with the clinical scales (Functional Reach Test and Unified Parkinson's Disease Rating Scale) in certain directions. In conclusion, the new model helps to better understand and quantify some PD symptoms in voluntary lean tasks.

Introduction: Postural instability is a restrictive feature in Parkinson’s disease (PD), usually assessed by clinical or laboratory tests. However, the exact quantification of postural stability, using stability theorems that take into account human dynamics, is still lacking. We investigated the feasibility of control theory and the Nyquist stability criterion—gain margin (GM) and phase margin (PM)—in discriminating postural instability in PD, as well as the effects of a balance-training program.Methods: Center-of-pressure (COP) data of 40 PD patients before and after a 4-week balance-training program, and 20 healthy control subjects (HCs) (Study1) as well as COP data of 20 other PD patients at four time points during a 6-week balance-training program (Study2), collected in two earlier studies, were used. COP was recorded in four tasks, two on a rigid surface and two on foam, both with eyes open and eyes closed. A postural control model (an inverted pendulum with a Proportional-integral-derivative (PID) controller and time delay) was fitted to the COP data to subject-specifically identify the model parameters thereby calculating |GM| and PM for each subject in each task.Results: PD patients had a smaller margin of stability (|GM| and PM) compared with HCs. Particularly, patients, unlike HCs, showed a drastic drop in PM on foam. Clinical outcomes and margins of stability improved in patients after balance training. |GM| improved early in week 4, followed by a plateau during the rest of the training. In contrast, PM improved late (week 6) in a relatively continuous-progression form.Conclusion: Using fundamental stability theorems is a promising technique for the standardized quantification of postural stability in various tasks.

Background: Pediatric neurorehabilitation has recently employed virtual reality (VR) technologies as a platform to design and implement novel modalities. Aims: To evaluate the feasibility of a multi-component VR-based program on motor skills and functional postural control for children with hemiplegic cerebral palsy (HCP). Methods: A single-case-experimental design was conducted on eight children with HCP (12.33 ± 4.71 years and GMFCS= II, I). The VR-based program consisted of 3 sessions per week for four weeks. Timed Up and Go (TUG) test, Functional Reach Test (FRT), Pediatric Balance Scale (PBS), Activities Scale for Kids (ASK), ABILHAND-Kids, and Box and Block Test (BBT) were used to evaluate functional changes. Outcomes and results: Statistical analysis showed that improvements in functional postural control were significant on at least one balance measure for seven out of eight participants during the intervention phase. For all participants, a significant increase was observed in the BBT scores. Before-after intervention analysis revealed statistically significant improvements in PBS (z = −2.52, p ≤ 0.01), ABILHAND-Kids (z = −2.25, p ≤ 0.01), and ASK (z = −2.38, p ≤ 0.01). Conclusions and implications: This study provided early evidence of the effectiveness of the multi-component VR-based program in children with HCP. However, future studies with randomized controlled trial design are needed to evaluate the long-term effects and compare them with conventional rehabilitation practice.

Objectives: This study aimed to investigate the effect of upper extremity coordination exercises based on fatigue prediction on fine and gross manual dexterity, upper limb motor function, shoulder and elbow proprioception, occupational performance, and activities of daily living in chronic stroke survivors. Methods: In this pilot double-blind randomized clinical trial, 24 chronic strokes were enrolled using the non-probability sampling method. Participants were randomly allocated to the control (received routine occupational therapy) and intervention (received upper extremity coordination exercises based on fatigue prediction using the Kinect) groups. Before and after the interventions (six weeks, three sessions/week, 45 min/session), as well as six weeks after completion of interventions, participants were assessed using the following tools: Box-Block Test, Purdue-Pegboard Test, Wolf-Motor Function Test, Action Research Arm Test, Manual Ability Measure-16, Grip Dynamometer, Shoulder Position Sense Test (SPST), Elbow Position Sense Test (EPST), Canadian Occupational Performance Measure, Shah-Barthel Index (SH-BI), and Multi-dimensional Fatigue Inventory. This project was carried out in the rehabilitation department of Shafa-Yahyaeian Hospital from May 2019 to June 2020. Results: The results showed a significant improvement in all assessments of both control and intervention groups (P≤0.05), except for SH-BI. Further, the improvement of EPST and SPST scores in the intervention group was significantly greater than the control group (P≤0.05). Also, a significant decrease in fatigue severity was observed in both control and intervention groups (P≤0.05). Conclusion: These results suggest that upper extremity coordination exercises based on fatigue prediction in combination with routine occupational therapy could lead to improvement of upper extremity sensory-motor functions and power grip and caused a decrease in fatigue severity in chronic stroke.

Abstract Background It is important to improve verbal Working Memory (WM) in reading disability, as it is a key factor in learning. There are commercial verbal WM training programs, which have some short-term effects only on the verbal WM capacity, not reading. However, because of some weaknesses in current verbal WM training programs, researchers suggested designing and developing newly structured programs that particularly target educational functions such as reading skills. In the current double-blind randomized clinical trial study, we designed a new Verbal Working Memory-Balance (VWM-B) program which was carried out using a portable robotic device. The short-term effects of the VWM-B program, on verbal WM capacity, reading skills, and postural control were investigated in Iranian children with developmental dyslexia. Results The effectiveness of the VWM-B program was compared with the VWM-program as a traditional verbal WM training. In comparison with VWM-program, the participants who received training by the VWM-B program showed superior performance on verbal WM capacity, reading skills, and postural control after a short-term intervention. Conclusions We proposed that the automatized postural control resulting from VWM-B training had a positive impact on improving verbal WM capacity and reading ability. Based on the critical role of the cerebellum in automatizing skills, our findings support the cerebellar deficit theory in dyslexia. Trial registration: This trial was (retrospectively) registered on 8 February 2018 with the Iranian Registry of Clinical Trials (IRCT20171219037953N1).

Background and Objectives: To investigate the correlation between reach and grasp kinematic measures and clinical measures of gross and fine manual dexterity in patients with idiopathic Parkinson Disease (PD). Methods: Sixty patients (44 men, 16 women) with idiopathic PD (Mean±SD of age: 59.85±11.89 years) were recruited in this non-experimental cross-sectional study using a non-probability sampling method. Their gross and fine manual dexterity were assessed using the Box and Block Test (BBT) and Nine Hole Peg Test (NHPT), respectively. Also, reach and grasp kinematic measures (including normalized movement time, peak velocity, Maximum Grip Aperture [MGA], and percentage of movement time in which MGA occurred [PMGA]) were measured in the more affected hand. Results: The results showed a significant and moderate correlation between reach kinematic measures (i.e. normalized movement time and peak velocity) and both gross and fine manual dexterity assessed by BBT (P=0.000) and NHPT (P=0.000), respectively. However, there was not a significant correlation between grasp kinematic measures (i.e. MGA and PMGA) and gross manual dexterity measured by BBT (P>0.05) as well as fine manual dexterity assessed by NHPT (P>0.05). Conclusion: This study showed no to moderate correlation between reach and grasp kinematic measures and clinical measures of gross and fine manual dexterity in patients with PD, supporting the significance of multi-level evaluation using both clinical and kinematic measures in the evaluation of upper limb function in patients with PD.

Abstract Background Fear of falling (FoF) is defined as a lasting concern about falling that causes a person to limit or even stop the daily activities that he/she is capable of. Seventy percent of Parkinson’s disease (PD) patients report activity limitations due to FoF. Timely identification of FoF is critical to prevent its additional adverse effects on the quality of life. Self-report questionnaires are commonly used to evaluate the FoF, which may be prone to human error. Objectives In this study, we attempted to identify a new postural stability-indicator to objectively predict the intensity of FoF and its related behavior(s) in PD patients. Methods Thirty-eight PD patients participated in the study (mean age, 61.2 years), among whom 10 (26.32%) were identified with low FoF and the rest (73.68%) with high FoF, based on Falls Efficacy Scale-International (FES-I). We used a limit of stability task calibrated to each individual and investigated the postural strategies to predict the intensity of FoF. New parameters (FTR i s; functional time ratio) were extracted based on the center of pressure presence pattern in different rectangular areas (i = 1, 2, and 3). The task was performed on two heights to investigate FoF-related behavior(s). Results FTR 1/2 (the ratio between FTR 1 and FTR 2 ) was strongly correlated with the FES-I (r = − 0.63, p

Abstract Background Balance training improves postural control in Parkinson’s disease (PD). However, a systematic approach for the development of individualized, optimal training programs is still lacking, as the learning dynamics of the postural control in PD, over a training program, are poorly understood. Objectives We investigated the learning dynamics of the postural control in PD, during a balance-training program, in terms of the clinical, posturographic, and novel model-based measures. Methods Twenty patients with PD participated in a balance-training program, 3 days a week, for 6 weeks. Clinical tests assessed functional balance and mobility pre-training, mid-training, and post-training. Center-of-pressure (COP) was recorded at four time-points during the training (pre-, week 2, week 4, and post-training). COP was used to calculate the sway measures and to identify the parameters of a patient-specific postural control model, at each time-point. The posturographic and model-based measures constituted the two sets of stability- and flexibility-related measures. Results Mobility- and flexibility-related measures showed a continuous improvement during the balance-training program. In particular, mobility improved at mid-training and continued to improve to the end of the training, whereas flexibility-related measures reached significance only at the end. The progression in the balance- and stability-related measures was characterized by early improvements over the first 3 to 4 weeks of training, and reached a plateau for the rest of the training. Conclusions The progression in balance and postural stability is achieved earlier and susceptible to plateau out, while mobility and flexibility continue to improve during the balance training.

Abstract Background Impaired postural control in Parkinson’s disease (PD) seriously compromises life quality. Although balance training improves mobility and postural stability, lack of quantitative studies on the neurophysiological mechanisms of balance training in PD impedes the development of patient-specific therapies. We evaluated the effects of a balance-training program using functional balance and mobility tests, posturography, and a postural control model. Methods Center-of-pressure (COP) data of 40 PD patients before and after a 12-session balance-training program, and 20 healthy control subjects were recorded in four conditions with two tasks on a rigid surface (R-tasks) and two on foam. A postural control model was fitted to describe the posturography data. The model comprises a neuromuscular controller, a time delay, and a gain scaling the internal disturbance torque. Results Patients’ axial rigidity before training resulted in slower COP velocity in R-tasks; which was reflected as lower internal torque gain. Furthermore, patients exhibited poor stability on foam, remarked by abnormal higher sway amplitude. Lower control parameters as well as higher time delay were responsible for patients’ abnormal high sway amplitude. Balance training improved all clinical scores on functional balance and mobility. Consistently, improved ‘flexibility’ appeared as enhanced sway velocity (increased internal torque gain). Balance training also helped patients to develop the ‘stability degree’ (increase control parameters), and to respond more quickly in unstable condition of stance on foam. Conclusions Projection of the common posturography measures on a postural control model provided a quantitative framework for unraveling the neurophysiological factors and different recovery mechanisms in impaired postural control in PD.

Background: Freezing of gait (FOG) is a disabling clinical phenomenon in patients with Parkinsonchr('39')s disease (PD), which is characterised by short episodes of inability to step and affect about 38.2 % of these patients. Abrupt FOG may disturb the balance and, thus, it is considered as a common cause of falls in PD. This study was designed to evaluate the fall diagnostic accuracy of the Timed Up and Go Test (TUG), a reliable and valid clinical test to assess mobility and risk of falls, in patients with PD who had FOG. Methods: In this cross-sectional study, 80 subjects with a diagnosis of idiopathic PD who had FOG by mean ± SD age of 63.63±9.76 years and mean ± SD disease duration of 7.82±5.76 years were enrolled by simple non-probability sampling method. They were divided into two faller and non-faller groups based on the history of fall during the past six months. Sensitivity, specificity, negative and positive likelihood ratios, and receiver operator characteristic curve was calculated for TUG. Results: The TUG score indicated significant differences between faller PD patients who had FOG and non-faller PD patients who had FOG (p=0.003). The best cut-off point for discriminating faller and non-faller PD patients who had FOG was 11.85 seconds (sensitivity= 68.97% and specificity= 86%). Conclusion: TUG demonstrated moderate sensitivity and specificity to fall status in patients with PD who had FOG, suggesting its use in conjunction with other tests for screening those who may need intervention for decreasing falls.

Although anxiety is a common non-motor outcome of Parkinson's disease (PD) affecting 40% of patients, little attention has been paid so far to its effects on balance impairment and postural control. Improvement of postural control through focusing on the environment (i.e. external focus) has been reported, but the role of anxiety, as a confounding variable, remains unclear.This study aimed to investigate the influence of anxiety and attentional focus instruction on the standing postural control of PD patients.Thirty-four patients with PD (17 with high anxiety (HA-PD) and 17 with low anxiety (LA-PD)), as well as 17 gender- and age-matched healthy control subjects (HC) participated in the study. Postural control was evaluated using a combination of two levels of postural difficulty (standing on a rigid force plate surface with open eyes (RO) and standing on a foam surface with open eyes (FO)), as well as three attentional focus instructions (internal, external and no focus).Only the HA-PD group demonstrated significant postural control impairment as compared to the control, as indicated by significantly greater postural sway measures. Moreover, external focus significantly reduced postural sway in all participants especially during the FO condition.The results of the current study provide evidence that anxiety influences balance control and postural stability in patients with PD, particularly those with high levels of anxiety. The results also confirmed that external focus is a potential strategy that significantly improves the postural control of these patients. Further investigation of clinical applicability is warranted towards developing effective therapeutic and rehabilitative treatment plans.

Purpose: Force control of robotic instruments is a difficult task due to the uncertainties causedby changes in the instrument’s geometrical and mechanical characteristics during surgery as well as the nonlinear dynamics of the instrument. A new approach based on an intelligent controller is developed to control the force interactions of a robotic surgical instrument with delicate soft tissues. This feature assists the surgeon by providing a safe grasp of soft tissues during dissection or suturing. Besides, by controlling and optimizing the magnitude of the instrument/tissue contact forces, controlled grasp will significantly reduce the surgery trauma. Method: The controller is devised using a neuro-fuzzy regulator that receives the tracking error and its derivative as inputs, and a PD critic that evaluates the actual pinch force and produces an emotional signal. The controller tunes its parameters by means of minimizing the critic’s output signal, i.e., stress, so that the force tracking error is reduced. Numerical simulations and experimental tests were performed to evaluate the controller. Results: Simulation tests revealed that the controller can effectively adapt its rules when the instrument’s geometry and frictional behavior changes. The experiments revealed a settling time of 0.7 s with 3.1% overshoot. In comparison with a PID, the proposed controller reduced the mean squared error (MSE) by 94% for a target constant force, and 24% for a target sinusoidal trajectory. Conclusion: the proposed controller showed a superior performance in force control of tissue in safe grasp in comparison with a PID particularly for constant target forces.