Proprioception and motor control in Parkinson's disease

Optimality of multisensory integration while compensating for uncertain visual target information with artificial vibrotactile cues during reach planning

BACKGROUND

Planning and executing movements requires the integration of different sensory modalities, such as vision and proprioception. However, neurological diseases like stroke can lead to full or partial loss of proprioception, resulting in impaired movements. Recent advances focused on providing additional sensory feedback to patients to compensate for the sensory loss, proving vibrotactile stimulation to be a viable option as it is inexpensive and easy to implement. Here, we test how such vibrotactile information can be integrated with visual signals to estimate the spatial location of a reach target.

METHODS

We used a center-out reach paradigm with 31 healthy human participants to investigate how artificial vibrotactile stimulation can be integrated with visual-spatial cues indicating target location. Specifically, we provided multisite vibrotactile stimulation to the moving dominant arm using eccentric rotating mass (ERM) motors. As the integration of inputs across multiple sensory modalities becomes especially relevant when one of them is uncertain, we additionally modulated the reliability of visual cues. We then compared the weighing of vibrotactile and visual inputs as a function of visual uncertainty to predictions from the maximum likelihood estimation (MLE) framework to decide if participants achieve quasi-optimal integration.

RESULTS

Our results show that participants could estimate target locations based on vibrotactile instructions. After short training, combined visual and vibrotactile cues led to higher hit rates and reduced reach errors when visual cues were uncertain. Additionally, we observed lower reaction times in trials with low visual uncertainty when vibrotactile stimulation was present. Using MLE predictions, we found that integration of vibrotactile and visual cues followed optimal integration when vibrotactile cues required the detection of one or two active motors. However, if estimating the location of a target required discriminating the intensities of two cues, integration violated MLE predictions.

CONCLUSION

We conclude that participants can quickly learn to integrate visual and artificial vibrotactile information. Therefore, using additional vibrotactile stimulation may serve as a promising way to improve rehabilitation or the control of prosthetic devices by patients suffering loss of proprioception.

Effect of Proprioceptive Training Compared With Other Interventions for Upper Limb Deficits in People With Parkinson Disease: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

This systematic review and meta-analysis aimed to determine the efficacy of proprioceptive training on hand dexterity, upper limb function, and quality of life (QoL) in people with Parkinson disease (PD) compared with no or other active interventions.

DATA SOURCES

Medline PubMed, Cochrane Library, CINAHL, PEDro, and Web of Science databases were searched to identify published studies until February 2023.

STUDY SELECTION

Peer-reviewed English publications of randomized controlled trials (RCTs) of proprioceptive training conducted among people with PD.

DATA EXTRACTION

Study characteristics, exercise program type and dosage, outcome of interest, and between-group comparisons of post-test results of intervention and comparison groups.

DATA SYNTHESIS

Eight RCTs were included, involving 344 people with PD. Six RCTs contributed to meta-analyses. There was very low certainty of evidence that proprioceptive training may improve dominant hand (standard mean difference [SMD] 0.34, 95% CI 0.08-0.60, P=.01) and non-dominant hand (SMD 0.36, 95% CI 0.10-0.63, P<.01) fine motor dexterity, and dominant hand gross manual dexterity (SMD 1.73, 95% CI 0.30-3.16, P=.02), following 2-8 weeks of proprioceptive training. There was no evidence of effects on non-dominant hand gross manual dexterity, upper limb function, and QoL after proprioceptive training.

CONCLUSIONS

Findings regarding the effect of proprioceptive training on hand dexterity in the short-term are inconclusive. The small sample size likely limited effect detection. Future large RCTs should compare proprioceptive training with no intervention and perform comprehensive biomechanical analysis to gain a clearer idea of its effects. Incorporating longer-duration proprioceptive training programs is also recommended to investigate long-lasting effects.

Influence of compression garments on proprioception: A systematic review and meta-analysis

Compression garments (CGs) are commonly used in rehabilitation and sports contexts to enhance performance and speed up recovery. Despite the growing use of CGs in recent decades, there is no unanimous consensus on their overall influence on joint proprioception. In this current meta-analysis, we aim to fill this knowledge gap by assessing the impact of CGs on joint proprioception. We conducted a literature search across seven databases and one registry. Ultimately, we included 27 studies with 671 participants. The meta-analysis revealed that wearing CGs resulted in a significant reduction in absolute error during joint position sensing (Hedges' g: -0.64, p = 0.006) as compared to no CGs. However, further analyses of variables such as constant error (p = 0.308), variable error (p = 0.541) during joint position sense tests, threshold to detect passive motion (p = 0.757), and active movement extent discrimination (p = 0.842) did not show a significant impact of CGs. The review also identified gaps in the reporting of certain outcomes, such as parameters of CGs, reporting of performance, individual-reported outcomes, and lack of placebo comparators. Consequently, this review provides guidelines for future studies that may facilitate evidence-based synthesis and ultimately contribute to a better understanding of the overall influence of CGs on joint proprioception.

Lipid and Transcriptional Regulation in a Parkinson's Disease Mouse Model by Intranasal Vesicular and Hexosomal Plasmalogen-Based Nanomedicines

Plasmalogens (vinyl-ether phospholipids) are an emergent class of lipid drugs against various diseases involving neuro-inflammation, oxidative stress, mitochondrial dysfunction, and altered lipid metabolism. They can activate neurotrophic and neuroprotective signaling pathways but low bioavailabilities limit their efficiency in curing neurodegeneration. Here, liquid crystalline lipid nanoparticles (LNPs) are created for the protection and non-invasive intranasal delivery of purified scallop-derived plasmalogens. The in vivo results with a transgenic mouse Parkinson's disease (PD) model (characterized by motor impairments and α-synuclein deposition) demonstrate the crucial importance of LNP composition, which determines the self-assembled nanostructure type. Vesicle and hexosome nanostructures (characterized by small-angle X-ray scattering) display different efficacy of the nanomedicine-mediated recovery of motor function, lipid balance, and transcriptional regulation (e.g., reduced neuro-inflammation and PD pathogenic gene expression). Intranasal vesicular and hexosomal plasmalogen-based LNP treatment leads to improvement of the behavioral PD symptoms and downregulation of the Il6, Il33, and Tnfa genes. Moreover, RNA-sequencing and lipidomic analyses establish a dramatic effect of hexosomal nanomedicines on PD amelioration, lipid metabolism, and the type and number of responsive transcripts that may be implicated in neuroregeneration.

A neurocomputational view of the effects of Parkinson's disease on speech production

The purpose of this article is to review the scientific literature concerning speech in Parkinson's disease (PD) with reference to the DIVA/GODIVA neurocomputational modeling framework. Within this theoretical view, the basal ganglia (BG) contribute to several different aspects of speech motor learning and execution. First, the BG are posited to play a role in the initiation and scaling of speech movements. Within the DIVA/GODIVA framework, initiation and scaling are carried out by initiation map nodes in the supplementary motor area acting in concert with the BG. Reduced support of the initiation map from the BG in PD would result in reduced movement intensity as well as susceptibility to early termination of movement. A second proposed role concerns the learning of common speech sequences, such as phoneme sequences comprising words; this view receives support from the animal literature as well as studies identifying speech sequence learning deficits in PD. Third, the BG may play a role in the temporary buffering and sequencing of longer speech utterances such as phrases during conversational speech. Although the literature does not support a critical role for the BG in representing sequence order (since incorrectly ordered speech is not characteristic of PD), the BG are posited to contribute to the scaling of individual movements in the sequence, including increasing movement intensity for emphatic stress on key words. Therapeutic interventions for PD have inconsistent effects on speech. In contrast to dopaminergic treatments, which typically either leave speech unchanged or lead to minor improvements, deep brain stimulation (DBS) can degrade speech in some cases and improve it in others. However, cases of degradation may be due to unintended stimulation of efferent motor projections to the speech articulators. Findings of spared speech after bilateral pallidotomy appear to indicate that any role played by the BG in adult speech must be supplementary rather than mandatory, with the sequential order of well-learned sequences apparently represented elsewhere (e.g., in cortico-cortical projections).

Lower Limb Proprioception in Low Back Pain and Its Relationship With Voluntary Postural Control

This study aimed to investigate whether patients with low back pain (LBP) had impaired lower limb proprioception and its association with somatosensory acuity. Thirty patients with LBP and 30 asymptomatic people volunteered, using Sway Discrimination Apparatus tests to assess somatosensory acuity during voluntary anteroposterior and mediolateral postural sway. Results showed significantly reduced somatosensory acuity in mediolateral sway in LBP patients (p = 0.005) with ankle, knee, and hip proprioception showing significantly impairment compared to asymptomatic controls (all p ≤ 0.012). Regression analysis showed that ankle and hip proprioception were significantly associated with somatosensory perception (0.001 ≤ p ≤ 0.026, 0.067 ≤ R2≤ 0.235). Overall, findings suggested a global deterioration of lower limb proprioception in LBP patients, with ankle and hip proprioception playing crucial role in somatosensory perception.

C. elegans: a prominent platform for modeling and drug screening in neurological disorders

INTRODUCTION

Human neurodevelopmental and neurodegenerative diseases (NDevDs and NDegDs, respectively) encompass a broad spectrum of disorders affecting the nervous system with an increasing incidence. In this context, the nematode C. elegans, has emerged as a benchmark model for biological research, especially in the field of neuroscience.

AREAS COVERED

The authors highlight the numerous advantages of this tiny worm as a model for exploring nervous system pathologies and as a platform for drug discovery. There is a particular focus given to describing the existing models of C. elegans for the study of NDevDs and NDegDs. Specifically, the authors underscore their strong applicability in preclinical drug development. Furthermore, they place particular emphasis on detailing the common techniques employed to explore the nervous system in both healthy and diseased states.

EXPERT OPINION

Drug discovery constitutes a long and expensive process. The incorporation of invertebrate models, such as C. elegans, stands as an exemplary strategy for mitigating costs and expediting timelines. The utilization of C. elegans as a platform to replicate nervous system pathologies and conduct high-throughput automated assays in the initial phases of drug discovery is pivotal for rendering therapeutic options more attainable and cost-effective.

Augmenting locomotor perception by remapping tactile foot sensation to the back

BACKGROUND

Sensory reafferents are crucial to correct our posture and movements, both reflexively and in a cognitively driven manner. They are also integral to developing and maintaining a sense of agency for our actions. In cases of compromised reafferents, such as for persons with amputated or congenitally missing limbs, or diseases of the peripheral and central nervous systems, augmented sensory feedback therefore has the potential for a strong, neurorehabilitative impact. We here developed an untethered vibrotactile garment that provides walking-related sensory feedback remapped non-invasively to the wearer's back. Using the so-called FeetBack system, we investigated if healthy individuals perceive synchronous remapped feedback as corresponding to their own movement (motor awareness) and how temporal delays in tactile locomotor feedback affect both motor awareness and walking characteristics (adaptation).

METHODS

We designed the system to remap somatosensory information from the foot-soles of healthy participants (N = 29), using vibrotactile apparent movement, to two linear arrays of vibrators mounted ipsilaterally on the back. This mimics the translation of the centre-of-mass over each foot during stance-phase. The intervention included trials with real-time or delayed feedback, resulting in a total of 120 trials and approximately 750 step-cycles, i.e. 1500 steps, per participant. Based on previous work, experimental delays ranged from 0ms to 1500ms to include up to a full step-cycle (baseline stride-time: µ = 1144 ± 9ms, range 986-1379ms). After each trial participants were asked to report their motor awareness.

RESULTS

Participants reported high correspondence between their movement and the remapped feedback for real-time trials (85 ± 3%, µ ± σ), and lowest correspondence for trials with left-right reversed feedback (22 ± 6% at 600ms delay). Participants further reported high correspondence of trials delayed by a full gait-cycle (78 ± 4% at 1200ms delay), such that the modulation of motor awareness is best expressed as a sinusoidal relationship reflecting the phase-shifts between actual and remapped tactile feedback (cos model: 38% reduction of residual sum of squares (RSS) compared to linear fit, p < 0.001). The temporal delay systematically but only moderately modulated participant stride-time in a sinusoidal fashion (3% reduction of RSS compared a linear fit, p < 0.01).

CONCLUSIONS

We here demonstrate that lateralized, remapped haptic feedback modulates motor awareness in a systematic, gait-cycle dependent manner. Based on this approach, the FeetBack system was used to provide augmented sensory information pertinent to the user's on-going movement such that they reported high motor awareness for (re)synchronized feedback of their movements. While motor adaptation was limited in the current cohort of healthy participants, the next step will be to evaluate if individuals with a compromised peripheral nervous system, as well as those with conditions of the central nervous system such as Parkinson's Disease, may benefit from the FeetBack system, both for maintaining a sense of agency over their movements as well as for systematic gait-adaptation in response to the remapped, self-paced, rhythmic feedback.

Proprioceptive and olfactory deficits in individuals with Parkinson disease and mild cognitive impairment

BACKGROUND

Individuals with neurodegenerative diseases such as Parkinson disease (PD) and Alzheimer's (AD) disease often present with perceptual impairments at an early clinical stage. Therefore, early identification and quantification of these impairments could facilitate diagnosis and early intervention.

OBJECTIVES

This study aimed to compare proprioceptive and olfactory sensitivities in individuals diagnosed with PD and mild cognitive impairment (MCI).

METHODS

Proprioception in the forearm and olfactory function were measured in neurotypical older adults, individuals with PD, and individuals with MCI. Position and passive motion senses were assessed using a passive motion apparatus. The traditional Chinese version of the University of Pennsylvania smell identification test (UPSIT-TC) and the smell threshold test (STT) were used to identify and discriminate smell, respectively.

RESULTS

Position sense threshold between the groups differed significantly (p < 0.001), with the PD (p < 0.001) and MCI (p = 0.004) groups showing significantly higher than the control group. The control group had significantly higher mean UPSIT-TC scores than the PD (p < 0.001) and MCI (p = 0.006) groups. The control group had a significantly lower mean STT threshold than the PD and MCI groups (p < 0.001 and p = 0.008, respectively). UPSIT-TC scores significantly correlated with disease progression in PD (r = - 0.50, p = 0.008) and MCI (r = 0.44, p = 0.04).

CONCLUSIONS

Proprioceptive and olfactory sensitivities were reduced in individuals with PD and MCI, and these deficits were related to disease severity. These findings support previous findings indicating that perceptual loss may be a potential biomarker for diagnosing and monitoring disease progression in individuals with neurodegenerative diseases.

Neural correlates of bilateral proprioception and adaptation with training

Bilateral proprioception includes the ability to sense the position and motion of one hand relative to the other, without looking. This sensory ability allows us to perform daily activities seamlessly, and its impairment is observed in various neurological disorders such as cerebral palsy and stroke. It can undergo experience-dependent plasticity, as seen in trained piano players. If its neural correlates were better understood, it would provide a useful assay and target for neurorehabilitation for people with impaired proprioception. We designed a non-invasive electroencephalography-based paradigm to assess the neural features relevant to proprioception, especially focusing on bilateral proprioception, i.e., assessing the limb distance from the body with the other limb. We compared it with a movement-only task, with and without the visibility of the target hand. Additionally, we explored proprioceptive accuracy during the tasks. We tested eleven Controls and nine Skilled musicians to assess whether sensorimotor event-related spectral perturbations in μ (8-12Hz) and low-β (12-18Hz) rhythms differ in people with musical instrument training, which intrinsically involves a bilateral proprioceptive component, or when new sensor modalities are added to the task. The Skilled group showed significantly reduced μ and low-β suppression in bilateral tasks compared to movement-only, a significative difference relative to Controls. This may be explained by reduced top-down control due to intensive training, despite this, proprioceptive errors were not smaller for this group. Target visibility significantly reduced proprioceptive error in Controls, while no change was observed in the Skilled group. During visual tasks, Controls exhibited significant μ and low-β power reversals, with significant differences relative to proprioceptive-only tasks compared to the Skilled group-possibly due to reduced uncertainty and top-down control. These results provide support for sensorimotor μ and low-β suppression as potential neuromarkers for assessing proprioceptive ability. The identification of these features is significant as they could be used to quantify altered proprioceptive neural processing in skill and movement disorders. This in turn can be useful as an assay for pre and post sensory-motor intervention research.

Comparing the efficacy of therapeutic Thai acupressure on plantar acupoints and laser cane therapy on freezing of gait in Parkinson's disease: a randomized non-inferiority trial

Background

ON-freezing of gait (ON-FOG) in Parkinson's disease (PD), often resistant to medication, is linked to sensory deficits and proprioceptive impairment, and results in falls and reduced life quality. While visual cues from a laser cane (LC), which rapidly accesses the motor cortex, are commonly used to compensate for proprioceptive impairment, increased visual reliance may be affected by disease progression. Emerging evidence suggests that modulation of peripheral sensory processing may alleviate ON-FOG, and therapeutic Thai acupressure (TTA) may be a solution. This study aims to evaluate the effect of TTA in alleviating ON-FOG and compare its effectiveness to LC in patients with PD.

Methods

This open-label, non-inferiority trial randomized 90 PD patients with ON-FOG equally into three arms: TTA for plantar nerve stimulation for 96 s, LC for visual cueing, and sham control (SC). Stride length was the primary non-inferiority endpoint [non-inferiority margin: lower limit of 95% confidence interval (CI) above -10 cm in mean change difference in pre- and immediately post-intervention in TTA versus LC (one-sided)]. Secondary outcomes included FOG episodes, double support time, velocity, cadence, step length, timed up and go (TUG) test, and visual analog scale (VAS) score.

Results

TTA showed non-inferiority to LC in stride length (mean = -0.7 cm; 95% CI: -6.55; 5.15) (one-sided). The improvements with TTA and LC versus SC were comparable between (mean = 13.11 cm; 95% CI: 7.26; 18.96) and (mean = 13.8 cm; 95% CI: 7.96; 19.65) (one-sided). Secondary outcomes favored TTA and LC over SC with improved FOG, velocity, step length, and VAS scores, while only TTA resulted in improved double support time, cadence, and TUG test results. No complications occurred.

Conclusion

The efficacy of TTA, which improves stride length, is non-inferior to that of LC and consequently alleviates FOG comparable to LC. TTA might enhance proprioceptive function and reduce visual dependence. Therefore, TTA, characterized by its non-invasive, simple, and safe techniques, is a potential non-pharmacological alternative for ON-FOG treatment and might enhance overall quality of life. However, further research into the mechanism, efficacy, and utilization of TTA is essential.

Clinical trial registration

https://www.thaiclinicaltrials.org/show/TCTR20200317001, identifier TCTR20200317001.

Exercise-Induced Functional Changes in People with Parkinson's Disease following External Cueing and Task-Based Intervention

Introduction

The purpose of this study was to evaluate change in motor function, gait speed, dynamic balance, balance confidence, and quality of life (QoL) in nine participants with Parkinson's disease (PwPD) completing Lee Silverman Voice Treatment BIG (LSVT-BIG), an external cueing and task-based intervention. Although supported as an efficacious treatment in PwPD, there is limited research examining clinically meaningful change in outcome measures related to external cueing and task-based interventions.

Materials and Methods

This was a case series of nine PwPD (age range 64-76 years, 55% male) who completed the LSVT-BIG protocol. Disease duration ranged from 1 to 17 years and was classified as moderate in all participants (Hoehn and Yahr = 2 or 3). Outcome measures included motor function (MDS-UPDRS Part III Motor), gait speed, dynamic balance (MiniBEST), Activities-specific Balance Confidence (ABC), and Summary Index for PD Quality of Life 39 (PDQ-SI). Assessments were completed at baseline (BASE), end of treatment (EOT), and 4 weeks after EOT (EOT+4).

Results

Minimal detectable change (MDC) or minimal clinical important difference (MCID) was observed in one or more outcome measures in 8 of 9 participants at EOT and EOT+4 across domains of motor function (67%, 78%), gait speed (78%, 67%), balance confidence (44%, 33%), quality of life (44%, 78%), and dynamic balance (22%, 22%). Discussion. In this case series, 8 of 9 participants showed MDC or MCID changes across multiple functional domains. Improvements were observed immediately post (EOT) and 4-week post-treatment (EOT+4) suggesting a temporal component of the LSVT-BIG impact on functional change. Future research should include clinical trials to examine additional external cueing and task-based intervention efficacy with consideration of intensity, frequency, and mode of delivery across disease severity.

Active and Passive Cycling Decrease Subthalamic β Oscillations in Parkinson's Disease

BACKGROUND

Preserved cycling capabilities in patients with Parkinson's disease, especially in those with freezing of gait are still poorly understood. Previous research with invasive local field potential recordings in the subthalamic nucleus has shown that cycling causes a stronger suppression of β oscillations compared to walking, which facilitates motor continuation.

METHODS

We recorded local field potentials from 12 patients with Parkinson's disease (six without freezing of gait, six with freezing of gait) who were bilaterally implanted with deep brain stimulation electrodes in the subthalamic nucleus. We investigated β (13-30 Hz) and high γ (60-100 Hz) power during both active and passive cycling with different cadences and compared patients with and without freezing of gait. The passive cycling experiment, where a motor provided a fixed cadence, allowed us to study the effect of isolated sensory inputs without physical exercise.

RESULTS

We found similarly strong suppression of pathological β activity for both active and passive cycling. In contrast, there was stronger high γ band activity for active cycling. Notably, the effects of active and passive cycling were all independent of cadence. Finally, β suppression was stronger for patients with freezing of gait, especially during passive cycling.

CONCLUSIONS

Our results provide evidence for a link between proprioceptive input during cycling and β suppression. These findings support the role of continuous external sensory input and proprioceptive feedback during rhythmic passive cycling movements and suggest that systematic passive mobilization might hold therapeutic potential. © 2023 International Parkinson and Movement Disorder Society.

Volitional muscle activation intensifies neuronal processing of proprioceptive afference in the primary sensorimotor cortex: an EEG study

Proprioception refers to the ability to perceive the position and movement of body segments in space. The cortical aspects of the proprioceptive afference from the body can be investigated using corticokinematic coherence (CKC). CKC accurately quantifies the degree of coupling between cortical activity and limb kinematics, especially if precise proprioceptive stimulation of evoked movements is used. However, there is no evidence on how volitional muscle activation during proprioceptive stimulation affects CKC strength. Twenty-five healthy volunteers (28.8 ± 7 yr, 11 females) participated in the experiment, which included electroencephalographic (EEG), electromyographic (EMG), and kinematic recordings. Ankle-joint rotations (2-Hz) were elicited through a movement actuator in two conditions: passive condition with relaxed ankle and active condition with constant 5-Nm plantar flexion exerted during the stimulation. In total, 6 min of data were recorded per condition. CKC strength was defined as the maximum coherence value among all the EEG channels at the 2-Hz movement frequency for each condition separately. Both conditions resulted in significant CKC peaking at the Cz electrode over the foot area of the primary sensorimotor (SM1) cortex. Stronger CKC was found for the active (0.13 ± 0.14) than the passive (0.03 ± 0.04) condition (P < 0.01). The results indicated that volitional activation of the muscles intensifies the neuronal proprioceptive processing in the SM1 cortex. This finding could be explained both by peripheral sensitization of the ankle joint proprioceptors and central modulation of the neuronal proprioceptive processing at the spinal and cortical levels.NEW & NOTEWORTHY The current study is the first to investigate the effect of volitional muscle activation on CKC-based assessment of cortical proprioception of the ankle joint. Results show that the motor efference intensifies the neuronal processing of proprioceptive afference of the ankle joint. This is a significant finding as it may extend the use of CKC method during active tasks to further evaluate the motor efference-proprioceptive afference relationship and the related adaptations to exercise, rehabilitation, and disease.

Does Impaired Plantar Cutaneous Vibration Perception Contribute to Axial Motor Symptoms in Parkinson's Disease? Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation

OBJECTIVE

To investigate whether impaired plantar cutaneous vibration perception contributes to axial motor symptoms in Parkinson's disease (PD) and whether anti-parkinsonian medication and subthalamic nucleus deep brain stimulation (STN-DBS) show different effects.

METHODS

Three groups were evaluated: PD patients in the medication "on" state (PD-MED), PD patients in the medication "on" state and additionally "on" STN-DBS (PD-MED-DBS), as well as healthy subjects (HS) as reference. Motor performance was analyzed using a pressure distribution platform. Plantar cutaneous vibration perception thresholds (VPT) were investigated using a customized vibration exciter at 30 Hz.

RESULTS

Motor performance of PD-MED and PD-MED-DBS was characterized by greater postural sway, smaller limits of stability ranges, and slower gait due to shorter strides, fewer steps per minute, and broader stride widths compared to HS. Comparing patient groups, PD-MED-DBS showed better overall motor performance than PD-MED, particularly for the functional limits of stability and gait. VPTs were significantly higher for PD-MED compared to those of HS, which suggests impaired plantar cutaneous vibration perception in PD. However, PD-MED-DBS showed less impaired cutaneous vibration perception than PD-MED.

CONCLUSIONS

PD patients suffer from poor motor performance compared to healthy subjects. Anti-parkinsonian medication in tandem with STN-DBS seems to be superior for normalizing axial motor symptoms compared to medication alone. Plantar cutaneous vibration perception is impaired in PD patients, whereas anti-parkinsonian medication together with STN-DBS is superior for normalizing tactile cutaneous perception compared to medication alone. Consequently, based on our results and the findings of the literature, impaired plantar cutaneous vibration perception might contribute to axial motor symptoms in PD.

Motion sense sensitivity of the ankle is abnormal and correlated with motor performance in children with and without a probable developmental coordination disorder

This study systematically examined ankle motion sense sensitivity and its relation to motor functions in children with and without a probable developmental coordination disorder (pDCD). Seventy-two children aged 10-11 years were recruited, including thirty-six children with pDCD and 36 age- and sex-matched typically developing (TD) children. Children placed their dominant foot on a passive ankle motion apparatus that induced plantar flexion of the ankle under nine constant velocities ranging between 0.15 and 1.35°/s. The adjusted movement detection time (ADT) to passive ankle motion was obtained to measure ankle motion sense sensitivity. The results showed that, in comparison to that in the TD group, ankle ADT was significantly increased by 22-59% for the range of velocities in the pDCD group. A correlation analysis showed that mean ADTs were significantly correlated with the manual dexterity (r = -0.33, p = 0.005) and balance (r = -0.24, p = 0.046) scores on the Movement Assessment Battery for Children (MABC-2) in the combined group. Similar correlations were found between the ADTs and the manual dexterity (r = -0.37, p = 0.028) and total motor (r = -0.34, p = 0.047) scores in the TD group. This study documents that ankle motion sense sensitivity to passive foot motion is reduced and is likely to contribute to poor motor performance in children with and without pDCD.

Proprioceptive Acuity Influences Speech Motor Control in Healthy Adult Talkers

PURPOSE

Somatosensory feedback, including proprioception, is important for speech production. This study evaluates proprioceptive acuity of the tongue using a position-matching task and determining if proprioceptive acuity impacts speech motor control in healthy adult talkers.

METHOD

Twenty-five young adults with no history of speech, language, or hearing disorders had their tongue movements recorded with an electromagnetic articulograph while completing a position-matching task. Participants were also asked to repeat two sentences that differed in the somatosensory feedback obtained. One sentence provided both tactile and proprioceptive feedback, whereas the other primarily provided proprioceptive feedback.

RESULTS

Participants ranged in proprioceptive acuity as measured by the position-matching task. Talkers with smaller position-matching errors and, therefore, higher proprioceptive acuity had smaller movements and slower speeds for both sentences. Talkers with lower proprioceptive acuity had reduced speech movement stability for the sentence that primarily provides proprioceptive feedback.

CONCLUSION

Proprioceptive acuity of the tongue can be evaluated using a position-matching task, and acuity is associated with more efficient speech movements and greater speech movement stability, particularly when producing utterances that provide less tactile feedback.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24293740.

Adapting to Altered Sensory Input: Effects of Induced Paresthesia on Goal-Directed Movement Planning and Execution

The current study investigated how temporarily induced paresthesia in the moving limb affects the performance of a goal-directed target aiming task. Three-dimensional displacement data of 14 neurotypical participants were recorded while they pointed to a target on a computer monitor in four conditions: (i) paresthesia-full-vision; (ii) paresthesia-without-target vision; (iii) no-paresthesia-full-vision; (iv) no paresthesia-without-target vision. The four conditions were blocked and counterbalanced such that participants performed the paresthesia and no-paresthesia conditions on two separate days. To assess how aiming performance changed in the presence of paresthesia, we compared early versus late performance (first and last 20% of trials). We found that endpoint accuracy and movement speed were reduced in the presence of paresthesia, but only without target vision. With repetition, participants adjusted their movement performance strategy, such that with induced paresthesia, they used a movement strategy that included more pre-planned movements that depended less on online control.

Visual velocity perception dysfunction in Parkinson's disease

OBJECTIVE

Compared with motor deficits, sensory information processing in Parkinson's disease (PD) is relatively unexplored. While there is increasing interest in understanding the sensory manifestations of PD, the extent of sensory abnormality in PD has remained relatively unexplored. Furthermore, most investigations on the sensory aspects of PD involve motor aspects, causing confounding results. As sensory deficits often arise in early PD development stages, they present a potential technological target for diagnosis and disease monitoring that is affordable and accessible. Considering this, the current study's aim is to assess visual spatiotemporal perception independent of goal directed movements in PD by designing and using a scalable computational tool.

METHODS

A flexible 2-D virtual reality environment was created to evaluate various cases of visual perception. Using the tool, an experimental task quantifying the visual perception of velocity was tested on 37 individuals with PD and 17 age-matched control participants.

RESULTS

PD patients, both ON and OFF PD therapy, displayed perceptual impairments (p = 0.001 and p = 0.008, respectively) at slower tested velocity magnitudes. These impairments were even observed in early stages of PD (p = 0.015).

CONCLUSION

Visual velocity perception is impaired in PD patients, which suggests impairments in visual spatiotemporal processing occur in PD and provides a promising modality to be used with disease monitoring software.

SIGNIFICANCE

Visual velocity perception shows high sensitivity to PD at all stages of the disease. Dysfunction in visual velocity perception may contribute to observed motor dysfunction in PD.

Cortex-wide topography of 1/f-exponent in Parkinson's disease

Parkinson's disease (PD) is a progressive and debilitating brain disorder. Besides the characteristic movement-related symptoms, the disease also causes decline in sensory and cognitive processing. The extent of symptoms and brain-wide projections of neuromodulators such as dopamine suggest that many brain regions are simultaneously affected in PD. To characterise brain-wide disease-related changes in neuronal function, we analysed resting state magnetoencephalogram (MEG) from two groups: PD patients and healthy controls. Besides standard spectral analysis, we quantified the aperiodic components (κ, λ) of the neural activity by fitting a power law κ/fλ - f is the frequency, κ and λ are the fitting parameters-to the MEG power spectrum and studied its relationship with age and Unified Parkinson's Disease Rating Scale (UPDRS). Consistent with previous results, the most significant spectral changes were observed in the high theta/low-alpha band (7-10 Hz) in all brain regions. Furthermore, analysis of the aperiodic part of the spectrum showed that in all but frontal regions λ was significantly larger in PD patients than in control subjects. Our results indicate that PD is associated with significant changes in aperiodic activity across the whole neocortex. Surprisingly, even early sensory areas showed a significantly larger λ in patients than in healthy controls. Moreover, λ was not affected by the Levodopa medication. Finally, λ was positively correlated with patient age but not with UPDRS-III. Because λ is closely associated with excitation-inhibition balance, our results propose new hypotheses about neural correlates of PD in cortical networks.

Physiological measures and anatomical correlates of subthalamic deep brain stimulation effect on gait in Parkinson's disease

We examined whether conflicting visual and non-visual information leads to gait abnormalities and how the subthalamic deep brain stimulation (STN DBS) influences gait dysfunction in Parkinson's disease (PD). We used a motion capture system to measure the kinematics of the lower limbs during treadmill walking in immersive virtual reality. The visual information provided in the virtual reality paradigm was modulated to create a mismatch between the optic-flow velocity of the visual scene and the walking speed on the treadmill. In each mismatched condition, we calculated the step duration, step length, step phase, step height, and asymmetries. The key finding of our study was that mismatch between treadmill walking speed and the optic-flow velocity did not consistently alter gait parameters in PD. We also found that STN DBS improved the PD gait pattern by changing the stride length and step height. The effects on phase and left/right asymmetry were not statistically significant. The DBS parameters and location also determined its effects on gait. Statistical effects on stride length and step height were noted when the DBS volume of activated tissue (VTA) was in the dorsal aspect of the subthalamus. The statistically significant effects of STN DBS was present when VTA significantly overlapped with MR tractogrphically measured motor and pre-motor hyperdirect pathways. In summary, our results provide novel insight into ways for controlling walking behavior in PD using STN DBS.

Robot-assisted investigation of sensorimotor control in Parkinson's disease

Sensorimotor control (SMC) is a complex function that involves sensory, cognitive, and motor systems working together to plan, update and execute voluntary movements. Any abnormality in these systems could lead to deficits in SMC, which would negatively impact an individual's ability to execute goal-directed motions. Recent studies have shown that patients diagnosed with Parkinson's disease (PD) have dysfunctions in sensory, motor, and cognitive systems, which could give rise to SMC deficits. However, SMC deficits in PD and how they affect a patient's upper-limb movements have not been well understood. The objective of the study was to investigate SMC deficits in PD and how they affect the planning and correction of upper-limb motions. This was accomplished using a robotic manipulandum equipped with a virtual-reality system. Twenty age-matched healthy controls and fifty-six PD patients (before and after medication) completed an obstacle avoidance task under dynamic conditions (target and obstacles in moving or stationary form, with and without mechanical perturbations). Kinematic information from the robot was used to extract eighteen features that evaluated the SMC functions of the participants. The findings show that the PD patients before medication were 32% slower, reached 16% fewer targets, hit 41% more obstacles, and were 26% less efficient than the control participants, and the difference in these features was statistically significant under dynamic conditions. In addition to the motor deficits, the PD patients also showed deficits in handling high cognitive loads and interpreting sensory cues. Further, the PD patients after medication exhibited worse sensory and cognitive performance than before medication under complex testing conditions. The PD patients also showed deficits in following the computational models leading to poor motor planning.

Differentiation of claustrum resting-state functional connectivity in healthy aging, Alzheimer's disease, and Parkinson's disease

The claustrum is a sheet-like of telencephalic gray matter structure whose function is poorly understood. The claustrum is considered a multimodal computing network due to its reciprocal connections with almost all cortical areas as well as subcortical structures. Although the claustrum has been involved in several neurodegenerative diseases, specific changes in connections of the claustrum remain unclear in Alzheimer's disease (AD), and Parkinson's disease (PD). Resting-state fMRI and T1-weighted structural 3D images from healthy elderly (n = 15), AD (n = 16), and PD (n = 12) subjects were analyzed. Seed-based FC analysis was performed using CONN FC toolbox and T1-weighted images were analyzed with the Computational Anatomy Toolbox for voxel-based morphometry analysis. While we observed a decreased FC between the left claustrum and sensorimotor cortex, auditory association cortex, and cortical regions associated with social cognition in PD compared with the healthy control group (HC), no significant difference was found in alterations in the FC of both claustrum comparing the HC and AD groups. In the AD group, high FC of claustrum with regions of sensorimotor cortex and cortical regions related to cognitive control, including cingulate gyrus, supramarginal gyrus, and insular cortex were demonstrated. In addition, the structural results show significantly decreased volume in bilateral claustrum in AD and PD compared with HC. There were no significant differences in the claustrum volumes between PD and AD groups so the FC may offer more precise findings in distinguishing changes for claustrum in AD and PD.

Comparing Backward Walking Performance in Parkinson's Disease with and without Freezing of Gait-A Systematic Review

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative disease characterized by motor symptoms and gait impairments. Among them, freezing of gait (FOG) is one of the most disabling manifestations. Backward walking (BW) is an activity of daily life that individuals with PD might find difficult and could cause falls. Recent studies have reported that gait impairments in PD were more pronounced in BW, particularly in people presenting FOG. However, to the best of our knowledge, no systematic review has synthetized the literature which compared BW performance in PD patients with and without FOG.

OBJECTIVE

The aim of this study was to evaluate the differences in BW performance between PD patients with FOG and PD patients without FOG.

METHODS

Two databases, PubMed and Web of Science, were systematically searched to identify studies comparing BW performance in PD patients with and without FOG. The National Institutes of Health (NIH) tool was used to assess the quality of the studies included.

RESULTS

Seven studies with 431 PD patients (179 PD with FOG and 252 PD without FOG) met the inclusion criteria and were included in this review. Among them, 5 studies reported walking speed, 3 studies step length, stride length and lower limb range of motion, 2 studies functional ambulation profile, toe clearance height, swing, and stance percent and 1 study reported the decomposition index and stepping coordination. Compared to PD patients without FOG, PD patients with FOG showed slower walking speed and reduced step length in 3 studies, shorter stride length, lower functional ambulation profile and decreased ankle range of motion in 2 studies, and smaller swing percent, higher stance percent, worse stepping coordination, greater decomposition between movements, and lower toe clearance height in one study.

CONCLUSION

Despite the small number of included studies, the findings of this review suggested that PD patients with FOG have worse gait performance during the BW task than PD without FOG.

Motor Memory Consolidation Deficits in Parkinson's Disease: A Systematic Review with Meta-Analysis

BACKGROUND

The ability to encode and consolidate motor memories is essential for persons with Parkinson's disease (PD), who usually experience a progressive loss of motor function. Deficits in memory encoding, usually expressed as poorer rates of skill improvement during motor practice, have been reported in these patients. Whether motor memory consolidation (i.e., motor skill retention) is also impaired is unknown.

OBJECTIVE

To determine whether motor memory consolidation is impaired in PD compared to neurologically intact individuals.

METHODS

We conducted a pre-registered systematic review (PROSPERO: CRD42020222433) following PRISMA guidelines that included 46 studies.

RESULTS

Meta-analyses revealed that persons with PD have deficits in retaining motor skills (SMD = -0.17; 95% CI = -0.32, -0.02; p = 0.0225). However, these deficits are task-specific, affecting sensory motor (SMD = -0.31; 95% CI -0.47, -0.15; p = 0.0002) and visuomotor adaptation (SMD = -1.55; 95% CI = -2.32, -0.79; p = 0.0001) tasks, but not sequential fine motor (SMD = 0.17; 95% CI = -0.05, 0.39; p = 0.1292) and gross motor tasks (SMD = 0.04; 95% CI = -0.25, 0.33; p = 0.7771). Importantly, deficits became non-significant when augmented feedback during practice was provided, and additional motor practice sessions reduced deficits in sensory motor tasks. Meta-regression analyses confirmed that deficits were independent of performance during encoding, as well as disease duration and severity.

CONCLUSION

Our results align with the neurodegenerative models of PD progression and motor learning frameworks and emphasize the importance of developing targeted interventions to enhance motor memory consolidation in PD.

Motion sickness susceptibility and visually induced motion sickness as diagnostic signs in Parkinson's disease

Postural instability and loss of vestibular and somatosensory acuity can be part of the signs encountered in Parkinson's Disease (PD). Visual dependency is described in PD. These modifications of sensory input hierarchy are predictors of motion sickness (MS). The aim of this study was to assess MS susceptibility and effects of real induced MS in posture. 63 PD patients, whose medication levels (levodopa) reflected the pathology were evaluated, and 27 healthy controls, filled a MS questionnaire; 9 PD patients and 43 healthy controls were assessed by posturography using virtual reality. Drug amount predicted visual MS (p=0.01), but not real induced MS susceptibility. PD patients did not experience postural instability in virtual reality, contrary to healthy controls. Since PD patients do not seem to feel vestibular stimulated MS, they may not rely on vestibular and somatosensory inputs during the stimulation. However, they feel visually induced MS more with increased levodopa drug effect. Levodopa amount can increase visual dependency. The strongest MS predictors must be studied in PD to better understand the effect of visual stimulation and its absence in vestibular stimulation.

Single-textured insole for the less affected leg in freezing of gait: A hypothesis

Freezing of gait (FoG) is one of the most widely distributed and disabling gait phenomena in people with Parkinson's disease (PD). The current therapeutic interventions show suboptimal efficacy in FoG. Lower extremity proprioception impairments, especially in the most affected leg, gait initiation hesitation, and gait asymmetry are FoG factors, and there is a need to accurately consider them in terms of therapeutic approaches. Accordingly, we hypothesize that using a single-textured insole for the less affected leg may improve FoG by providing proprioceptive stimulation that enhances sensory processing and reduces gait hesitation and asymmetry. Proprioceptive sensory stimulation for the less affected limb could be more effective than for the double legs that are currently used in rehabilitation settings due to the sensory processing in the less affected basal ganglia being better.

Encoding type, medication, and deep brain stimulation differentially affect memory-guided sequential reaching movements in Parkinson's disease

Memory-guided movements, vital to daily activities, are especially impaired in Parkinson's disease (PD). However, studies examining the effects of how information is encoded in memory and the effects of common treatments of PD, such as medication and subthalamic nucleus deep brain stimulation (STN-DBS), on memory-guided movements are uncommon and their findings are equivocal. We designed two memory-guided sequential reaching tasks, peripheral-vision or proprioception encoded, to investigate the effects of encoding type (peripheral-vision vs. proprioception), medication (on- vs. off-), STN-DBS (on- vs. off-, while off-medication), and compared STN-DBS vs. medication on reaching amplitude, error, and velocity. We collected data from 16 (analyzed n = 7) participants with PD, pre- and post-STN-DBS surgery, and 17 (analyzed n = 14) healthy controls. We had four important findings. First, encoding type differentially affected reaching performance: peripheral-vision reaches were faster and more accurate. Also, encoding type differentially affected reaching deficits in PD compared to healthy controls: peripheral-vision reaches manifested larger deficits in amplitude. Second, the effect of medication depended on encoding type: medication had no effect on amplitude, but reduced error for both encoding types, and increased velocity only during peripheral-vision encoding. Third, the effect of STN-DBS depended on encoding type: STN-DBS increased amplitude for both encoding types, increased error during proprioception encoding, and increased velocity for both encoding types. Fourth, STN-DBS was superior to medication with respect to increasing amplitude and velocity, whereas medication was superior to STN-DBS with respect to reducing error. We discuss our findings in the context of the previous literature and consider mechanisms for the differential effects of medication and STN-DBS.

Sensory Processing Impairments in Children with Developmental Coordination Disorder

The two objectives of this systematic review were to examine the following: (1) the difference in sensory processing areas (auditory, visual, vestibular, touch, proprioceptive, and multi-sensory) between children with and without developmental coordination disorder (DCD), and (2) the relationship between sensory processing and motor coordination in DCD. The following databases were comprehensively searched for relevant articles: PubMed, Science Direct, Web of Science, and Cochrane library. There were 1107 articles (published year = 2010 to 2021) found in the initial search. Full-text articles of all possibly relevant citations were obtained and inspected for suitability by two authors. The outcome measures were sensory processing impairments and their relationship with motor coordination. A total of 10 articles met the inclusion criteria. Children with DCD showed significant impairments in visual integration, tactile integration, proprioceptive integration, auditory integration, vestibular integration, and oral integration processes when compared with typically developing children. Evidence also supported that sensory processing impairments were associated with poor motor coordination in DCD. Preliminary support indicated that DCD have sensory processing impairments in visual, tactile, proprioceptive, auditory, and vestibular areas, which might contribute to participation restriction in motor activities. It is important to apply sensory integration therapy in rehabilitation programs for DCD in order to facilitate participation in daily activities.

Principles of gait encoding in the subthalamic nucleus of people with Parkinson's disease

Disruption of subthalamic nucleus dynamics in Parkinson's disease leads to impairments during walking. Here, we aimed to uncover the principles through which the subthalamic nucleus encodes functional and dysfunctional walking in people with Parkinson's disease. We conceived a neurorobotic platform embedding an isokinetic dynamometric chair that allowed us to deconstruct key components of walking under well-controlled conditions. We exploited this platform in 18 patients with Parkinson's disease to demonstrate that the subthalamic nucleus encodes the initiation, termination, and amplitude of leg muscle activation. We found that the same fundamental principles determine the encoding of leg muscle synergies during standing and walking. We translated this understanding into a machine learning framework that decoded muscle activation, walking states, locomotor vigor, and freezing of gait. These results expose key principles through which subthalamic nucleus dynamics encode walking, opening the possibility to operate neuroprosthetic systems with these signals to improve walking in people with Parkinson's disease.

A multiple domain postural control assessment in people with Parkinson's disease: traditional, non-linear, and rambling and trembling trajectories analysis

BACKGROUND

Postural impairment is one of the most debilitating symptoms in people with Parkinson's disease (PD), which show faster and more variable oscillation during quiet stance than neurologically healthy individuals. Despite the center of pressure parameters can characterize PD's body sway, they are limited to uncover underlying mechanisms of postural stability and instability.

RESEARCH QUESTION

Do a multiple domain analysis, including postural adaptability and rambling and trembling components, explain underlying postural stability and instability mechanisms in people with PD?

METHOD

Twenty-four individuals (12 people with PD and 12 neurologically healthy peers) performed three 60-s trials of upright quiet standing on a force platform. Traditional and non-linear parameters (Detrended Fluctuation Analysis- DFA and Multiscale Entropy- MSE) and rambling and trembling trajectories were calculated for anterior-posterior (AP) and medial-lateral (ML) directions.

RESULTS

PDG's postural control was worse compared to CG, displaying longer displacement, higher velocity, and RMS. Univariate analyses revealed largely longer displacement and RMS only for the AP direction and largely higher velocity for both AP and ML directions. Also, PD individuals showed lower AP complexity, higher AP and ML DFA, and increased AP and ML displacement, velocity, and RMS of rambling and trembling components compared to neurologically healthy individuals.

SIGNIFICANCE

Based upon these results, people with PD have a lower capacity to adapt posture and impaired both rambling and trembling components compared to neurologically healthy individuals. These findings provide new insights to explain the larger, faster, and more variable sway in people with PD.

Swallow Safety and Laryngeal Kinematics: A Comparison of Dysphagia Between Parkinson's Disease and Cerebrovascular Accident

BACKGROUND

Cerebrovascular accident (CVA) and Parkinson's disease (PD) are well established etiologies of dysphagia. However, differing physiological mechanisms underlying dysphagia may exist between these two causes. There have been limited investigations specifically comparing dysphagia between these two groups. Comparing dysphagia presentation in two different populations may improve clinical expectations, guide treatment approaches, and inform future research.

OBJECTIVE

This study examined the differences in presentation of dysphagia between PD and CVA. Dysphagia presentation, swallow safety, and laryngeal kinematics were compared between two clinical cohorts. What factors best predicted airway invasion in each group were explored.

METHODS

110 swallow studies of individuals with PD and CVA who were referred for swallowing evaluation were obtained. Each video was analyzed for quantitative dysphagia presentation using the Videofluoroscopic Dysphagia Scale (VDS), swallow safety using the Penetration-Aspiration scale, and kinematic timings of the laryngeal vestibule (time-to-laryngeal vestibule closure [LVC] and closure duration [LVCd]).

RESULTS

Frequencies of penetration or aspiration were similar between groups. The PD group displayed significantly greater pharyngeal stage swallow impairment than CVA, with more frequent reduced laryngeal elevation and increased vallecular residue. The CVA group displayed significantly greater oral stage impairment, with prolonged oral transit times. Time-to-LVC was significantly prolonged and was the strongest predictor of airway invasion in the PD group, but not for CVA.

CONCLUSION

Similar airway invasion rates for PD and CVA indicate the importance of screening for dysphagia in PD. Laryngeal kinematics as significant contributors to airway invasion in PD but not for CVA highlight the need for further research into these mechanisms and for targeted treatment approaches to dysphagia.

Effectiveness of Therapies Based on Mirror Neuron System to Treat Gait in Patients with Parkinson’s Disease—A Systematic Review

Parkinson’s disease (PD) is a neurodegenerative disease that alters gait patterns from early stages. The visuo-motor training strategies such as action observation (AO) and motor imagery (MI) that are based on the activity of the mirror neuron system (MNS) facilitate motor re-learning. The main purpose of this systematic review was to analyze the current scientific evidence about the effectiveness of MNS’s treatments (AO and MI) to treat gait in patients with PD. Searches were completed from the databases PubMed, Web of Science, and PEDro between November and December 2021. The following keywords were used: “Parkinson disease”, “mirror neurons”, “gait”, “action observation”, and “motor imagery”. Randomized control trials of the last 5 years written in English or Spanish were included. Two independent reviewers screened the articles and applied the eligibility criteria, and a third reviewer assisted in this process. A total of six articles were included for final revision. The risk of bias was assessed with the PEDro Scale. The effects of AO and MI using different outcome measures were referenced in terms of disease severity, quality of life, balance, and gait. Training with AO and MI are effective in improving disease severity, quality of life, balance, and gait in patients with PD.

The influence of visual feedback on alleviating freezing of gait in Parkinson's disease is reduced by anxiety

BACKGROUND

Previous research has established that anxiety is associated with freezing of gait (FOG) in Parkinson's disease (PD). Although providing body-related visual feedback has been previously suggested to improve FOG, it remains unclear whether anxiety-induced FOG might be improved.

RESEARCH QUESTION

The current study aimed to evaluate whether body-related visual feedback (VF) improves FOG consistently across low and high threat conditions.

METHODS

Sixteen PD patients with FOG were instructed to walk across a plank in a virtual environment that was either located on the ground (low threat) or elevated above a deep pit (high threat). Additionally, visual feedback (VF) was either provided (+) or omitted (-) using an avatar that was synchronised in real-time with the participants movements.

RESULTS

revealed that in the low threat condition (i.e., ground), %FOG was significantly reduced when VF was provided (VF+) compared to when VF was absent (VF-). In contrast, during the elevated high threat condition, there were no differences in %FOG regardless of whether VF was provided or not.

SIGNIFICANCE

These findings confirm that although VF can aid in the reduction of FOG, anxiety may interfere with freezers' ability to use sensory feedback to improve FOG and hence, in high threat conditions, VF was unable to aid in the reduction of FOG. Future studies should direct efforts towards the treatment of anxiety to determine whether better management of anxiety may improve FOG.

The Effectiveness of Proprioceptive Training for Improving Motor Performance and Motor Dysfunction: A Systematic Review

Objective

Proprioceptive training is any intervention aiming to improve proprioceptive function with the ultimate goal to enhance motor function and performance. It has been promoted as an approach to enhance athletic performance and as a tool for sensorimotor rehabilitation. Numerous studies sought to provide evidence on the effectiveness of the approach. However, many different training regimes claiming to train proprioception report a variety of sensorimotor measures that are not directly comparable. This, in turn, makes it difficult to assess effectiveness across approaches. It is the objective of this study to systematically review recent empirical evidence to gain an understanding of which outcome measures are most sensitive, which populations may benefit most from proprioceptive training, and what are the effects on proprioceptive and motor systems.

Methods

Four major databases were searched. The following inclusion criteria were applied: (1) A quantified pre- and post-treatment measure of proprioceptive function. (2) An intervention or training program believed to influence or enhance proprioceptive function. (3) Contained at least one form of treatment or outcome measure that is indicative of somatosensory function and not confounded by information from other sensory modalities. 4) The study reported of at least one quantified measure of motor performance.

Results

Of the 3,297 articles identified by the database search, 70 studies met the inclusion criteria and were included for further review. Across studies, proprioceptive training led to comparable gains in both proprioceptive (+46%) and motor performance (+45%). The majority of studies (50/70) applied active movement interventions. Interventions applying somatosensory stimulation were most successful in clinical populations. Joint position sense error (JPSE) was the most commonly used proprioceptive measure and presents a reliable and feasible measure for clinical use.

Conclusion

Proprioceptive training can lead to significant improvements in proprioceptive and motor function across a range healthy and clinical populations. Regimens requiring active movement of the trainee tended to be most successful in improving sensorimotor performance. Conclusive evidence on how long training gains are retained is still lacking. There is no solid evidence about the underlying long-term neuroplastic changes associated proprioceptive training.

Therapeutic Devices for Motor Symptoms in Parkinson’s Disease: Current Progress and a Systematic Review of Recent Randomized Controlled Trials

Background

Pharmacotherapy is the first-line treatment option for Parkinson’s disease, and levodopa is considered the most effective drug for managing motor symptoms. However, side effects such as motor fluctuation and dyskinesia have been associated with levodopa treatment. For these conditions, alternative therapies, including invasive and non-invasive medical devices, may be helpful. This review sheds light on current progress in the development of devices to alleviate motor symptoms in Parkinson’s disease.

Methods

We first conducted a narrative literature review to obtain an overview of current invasive and non-invasive medical devices and thereafter performed a systematic review of recent randomized controlled trials (RCTs) of these devices.

Results

Our review revealed different characteristics of each device and their effectiveness for motor symptoms. Although invasive medical devices are usually highly effective, surgical procedures can be burdensome for patients and have serious side effects. In contrast, non-pharmacological/non-surgical devices have fewer complications. RCTs of non-invasive devices, especially non-invasive brain stimulation and mechanical peripheral stimulation devices, have proven effectiveness on motor symptoms. Nearly no non-invasive devices have yet received Food and Drug Administration certification or a CE mark.

Conclusion

Invasive and non-invasive medical devices have unique characteristics, and several RCTs have been conducted for each device. Invasive devices are more effective, while non-invasive devices are less effective and have lower hurdles and risks. It is important to understand the characteristics of each device and capitalize on these.

A Fully-Immersive Virtual Reality Setup to Study Gait Modulation

Objective: Gait adaptation to environmental challenges is fundamental for independent and safe community ambulation. The possibility of precisely studying gait modulation using standardized protocols of gait analysis closely resembling everyday life scenarios is still an unmet need.

Methods: We have developed a fully-immersive virtual reality (VR) environment where subjects have to adjust their walking pattern to avoid collision with a virtual agent (VA) crossing their gait trajectory. We collected kinematic data of 12 healthy young subjects walking in real world (RW) and in the VR environment, both with (VR/A+) and without (VR/A-) the VA perturbation. The VR environment closely resembled the RW scenario of the gait laboratory. To ensure standardization of the obstacle presentation the starting time speed and trajectory of the VA were defined using the kinematics of the participant as detected online during each walking trial.

Results: We did not observe kinematic differences between walking in RW and VR/A-, suggesting that our VR environment per se might not induce significant changes in the locomotor pattern. When facing the VA all subjects consistently reduced stride length and velocity while increasing stride duration. Trunk inclination and mediolateral trajectory deviation also facilitated avoidance of the obstacle.

Conclusions: This proof-of-concept study shows that our VR/A+ paradigm effectively induced a timely gait modulation in a standardized immersive and realistic scenario. This protocol could be a powerful research tool to study gait modulation and its derangements in relation to aging and clinical conditions.

Predicting UPDRS Motor Symptoms in Individuals with Parkinsons Disease from Force Plates Using Machine Learning

Parkinsons disease (PD) is a neurodegenerative disease that affects motor abilities with increasing severity as the disease progresses. Traditional methods for diagnosing PD include a section where a trained specialist scores qualitative symptoms using the motor subscale of the Unified Parkinsons Disease Rating Scale (UPDRS-III). The aim of this feasibility study was twofold. First, to evaluate quiet standing as an additional, out-of-clinic, objective feature to predict UPDRS-III subscores related to motor symptom severity; and second, to use quiet standing to detect the presence of motor symptoms. Force plate data were collected from 42 PD patients and 43 healthy controls during quiet standing (a task involving standing still with eyes open and closed) as a feasible task in clinics. Predicting each subscore of the UPDRS-III could aid in identifying progression of PD and provide specialists additional tools to make an informed diagnosis. Random Forest feature importance indicated that features correlated with range of center of pressure (i.e. the medial-lateral and anterior-posterior sway) were most useful in the prediction of the top PD prediction subscores of postural stability (r = 0.599; p = 0.014), hand tremor of the left hand (r = 0.650; p = 0.015), and tremor at rest of the left upper extremity (r = 0.703; p = 0.016). Quiet standing can detect body bradykinesia (AUC-ROC = 0.924) and postural stability (AUC-ROC = 0.967) with high predictability. Although there are limited data, these results should be used as a feasibility study that evaluates the predictability of individual UPDRS-III subscores using quiet standing data.

The Impact of Parkinson's Disease on General and Specific Motor Aptitudes: A Study of Older Brazilian Adults

This study investigated motor aptitude in older adults with and without Parkinson's disease (PD) to further specify known motor-related changes of PD. We divided 671 older adults (23.5% male; M_age = 69.6, SD = 6.6 years) into a Parkinson's Disease Group (PDG) and a non-Parkinson's Disease Group (NPG) and assessed their general motor aptitude (GMA) and their specific motor aptitudes (in Coordinative, Proprioceptive, and Perceptive domains) using the Motor Scale for Older Adults. We used the chi-squared tests and logistic regression to identify and affirm an associations between PD and motor aptitude, we found that most adults without PD showed normal motor aptitude (GMA: 80.7%; Proprioceptive: 82.3%; Perceptive: 81.4%) except for the Coordinative skills, for which 56.4% of these participants had motor impairment. Most partipants with PD showed motor impairments (GMA: 94.7%; Coordinative: 97.4%; Proprioceptive: 97.4%), except in the Perceptive domain, for which 68.4% of participants with PD showed normal aptitude. There were significant associations between PD and GMA (OR = 127.6), Coordinative motor skills (OR = 48.0), and Proprioceptive skills (OR = 204.4), even after the model was adjusted for gender and age. Our use of the Motor Scale for Older Adults in contrasting groups of older Brazilian adults provides further specificity to the motor aptitude characteristics of older adults with PD.

Analysis of Movement Entropy during Community Dance Programs for People with Parkinson's Disease and Older Adults: A Cohort Study

Dance therapy can improve motor skills, balance, posture, and gait in people diagnosed with Parkinson’s disease (PD) and healthy older adults (OA). It is not clear how specific movement patterns during dance promote these benefits. The purpose of this cohort study was to identify differences and complexity in dance movement patterns among different dance styles for PD and OA participants in community dance programs using approximate entropy (ApEn) analysis. The hypothesis was that PD participants will show greater ApEn during dance than OA participants and that the unique dance style of tango with more pronounced foot technique and sharp direction changes will show greater ApEn than smoother dance types such as foxtrot and waltz characterized by gradual changes in direction and gliding movement with rise and fall. Individuals participated in one-hour community dance classes. Movement data were captured using porTable 3D motion capture sensors attached to the arms, torso and legs. Classes were also video recorded to assist in analyzing the dance steps. Movement patterns were captured and ApEn was calculated to quantify the complexity of movements. Participants with PD had greater ApEn in right knee flexion during dance movements than left knee flexion (p = 0.02), greater ApEn of right than left hip flexion (p = 0.05), and greater left hip rotation than right (p = 0.03). There was no significant difference in ApEn of body movements (p > 0.4) or mean body movements (p > 0.3) at any body-segment in OA. ApEn analysis is valuable for quantifying the degree of control and predictability of dance movements and could be used as another tool to assess the movement control of dancers and aid in the development of dance therapies.

Reaching and Grasping Movements in Parkinson's Disease: A Review

Parkinson's disease (PD) is known to affect the brain motor circuits involving the basal ganglia (BG) and to induce, among other signs, general slowness and paucity of movements. In upper limb movements, PD patients show a systematic prolongation of movement duration while maintaining a sufficient level of endpoint accuracy. PD appears to cause impairments not only in movement execution, but also in movement initiation and planning, as revealed by abnormal preparatory activity of motor-related brain areas. Grasping movement is affected as well, particularly in the coordination of the hand aperture with the transport phase. In the last fifty years, numerous behavioral studies attempted to clarify the mechanisms underlying these anomalies, speculating on the plausible role that the BG-thalamo-cortical circuitry may play in normal and pathological motor control. Still, many questions remain open, especially concerning the management of the speed-accuracy tradeoff and the online feedback control. In this review, we summarize the literature results on reaching and grasping in parkinsonian patients. We analyze the relevant hypotheses on the origins of dysfunction, by focusing on the motor control aspects involved in the different movement phases and the corresponding role played by the BG. We conclude with an insight into the innovative stimulation techniques and computational models recently proposed, which might be helpful in further clarifying the mechanisms through which PD affects reaching and grasping movements.

Swallow Safety and Laryngeal Kinematics: A Comparison of Dysphagia Between Parkinson's Disease and Cerebrovascular Accident

BACKGROUND

Cerebrovascular accident (CVA) and Parkinson's disease (PD) are well established etiologies of dysphagia. However, differing physiological mechanisms underlying dysphagia may exist between these two causes. There have been limited investigations specifically comparing dysphagia between these two groups. Comparing dysphagia presentation in two different populations may improve clinical expectations, guide treatment approaches, and inform future research.

OBJECTIVE

This study examined the differences in presentation of dysphagia between PD and CVA. Dysphagia presentation, swallow safety, and laryngeal kinematics were compared between two clinical cohorts. What factors best predicted airway invasion in each group were explored.

METHODS

110 swallow studies of individuals with PD and CVA who were referred for swallowing evaluation were obtained. Each video was analyzed for quantitative dysphagia presentation using the Videofluoroscopic Dysphagia Scale (VDS), swallow safety using the Penetration-Aspiration scale, and kinematic timings of the laryngeal vestibule (time-to-laryngeal vestibule closure [LVC] and closure duration [LVCd]).

RESULTS

Frequencies of penetration or aspiration were similar between groups. The PD group displayed significantly greater pharyngeal stage swallow impairment than CVA, with more frequent reduced laryngeal elevation and increased vallecular residue. The CVA group displayed significantly greater oral stage impairment, with prolonged oral transit times. Time-to-LVC was significantly prolonged and was the strongest predictor of airway invasion in the PD group, but not for CVA.

CONCLUSION

Similar airway invasion rates for PD and CVA indicate the importance of screening for dysphagia in PD. Laryngeal kinematics as significant contributors to airway invasion in PD but not for CVA highlight the need for further research into these mechanisms and for targeted treatment approaches to dysphagia.

Use of Real-time Multimodal Sensory Feedback Home Program Improved Backward Stride and Retention for People with Parkinson Disease: a Pilot Study

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Multimodal sensory feedback with home exercises increased backward stride for PwPD.

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Retention of gains occurred 6 weeks after exercise ended for participants using MMSF.

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The MMSF home program improvements were likely due to integration of proprioception.

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Outcomes were highly rated by MMSF participants on a Perceived Outcome Scale.

Introduction

Parkinson disease (PD) impairs sensory integration, contributes to motor dysfunction, loss of gait automaticity, and increased fall risk. Employing multimodal sensory feedback (MMSF) has the potential to improve proprioceptive integration and gait safety while reducing exercise burden especially for backward gait.

Methods

This single-blinded, randomized controlled pilot study used a home program with or without real-time visual, proprioceptive, and auditory feedback with stepping exercises which progressed in speed and distance. Both groups completed a six-week intervention followed by 6 weeks without exercise to assess long-term retention. Six additional weeks of exercises were completed to assess recovery of potential losses after the washout session.

Eleven people with PD exercised with real-time MMSF and 7 exercised without MMSF. Outcome measures included backward stride length, velocity, cadence, and double support time. The Dual Timed Up and Go measured automaticity. Self-perceived improvements in gait, activities of daily living, participation, and quality of life were registered by a questionnaire.

Results

Analysis was by repeated measures ANOVA. Using MMSF significantly improved backward stride length at 12 and 18 weeks, p = .007, η² = 0.239. Both groups improved in all outcome measures after the initial 6-week exercise program, supporting efficacy of stepping exercises. The MMSF + ex group's significant improvements after a 6-week washout supported automaticity development. Questionnaire items received higher agreement percentages from MMSF + ex participants.

Conclusion

Using real-time MMSF in a home program for pwPD provided significant and lasting improvements in backward stride, and potentially decreased fall risk and exercise burden compared to the same program without MMSF.

Quantitative trunk sway analysis under challenging gait conditions in early and untreated Parkinson's disease

INTRODUCTION

Even experienced clinicians may encounter difficulties in making a definitive diagnosis in the early motor stages of Parkinson's disease (PD). We investigated whether quantitative biomechanical trunk sway analysis could support the diagnosis of PD early on.

METHODS

We quantified trunk sway performance using body-worn sensors during a test battery of six challenging gait conditions in a cohort of 17 early and untreated PD patients (with evidence of reduced tracer uptake in the basal ganglia on dopamine transporter scans) and 17 age- and sex-matched healthy controls (HCs).

RESULTS

Compared to HC, the PD group (Hoehn & Yahr ≤ 2, Unified Parkinson's Disease Rating Scale motor score: mean 13.7 ± 3.5 points) showed significant trunk rigidity in five challenging gait tasks (decreased medio-lateral direction and sway angle area). Post hoc receiver operating characteristic analysis of the significant parameters revealed excellent discrimination with high sensitivity and specificity.

CONCLUSION

In the early and untreated motor stages of PD, patients exhibit significant trunk rigidity during challenging gait tasks. Trunk sway motion recorded with body-worn sensors might be a useful tool to disclose a sometimes hard-to-trace cardinal motor sign of PD and support an early clinical diagnosis.

Study on the Influence of Proprioceptive Control versus Visual Control on Reaction Speed, Hand Coordination, and Lower Limb Balance in Young Students 14-15 Years Old

Currently, sports activities require a high reaction speed, coordination, and balance, highlighting the relationship between proprioceptive control, visual control, and hand–eye coordination in youth. The present research assessed the proprioceptive control, reaction speed, and lower limb balance of youth from five different schools to identify the level of physical preparation of children in this direction. This prospective study was conducted between 1 January 2020 and 29 February 2020. A total of 107 healthy children (33 females and 74 males) with appropriate medical conditions, aged between 14 and 15 years, from five Romanian schools were included in the experiment. All children were assessed for visual control and reaction speed with the ruler drop test, and for lower limb balance, the standing stork test was used. Statistical analysis included descriptive statistics, data series distribution, and comparison of means and medians using specific statistical programs. Comparison of medians highlighted significant statistical differences in the standing stork test with eyes closed and the dominant leg compared with the nondominant leg (p = 0.0057). Males were compared to females at the nondominant leg (p = 0.0179); closed eyes were compared with opened eyes for the nondominant leg (p = 0.0175 and 0.0006) for the ruler drop test comparing the dominant hand with the nondominant hand (p = 0.0212). Children who engage in sports activities better integrated sensory information in motor action execution based on reaction speed and coordination with the nondominant hand.

Using virtual reality to assess vestibulo-visual interaction in people with Parkinson's disease compared to healthy controls

People with Parkinson's disease (PD) have increased visual dependency for balance and suspected vestibular dysfunction. Immersive virtual reality (VR) allows graded manipulation of visual sensory inputs during balance tasks, and hence VR coupled with portable force platforms have emerged as feasible, affordable, and validated tools for assessing sensory-motor integration of balance. This study aims to determine (i) how people with PD perform on a VR-based visual perturbation standing balance task compared to healthy controls (HC), and (ii) whether balance performance is influenced by vestibular function, when other known factors are controlled for. This prospective observational study compared the balance performance under varying sensory conditions in 40 people with mild to moderate PD with 40 age-matched HC. Vestibular function was assessed via Head Impulse Test (HIMP), cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs) and subjective visual vertical (SVV). Regression analyses were used to determine associations between VR balance performance on firm and foam surfaces with age, group, vestibular function, and lower limb proprioception. PD failed at significantly lower levels of visual perturbation than HC on both surfaces. In PD, greater disease severity was significantly associated with lower fall thresholds on both surfaces. Multiple PD participants failed prior to visual perturbation on foam. On firm, PD had a greater visual dependency. Increasing age, impaired proprioception, impaired SVV, abnormal HIMP and cVEMP scores were associated with worse balance performance. The multivariate model containing these factors explained 29% of the variability in balance performance on both surfaces. Quantitative VR-based balance assessment is safe and feasible in PD. Balance performance on both surfaces was associated with age, HIMP abnormality and proprioception.

Altered microstructural properties of superficial white matter in patients with Parkinson's disease

Parkinson's disease (PD), a chronic neurodegenerative disease, is characterized by sensorimotor and cognitive deficits. Previous diffusion tensor imaging (DTI) studies found abnormal DTI metrics in white matter bundles, such as the corpus callosum, cingulate, and frontal-parietal bundles, in PD patients. These studies mainly focused on alterations in microstructural features of long-range bundles within the deep white matter (DWM) that connects pairs of distant cortical regions. However, less is known about the DTI metrics of the superficial white matter (SWM) that connects local cortical regions in PD patients. To determine whether the DTI metrics of the SWM were different between the PD patients and the healthy controls, we recruited DTI data from 34 PD patients and 29 gender- and age-matched healthy controls. Using a probabilistic tractographic approach, we first defined a population-based SWM mask across all the subjects. Using a tract-based spatial statistical (TBSS) analytic approach, we then identified the SWM bundles showing abnormal DTI metrics in the PD patients. We found that the PD patients showed significantly lower DTI metrics in the SWM bundles connecting the sensorimotor cortex, cingulate cortex, posterior parietal cortex (PPC), and parieto-occipital cortex than the healthy controls. We also found that the clinical measures in the PD patients was significantly negatively correlated with the fractional anisotropy in the SWM (FA_SWM) that connects core regions in the default mode network (DMN). The FA_SWM in the bundles that connected the PPC was significantly positively correlated with cognitive performance in the PD patients. Our findings suggest that SWM may serve as the brain structural basis underlying the sensorimotor deficits and cognitive degeneration in PD patients.

Relationship between Trunk Position Sense and Trunk Control in Children with Spastic Cerebral Palsy: A Cross-Sectional Study

METHODS

In this study, 24 children with spastic CP aged between 8 and 15 years were recruited. They were classified based on their functional performance using Gross Motor Function Classification System (GMFCS). Trunk control and trunk position sense were assessed using the trunk control measurement scale (TCMS) and digital goniometer, respectively. The correlation between these variables was tested using Spearman's correlation coefficient.

RESULTS

Significant negative correlation was found between trunk position sense and TCMS score. Similarly, a significant moderate correlation was found between trunk position sense and GMFCS. A strong negative correlation was also found between GMFCS and TCMS.

CONCLUSION

Children with spastic CP with better trunk position sense had better trunk control. Similarly, children with higher functional performance had better trunk control and lesser error in trunk position sense. The current findings imply the relevance of proprioceptive training of the trunk for enhancing trunk motor control in children with spastic CP.

A new approach of inducing proprioceptive illusion by transcutaneous electrical stimulation

BACKGROUND

Neurotraumas or neurodegenerative diseases often result in proprioceptive deficits, which makes it challenging for the nervous system to adapt to the compromised sensorimotor conditions. Also, in human machine interactions, such as prosthesis control and teleoperation, proprioceptive mismatch limits accuracy and intuitiveness of controlling active joints in robotic agents. To address these proprioceptive deficits, several invasive and non-invasive approaches like vibration, electrical nerve stimulation, and skin stretch have been introduced. However, proprioceptive modulation is still challenging as the current solutions have limitations in terms of effectiveness, usability, and consistency. In this paper, we propose a new way of modulating proprioception using transcutaneous electrical stimulation. We hypothesized that transcutaneous electrical stimulation on elbow flexor muscles will induce illusion of elbow joint extension.

METHOD

Eight healthy human subjects participated in the study to test the hypothesis. Transcutaneous electrodes were placed on different locations targeting elbow flexor muscles on human subjects and experiments were conducted to identify the best locations for electrode placement, and best electrical stimulation parameters, to maximize induced proprioceptive effect. Arm matching experiments and Pinocchio illusion test were performed for quantitative and qualitative analysis of the observed effects. One-way repeated ANOVA test was performed on the data collected in arm matching experiment for statistical analysis.

RESULTS

We identified the best location for transcutaneous electrodes to induce the proprioceptive illusion, as one electrode on the muscle belly of biceps brachii short head and the other on the distal myotendinous junction of brachioradialis. The results for arm-matching and Pinocchio illusion tests showed that transcutaneous electrical stimulation using identified electrode location and electrical stimulation parameters evoked the illusion of elbow joint extension for all eight subjects, which supports our hypothesis. On average, subjects reported 6.81° angular illusion of elbow joint extension in arm-matching tests and nose elongated to 1.78 × height in Pinocchio illusion test.

CONCLUSIONS

Transcutaneous electrical stimulation, applied between the the synergistic elbow flexor muscles, consistently modulated elbow joint proprioception with the illusion of elbow joint extension, which has immense potential to be translated into various real-world applications, including neuroprosthesis, rehabilitation, teleoperation, mixed reality, and etc.