Pupillary Response to Postural Demand in Parkinson’s Disease

Behavioural Brain Research

The relationship between cognitive workload and cognitive impairments in Parkinson's disease (PD) is currently not well known. This study compared cognitive workload during saccadic tasks between patients with PD and controls. Sixteen controls, 11 patients with no obvious cognitive impairment (PD-NCI) (MOCA score ≥ 26), and 10 PD patients with cognitive impairment (PD-CI) (MOCA score < 26) performed prosaccade and antisaccade tasks. Cognitive workload, extracted via pupil recording, and other eye metrics were compared between the three groups. PD-NCI patients exhibited greater cognitive workload than controls in the prosaccade task. PD-CI patients also showed more cognitive workload in the prosaccade task than PD-NCI patients and controls. No other differences in eye metrics were found between the three groups. Cognitive workload could be used to differentiate between different cognitive states in PD. The causal relationship between increased cognitive workload and cognitive decline in PD-NCI should be the focus of future studies.

Frontiers in aging neuroscience, 2018

Previous studies have shown that pupillary response, a physiological measure of cognitive workload, reflects cognitive demand in healthy younger and older adults. However, the relationship between cognitive workload and cognitive demand in Parkinson&#39;s disease (PD) remains unclear. The aim of this pilot study was to examine the pupillary response to cognitive demand in a letter-number sequencing (LNS) task between 16 non-demented individuals with PD (age, median (Q1-Q3): 68 (62-72); 10 males) and 10 control participants (age: 63 (59-67); 2 males), matched for age, education, and Montreal Cognitive Assessment (MOCA) scores. A mixed model analysis was employed to investigate cognitive workload changes as a result of incremental cognitive demand for both groups. As expected, no differences were found in cognitive scores on the LNS between groups. Cognitive workload, exemplified by greater pupil dilation, increased with incremental cognitive demand in both groups ( = 0.003). No signi...

Frontiers in Neurology

Early features of Parkinson's disease (PD) include both motor and cognitive changes, suggesting shared common pathways. A common motor dysfunction is postural instability, a known predictor of falls, which have a major impact on quality of life. Understanding mechanisms of postural dynamics in PD and specifically how they relate to cognitive changes is essential for developing effective interventions. The aims of this study were to examine the changes that occur in postural metrics over time and explore the relationship between postural and cognitive dysfunction. The study group consisted of 35 people (66 ± 8years, 12 female, UPDRS III: 22.5 ± 9.6) diagnosed with PD who were recruited as part of the Incidence of Cognitive Impairment in Cohorts with Longitudinal Evaluation-PD Gait (ICICLE-GAIT) study. Postural and cognitive assessments were performed at 18, 36, and 54 months after enrolment. Participants stood still for 120 s, eyes open and arms by their side. Postural dynamics were measured using metrics derived from a single tri-axial accelerometer (Axivity AX3, York, UK) on the lower back. Accelerometry metrics included jerk (derivative of acceleration), root mean square, frequency, and ellipsis (acceleration area). Cognition was evaluated by neuropsychological tests including the Montreal Cognitive Assessment (MoCA) and digit span. There was a significant decrease in accelerometry parameters, greater in the anteroposterior direction, and a decline in cognitive function over time. Accelerometry metrics were positively correlated with lower cognitive function and increased geriatric depression score and negatively associated with a qualitative measure of balance confidence. In conclusion, people with PD showed reduced postural dynamics that may represent a postural safety strategy. Associations with cognitive function and depression, both symptoms that may pre-empt motor symptoms, suggest shared neural pathways. Further studies, involving neuroimaging, may determine how these postural parameters relate to underlying neural and clinical correlates.

Motricidade, 2015

Postural sway variability was evaluated in Parkinson's disease (PD) patients at different stages of disease. Twenty PD patients were grouped into two groups (unilateral, 14; bilateral, 6) according to disease severity. The results showed no significant differences in postural sway variability between the groups (p ≥ 0.05). Postural sway variability was higher in the antero-posterior direction and with the eyes closed. Significant differences between the unilateral and bilateral groups were observed in clinical tests (UP-DRS, Berg Balance Scale, and retropulsion test; p ≤ 0.05, all). Postural sway variability was unaffected by disease severity, indicating that neurological mechanisms for postural control still function at advanced stages of disease. Postural sway instability appears to occur in the antero-posterior direction to compensate for the stooped posture. The eyes-closed condition during upright stance appears to be challenging for PD patients because of the associated sensory integration deficit. Finally, objective measures such as postural sway variability may be more reliable than clinical tests to evaluate changes in balance control in PD patients.

Turkish Journal Of Neurology, 2020

Objective: The purpose of this study was to identify the predictors of future falls in mild-to-moderate stage Parkinson's disease (PD) without cognitive impairment. We evaluated motor findings, non-motor findings, and different cognitive dual tasks such as memory, attention, and executive functions added to the 10-meter walk test (10MWT), which has been used to measure walking speed in PD. Materials and Methods: A total of 62 subjects were evaluated in terms of eligibility for the study. Thirty-six patients with PD who met the inclusion criteria were included in the study. Demographic characteristics were identified and clinical findings were examined. Motor and non-motor findings were evaluated using the Turkish version of the Movement Disorder Society-Unified PD Rating scale (MDS-UPDRS). Walking speed was measured with the 10MWT as single task and with different cognitive domains added to the 10MWT as cognitive dual task activities. After the initial evaluation, falls within six months were recorded. Results: The previous history of falls, high scores of MDS-UPDRS 1.A, MDS-UPDRS 1.B, and MDS-UPDRS 2, walking speed under a single task (10MWT) and different cognitive (memory, digit span-forwards, digit span-backwards, and serial 7s) dual tasks were significantly different in terms of the future falls within six months (p<0.05). According to the results of multiple logistic regression analysis using these variables, it was observed that the increase in 10MWT speed decreased the risk of future falls by 0.76 times, and an increase in MDS-UPDS 1.B score increased the risk of future falls by 2.06 times. Conclusion: In our study, in which the known risk factors associated with falls in PD were examined together, the risk of falls in patients with mild-to-moderate stage PD without cognitive impairment was found to be predicted by gait speed and the MDS-UPDRS 1.B score, which evaluated non-motor findings such as sleep disorder, sensory problems, and autonomic dysfunction.

Gait & Posture, 2015

This study aimed to examine the differences in standing balance between individuals with Parkinson's disease (PD) and subjects without PD (control group), under single and dual-task conditions. A cross-sectional study was designed using a non-probabilistic sample of 110 individuals (50 participants with PD and 60 controls) aged 50 years old and over. The individuals with PD were in the early or middle stages of the disease (characterized by Hoehn and Yahr as stages 1-3). The standing balance was assessed by measuring the centre of pressure (CoP) displacement in single-task

Physiotherapy, 2016

Objectives Postural instability is one of the most disabling features in Parkinson's disease (PD), and often leads to falls that reduce mobility and functional capacity. The objectives of this study were to analyse the limit of stability (LOS) and influence of the manipulation of visual, somatosensorial and visual-vestibular information on postural control in patients with PD and healthy subjects. Design Cross-sectional. Setting Movement Disorders Unit, university setting. Participants Eighty-two subjects aged between 37 and 83 years: 41 with Parkinson's disease in the 'on' state and 41 healthy subjects with no neurological disorders. Both groups were matched in terms of sex and age. Main outcome measures Unified Parkinson's Disease Rating Scale (UPDRS)-motor score, modified Hoehn and Yahr staging, Dynamic Gait Index (DGI) and posturography with integrated virtual reality. The parameters analysed by posturography were LOS area, area of body centre of pressure excursion and balance functional reserve in the standing position in 10 conditions (open and closed eyes, unstable surface with eyes closed, saccadic and optokinetic stimuli, and visual-vestibular interaction). Results The mean UPDRS motor score and DGI score were 27 [standard deviation (SD) 14] and 21 (SD 3), respectively. Thirteen participants scored between 0 and 19 points, indicating major risk of falls. Posturographic assessment showed that patients with PD had significantly lower LOS area and balance functional reserve values, and greater body sway area in all posturographic conditions compared with healthy subjects.

Experimental Brain Research, 2007

Postural instability is one of the most disabling features of idiopathic Parkinson's disease (PD). In this study, we focused on postural instability as the main factor predisposing parkinsonians to falls. For this purpose, changes in sway characteristics during quiet stance due to visual feedback exclusion were studied. We searched for postural sway measures that could be potential discriminators for an increased fall risk. A group of 110 subjects: 55 parkinsonians (Hoehn and Yahr: 1-3), and 55 age-matched healthy volunteers participated in the experiment. Their spontaneous sway characteristics while standing quiet with eyes open and eyes closed were analyzed. We found that an increased mediolateral sway and sway area while standing with eyes closed are characteristic of parkinsonian postural instability and may serve to quantify well a tendency to fall. These sway indices signiWcantly correlated with disease severity rated both by the Hoehn and Yahr scale as well as by the Motor Section of the UPDRS. A forward shift of a mean COP position in parkinsonians which reXects their Xexed posture was also signiWcantly greater to compare with the elderly subjects and exhibited a high sensitivity to visual conditions. Both groups of postural sway abnormalities identiWed here may be used as accessible and reliable measures which allow for quantitative assessment of postural instability in Parkinson's disease.

Frontiers in Human Neuroscience

Introduction: Balance tasks require cognitive resources to ensure postural stability. Pupillometry has been used to quantify cognitive workload of various cognitive tasks, but has not been studied in postural control. The current investigation utilized pupillometry to quantify the cognitive workload of postural control in healthy young adults. We hypothesized that cognitive workload, indexed by pupil size, will increase with challenging postural control conditions including visual occlusion and cognitive dual tasking. Methods: Twenty-one young healthy adults (mean ± standard error of the mean), (age = 23.2 ± 0.49 years; 12 females) were recruited for this study. Participants completed four tasks: (1) standing with eyes open; (2) standing with eyes occluded (3) standing with eyes open while performing an auditory Stroop task; and (4) standing with eyes occluded while performing an auditory Stroop task. Participants wore eye tracking glasses while standing on a force platform. The eye tracking glasses recorded changes in pupil size that in turn were converted into the Index of Cognitive Activity (ICA). ICA values were averaged for each eye and condition. A two-way Analysis of Variance with post-hoc Sidak correction for pairwise comparisons was run to examine the effect of visual occlusion and dual tasking on ICA values as well on Center of Pressure (CoP) sway velocity in anterior-posterior (AP) and medio-lateral (ML) directions. A Pearson's correlation coefficient was utilized to determine the relationship between ICA values and CoP sway velocity. Results: Significant within-condition effect was observed with visual occlusion for the right eye ICA values (p = 0.008). Right eye ICA increased from eyes open to eyes occluded conditions (p = 0.008). In addition, a significant inverse correlation was observed between right eye ICA values and CoP sway velocity in the ML direction across all the conditions (r = −0.25, p = 0.02). Conclusion: This study demonstrated support for increased cognitive workload, measured by pupillometry, as a result of changes in postural control in healthy young adults. Further research is warranted to investigate the clinical application of pupillometry in balance assessment.

International Journal of Current Pharmaceutical Research

Objective: Parkinson&#39;s disease (PD) is a neurodegenerative disorder characterized by motor symptoms and various non-physical symptoms. Balance impairments are common in individuals with PD and can increase the risk of falls. Gaze stability, the ability to maintain a stable gaze while the head is moving, is an important aspect of postural control and can contribute to balance impairments in PD. Methods: The study conducted a randomized controlled trial (RCT) with individuals diagnosed with PD. Two groups were formed: one receiving balance training with gaze stability exercises and the other receiving balance training without gaze stability exercises. Measurements were taken before and after the two-month intervention period. Results: The gender distribution showed that there were 12 men and 18 women in Group A, and 17 men and 13 women in Group B. Within both groups, there were significant improvements in self-care, range of motion, postural instability, and falling values after t...