A mismatch between kinesthetic and visual perception in Parkinson's disease

The lateralized effects of Parkinson's Disease on motor imagery: Evidence from mental chronometry

Alterations to the content of action representations may contribute to the movement challenges that characterize Parkinson's Disease (PD). One way to investigate action representations is through motor imagery. As PD motor symptoms typically have a unilateral onset, disease-related deficits related to action representations may follow a similarly lateralized pattern. The present study examined if temporal accuracy of motor imagery in individuals with PD differed according to the side of the body involved in the task. Thirty-eight participants with PD completed a mental chronometry task using their more affected and less affected side. Participants had significantly shorter mental versus physical movement times for the more affected. Higher imagery vividness in the kinaesthetic domain predicted shorter mental versus physical movement times for the more affected side, as did lower imagery vividness in the visual domain and poorer cognitive function. These results indicate that people with PD imagine movements differently when the target actions their more affected versus less affected side. It is additionally possible that side-specific deficits in the accurate processing of kinaesthetic information lead to an increased reliance on visual processes and cognitive resources to successfully execute motor imagery involving the more affected side.

Treatment of Hypophonia in Parkinson's Disease Through Biofeedback in Daily Life Administered with A Portable Voice Accumulator

OBJECTIVES

The purpose of this study was to assess the outcome following continuous tactile biofeedback of voice sound level administered, with a portable voice accumulator to individuals with Parkinson's disease (PD).

METHOD

Nine out of 16 participants with PD completed a 4-week intervention program where biofeedback of voice sound level was administered with the portable voice accumulator VoxLog during speech in daily life. The feedback, a tactile vibration signal from the device, was activated when the wearer used a voice sound level below an individually predetermined threshold level, reminding the wearer to increase voice sound level during speech. Voice use was registered in daily life with the VoxLog during the intervention period as well as during one baseline week, one follow-up week post intervention and 1 week 3 months post intervention. Self-to-other ratio (SOR), which is the difference between voice sound level and environmental noise, was studied in multiple noise ranges.

RESULTS

A significant increase in SOR across all noise ranges of 2.28 dB (SD: 0.55) was seen for participants with scores above the cut-off for normal function (>26 points) on the cognitive screening test Montreal Cognitive Assessment (MoCA) (n = 5). No significant increase was seen for the group of participants with MoCA scores below 26 (n = 4). Forty-four percent ended their participation early, all which scored below 26 on MoCA (n = 7).

CONCLUSIONS

Biofeedback administered in daily life regarding voice level may help individuals with PD to increase their voice sound level in relation to environmental noise in daily life, but only for a limited subset. Only participants with normal cognitive function as screened by MoCA improved their voice sound level in relation to environmental noise.

Rethinking Movement Disorders

At present, clinical practice and research in movement disorders (MDs) focus on the "normalization" of altered movements. In this review, rather than concentrating on problems and burdens people with MDs undoubtedly have, we highlight their hidden potentials. Starting with current definitions of Parkinson's disease (PD), dystonia, chorea, and tics, we outline that solely conceiving these phenomena as signs of dysfunction falls short of their complex nature comprising both problems and potentials. Such potentials can be traced and understood in light of well-established cognitive neuroscience frameworks, particularly ideomotor principles, and their influential modern derivatives. Using these frameworks, the wealth of data on altered perception-action integration in the different MDs can be explained and systematized using the mechanism-oriented concept of perception-action binding. According to this concept, MDs can be understood as phenomena requiring and fostering flexible modifications of perception-action associations. Consequently, although conceived as being caught in a (trough) state of deficits, given their high flexibility, people with MDs also have high potential to switch to (adaptive) peak activity that can be conceptualized as hidden potentials. Currently, clinical practice and research in MDs are concerned with deficits and thus the "deep and wide troughs," whereas "scattered narrow peaks" reflecting hidden potentials are neglected. To better delineate and utilize the latter to alleviate the burden of affected people, and destigmatize their conditions, we suggest some measures, including computational modeling combined with neurophysiological methods and tailored treatment. © 2024 International Parkinson and Movement Disorder Society.

Grid cells: the missing link in understanding Parkinson's disease?

The mechanisms underlying Parkinson's disease (PD) are complex and not fully understood, and the box-and-arrow model among other current models present significant challenges. This paper explores the potential role of the allocentric brain and especially its grid cells in several PD motor symptoms, including bradykinesia, kinesia paradoxa, freezing of gait, the bottleneck phenomenon, and their dependency on cueing. It is argued that central hubs, like the locus coeruleus and the pedunculopontine nucleus, often narrowly interpreted in the context of PD, play an equally important role in governing the allocentric brain as the basal ganglia. Consequently, the motor and secondary motor (e.g., spatially related) symptoms of PD linked with dopamine depletion may be more closely tied to erroneous computation by grid cells than to the basal ganglia alone. Because grid cells and their associated central hubs introduce both spatial and temporal information to the brain influencing velocity perception they may cause bradykinesia or hyperkinesia as well. In summary, PD motor symptoms may primarily be an allocentric disturbance resulting from virtual faulty computation by grid cells revealed by dopamine depletion in PD.

An Overview of the Body Schema and Body Image: Theoretical Models, Methodological Settings and Pitfalls for Rehabilitation of Persons with Neurological Disorders

Given the widespread debate on the definition of the terms "Body Schema" and "Body Image", this article presents a broad overview of the studies that have investigated the nature of these types of body representations, especially focusing on the innovative information about these two representations that could be useful for the rehabilitation of patients with different neurological disorders with motor deficits (especially those affecting the upper limbs). In particular, we analyzed (i) the different definitions and explicative models proposed, (ii) the empirical settings used to test them and (iii) the clinical and rehabilitative implications derived from the application of interventions on specific case reports. The growing number of neurological diseases with motor impairment in the general population has required the development of new rehabilitation techniques and a new phenomenological paradigm placing body schema as fundamental and intrinsic parts for action in space. In this narrative review, the focus was placed on evidence from the application of innovative rehabilitation techniques and case reports involving the upper limbs, as body parts particularly involved in finalistic voluntary actions in everyday life, discussing body representations and their functional role.

Anticipatory Postural Adjustments and Compensatory Postural Responses to Multidirectional Perturbations-Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Postural instability is one of the most restricting motor symptoms for patients with Parkinson's disease (PD). While medication therapy only shows minor effects, it is still unclear whether medication in conjunction with deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves postural stability. Hence, the aim of this study was to investigate whether PD patients treated with medication in conjunction with STN-DBS have superior postural control compared to patients treated with medication alone.

METHODS

Three study groups were tested: PD patients on medication (PD-MED), PD patients on medication and on STN-DBS (PD-MED-DBS), and healthy elderly subjects (HS) as a reference. Postural performance, including anticipatory postural adjustments (APA) prior to perturbation onset and compensatory postural responses (CPR) following multidirectional horizontal perturbations, was analyzed using force plate and electromyography data.

RESULTS

Regardless of the treatment condition, both patient groups showed inadequate APA and CPR with early and pronounced antagonistic muscle co-contractions compared to healthy elderly subjects. Comparing the treatment conditions, study group PD-MED-DBS only showed minor advantages over group PD-MED. In particular, group PD-MED-DBS showed faster postural reflexes and tended to have more physiological co-contraction ratios.

CONCLUSION

medication in conjunction with STN-DBS may have positive effects on the timing and amplitude of postural control.

The effects of supervised and non-supervised upper limb virtual reality exercises on upper limb sensory-motor functions in patients with idiopathic Parkinson's disease

BACKGROUND

Impairments of upper limb (UL) sensory-motor functions are common in Parkinson's disease (PD). Virtual reality exercises may improve sensory-motor functions in a safe environment and can be used in tele-rehabilitation. This study aimed to investigate the effects of supervised and non-supervised UL virtual reality exercises (ULVRE) on UL sensory-motor functions in patients with idiopathic PD.

METHODS

In this clinical trial study, 45 patients with idiopathic PD (29 male) by mean ± SD age of 58.64 ± 8.69 years were randomly allocated to either the control group (conventional rehabilitation exercises), supervised ULVRE or non-supervised ULVRE. Interventions were 24 sessions, 3 sessions/week. Before/after of interventions and follow-up period all assessment was done. Hand Active Sensation Test and Wrist Position Sense Test were used for assessing UL sensory function. Gross and fine manual dexterity were assessed by Box-Block Test and Nine-Hole Peg Test, respectively. Grip and pinch strength were evaluated by a dynamometer and pinch gauge, respectively.

RESULTS

The results showed significant improvement in discriminative sensory function (HAST-weight and HAST-total), wrist proprioception, gross manual dexterity and grip strength of both less and more affected hands as well as fine manual dexterity of the more affected hand in the three groups in patients with idiopathic PD (P < 0.05).

CONCLUSION

The results of this study indicated that both supervised and non-supervised ULVRE using the Kinect device might potentially improve some aspects of UL sensory-motor functions in patients with PD. Therefore, ULVRE using the Kinect device can be used in tele-rehabilitation, especially in the current limitations induced by the COVID-19 pandemic, for improving UL functions in patients with PD.

Neurofeedback-guided kinesthetic motor imagery training in Parkinson's disease: Randomized trial

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Parkinson’s disease causes difficulty with sustained motor performance.

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Insula and dorsomedial frontal cortex (dmFC) are implicated in motivating movement.

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Regulation of insula-dmFC functional connectivity with neurofeedback (NF) failed.

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Motor imagery practice regardless of NF improved motor function and body awareness.

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Visual imagery practice without NF also improved motor function.

Background

Parkinson’s disease (PD) causes difficulty with maintaining the speed, size, and vigor of movements, especially when they are internally generated. We previously proposed that the insula is important in motivating intentional movement via its connections with the dorsomedial frontal cortex (dmFC). We demonstrated that subjects with PD can increase the right insula-dmFC functional connectivity using fMRI-based neurofeedback (NF) combined with kinesthetic motor imagery (MI). The current study is a randomized clinical trial testing whether NF-guided kinesthetic MI training can improve motor performance and increase task-based and resting-state right insula-dmFC functional connectivity in subjects with PD.

Methods

We assigned nondemented subjects with mild PD (Hoehn & Yahr stage ≤ 3) to the experimental kinesthetic MI with NF (MI-NF, n = 22) and active control visual imagery (VI, n = 22) groups. Only the MI-NF group received NF-guided MI training (10–12 runs). The NF signal was based on the right insula-dmFC functional connectivity strength. All subjects also practiced their respective imagery tasks at home daily for 4 weeks. Post-training changes in 1) task-based and resting-state right insula-dmFC functional connectivity were the primary imaging outcomes, and 2) MDS-UPDRS motor exam and motor function scores were the primary and secondary clinical outcomes, respectively.

Results

The MI-NF group was not significantly different from the VI group in any of the primary imaging or clinical outcome measures. The MI-NF group reported subjective improvement in kinesthetic body awareness. There was significant and comparable improvement only in motor function scores in both groups (secondary clinical outcome). This improvement correlated with NF regulation of the right insula-dmFC functional connectivity only in the MI-NF group. Both groups showed specific training effects in whole-brain functional connectivity with distinct neural circuits supporting kinesthetic motor and visual imagery (exploratory imaging outcome).

Conclusions

The functional connectivity-based NF regulation was unsuccessful, however, both kinesthetic MI and VI practice improved motor function in our cohort with mild PD.

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.

Influence of radial optic flow stimulation on static postural balance in Parkinson's disease: A preliminary study

The role of optic flow in the control of balance in persons with Parkinson's disease (PD) has yet to be studied. Since basal ganglia are understood to have a role in controlling ocular fixation, we have hypothesized that persons with PD would exhibit impaired performance in fixation tasks, i.e., altered postural balance due to the possible relationships between postural disorders and visual perception. The aim of this preliminary study was to investigate how people affected by PD respond to optic flow stimuli presented with radial expanding motion, with the intention to see how the stimulation of different retinal portions may alter the static postural sway. We measured the body sway using center of pressure parameters recorded from two force platforms during the presentation of the foveal, peripheral and full field radial optic flow stimuli. Persons with PD had different visual responses in terms of fixational eye movement characteristics, with greater postural alteration in the sway area and in the medio-lateral direction than the age-matched control group. Balance impairment in the medio-lateral oscillation is often observed in persons with atypical Parkinsonism, but not in Parkinson's disease. Persons with PD are more dependent on visual feedback with respect to age-matched control subjects, and this could be due to their impaired peripheral kinesthetic feedback. Visual stimulation of standing posture would provide reliable signs in the differential diagnosis of Parkinsonism.

Abnormal Vision-Based Displacement Perception in Parkinson's Disease

In this work, we investigate the effect of Parkinson’s disease (PD), and common corresponding therapies on vision-based perception of motion, a critical perceptual ability required for performing a wide range of activities of daily livings. While PD has been recognized as mainly a motor disorder, sensory manifestation of PD can also play a major role in the resulting disability. In this paper, for the first time, the effect of disease duration and common therapies on vision-based perception of displacement were investigated. The study is conducted in a movement-independent manner, to reject the shadowing effects and isolate the targeted perceptual disorder to the maximum possible extent. Data was collected using a computerized graphical tool on 37 PD patients [6 early-stage de novo, 25 mid-stage using levodopa therapy, six later-stage using deep brain stimulation (DBS)] and 15 control participants. Besides the absolute measurement of perception through a psychometric analysis on two tested position reference magnitudes, we also investigated the linearity in perception using Weber’s fraction. The results showed that individuals with PD displayed significant perceptual impairments compared to controls, though early-stage patients were not impaired. Mid-stage patients displayed impairments at the greater of the two tested reference magnitudes, while late-stage patients were impaired at both reference magnitudes. Levodopa and DBS use did not cause statistically significant differences in absolute displacement perception. The findings suggest abnormal visual processing in PD increasing with disease development, perhaps contributing to sensory-based impairments of PD such as bradykinesia, visuospatial deficits, and abnormal object recognition.

Stability of Action and Kinesthetic Perception in Parkinson's Disease

We present a review of action and perception stability within the theoretical framework based on the idea of control with spatial referent coordinates for the effectors at a number of hierarchical levels. Stability of salient variables is ensured by synergies, neurophysiological structures that act in multi-dimensional spaces of elemental variables and limit variance to the uncontrolled manifold during action and iso-perceptual manifold during perception. Patients with Parkinson’s disease show impaired synergic control reflected in poor stability (low synergy indices) and poor agility (low indices of anticipatory synergy adjustments prior to planned quick actions). They also show impaired perception across modalities, including kinesthetic perception. We suggest that poor stability at the level of referent coordinates can be the dominant factor leading to poor stability of percepts.

Subthalamic Deep Brain Stimulation Modulates Proprioceptive Integration in Parkinson's Disease During a Postural Task

Defective proprioceptive integration may play a role in the pathophysiology of motor symptoms in Parkinson's disease (PD). Dysfunction related to proprioceptively-evoked postural reactions in PD patients is still a controversial issue, with only a limited number of studies to date and mostly discordant results. The aims of the present study were (1) to determine whether or not the proprioceptive defect in PD underlies postural impairment and (2) whether or not deep brain stimulation of the subthalamic nucleus (STN-DBS) affects proprioceptive integration. We examined proprioceptive integration during a postural task in 13 PD patients and 12 age-matched control subjects, using a muscle-tendon vibration paradigm. Analysis of the center of pressure displacement and kinematic data indicates a greater degree of postural destabilization and a reduced ability to maintain a vertical orientation in PD. We found a significant positive effect of STN-DBS on these postural features. Our findings indicate that Parkinson patients, even in the absence of any clinical evidence of instability, falls, or freezing, use proprioceptive information for postural control less efficiently than healthy subjects. Furthermore, STN-DBS was found to improve proprioceptive integration, with positive impacts on postural orientation and balance.

Evolving concepts on bradykinesia

Bradykinesia is one of the cardinal motor symptoms of Parkinson's disease and other parkinsonisms. The various clinical aspects related to bradykinesia and the pathophysiological mechanisms underlying bradykinesia are, however, still unclear. In this article, we review clinical and experimental studies on bradykinesia performed in patients with Parkinson's disease and atypical parkinsonism. We also review studies on animal experiments dealing with pathophysiological aspects of the parkinsonian state. In Parkinson's disease, bradykinesia is characterized by slowness, the reduced amplitude of movement, and sequence effect. These features are also present in atypical parkinsonisms, but the sequence effect is not common. Levodopa therapy improves bradykinesia, but treatment variably affects the bradykinesia features and does not significantly modify the sequence effect. Findings from animal and patients demonstrate the role of the basal ganglia and other interconnected structures, such as the primary motor cortex and cerebellum, as well as the contribution of abnormal sensorimotor processing. Bradykinesia should be interpreted as arising from network dysfunction. A better understanding of bradykinesia pathophysiology will serve as the new starting point for clinical and experimental purposes.

'Draw your pelvis' test for assessing pelvic schema in people with Parkinson's disease: a validity and reliability study

Aim: Body schema (i.e., the mental representation of the body and its parts) is important for cognitive and motor functions, with the pelvis constituting a core element in such schema. Although people with Parkinson's disease exhibit misperceptions and deficits in body schema, there are currently no published tools available for assessing pelvic schema in this population. This study aimed to develop and establish feasibility, reliability, and validity of a novel drawing test - 'Draw Your Pelvis' - for assessing pelvic schema in people with Parkinson's disease. Materials and methods: Twenty people with idiopathic Parkinson's disease (Hoehn &Yahr stages I-III; M age: 65.75 ± 10.13) volunteered and were asked to manually draw a picture of their pelvis. Drawings were assessed and scored by 13 blinded raters over two sessions. Intra- and inter-rater reliability and content and criterion validity were investigated. Results: The 'Draw Your Pelvis' test is shown to be feasible and quick to administer, with excellent inter-rater reliability for consistency (0.954-0.968) and absolute agreement (0.946-0.961). It also demonstrates good-excellent (0.614-0.950) intra-rater reliability, and is content valid. Conclusions: The 'Draw Your Pelvis' test holds potential for clinicians and researchers in assessing pelvic schema and its deficits in people with Parkinson's disease. In addition, this test could be used for investigating the effect of therapeutic interventions on body schema in this population. Future studies should explore this test in additional populations.

Fast Intracortical Sensory-Motor Integration: A Window Into the Pathophysiology of Parkinson's Disease

Parkinson's Disease (PD) is a prototypical basal ganglia disorder. Nigrostriatal dopaminergic denervation leads to progressive dysfunction of the cortico-basal ganglia-thalamo-cortical sensorimotor loops, causing the classical motor symptoms. Although the basal ganglia do not receive direct sensory input, they are important for sensorimotor integration. Therefore, the basal ganglia dysfunction in PD may profoundly affect sensory-motor interaction in the cortex. Cortical sensorimotor integration can be probed with transcranial magnetic stimulation (TMS) using a well-established conditioning-test paradigm, called short-latency afferent inhibition (SAI). SAI probes the fast-inhibitory effect of a conditioning peripheral electrical stimulus on the motor response evoked by a TMS test pulse given to the contralateral primary motor cortex (M1). Since SAI occurs at latencies that match the peaks of early cortical somatosensory potentials, the cortical circuitry generating SAI may play an important role in rapid online adjustments of cortical motor output to changes in somatosensory inputs. Here we review the existing studies that have used SAI to examine how PD affects fast cortical sensory-motor integration. Studies of SAI in PD have yielded variable results, showing reduced, normal or even enhanced levels of SAI. This variability may be attributed to the fact that the strength of SAI is influenced by several factors, such as differences in dopaminergic treatment or the clinical phenotype of PD. Inter-individual differences in the expression of SAI has been shown to scale with individual motor impairment as revealed by UPDRS motor score and thus, may reflect the magnitude of dopaminergic neurodegeneration. The magnitude of SAI has also been linked to cognitive dysfunction, and it has been suggested that SAI also reflects cholinergic denervation at the cortical level. Together, the results indicate that SAI is a useful marker of disease-related alterations in fast cortical sensory-motor integration driven by subcortical changes in the dopaminergic and cholinergic system. Since a multitude of neurobiological factors contribute to the magnitude of inhibition, any mechanistic interpretation of SAI changes in PD needs to consider the group characteristics in terms of phenotypical spectrum, disease stage, and medication.

Attenuated beta rebound to proprioceptive afferent feedback in Parkinson's disease

Motor symptoms are defining traits in the diagnosis of Parkinson’s disease (PD). A crucial component in motor function is the integration of afferent proprioceptive sensory feedback. Previous studies have indicated abnormal movement-related cortical oscillatory activity in PD, but the role of the proprioceptive afference on abnormal oscillatory activity in PD has not been elucidated. We examine the cortical oscillations in the mu/beta-band (8–30 Hz) in the processing of proprioceptive stimulation in PD patients, ON/OFF levodopa medication, as compared to that of healthy controls (HC). We used a proprioceptive stimulator that generated precisely controlled passive movements of the index finger and measured the induced cortical oscillatory responses following the proprioceptive stimulation using magnetoencephalography. Both PD patients and HC showed a typical beta-band desynchronization during the passive movement. However, the subsequent beta rebound after the passive movement that was almost absent in PD patients compared to HC. Furthermore, we found no difference in the degree of beta rebound attenuation between patients ON and OFF levodopa medication. The results demonstrate a disease-related deterioration in cortical processing of proprioceptive afference in PD.

"Will you draw me a pelvis?ˮ Dynamic neuro-cognitive imagery improves pelvic schema and graphic-metric representation in people with Parkinson's Disease: A randomized controlled trial

BACKGROUND

Body schema (i.e., the mental representations of the body), vital for motor and cognitive functions, is often distorted in people with Parkinson's disease (PD). Deficits in body, and especially pelvic, schema can further exacerbate motor and cognitive deficits associated with PD. Such deficits, including those in graphic and metric misjudgments, can manifest in drawing tasks. Mental imagery is a recommended approach for PD rehabilitation with potential for ameliorating body schema.

OBJECTIVE

To investigate the effect of a two-week dynamic neuro-cognitive imagery (DNI) training versus in-home learning and exercise control (learning/exercise) on pelvic schema and graphic representation (i.e., drawing height and width).

DESIGN

Twenty participants with idiopathic PD (Hoehn&Yahr I-III; M age: 65.75 ± 10.13) were randomly allocated into either a DNI or a learning/exercise group. Participants were asked to complete the "Draw Your Pelvisˮ test in which they drew their pelvis at pre- and post-intervention. Drawings were assessed for pelvic schema score and drawing dimensions (i.e., height and weight).

INTERVENTION

DNI anatomical and metaphorical imagery focusing on pelvic anatomy and biomechanics.

RESULTS

No difference (p > .05) was detected at baseline between drawn pelvis height and width. Following intervention, improvements were greater in the DNI group for pelvic schema (p < .01), drawn pelvic width (p < .05) and width-height difference (p < .05).

CONCLUSIONS

This study suggests that DNI could serve as a rehabilitation path for improving body schema in people with PD. Future studies should explore DNI mechanisms of effect and the effect of enhanced pelvic schema on motor and non-motor deficits in this population.

Somatosensory Training Improves Proprioception and Untrained Motor Function in Parkinson's Disease

Background: Proprioceptive impairment is a common feature of Parkinson's disease (PD). Proprioceptive function is only partially restored with anti-parkinsonian medication or deep brain stimulation. Behavioral exercises focusing on somatosensation have been promoted to overcome this therapeutic gap. However, conclusive evidence on the effectiveness of such somatosensory-focused behavioral training for improving somatosensory function is lacking. Moreover, it is unclear, if such training has any effect on motor performance in PD.

Objective: To investigate, whether proprioception improves with a somatosensory focused, robot-aided training in people with PD (PWPs), and whether enhanced proprioception translates to improved motor performance.

Method: Thirteen PWPs of mild-moderate clinical severity were assessed and trained ON medication using a robotic wrist exoskeleton. Thirteen healthy elderly participants served as controls. Training involved making increasingly accurate, continuous, precise small amplitude wrist flexion/extension movements. Wrist position sense acuity, as a marker of proprioception function, and spatial error during wrist pointing, as a marker of untrained motor performance, were recorded twice before and once after training. Functional hand writing kinematics exhibited during training were evaluated in the PD group for determining training-induced changes.

Results: Training improved position sense acuity in all PWPs (mean change: 28%; p < 0.001) and healthy controls (mean change: 23%; p < 0.01). Second, 10/13 PD participants and 10/13 healthy control participants had reduced spatial movement error in the untrained wrist pointing task after training. Third, spatial error for the functional handwriting tasks (line tracing and tracking) did not improve with training in the PD group.

Conclusion: Proprioceptive function in mild to moderate PD is trainable and improves with a somatosensory-focused motor training. Learning showed a local transfer within the trained joint degree-of-freedom as improved spatial accuracy in an unpracticed motor task. No learning gains were observed for the untrained functional handwriting task, indicating that training may be specific to the trained joint degree-of-freedom.

Insula as the Interface Between Body Awareness and Movement: A Neurofeedback-Guided Kinesthetic Motor Imagery Study in Parkinson's Disease

Intentional movement is an internally driven process that requires the integration of motivational and sensory cues with motor preparedness. In addition to the motor cortical-basal ganglia circuits, the limbic circuits are also involved in the integration of these cues. Individuals with Parkinson's disease (PD) have a particular difficulty with internally generating intentional movements and maintaining the speed, size, and vigor of movements. This difficulty improves when they are provided with external cues suggesting that there is a problem with the internal motivation of movement in PD. The prevailing view attributes this difficulty in PD to the dysfunction of motor cortical-basal ganglia circuits. First, we argue that the standard cortical-basal ganglia circuit model of motor dysfunction in PD needs to be expanded to include the insula which is a major hub within the limbic circuits. We propose a neural circuit model highlighting the interaction between the insula and dorsomedial frontal cortex which is involved in generating intentional movements. The insula processes a wide range of sensory signals arising from the body and integrates them with the emotional and motivational context. In doing so, it provides the impetus to the dorsomedial frontal cortex to initiate and sustain movement. Second, we present the results of our proof-of-concept experiment demonstrating that the functional connectivity of the insula-dorsomedial frontal cortex circuit can be enhanced with neurofeedback-guided kinesthetic motor imagery using functional magnetic resonance imaging in subjects with PD. Specifically, we found that the intensity and quality of body sensations evoked during motor imagery and the emotional and motivational context of motor imagery determined the direction (i.e., negative or positive) of the insula-dorsomedial frontal cortex functional connectivity. After 10-12 neurofeedback sessions and "off-line" practice of the successful motor imagery strategies all subjects showed a significant increase in the insula-dorsomedial frontal cortex functional connectivity. Finally, we discuss the implications of these results regarding motor function in patients with PD and propose suggestions for future studies.

The Body Position Spatial Task, a Test of Whole-Body Spatial Cognition: Comparison Between Adults With and Without Parkinson Disease

BACKGROUND

The Body Position Spatial Task (BPST) is a novel measure of whole-body spatial cognition involving multidirectional steps and turns. Individuals with Parkinson disease (PD) are affected by motor and cognitive impairments, particularly in spatial function, which is important for mental imagery and navigation. Performance on the BPST may inform understanding of motor-cognitive and spatial cognitive function of individuals with PD.

OBJECTIVES

We conducted this study to determine feasibility and validity of the BPST with standard, validated, and reliable measures of spatial cognition and motor-cognitive integration and to compare BPST performance in adults with and without PD.

METHODS

A total of 91 individuals with mild-moderate PD and 112 neurotypical (NT) adults of similar age were recruited for the study to complete the BPST and other measures of mobility and cognition. Correlations were used to determine construct and concurrent validity of BPST with valid measures of spatial cognition and motor-cognitive integration. Performance was compared between PD and NT adults using independent t-tests.

RESULTS

BPST was feasible to administer. Analyses show evidence of construct validity for spatial cognition and for motor-cognitive integration. Concurrent validity was demonstrated with other tests of mobility and cognition. Relationships were stronger and more significant for individuals with PD than for NT individuals. BPST performance was not significantly different between groups.

CONCLUSION

Tests that integrate cognitive challenge in mobility contexts are necessary to assess the health of spatial cognitive and motor-cognitive integration. The BPST is a feasible and valid test of whole-body spatial cognition and motor-cognitive integration in individuals with PD.

Variability of crossing phase in older people with Parkinson's disease is dependent of obstacle height

Our aim was investigating variability in spatiotemporal parameters and kinetics of obstacle avoidance steps of different height obstacles in people with Parkinson's disease (PD) and healthy older people. Twenty-eight participants have included (15 PD - stage disease: 2.1 ± 0.4 pts) and 13 healthy older people (control group). Each subject performed 10 trials of the following tasks: low obstacle, intermediate obstacle and high obstacle. The presentation order was randomized by block for each condition and participant. The spatiotemporal parameters was collected by GAITRite. An optoelectronic system (Optotrak Northern Digital Inc.) with 100 Hz of frequency was used to collect obstacle parameters. The kinect parameters (propulsion impulse and braking impulse) were acquire through two force plates (AccuGait), with a frequency of acquisition 200 Hz. Intersteps variability was calculated throughout mean values, standard deviation and coefficient of variation of two obstacle avoidance steps for each trial. PD group presented greater variability than control group on vertical and horizontal distances to the obstacle. Obstacle height did not change kinect's parameters for both groups. The combination of task complexity (obstacle height) and disease impairments (gait alteration, loss of balance, etc) contributing for greater variability of Parkinson's group. Besides, low obstacle and high obstacle seem to exacerbate variability of distance between obstacle and foot.

What If Low Back Pain Is the Most Prevalent Parkinsonism in the World?

Low back pain (LBP) has a point prevalence of nearly 10% and ranks highest in global disease burden for years lived with disability; Parkinson’s disease (PD) ranks in the top 100 most disabling health conditions for years lost and years lived with disability (1). Recent evidence suggests that people with chronic, recurrent LBP exhibit many postural impairments reminiscent of a neurological postural disorder such as PD. We compare and contrast postural impairments associated with LBP and PD in order to inform treatment strategies for both conditions. The literature suggests that both LBP and PD associate with impaired proprioceptive function, sensory orientation during standing balance, anticipatory postural adjustments, automatic postural responses, and striatal-cortical function. Although postural impairments are similar in nature for LBP and PD, the postural impairments with LBP appear more specific to the trunk than for PD. Likewise, although both health conditions associate with altered striatal-cortical function, the nature of the altered neural structure or function differ for PD and LBP. Due to the high prevalence of LBP associated with PD, focused treatment of LBP in people with PD may render benefit to their postural impairments and disabilities. In addition, LBP would likely benefit from being considered more than just a musculoskeletal injury; as such, clinicians should consider including approaches that address impairments of postural motor control.

Dynamic Neuro-Cognitive Imagery Improves Mental Imagery Ability, Disease Severity, and Motor and Cognitive Functions in People with Parkinson's Disease

People with Parkinson's disease (PD) experience kinesthetic deficits, which affect motor and nonmotor functions, including mental imagery. Imagery training is a recommended, yet underresearched, approach in PD rehabilitation. Dynamic Neuro-Cognitive Imagery (DNI™) is a codified method for imagery training. Twenty subjects with idiopathic PD (Hoehn and Yahr stages I–III) were randomly allocated into DNI training (experimental; n = 10) or in-home learning and exercise program (control; n = 10). Both groups completed at least 16 hours of training within two weeks. DNI training focused on anatomical embodiment and kinesthetic awareness. Imagery abilities, disease severity, and motor and nonmotor functions were assessed pre- and postintervention. The DNI participants improved (p < .05) in mental imagery abilities, disease severity, and motor and spatial cognitive functions. Participants also reported improvements in balance, walking, mood, and coordination, and they were more physically active. Both groups strongly agreed they enjoyed their program and were more mentally active. DNI training is a promising rehabilitation method for improving imagery ability, disease severity, and motor and nonmotor functions in people with PD. This training might serve as a complementary PD therapeutic approach. Future studies should explore the effect of DNI on motor learning and control strategies.

Peripheral neurostimulation breaks the shuffling steps patterns in Parkinsonian gait: a double blind randomized longitudinal study with automated mechanical peripheral stimulation

BACKGROUND

The shuffling steps pattern is a typical feature of gait in patients affected by Parkinson's disease (PD), which progressively reduces their quality of life, being related to the risk of falls in this population. Recently, Automated Mechanical Peripheral Stimulation (AMPS) was presented as an integrative rehabilitative treatment based on peripheral stimulation able to improve the gait spatiotemporal parameters in PD patients.

AIM

The aim of this study was to evaluate the effects of AMPS on shuffling steps pattern by analyzing the kinematic and spatio-temporal gait parameters.

DESIGN

Double blind randomized longitudinal study.

SETTING

Outpatients.

POPULATION

PD patients.

METHODS

In this double blind randomized longitudinal study, 14 patients with PD were treated with effective-AMPS (AMPS group), while 14 PD patients were treated with placebo-AMPS (SHAM group); 32 healthy subjects were deemed the control group (CG). A dedicated medical device (Gondola™ Medical Technologies, Stabio, Switzerland) was used to deliver both stimulations. Each treatment session lasted about 15 minutes, including preparation (approx. 10 to 13 minutes) and stimulation (approx. 2 minutes). All PD patients were given six AMPS/SHAM treatments sessions, twice a week, delivered during the off-levodopa phase, having withdrawn from dopaminergic medication overnight. We evaluated spatio-temporal and kinematic variables of gait with quantitative 3D-gait analysis as follows: before and after the first intervention (acute phase), then after the sixth session (long term phase).

RESULTS

We detected differences in all gait variables immediately after the first session of AMPS treatment and again after the sixth stimulation session.

CONCLUSIONS

AMPS treatment changes the shuffling steps pattern that is typical of PD subjects, increasing the ROM of hip, knee and ankle joints during the gait cycle.

CLINICAL REHABILITATION IMPACT

This data presents further evidence that a rehabilitative approach based on the AMPS treatment can induce improvements in the gait pattern of patients affected by PD.

Long-term effects of Lee Silverman Voice Treatment on daily voice use in Parkinson's disease as measured with a portable voice accumulator

This study examines the effects of an intensive voice treatment focusing on increasing voice intensity, LSVT LOUD^® Lee Silverman Voice Treatment, on voice use in daily life in a participant with Parkinson's disease, using a portable voice accumulator, the VoxLog. A secondary aim was to compare voice use between the participant and a matched healthy control. Participants were an individual with Parkinson's disease and his healthy monozygotic twin. Voice use was registered with the VoxLog during 9 weeks for the individual with Parkinson's disease and 2 weeks for the control. This included baseline registrations for both participants, 4 weeks during LSVT LOUD for the individual with Parkinson's disease and 1 week after treatment for both participants. For the participant with Parkinson's disease, follow-up registrations at 3, 6, and 12 months post-treatment were made. The individual with Parkinson's disease increased voice intensity during registrations in daily life with 4.1 dB post-treatment and 1.4 dB at 1-year follow-up compared to before treatment. When monitored during laboratory recordings an increase of 5.6 dB was seen post-treatment and 3.8 dB at 1-year follow-up. Changes in voice intensity were interpreted as a treatment effect as no significant correlations between changes in voice intensity and background noise were found for the individual with Parkinson's disease. The increase in voice intensity in a laboratory setting was comparable to findings previously reported following LSVT LOUD. The increase registered using ambulatory monitoring in daily life was lower but still reflecting a clinically relevant change.

Effects of a sensory-motor orthotic on postural instability rehabilitation in Parkinson's disease: a pilot study

BACKGROUND

Proprioceptive deficits have been largely documented in PD patients, thus external sensory signals (peripheral sensory feedback) are often used to compensate the abnormalities of proprioceptive integration. This pilot study aims to evaluate the feasibility and the effectiveness of a rehabilitation-training program, combined with the use of a sensory-motor orthotic in improving balance in a small sample of PD patients.

METHODS

Twenty PD patients were randomly allocated into two groups: (i) the Experimental group, where participants were asked to wear a sensory-motor orthotic during the balance training program and (ii) the Control group, where subjects performed an identical training program without wearing any kind of orthotics. In all, the training program lasted 10 sessions (5 days a week for 2 weeks) and the clinical and instrumental assessments were performed at baseline, immediately after the end of the training and 4 weeks after the rehabilitative program was stopped.

RESULTS

All clinical outcome measures tested improved significantly at post and follow-up evaluations in both groups. Interestingly, at the end of the training, only the experimental group obtained a significant improvement in the functional reaching test (sway area - eyes closed) measured by means of stabilometric platform and this result was maintained in the follow-up evaluation.

CONCLUSIONS

Our preliminary results suggested that the use of a sensory-motor orthotic, in combination with a tailored balance training, is feasible and it seems to positively impact on balance performance in Parkinson's disease.

TRIAL REGISTRATION

EudraCT N. 003020-36 - 2013.

The Phenomenology of Parkinson's Disease

The motor symptoms of Parkinson's disease are not limited to the cardinal symptoms of bradykinesia, rigidity, and resting tremor, but also include a variety of interrelated motor phenomena such as deficits in spatiotemporal planning and movement sequencing, scaling and timing of movements, and intermuscular coordination that can be clinically observed. Although many of these phenomena overlap, a review of the full breadth of the motor phenomenon can aid in the diagnosis and monitoring of disease progression.

Use of Mobile Device Accelerometry to Enhance Evaluation of Postural Instability in Parkinson Disease

OBJECTIVE

To determine the accuracy of inertial measurement unit data from a mobile device using the mobile device relative to posturography to quantify postural stability in individuals with Parkinson disease (PD).

DESIGN

Criterion standard.

SETTING

Motor control laboratory at a clinic.

PARTICIPANTS

A sample (N=28) of individuals with mild to moderate PD (n=14) and age-matched community-dwelling individuals without PD (n=14) completed the study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Center of mass (COM) acceleration measures were compared between the mobile device and the NeuroCom force platform to determine the accuracy of mobile device measurements during performance of the Sensory Organization Test (SOT). Analyses examined test-retest reliability of both systems and sensitivity of (1) the equilibrium score from the SOT and (2) COM acceleration measures from the force platform and mobile device to quantify postural stability across populations.

RESULTS

Metrics of COM acceleration from inertial measurement unit data and the NeuroCom force platform were significantly correlated across balance conditions and groups (Pearson r range, .35 to .97). The SOT equilibrium scores failed to discriminate individuals with and without PD. However, the multiplanar measures of COM acceleration from the mobile device exhibited good to excellent reliability across SOT conditions and were able to discriminate individuals with and without PD in conditions with the greatest balance demands.

CONCLUSIONS

Metrics employing medial-lateral movement produce a more sensitive outcome than the equilibrium score in identifying postural instability associated with PD. Overall, the output from the mobile device provides an accurate and reliable method of rapidly quantifying balance in individuals with PD. The portable and affordable nature of a mobile device with the application makes it ideally suited to use biomechanical data to aid in clinical decision making.

Sequence Effect in Parkinson's Disease Is Related to Motor Energetic Cost

Bradykinesia is the most disabling motor symptom of Parkinson's disease (PD). The sequence effect (SE), a feature of bradykinesia, refers to the rapid decrement in amplitude and speed of repetitive movements (e.g., gait, handwriting) and is a major cause of morbidity in PD. Previous research has revealed mixed results regarding the role of dopaminergic treatment in the SE. However, external cueing has been shown to improve it. In this study, we aimed to characterize the SE systematically and relate this phenomenon to the energetic cost of movement within the context of cost-benefit framework of motor control. We used a dynamic isometric motor task with auditory pacing to assess the SE in motor output during a 15-s task segment in PD patients and matched controls. All participants performed the task with both hands, and without and with visual feedback (VF). Patients were also tested in "on"- and "off"-dopaminergic states. Patients in the "off" state did not show higher SE compared to controls, partly due to large variance in their performance. However, patients in the "on" state and in the absence of VF showed significantly higher SE compared to controls. Patients expended higher total motor energy compared to controls in all conditions and regardless of their medication status. In this experimental situation, the SE in PD is associated with the cumulative energetic cost of movement. Dopaminergic treatment, critical for internal triggering of movement, fails to maintain the motor vigor across responses. The high motor cost may be related to failure to incorporate limbic/motivational cues into the motor plan. VF may facilitate performance by shifting the driving of movement from internal to external or, alternatively, by functioning as a motivational cue.

Impact of Parkinson's disease on proprioceptively based on-line movement control

Evidence suggests that Parkinson's disease (PD) patients produce large spatial errors when reaching to proprioceptively defined targets. Here, we examined whether these movement inaccuracies result mainly from impaired use of proprioceptive inputs for movement planning mechanisms or from on-line movement guidance. Medicated and non-medicated PD patients and healthy controls performed three-dimensional reaching movements in four sensorimotor conditions that increase proprioceptive processing requirements. We assessed the influence of these sensorimotor conditions on the final accuracy and initial kinematics of the movements. If the patterns of final errors are primarily determined by planning processes before the initiation of the movement, the initial kinematics of reaching movements should show similar trends and predict the pattern of final errors. Medicated and non-medicated PD patients showed a greater mean level of final 3D errors than healthy controls when proprioception was the sole source of information guiding the movement, but this difference reached significance only for medicated PD patients. However, the pattern of initial kinematics and final spatial errors were markedly different both between sensorimotor conditions and between groups. Furthermore, medicated and non-medicated PD patients were less efficient than healthy controls in compensating for their initial spatial errors (hand distance from target location at peak velocity) when aiming at proprioceptively defined compared to visually defined targets. Considered together, the results are consistent with a selective deficit in proprioceptively based movement guidance in PD. Furthermore, dopaminergic medication did not improve proprioceptively guided movements in PD patients, indicating that dopaminergic dysfunction within the basal ganglia is not solely responsible for these deficits.

StartReact effects support different pathophysiological mechanisms underlying freezing of gait and postural instability in Parkinson's disease

Introduction

The pathophysiology underlying postural instability in Parkinson’s disease is poorly understood. The frequent co-existence with freezing of gait raises the possibility of shared pathophysiology. There is evidence that dysfunction of brainstem structures contribute to freezing of gait. Here, we evaluated whether dysfunction of these structures contributes to postural instability as well. Brainstem function was assessed by studying the StartReact effect (acceleration of latencies by a startling acoustic stimulus (SAS)).

Methods

We included 25 patients, divided in two different ways: 1) those with postural instability (HY = 3, n = 11) versus those without (HY<3, n = 14); and 2) those with freezing (n = 11) versus those without freezing (n = 14). We also tested 15 matched healthy controls. We tested postural responses by translating a balance platform in the forward direction, resulting in backward balance perturbations. In 25% of trials, the start of the balance perturbation was accompanied by a SAS.

Results

The amplitude of automatic postural responses and length of the first balance correcting step were smaller in patients with postural instability compared to patients without postural instability, but did not differ between freezers and non-freezers. In contrast, the StartReact effect was intact in patients with postural instability but was attenuated in freezers.

Discussion

We suggest that the mechanisms underlying freezing of gait and postural instability in Parkinson’s disease are at least partly different. Underscaling of automatic postural responses and balance-correcting steps both contribute to postural instability. The attenuated StartReact effect was seen only in freezers and likely reflects inadequate representation of motor programs at upper brainstem level.

Impaired Limb Proprioception in Adults With Spasmodic Dysphonia

OBJECTIVES

Focal dystonia of the head and neck are associated with a loss of kinesthetic acuity at muscles distant from the dystonic sites. That is, while the motor deficits in focal dystonia are confined, the associated somatosensory deficits are generalized. This is the first systematic study to examine, if patients diagnosed with spasmodic dystonia (SD) show somatosensory impairments similar in scope to other forms of focal dystonia.

METHODS

Proprioceptive acuity (ability to discriminate between two stimuli) for forearm position and motion sense was assessed in 14 spasmodic dystonia subjects and 28 age-matched controls using a passive motion apparatus. Psychophysical thresholds, uncertainty area (UA), and a proprioceptive acuity index (AI) were computed based on the subjects' verbal responses.

RESULTS

The main findings are as follows: first, the SD group showed significantly elevated thresholds and UAs for forearm position sense compared with the control group. Second, 9 of 14 dystonia subjects (64%) exhibited an AI for position sense above the control group maximum. Three SD subjects had a motion sense AI above the control group maximum.

CONCLUSIONS

The results indicate that impaired limb proprioception is a common feature of SD. Like other forms of focal dystonia, spasmodic dystonia does affect the somatosensation of nondystonic muscle systems. That is, SD is associated with a generalized somatosensory deficit.

Proprioceptive rehabilitation of upper limb dysfunction in movement disorders: a clinical perspective

Movement disorders (MDs) are frequently associated with sensory abnormalities. In particular, proprioceptive deficits have been largely documented in both hypokinetic (Parkinson’s disease) and hyperkinetic conditions (dystonia), suggesting a possible role in their pathophysiology. Proprioceptive feedback is a fundamental component of sensorimotor integration allowing effective planning and execution of voluntary movements. Rehabilitation has become an essential element in the management of patients with MDs, and there is a strong rationale to include proprioceptive training in rehabilitation protocols focused on mobility problems of the upper limbs. Proprioceptive training is aimed at improving the integration of proprioceptive signals using “task-intrinsic” or “augmented feedback.” This perspective article reviews the available evidence on the effects of proprioceptive stimulation in improving upper limb mobility in patients with MDs and highlights the emerging innovative approaches targeted to maximizing the benefits of exercise by means of enhanced proprioception.

A wearable proprioceptive stabilizer (Equistasi®) for rehabilitation of postural instability in Parkinson's disease: a phase II randomized double-blind, double-dummy, controlled study

Background

Muscle spindles endings are extremely sensitive to externally applied vibrations, and under such circumstances they convey proprioceptive inflows to the central nervous system that modulate the spinal reflexes excitability or the muscle responses elicited by postural perturbations. The aim of this pilot study is to test the feasibility and effectiveness of a balance training program in association with a wearable proprioceptive stabilizer (Equistasi) that emits focal mechanical vibrations in patients with PD.

Methods

Forty patients with PD were randomly divided in two groups wearing an active or inactive device. All the patients received a 2-month intensive program of balance training. Assessments were performed at baseline, after the rehabilitation period (T1), and two more months after (T2). Posturographic measures were used as primary endpoint; secondary measures of outcome included the number of falls and several clinical scales for balance and quality of life.

Results

Both groups improved at the end of the rehabilitation period and we did not find significant between-group differences in any of the principal posturographic measures with the exception of higher sway area and limit of stability on the instrumental functional reach test during visual deprivation at T1 in the Equistasi group. As for the secondary outcome, we found an overall better outcome in patients enrolled in the Equistasi group: 1) significant improvement at T1 on Berg Balance Scale (+45.0%, p = .026), Activities-specific Balance Confidence (+83.7, p = .004), Falls Efficacy Scale (−33.3%, p = .026) and PDQ-39 (−48.8%, p = .004); 2) sustained improvement at T2 in terms of UPDRS-III, Berg Balance Scales, Time Up and Go and PDQ-39; 3) significant and sustained reduction of the falls rate.

Conclusions

This pilot trial shows that a physiotherapy program for training balance in association with focal mechanical vibration exerted by a wearable proprioceptive stabilizer might be superior than rehabilitation alone in improving patients’ balance.

Trial Registration

EudraCT 2013-003020-36 and ClinicalTrials.gov (number not assigned)

Instrumented functional reach test differentiates individuals at high risk for Parkinson's disease from controls

The functional reach (FR) test as a complex measure of balance including limits of stability has been proven to differentiate between patients with Parkinson’s disease (PD) and controls (CO). Recently, it has been shown that the instrumentation of the FR (iFR) with a wearable sensor may increase this diagnostic accuracy. This cross-sectional study aimed at investigating whether the iFR has the potential to differentiate individuals with high risk for PD (HRPD) from CO, as the delineation of such individuals would allow for, e.g., early neuromodulation. Thirteen PD patients, 13 CO, and 31 HRPD were investigated. HRPD was defined by presence of an enlarged area of hyperechogenicity in the mesencephalon on transcranial sonography and either one motor sign or two risk and prodromal markers of PD. All participants were asked to reach with their right arm forward as far as possible and hold this position for 10 s. During this period, sway parameters were assessed with an accelerometer (Dynaport, McRoberts) worn at the lower back. Extracted parameters that differed significantly between PD patients and CO in our cohort [FR distance (shorter in PD), anterior–posterior and mediolateral acceleration (both lower in PD)] as well as JERK, which has been shown to differentiate HRPD from CO and PD in a previous study, were included in a model, which was then used to differentiate HRPD from CO. The model yielded an area under the curve of 0.77, with a specificity of 85%, and a sensitivity of 74%. These results suggest that the iFR can contribute to an assessment panel focusing on the definition of HRPD individuals.

Neural correlates of progressive reduction of bradykinesia in de novo Parkinson's disease

BACKGROUND

A progressive reduction in the speed and amplitude of repetitive action is an essential component of bradykinesia, which is called sequence effect (SE). Because SE is specific to Parkinson's disease (PD) and is suggested to be associated with motor arrest, its features are of great interest. The aim of this study was, for the first time, to find the neural correlates of SE and to demonstrate whether dopaminergic deficit is correlated with SE.

METHODS

We enrolled 12 patients with de novo PD at a tertiary referral hospital. Correlations between SE severity and alterations in gray and white matter were studied. The association between severity of the SE and striatal dopaminergic deficits was also analyzed.

RESULTS

There was a significant negative correlation between the volumetric changes in the anterior cingulate cortex (ACC) and the inferior semilunar lobule of the cerebellum and the degree of SE. There was a significant correlation between the long association fibers (the superior longitudinal fasciculus, the uncinate fasciculus, and the inferior fronto-occipital fasciculus) connecting the frontal lobes to the temporal, parietal, and occipital lobes and SE. There was a significant negative correlation between SE in the more affected hand and the caudate dopamine transporter binding in the more affected hemisphere.

CONCLUSIONS

Our results suggest that the ACC and the cerebellum (inferior semilunar lobule) are associated with the severity of SE. Taken together with DTI findings, the present study proposes that ACC may have an important role. Our data show that the caudate dopaminergic activity may be related to SE.

Aristotle's illusion in Parkinson's disease: evidence for normal interdigit tactile perception

Sensory alterations, a common feature of such movement disorders as Parkinson’s disease (PD) and dystonia, could emerge as epiphenomena of basal ganglia dysfunction. Recently, we found a selective reduction of tactile perception (Aristotle’s illusion, the illusory doubling sensation of one object when touched with crossed fingers) in the affected hand of patients with focal hand dystonia. This suggests that reduced tactile illusion might be a specific feature of this type of dystonia and could be due to abnormal somatosensory cortical activation. The aim of the current study was to investigate whether Aristotle’s illusion is reduced in the affected hand of patients with PD. We tested 15 PD patients, in whom motor symptoms were mainly localised to one side of the body, and 15 healthy controls. Three pairs of fingers were tested in crossed (evoking the illusion) or parallel position (not evoking the illusion). A sphere was placed in the contact point between the two fingers and the blindfolded participants had to say whether they felt one or two stimuli. Stimuli were applied on the affected and less or unaffected side of the PD patients. We found no difference in illusory perception between the PD patients and the controls, nor between the more affected and less/unaffected side, suggesting that Aristotle’s illusion is preserved in PD. The retained tactile illusion in PD and its reduction in focal hand dystonia suggest that the basal ganglia, which are dysfunctional in both PD and dystonia, may not be causally involved in this function. Instead, the level of activation between digits in the somatosensory cortex may be more directly involved. Finally, the similar percentage of illusion in the more affected and less or unaffected body sides indicates that the illusory perception is not influenced by the presence or amount of motor symptoms.

Sensory aspects of movement disorders

Movement disorders, which include disorders such as Parkinson's disease, dystonia, Tourette's syndrome, restless legs syndrome, and akathisia, have traditionally been considered to be disorders of impaired motor control resulting predominantly from dysfunction of the basal ganglia. This notion has been revised largely because of increasing recognition of associated behavioural, psychiatric, autonomic, and other non-motor symptoms. The sensory aspects of movement disorders include intrinsic sensory abnormalities and the effects of external sensory input on the underlying motor abnormality. The basal ganglia, cerebellum, thalamus, and their connections, coupled with altered sensory input, seem to play a key part in abnormal sensorimotor integration. However, more investigation into the phenomenology and physiological basis of sensory abnormalities, and about the role of the basal ganglia, cerebellum, and related structures in somatosensory processing, and its effect on motor control, is needed.

Reaching to proprioceptively defined targets in Parkinson's disease: effects of deep brain stimulation therapy

Deep brain stimulation of the subthalamic nucleus (STN DBS) provides a unique window into human brain function since it can reversibly alter the functioning of specific brain circuits. Basal ganglia-cortical circuits are thought to be excessively noisy in patients with Parkinson's disease (PD), based in part on the lack of specificity of proprioceptive signals in basal ganglia-thalamic-cortical circuits in monkey models of the disease. PD patients are known to have deficits in proprioception, but the effects are often subtle, with paradigms typically restricted to one or two joint movements in a plane. Moreover, the effects of STN DBS on proprioception are virtually unexplored. We tested the following hypotheses: first, that PD patients will show substantial deficits in unconstrained, multi-joint proprioception, and, second, that STN DBS will improve multi-joint proprioception. Twelve PD patients with bilaterally implanted electrodes in the subthalamic nucleus and 12 age-matched healthy subjects were asked to position the left hand at a location that was proprioceptively defined in 3D space with the right hand. In a second condition, subjects were provided visual feedback during the task so that they were not forced to rely on proprioception. Overall, with STN DBS switched off, PD patients showed significantly larger proprioceptive localization errors, and greater variability in endpoint localizations than the control subjects. Visual feedback partially normalized PD performance, and demonstrated that the errors in proprioceptive localization were not simply due to a difficulty in executing the movements or in remembering target locations. Switching STN DBS on significantly reduced localization errors from those of control subjects when patients moved without visual feedback relative to when they moved with visual feedback (when proprioception was not required). However, this reduction in localization errors without vision came at the cost of increased localization variability.

[Visual cues as a therapeutic tool in Parkinson's disease. A systematic review]

Sensory stimuli or sensory cues are being used as a therapeutic tool for improving gait disorders in Parkinson's disease patients, but most studies seem to focus on auditory stimuli. The aim of this study was to conduct a systematic review regarding the use of visual cues over gait disorders, dual tasks during gait, freezing and the incidence of falls in patients with Parkinson to obtain therapeutic implications. We conducted a systematic review in main databases such as Cochrane Database of Systematic Reviews, TripDataBase, PubMed, Ovid MEDLINE, Ovid EMBASE and Physiotherapy Evidence Database, during 2005 to 2012, according to the recommendations of the Consolidated Standards of Reporting Trials, evaluating the quality of the papers included with the Downs & Black Quality Index. 21 articles were finally included in this systematic review (with a total of 892 participants) with variable methodological quality, achieving an average of 17.27 points in the Downs and Black Quality Index (range: 11-21). Visual cues produce improvements over temporal-spatial parameters in gait, turning execution, reducing the appearance of freezing and falls in Parkinson's disease patients. Visual cues appear to benefit dual tasks during gait, reducing the interference of the second task. Further studies are needed to determine the preferred type of stimuli for each stage of the disease.

Haptic feedback from manual contact improves balance control in people with Parkinson's disease

Parkinson's disease (PD) degrades balance control. Haptic (touch and proprioception) feedback from light contact with a stationary surface inadequate to mechanically stabilize balance improves balance control in healthy people. In this study we tested whether PD impairs use of haptic cues independent of mechanical support to control balance. We measured postural sway in thirteen individuals with PD (H&Y 1-3, median=2, Q1=2, Q3=2) and thirteen age-matched controls balancing in a widened, sharpened Romberg stance in four conditions: eyes-closed, no manual contact; eyes-closed light-touch contact (<1N), eyes-closed, unrestricted contact; and eyes-open, no contact. To determine whether PD-severity affects any of these balance strategies, PD participants were tested on- and off-medication, and using the more- and less-affected body side in the stance and manual contact. Individuals with PD simultaneously maintained non-supportive fingertip contact and balance in this task without practice. PD participants swayed more than control participants (ML CP p=0.010; shoulder p<0.001), but manual contact reduced sway. Non-supportive manual contact stabilized balance more than vision (p<0.05). PD-severity factors had no significant effect (p>0.05). We conclude the effect of PD on balance is not specific to vision or haptic feedback. Nevertheless, haptic cues from manual contact, independent of mechanical support, improve balance control in individuals with PD. We discuss the implication that PD or associated dopaminergic pathways do not directly affect haptic feedback balance control mechanisms, including arm/posture coordination and proprioceptive integration.

Postural instability in patients with Parkinson's disease. Epidemiology, pathophysiology and management

Postural instability is one of the cardinal signs in Parkinson's disease (PD). It can be present even at diagnosis, but becomes more prevalent and worsens with disease progression. It represents one of the most disabling symptoms in the advanced stages of the disease, as it is associated with increased falls and loss of independence. Clinical and posturographic studies have contributed to significant advances in unravelling the complex pathophysiology of postural instability in patients with PD, but it still remains yet to be fully clarified, partly due to the difficulty in distinguishing between the disease process and the compensatory mechanisms, but also due to the fact that non-standardized techniques are used to measure balance and postural instability. There is increasing evidence that physical therapy, especially highly challenging balance exercises, can improve postural stability and reduce the risk of falls, although the long-term effects of physical therapy interventions on postural stability need to be explored given the progressive nature of PD. Pharmacotherapy with dopaminergic medications can provide significant improvements in postural instability in early- to mid-stage PD but the effects tend to wane with time consistent with spread of the disease process to non-dopaminergic pathways in advanced PD. Donepezil has been associated with a reduced risk of falls and methylphenidate has shown potential benefit against freezing of gait, but the results are yet to be replicated in large randomized studies. Surgical treatments, including lesioning and deep brain stimulation surgery targeting the subthalamic nucleus and the globus pallidus internus, tend to only provide modest benefit for postural instability. New surgical targets such as the pedunculopontine nucleus have emerged as a potential specific therapy for postural instability and gait disorder but remain experimental.