Compensatory activity in the extrastriate body area of Parkinson's disease patients

The use of motor imagery in 6-7-year-old children is not robust: Evidence from two motor imagery tasks

Motor imagery (MI) is a dynamic cognitive process in which an individual mentally simulates a movement without an external demonstration of the actual movement. The ability of adults to use MI has been well documented, but the ability of children to use MI is less clear. The current study examined age-related differences in MI using two MI tasks, the hand laterality recognition (HLR) and bimanual motor (BM) tasks, in 6-13-year-old typically developing children. Biomechanical constraint effects in the HLR task and the ovalization index (OI) of the imagery condition and the imagery coupling effect in the BM task, among others, were quantitative indicators of the ability to use MI. Significant biomechanical constraint effects in the HLR task and significant imagery coupling effects in the BM task were not observed in 6-7-year-old children, but were evident in 8-13-year-old children, indicating that the use of MI in 6-7-year-old children is not robust in either MI task. There was significant shortening of correct reaction time and improvement of accuracy in the HLR task with increasing age, but there was no significant age difference or correlation with age in the imagery coupling effect in the BM task. Therefore, the results suggest that MI ability as measured by the HLR task shows age-related improvements between 6 and 13 years of age, whereas MI ability, as measured by the BM task, does not show significant age-related differences over the same period.

Sensorimotor simulation and distributed processing of biological motion: Insights from healthy and paraplegic adults

The processing of biological motion (BM), particularly the local motion cues tracing the movements of crucial joints, is vital for social interaction and human survival. While numerous studies have focused on the brain mechanisms underlying BM processing, the contribution of sensorimotor simulation at peripheral effectors remains unclear. In this study, we examined healthy adults and paraplegic spinal cord injury participants to investigate this issue. For healthy adults, both intact BM stimuli and local BM cues without global configuration induced a temporal dilation effect when sitting (sensorimotor simulation accessible), but not when standing (sensorimotor simulation temporarily hindered). In contrast, for participants with permanently hindered sensorimotor simulation, the temporal dilation effect was observed only with intact BM stimuli but not with local BM cues, indicating a robust reliance on sensorimotor simulation during the processing of local BM cues and a selective compensation based on global configuration cues for the permanent loss of sensorimotor simulation. These findings highlight the role of embodied cognition in the distributed processing of biological motion and suggest the importance of selective compensation under damaged sensorimotor circuits.

Parkinson's disease impairs the controllability of imagined action sequences

Parkinson's Disease (PD) leads to deficits in motor control that may stem in part from impaired processing of action representations, which can be investigated using motor imagery. The controllability component of motor imagery in particular refers to the ability to precisely manipulate a motor image. Research measuring this component in PD via the Hand Laterality Judgment Task has generated inconsistent results. We sought to examine whether PD affects the controllability of motor imagery using a test that explicitly directs the use of motor imagery and involves complex action sequences. Thirty-nine people with PD on their regular medication regimen and thirty-eight controls completed the Test of Ability in Movement Imagery (TAMI). The PD group scored significantly worse than controls on the TAMI. Poorer cognitive function predicted lower TAMI scores for the PD group only. These results indicate that people with PD imagine action sequences less accurately than healthy older adults. It is possible that the disease impairs the ability to transfer sensorimotor information across sequential actions, an ability that is key to efficient motor behaviour. An alternative explanation is that motor dysfunction leads to less well-developed action representations for the actions featured in the TAMI, resulting in motor images that were of low fidelity to the target actions in the PD group. Given the documented effects of dopaminergic medication on the cognitive control process that support action sequencing, it would be of interest to determine if a similar pattern of results emerged in people with PD who are off medication.

Exploring motor imagery as a therapeutic intervention for Parkinson's disease patients: a scoping review

Background

Motor imagery (MI) has emerged as a promising therapeutic approach for Parkinson's disease (PD). MI entails mentally rehearsing motor actions without executing them. This cognitive process has garnered attention due to its potential benefits in aiding motor function recovery in patients. The purpose of this review was to highlight the findings observed in motor symptoms, balance, gait, and quality of life.

Methods

A literature search was carried out in Medline, Embase, Cochrane, and Physiotherapy Evidence Database (PEDro), from the first publication to February 2024. Studies with at least one keyword to PD and MI in the title were included.

Results

The analysis included 53 studies out of the 262 identified. These comprised 12 randomized controlled trials (RCTs) with an average PEDro score of 6.6 out of 10, as well as 41 non-RCT studies. Notably, the majority of the RCTs focused on balance, gait, and lower limb exercises. The experimental group found an 85.2% improvement on the Timed Up and Go (TUG) with a cognitive task (p < 0.02), 5.8% improvement on the TUG (p < 0.05), and 5.1% improvement in walking speed (p < 0.05). Other variables did not show significant improvement. In descriptive and non-RCT studies, there were various tasks and outcomes for the lower and upper limbs. It has been demonstrated that there was no difference in execution time in MI between patients and healthy subjects (HS), whereas motor execution was slower in patients. Several tasks were analyzed for the upper limb, including thumb opposition, joystick movements, and writing tasks with variable results. RCTs were more focused on balance, lower limbs, and walking. There was no specific outcome regarding the upper limb or speech. Additionally, the heterogeneity of tasks and outcomes across studies is also a limitation.

Conclusion

Current research on walking disorders in PD shows promise, but further investigations are crucial, particularly with an emphasis on upper limb function and speech. Studies with larger sample sizes and more precise methodologies are needed to enhance our understanding of the potential benefits of MI within the framework of comprehensive PD rehabilitation.

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.

Defining the concept of reserve in the motor domain: a systematic review

A reserve in the motor domain may underlie the capacity exhibited by some patients to maintain motor functionality in the face of a certain level of disease. This form of "motor reserve" (MR) could include cortical, cerebellar, and muscular processes. However, a systematic definition has not been provided yet. Clarifying this concept in healthy individuals and patients would be crucial for implementing prevention strategies and rehabilitation protocols. Due to its wide application in the assessment of motor system functioning, non-invasive brain stimulation (NIBS) may support such definition. Here, studies focusing on reserve in the motor domain and studies using NIBS were revised. Current literature highlights the ability of the motor system to create a reserve and a possible role for NIBS. MR could include several mechanisms occurring in the brain, cerebellum, and muscles, and NIBS may support the understanding of such mechanisms.

Clinical severity in Parkinson's disease is determined by decline in cortical compensation

Dopaminergic dysfunction in the basal ganglia, particularly in the posterior putamen, is often viewed as the primary pathological mechanism behind motor slowing (i.e. bradykinesia) in Parkinson's disease. However, striatal dopamine loss fails to account for interindividual differences in motor phenotype and rate of decline, implying that the expression of motor symptoms depends on additional mechanisms, some of which may be compensatory in nature. Building on observations of increased motor-related activity in the parieto-premotor cortex of Parkinson patients, we tested the hypothesis that interindividual differences in clinical severity are determined by compensatory cortical mechanisms and not just by basal ganglia dysfunction. Using functional MRI, we measured variability in motor- and selection-related brain activity during a visuomotor task in 353 patients with Parkinson's disease (≤5 years disease duration) and 60 healthy controls. In this task, we manipulated action selection demand by varying the number of possible actions that individuals could choose from. Clinical variability was characterized in two ways. First, patients were categorized into three previously validated, discrete clinical subtypes that are hypothesized to reflect distinct routes of α-synuclein propagation: diffuse-malignant (n = 42), intermediate (n = 128) or mild motor-predominant (n = 150). Second, we used the scores of bradykinesia severity and cognitive performance across the entire sample as continuous measures. Patients showed motor slowing (longer response times) and reduced motor-related activity in the basal ganglia compared with controls. However, basal ganglia activity did not differ between clinical subtypes and was not associated with clinical scores. This indicates a limited role for striatal dysfunction in shaping interindividual differences in clinical severity. Consistent with our hypothesis, we observed enhanced action selection-related activity in the parieto-premotor cortex of patients with a mild-motor predominant subtype, both compared to patients with a diffuse-malignant subtype and controls. Furthermore, increased parieto-premotor activity was related to lower bradykinesia severity and better cognitive performance, which points to a compensatory role. We conclude that parieto-premotor compensation, rather than basal ganglia dysfunction, shapes interindividual variability in symptom severity in Parkinson's disease. Future interventions may focus on maintaining and enhancing compensatory cortical mechanisms, rather than only attempting to normalize basal ganglia dysfunction.

Loss of action-related function and connectivity in the blind extrastriate body area

The Extrastriate Body Area (EBA) participates in the visual perception and motor actions of body parts. We recently showed that EBA’s perceptual function develops independently of visual experience, responding to stimuli with body-part information in a supramodal fashion. However, it is still unclear if the EBA similarly maintains its action-related function. Here, we used fMRI to study motor-evoked responses and connectivity patterns in the congenitally blind brain. We found that, unlike the case of perception, EBA does not develop an action-related response without visual experience. In addition, we show that congenital blindness alters EBA’s connectivity profile in a counterintuitive way—functional connectivity with sensorimotor cortices dramatically decreases, whereas connectivity with perception-related visual occipital cortices remains high. To the best of our knowledge, we show for the first time that action-related functions and connectivity in the visual cortex could be contingent on visuomotor experience. We further discuss the role of the EBA within the context of visuomotor control and predictive coding theory.

A systematic review of brain morphometry related to deep brain stimulation outcome in Parkinson's disease

While the efficacy of deep brain stimulation (DBS) is well-established in Parkinson’s Disease (PD), the benefit of DBS varies across patients. Using imaging features for outcome prediction offers potential in improving effectiveness, whereas the value of presurgical brain morphometry, derived from the routinely used imaging modality in surgical planning, remains under-explored. This review provides a comprehensive investigation of links between DBS outcomes and brain morphometry features in PD. We systematically searched PubMed and Embase databases and retrieved 793 articles, of which 25 met inclusion criteria and were reviewed in detail. A majority of studies (24/25), including 1253 of 1316 patients, focused on the outcome of DBS targeting the subthalamic nucleus (STN), while five studies included 57 patients receiving globus pallidus internus (GPi) DBS. Accumulated evidence showed that the atrophy of motor cortex and thalamus were associated with poor motor improvement, other structures such as the lateral-occipital cortex and anterior cingulate were also reported to correlated with motor outcome. Regarding non-motor outcomes, decreased volume of the hippocampus was reported to correlate with poor cognitive outcomes. Structures such as the thalamus, nucleus accumbens, and nucleus of basalis of Meynert were also reported to correlate with cognitive functions. Caudal middle frontal cortex was reported to have an impact on postsurgical psychiatric changes. Collectively, the findings of this review emphasize the utility of brain morphometry in outcome prediction of DBS for PD. Future efforts are needed to validate the findings and demonstrate the feasibility of brain morphometry in larger cohorts.

Functional topologies of spatial cognition predict cognitive and motor progression in Parkinson’s

Background

Spatial cognition deteriorates in Parkinson’s disease (PD), but the neural substrates are not understood, despite the risk for future dementia. It is also unclear whether deteriorating spatial cognition relates to changes in other cognitive domains or contributes to motor dysfunction.

Objective

This study aimed to identify functional connectivity abnormalities in cognitively normal PD (PDCN) in regions that support spatial cognition to determine their relationship to interfacing cognitive functions and motor disability, and to determine if they predict cognitive and motor progression 2 years later in a PDCN subsample.

Methods

Sixty-three PDCN and 43 controls underwent functional MRI while judging whether pictures, rotated at various angles, depicted the left or right hand. The task activates systems that respond to increases in rotation angle, a proxy for visuospatial difficulty. Angle-modulated functional connectivity was analyzed for frontal cortex, posterior cortex, and basal ganglia regions.

Results

Two aberrant connectivity patterns were found in PDCN, which were condensed into principal components that characterized the strength and topology of angle-modulated connectivity. One topology related to a marked failure to amplify frontal, posterior, and basal ganglia connectivity with other brain areas as visuospatial demands increased, unlike the control group (control features). Another topology related to functional reorganization whereby regional connectivity was strengthened with brain areas not recruited by the control group (PDCN features). Functional topologies correlated with diverse cognitive domains at baseline, underscoring their influences on spatial cognition. In PDCN, expression of topologies that were control features predicted greater cognitive progression longitudinally, suggesting inefficient communications within circuitry normally recruited to handle spatial demands. Conversely, stronger expression of topologies that were PDCN features predicted less longitudinal cognitive decline, suggesting functional reorganization was compensatory. Parieto-occipital topologies (control features) had different prognostic implications for longitudinal changes in motor disability. Expression of one topology predicted less motor decline, whereas expression of another predicted increased postural instability and gait disturbance (PIGD) feature severity. Concurrently, greater longitudinal decline in spatial cognition predicted greater motor and PIGD feature progression, suggesting deterioration in shared substrates.

Conclusion

These novel discoveries elucidate functional mechanisms of visuospatial cognition in PDCN, which foreshadow future cognitive and motor disability.

Mental rotation of hands and objects in ageing and Parkinson's disease: differentiating motor imagery and visuospatial ability

Motor imagery supports motor learning and performance and has the potential to be a useful strategy for neurorehabilitation. However, motor imagery ability may be impacted by ageing and neurodegeneration, which could limit its therapeutic effectiveness. Motor imagery can be assessed implicitly using a hand laterality task (HLT), whereby laterality judgements are slower for stimuli corresponding to physically more difficult postures, as indicated by a “biomechanical constraint” effect. Performance is also found to differ between back and palm views of the hand, which may differentially recruit visual and sensorimotor processes. Older adults and individuals with Parkinson’s disease (PD) have shown altered performance on the HLT; however, the effects of both ageing and PD on laterality judgements for the different hand views (back and palm) have not been directly examined. The present study compared healthy younger, healthy older, and PD groups on the HLT, an object-based mental rotation task, and an explicit motor imagery measure. The older and PD groups were slower than the younger group on the HLT, particularly when judging laterality from the back view, and exhibited increased biomechanical constraint effects for the palm. While response times were generally similar between older and PD groups, the PD group showed reduced accuracy for the back view. Letter rotation was slower and less accurate only in the PD group, while explicit motor imagery ratings did not differ significantly between groups. These results suggest that motor imagery may be slowed but relatively preserved in both typical ageing and neurodegeneration, while a PD-specific impairment in visuospatial processing may influence task performance. The findings have implications for the use of motor imagery in rehabilitation protocols.

Differences in neuroanatomy and functional connectivity between motor subtypes of Parkinson’s disease

Background

The “postural instability/gait difficulty” (PIGD) and “tremor-dominant” (TD) motor subtypes of Parkinson’s disease (PD) differ in their clinical manifestations. The neurological basis of these differences is unclear.

Methods

We performed voxel-based morphometric analysis and measured amplitudes of low-frequency fluctuation (ALFF) on 87 PIGD patients and 51 TD patients. We complemented this neuroanatomical comparison with seed-to-voxel analysis to explore differences in functional connectivity.

Results

The PIGD group showed significantly smaller gray matter volume in the medial frontal gyrus (mainly on the right side) than the TD group. Across all patients, gray matter volume in the medial frontal gyrus correlated negatively with severity of PIGD symptoms after controlling for age (r = −0.250, p = 0.003), but this correlation was not observed in separate analyses of only PIGD or TD patients. The PIGD group showed greater functional connectivity of the right superior frontal gyrus with the left lingual gyrus, right lateral occipital cortex, and right lingual gyrus. ALFF did not differ significantly between the two groups.

Conclusion

Postural instability/gait difficulty may be associated with smaller gray matter volume in medial frontal gyrus than TD, as well as with greater functional connectivity between the right superior frontal gyrus and occipital cortex. These results may help explain the clinical differences between the two motor subtypes of PD.

OUP accepted manuscript

Neuralgic amyotrophy is a common peripheral nerve disorder caused by autoimmune inflammation of the brachial plexus, clinically characterized by acute pain and weakness of the shoulder muscles, followed by motor impairment. Despite recovery of the peripheral nerves, patients often have residual motor dysfunction of the upper extremity, leading to persistent pain related to altered biomechanics of the shoulder region. Building on clinical signs that suggest a role for cerebral mechanisms in these residual complaints, here we show and characterize cerebral alterations following neuralgic amyotrophy. Neuralgic amyotrophy patients often develop alternative motor strategies, which suggests that (mal)adaptations may occur in somatomotor and/or visuomotor brain areas. Here, we tested where changes in cerebral sensorimotor representations occur in neuralgic amyotrophy, while controlling for altered motor execution due to peripheral neuropathy. We additionally explore the relation between potential cerebral alterations in neuralgic amyotrophy and clinical symptoms. During functional MRI scanning, 39 neuralgic amyotrophy patients with persistent, lateralized symptoms in the right upper extremity and 23 matched healthy participants solved a hand laterality judgement task that can activate sensorimotor representations of the upper extremity, across somatomotor and visuomotor brain areas. Behavioural and cerebral responses confirmed the involvement of embodied, sensorimotor processes across groups. Compared with healthy participants, neuralgic amyotrophy patients were slower in hand laterality judgement and had decreased cerebral activity specific to their affected limb in two higher-order visual brain regions: the right extrastriate cortex and the parieto-occipital sulcus. Exploratory analyses revealed that across patients, extrastriate activity specific to the affected limb decreased as persistent pain increased, and affected limb-related parieto-occipital activity decreased as imagery performance of the affected limb became slower. These findings suggest that maladaptive cerebral plasticity in visuomotor areas involved in sensorimotor integration plays a role in residual motor dysfunction and subsequent persistent pain in neuralgic amyotrophy. Rehabilitation interventions that apply visuomotor strategies to improve sensorimotor integration may help to treat neuralgic amyotrophy patients.

Continuous Theta Burst Stimulation to the Secondary Visual Cortex at 80% Active Motor Threshold Does Not Impair Central Vision in Humans During a Simple Detection Task

Continuous theta burst stimulation (cTBS) is a powerful form of repetitive transcranial magnetic stimulation capable of suppressing cortical excitability for up to 50 min. A growing number of studies have applied cTBS to the visual cortex in human subjects to investigate the neural dynamics of visual processing, but few have specifically examined its effects on central vision, which has crucial implications for safety and inference on downstream cognitive effects. The present study assessed the safety of offline, neuronavigated cTBS to V2 by examining its effects on central vision performance. In this single-blind, randomized sham-controlled, crossover study, 17 healthy adults received cTBS (at 80% active motor threshold) and sham to V2 1–2 weeks apart. Their central vision (≤8°) was tested at 1-min (T1) and again at 50-min (T50) post-stimulation. Effects of condition (cTBS vs. sham) and time (T1 vs. T50) on accuracy and reaction time were examined using Bayes factor. Bayes factor results suggested that cTBS did not impair stimulus detection over the entire central visual field nor subfields at T1 or T50. Our results offer the first explicit evidence supporting that cTBS applied to V2 does not create blind spots in the central visual field in humans during a simple detection task. Any subtler changes to vision and downstream visual perception should be investigated in future studies.

Action Imagery and Observation in Neurorehabilitation for Parkinson's Disease (ACTION-PD): Development of a User-Informed Home Training Intervention to Improve Functional Hand Movements

Background

Parkinson's disease (PD) causes difficulties with hand movements, which few studies have addressed therapeutically. Training with action observation (AO) and motor imagery (MI) improves performance in healthy individuals, particularly when the techniques are applied simultaneously (AO + MI). Both AO and MI have shown promising effects in people with PD, but previous studies have only used these separately.

Objective

This article describes the development and pilot testing of an intervention combining AO + MI and physical practice to improve functional manual actions in people with PD.

Methods

The home-based intervention, delivered using a tablet computer app, was iteratively designed by an interdisciplinary team, including people with PD, and further developed through focus groups and initial field testing. Preliminary data on feasibility were obtained via a six-week pilot randomised controlled trial (ISRCTN 11184024) of 10 participants with mild to moderate PD (6 intervention; 4 treatment as usual). Usage and adherence data were recorded during training, and semistructured interviews were conducted with participants. Exploratory outcome measures included dexterity and timed action performance.

Results

Usage and qualitative data provided preliminary evidence of acceptability and usability. Exploratory outcomes also suggested that subjective and objective performance of manual actions should be tested in a larger trial. The importance of personalisation, choice, and motivation was highlighted, as well as the need to facilitate engagement in motor imagery.

Conclusions

The results indicate that a larger RCT is warranted, and the findings also have broader relevance for the feasibility and development of AO + MI interventions for PD and other conditions.

The Relationship Between Corticomotor Reorganization and Acute Pain Severity: A Randomized, Controlled Study Using Rapid Transcranial Magnetic Stimulation Mapping

OBJECTIVE

Although acute pain has been shown to reduce corticomotor excitability, it remains unknown whether this response resolves over time or is related to symptom severity. Furthermore, acute pain research has relied upon data acquired from the cranial "hotspot," which do not provide valuable information regarding reorganization, such as changes to the distribution of a painful muscle's representation within M1. Using a novel, rapid transcranial magnetic stimulation (TMS) mapping method, this study aimed to 1) explore the temporal profile and variability of corticomotor reorganization in response to acute pain and 2) determine whether individual patterns of corticomotor reorganization are associated with differences in pain, sensitivity, and somatosensory organization.

METHODS

Corticomotor (TMS maps), pain processing (pain intensity, pressure pain thresholds), and somatosensory (two-point discrimination, two-point estimation) outcomes were taken at baseline, immediately after injection (hypertonic [n = 20] or isotonic saline [n = 20]), and at pain resolution. Follow-up measures were recorded every 15 minutes until 90 minutes after injection.

RESULTS

Corticomotor reorganization persisted at least 90 minutes after pain resolution. Corticomotor depression was associated with lower pain intensity than was corticomotor facilitation (r = 0.47 [P = 0.04]). These effects were not related to somatosensory reorganization or peripheral sensitization mechanisms.

CONCLUSIONS

Individual patterns of corticomotor reorganization during acute pain appear to be related to symptom severity, with early corticomotor depression possibly reflecting a protective response. These findings hold important implications for the management and potential prevention of pain chronicity. However, further research is required to determine whether these adaptations relate to long-term outcomes in clinical populations.

Action observation and imitation in Parkinson's disease: The influence of biological and non-biological stimuli

Action observation and imitation have been found to influence movement in people with Parkinson's disease (PD), but simple visual stimuli can also guide their movement. To investigate whether action observation may provide a more effective stimulus than other visual cues, the present study examined the effects of observing human pointing movements and simple visual stimuli on hand kinematics and eye movements in people with mild to moderate PD and age-matched controls. In Experiment 1, participants observed videos of movement sequences between horizontal positions, depicted by a simple cue with or without a moving human hand, then imitated the sequence either without further visual input (consecutive task) or while watching the video again (concurrent task). Modulation of movement duration, in accordance with changes in the observed stimulus, increased when the simple cue was accompanied by the hand and in the concurrent task, whereas modulation of horizontal amplitude was greater with the simple cue alone and in the consecutive task. Experiment 2 compared imitation of kinematically-matched dynamic biological (human hand) and non-biological (shape) stimuli, which moved with a high or low vertical trajectory. Both groups exhibited greater modulation for the hand than the shape, and differences in eye movements suggested closer tracking of the hand. Despite producing slower and smaller movements overall, the PD group showed a similar pattern of imitation to controls across tasks and conditions. The findings demonstrate that observing human action influences aspects of movement such as duration or trajectory more strongly than non-biological stimuli, particularly during concurrent imitation.

Implicit Motor Imagery and the Lateral Occipitotemporal Cortex: Hints for Tailoring Non-Invasive Brain Stimulation

Background: Recent evidence has converged in showing that the lateral occipitotemporal cortex is over-recruited during implicit motor imagery in elderly and in patients with neurodegenerative disorders, such as Parkinson’s disease. These data suggest that when automatically imaging movements, individuals exploit neural resources in the visual areas to compensate for the decline in activating motor representations. Thus, the occipitotemporal cortex could represent a cortical target of non-invasive brain stimulation combined with cognitive training to enhance motor imagery performance. Here, we aimed at shedding light on the role of the left and right lateral occipitotemporal cortex in implicit motor imagery. Methods: We applied online, high-frequency, repetitive transcranial magnetic stimulation (rTMS) over the left and right lateral occipitotemporal cortex while healthy right-handers judged the laterality of hand images. Results: With respect to the sham condition, left hemisphere stimulation specifically reduced accuracy in judging the laterality of right-hand images. Instead, the hallmark of motor simulation, i.e., the biomechanical effect, was never influenced by rTMS. Conclusions: The lateral occipitotemporal cortex seems to be involved in mental representation of the dominant hand, at least in right-handers, but not in reactivating sensorimotor information during simulation. These findings provide useful hints for developing combined brain stimulation and behavioural trainings to improve motor imagery.

Motor Imagery Development in Children: Changes in Speed and Accuracy With Increasing Age

Although motor imagery has been pointed as a promising strategy for the rehabilitation of children with neurological disorders, information on their development throughout childhood and adolescence is still scarce. For instance, it is still unclear at what age they reach a development comparable to the motor imagery performance observed in adults. Herein we used a mental rotation task to assess motor imagery in 164 typically developing children and adolescents, which were divided into four age groups (6-7, 8-9, 10-11, and 12-13 years) and 30 adults. The effects of biomechanical constraints, accuracy, and reaction time of the mental rotation task were considered. ANOVA showed that all groups had the effect of biomechanical restrictions of the mental rotation task. We found a group effect for accuracy [F (4, 180) = 17,560; p < 0.00; η2 = 3.79] and reaction time [F (4, 180) = 17.5; p < 0.001, η2 = 0.615], with the results of children groups 6-7 and 8-9 years being significantly lower than the other groups (p < 0.05). In all the analyses, there were no differences regarding accuracy and reaction time among the participants of the age groups 10-11 and 12-13 years and adults (p > 0.05). Concluding, children aged 6-7 years were able to perform motor imagery, motor imagery ability improved as the participants' ages increased, and children aged 10 and over-performed similarly to adults.

Altered sensorimotor representations after recovery from peripheral nerve damage in neuralgic amyotrophy

Neuralgic amyotrophy is a common peripheral nerve disorder caused by acute autoimmune inflammation of the brachial plexus. Subsequent weakness of the stabilizing shoulder muscles leads to compensatory strategies and abnormal motor control of the shoulder. Despite recovery of peripheral nerves and muscle strength over time, motor dysfunction often persists. Suboptimal motor recovery has been linked to maladaptive changes in the central motor system in several nervous system disorders. We therefore hypothesized that neuralgic amyotrophy patients with persistent motor dysfunction may have altered cerebral sensorimotor representations of the affected upper limb. To test this hypothesis, 21 neuralgic amyotrophy patients (mean age 45 ± 12 years, 5 female) with persistent lateralized symptoms in the right upper limb and 20 age- and sex-matched healthy controls, all right-handed, performed a hand laterality judgement task in a cross-sectional comparison. Previous evidence has shown that to solve this task, subjects rely on sensorimotor representations of their own upper limb, using a first-person imagery perspective without actual motor execution. This enabled us to investigate altered central sensorimotor representations while controlling for altered motor output and altered somatosensory afference. We found that neuralgic amyotrophy patients were specifically less accurate for laterality judgments of their affected right limb, as compared to healthy controls. There were no significant group differences in reaction times. Both groups used a first-person imagery perspective, as evidenced by changes in reaction times as a function of participants' own arm posture. We conclude that cerebral sensorimotor representations of the affected upper limb are altered in neuralgic amyotrophy patients. This suggests that maladaptive central neuroplasticity may occur in response to peripheral nerve damage, thereby contributing to motor dysfunction. Therapies focused on altering cerebral sensorimotor representations may help to treat peripheral nerve disorders such as neuralgic amyotrophy.

Cortical thickness in visuo-motor areas is related to motor outcomes after STN DBS for Parkinson's disease

INTRODUCTION

Deep brain stimulation (DBS) is a widely accepted therapy for Parkinson's disease. While outcome predictors such as levodopa-response are well established, there remains a need for objective and unbiased predictors in clinical practice. We performed an exploratory study to examine whether cortical thickness, derived from preoperative MRI, correlates with postoperative outcome.

METHODS

Using freesurfer, we retrospectively measured cortical thickness on the preoperative MRI of 38 patients who underwent bilateral STN-DBS for PD during a 4-year period. The Unified Parkinson Disease Rating motor (UPDRS III) and experiences of daily living subscales (UPDRS II) were collected at baseline and six months after surgery. As an initial analysis, a series of partial correlations was conducted to evaluate the association between postoperative outcome scores and average cortical thickness from predefined regions of interest, adjusting for candidate confounders, without correcting for multiple comparisons. A confirmatory vertex-wise analysis was performed using a cluster-wise correction for multiple comparisons.

RESULTS

Based on the ROI analysis, the strongest correlation with motor outcome was found to be with the left lateral-occipital cortex. Patients with greater cortical thickness in this area presented with greater improvements in motor scores. This relationship was also supported by the vertex-wise analysis. Greater cortical thickness in frontal and temporal regions may be correlated with greater post-operative improvements in UPDRS II, but this was not confirmed in the vertex-wise analysis.

CONCLUSIONS

Our data indicate that greater cortical thickness in visuo-motor areas is correlated with motor outcomes after DBS for PD. Further prospective investigations are needed to confirm our findings and better-investigate potential image biomarkers.

Dance and Parkinson's: A review and exploration of the role of cognitive representations of action

Parkinson's disease (PD) is a neurodegenerative condition that causes both sensorimotor and non-motor impairments, and there is a clear need for non-medical approaches to improve quality of life. Dance is an increasingly popular activity among people with PD, which demonstrates potential therapeutic benefits. However, findings to date have been inconsistent, and little is known about the mechanisms underlying benefits of dance in PD. In this review, we provide an overview of research into dance for people with PD. The majority of quantitative evidence is in the sensorimotor domain, but cognitive, psychological and social effects have also been reported. We consider the role of cognitive representations of action within dance through observation, imitation and imagery, which may contribute to both sensorimotor and non-motor outcomes for people with PD. Moreover, we discuss how these processes may be enhanced through dance to provide further benefits in everyday life. Finally, we propose avenues for future research to increase understanding of action representation in dance for PD, which has the potential to inform practice and maximize benefits.

NA-CONTROL: a study protocol for a randomised controlled trial to compare specific outpatient rehabilitation that targets cerebral mechanisms through relearning motor control and uses self-management strategies to improve functional capability of the upper extremity, to usual care in patients with neuralgic amyotrophy

Background

Neuralgic amyotrophy (NA) is a distinct peripheral neurological disorder of the brachial plexus with a yearly incidence of 1/1000, which is characterised by acute severe upper extremity pain. Weakness of the stabilising shoulder muscles in the acute phase leads to compensatory strategies and abnormal motor control of the shoulder - scapular dyskinesia. Despite peripheral nerve recovery, scapular dyskinesia often persists, leading to debilitating residual complaints including pain and fatigue. Evidence suggests that persistent scapular dyskinesia in NA may result from maladaptive cerebral neuroplasticity, altering motor planning. Currently there is no proven effective causative treatment for the residual symptoms in NA. Moreover, the role of cerebral mechanisms in persistent scapular dyskinesia remains unclear.

Methods

NA-CONTROL is a single-centre, randomised controlled trial comparing specific rehabilitation to usual care in NA. The rehabilitation programme combines relearning of motor control, targeting cerebral mechanisms, with self-management strategies. Fifty patients will be included. Patients are recruited through the Radboud university medical center Nijmegen, the Netherlands. Patients with a (suspected) diagnosis of NA, with lateralized symptoms and scapular dyskinesia in the right upper extremity, who are 18 years or older and not in the acute phase can be included. The primary outcome is the Shoulder Rating Questionnaire score, which measures functional capability of the upper extremity. Secondary clinical outcomes include measures of pain, fatigue, participation, reachable workspace, muscle strength and quality of life. In addition, motor planning is assessed with first-person motor imagery and functional magnetic resonance imaging. In a sub-study the patients are compared to 25 healthy participants, to determine the involvement of cerebral mechanisms. This will enable interpretation of cerebral changes associated with the rehabilitation programme and functional impairments in NA.

Discussion

NA-CONTROL is the first randomised trial to investigate the effect of specific rehabilitation on residual complaints in NA. It also is the first study into the cerebral mechanisms that might underlie persistent scapular dyskinesia in NA. It thus may aid the further development of mechanism-based interventions for disturbed motor control in NA and in other peripheral neurological disorders.

Trial registration

ClinicalTrials.gov, NCT03441347. Registered on 20 February 2018.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3556-4) contains supplementary material, which is available to authorized users.

Mental representation of the body in action in Parkinson's disease

Mixed findings characterize studies in Parkinson's disease (PD): some studies indicate a relationship between physical impairments and the ability to mentally represent the body, while others suggest spared abilities for this cognitive function. To clarify the matter, in the present study we explored the mental representations of the body in action in the same PD patients, taking also into account lateralization of symptoms and visual imagery skills. 10 PD patients with left- (lPD), 10 with right (rPD) lateralized symptoms (lPD), and 20 matched healthy controls have been recruited for the study. All patients were screened for neuropsychological impairments. To explore a more implicit component we used the hand laterality task (HLT), while the mental motor chronometry (MMC) was used to explore a more explicit one. Two control tasks, with objects instead of body parts, were administered to control for visual imagery skills. In the HLT, we detected the effects of biomechanical constraints effects in both controls and PD patients. In the latter group, importantly, this was true independently from lateralization of symptoms. In the MMC, we found the expected positive correlation between executed and imagined movements for both hands in controls only, while all PD patients, again independently form lateralization, only showed this effect for the left hand. In terms of visual imagery, only rPD patients differed from controls when asked to implicitly rotate letters, and in terms of accuracy only. However, this difference is explained by executive functions measured through the neuropsychological assessment rather than by a "pure" visual imagery impairment. In summary, our findings suggest that two different aspects of the mental representations of the body in action, one more implicit and the other more explicit, can be differently affected by PD. These impairments are unlikely explained by a basic visual imagery deficit. When present, impairments concern a higher dimension, related to motor functions and awareness, and not driven by sensory impairments, as shown by the independence of effects from physical laterality of symptoms.

The reliability and validity of rapid transcranial magnetic stimulation mapping

BACKGROUND

Traditional transcranial magnetic stimulation mapping involves systematically delivering stimuli over a predefined grid. The pseudorandom walk method seeks to improve map acquisition times by abandoning the grid in favour of delivering stimuli randomly over a given area.

OBJECTIVES

To i) determine the minimum interstimulus interval (ISI) required for reliable mapping outcomes within and between sessions using the pseudorandom walk method and ii) assess the validity of the pseudorandom walk method by testing its equivalence with traditional mapping.

METHODS

Maps collected using the pseudorandom walk method at four ISIs (4, 3, 2, and 1s) were compared to maps collected using traditional mapping in twenty healthy individuals. Outcomes included map area, volume, centre of gravity, mean MEP amplitude, and number of discrete peaks.

RESULTS AND CONCLUSIONS

The pseudorandom walk method was valid and reliable with a 2-second ISI for all outcomes except number of discrete peaks, which was less reliable than other measures.

Action observation produces motor resonance in Parkinson's disease

Observation of movement activates the observer's own motor system, influencing the performance of actions and facilitating social interaction. This motor resonance is demonstrated behaviourally through visuomotor priming, whereby response latencies are influenced by the compatibility between an intended action and an observed (task-irrelevant) action. The impact of movement disorders such as Parkinson's disease (PD) on motor resonance is unclear, as previous studies of visuomotor priming have not separated imitative compatibility (specific to human movement) from general stimulus-response compatibility effects. We examined visuomotor priming in 23 participants with mild-to-moderate PD and 24 healthy older adults, using a task that pitted imitative compatibility against general stimulus-response compatibility. Participants made a key press after observing a task-irrelevant moving human finger or rectangle that was either compatible or incompatible with their response. Imitative compatibility effects, rather than general stimulus-response compatibility effects, were found specifically for the human finger. Moreover, imitative compatibility effects did not differ between groups, indicating intact motor resonance in the PD group. These findings constitute the first unambiguous demonstration of imitative priming in both PD and healthy ageing, and have implications for therapeutic techniques to facilitate action, as well as the understanding of social cognition in PD.

Effect of Fear of Falling on Turning Performance in Parkinson's Disease in the Lab and at Home

Background: Parkinson’s disease (PD) is a neurodegenerative movement disorder associated with gait and balance problems and a substantially increased risk of falling. Falls occur often during complex movements, such as turns. Both fear of falling (FOF) and previous falls are relevant risk factors for future falls. Based on recent studies indicating that lab-based and home assessment of similar movements show different results, we hypothesized that FOF and a positive fall history would influence the quantitative turning parameters differently in the laboratory and home.

Methods: Fifty-five PD patients (43 underwent a standardized lab assessment; 40 were assessed over a mean of 12 days at home with approximately 10,000 turns per participant; and 28 contributed to both assessments) were classified regarding FOF and previous falls as “vigorous” (no FOF, negative fall history), “anxious” (FOF, negative fall history), “stoic” (no FOF, positive fall history) and “aware” (FOF, positive fall history). During the assessments, each participant wore a sensor on the lower back.

Results: In the lab assessment, FOF was associated with a longer turning duration and lowered maximum and middle angular velocities of turns. In the home evaluations, a lack of FOF was associated with lowered maximum and average angular velocities of turns. Positive falls history was not significantly associated with turning parameters, neither in the lab nor in the home.

Conclusion: FOF but not a positive fall history influences turning metrics in PD patients in both supervised and unsupervised environments, and this association is different between lab and home assessments. Our findings underline the relevance of comprehensive assessments including home-based data collection strategies for fall risk evaluation.

Inhibition or facilitation? Modulation of corticospinal excitability during motor imagery

Motor imagery (MI) is the mental simulation of an action without any overt movement. Functional evidences show that brain activity during MI and motor execution (ME) largely overlaps. However, the role of the primary motor cortex (M1) during MI is controversial. Effective connectivity techniques show a facilitation on M1 during ME and an inhibition during MI, depending on whether an action should be performed or suppressed. Conversely, Transcranial Magnetic Stimulation (TMS) studies report facilitatory effects during both ME and MI. The present TMS study shed light on MI mechanisms, by manipulating the instructions given to the participants. In both Experimental and Control groups, participants were asked to mentally simulate a finger-thumb opposition task, but only the Experimental group received the explicit instruction to avoid any unwanted fingers movements. The amplitude of motor evoked potentials (MEPs) to TMS during MI was compared between the two groups. If the M1 facilitation actually pertains to MI per se, we should have expected to find it, irrespective of the instructions. Contrariwise, we found opposite results, showing facilitatory effects (increased MEPs amplitude) in the Control group and inhibitory effects (decreased MEPs amplitude) in the Experimental group. Control experiments demonstrated that the inhibitory effect was specific for the M1 contralateral to the hand performing the MI task and that the given instructions did not compromise the subjects' MI abilities. The present findings suggest a crucial role of motor inhibition when a "pure" MI task is performed and the subjects are explicitly instructed to avoid overt movements.

Is the extrastriate body area part of the dorsal visuomotor stream?

The extrastriate body area (EBA) processes visual information about body parts, and it is considered one among a series of category-specific perceptual modules distributed across the occipito-temporal cortex. However, recent evidence raises the possibility that EBA might also provide an interface between perception and action, linking the ventral and dorsal streams of visual information processing. Here, we assess anatomical evidence supporting this possibility. We localise EBA in individual subjects using a perceptual task and compare the characteristics of its functional and structural connectivity to those of two perceptual areas, the lateral occipital complex (LOC) and the fusiform body area (FBA), separately for each hemisphere. We apply complementary analyses of resting-state fMRI and diffusion-weighted MRI data in a group of healthy right-handed human subjects (N = 31). Functional and structural connectivity profiles indicate that EBA interacts more strongly with dorsal-stream regions compared to other portions of the occipito-temporal cortex involved in processing body parts (FBA) and object identification (LOC). These findings provide anatomical ground for a revision of the functional role of EBA. Building on a number of recent observations, we suggest that EBA contributes to planning goal-directed actions, possibly by specifying a desired postural configuration to parieto-frontal areas involved in computing movement parameters.

The Lateral Occipito-temporal Cortex Is Involved in the Mental Manipulation of Body Part Imagery

The lateral occipito-temporal cortex (LOTC), including the extrastriate body area, is known to be involved in the perception of body parts. Although still controversial, recent studies have demonstrated the role of the LOTC in higher-level body-related cognition in humans. This study consisted of two experiments (E1 and E2). The first (E1) was an exploratory experiment to find the neural correlate of the mental manipulation of body part imagery, in which brain cerebral glucose metabolic rates and the performance of mental rotation of the hand were measured in 100 subjects who exhibited a range of symptoms of cognitive decline. In E1, we found that the level of glucose metabolism in the right LOTC was significantly correlated with performance in a task involving mental manipulation of the hand. Next, in E2, we performed a randomized, double-blind, controlled intervention study (clinical trial number: UMIN 000018310) in younger healthy adults to test whether right occipital (corresponding to the right LOTC) anodal stimulation using transcranial direct current stimulation (tDCS) could enhance the mental manipulation of the hand. In E2, we demonstrated a significant effect of tDCS on the accuracy rate in a task involving mental manipulation of the hand. Although further study is necessary to answer the question of whether these results are specific for the mental manipulation of body parts but not non-body parts, E1 demonstrated a possible role of the LOTC in carrying out the body mental manipulation task in patients with dementia, and E2 suggested the possible effect of tDCS on this task in healthy subjects.

Experience-dependent modulation of alpha and beta during action observation and motor imagery

Background

EEG studies investigating the neural networks that facilitate action observation (AO) and kinaesthetic motor imagery (KMI) have shown reduced, or desynchronized, power in the alpha (8–12 Hz) and beta (13–30 Hz) frequency bands relative to rest, reflecting efficient activation of task-relevant areas. Functional modulation of these networks through expertise in dance has been established using fMRI, with greater activation among experts during AO. While there is evidence for experience-dependent plasticity of alpha power during AO of dance, the influence of familiarity on beta power during AO, and alpha and beta activity during KMI, remain unclear. The purpose of the present study was to measure the impact of familiarity on confidence ratings and EEG activity during (1) AO of a brief ballet sequence, (2) KMI of this same sequence, and (3) KMI of non-dance movements among ballet dancers, dancers from other genres, and non-dancers.

Results

Ballet dancers highly familiar with the genre of the experimental stimulus demonstrated higher individual alpha peak frequency (iAPF), greater alpha desynchronization, and greater task-related beta power during AO, as well as faster iAPF during KMI of non-dance movements. While no between-group differences in alpha or beta power were observed during KMI of dance or non-dance movements, all participants showed significant desynchronization relative to baseline, and further desynchronization during dance KMI relative to non-dance KMI indicative of greater cognitive load.

Conclusions

These findings confirm and extend evidence for experience-dependent plasticity of alpha and beta activity during AO of dance and KMI. We also provide novel evidence for modulation of iAPF that is faster when tuned to the specific motor repertoire of the observer. By considering the multiple functional roles of these frequency bands during the same task (AO), we have disentangled the compounded contribution of familiarity and expertise to alpha desynchronization for mediating task engagement among familiar ballet dancers and reflecting task difficulty among unfamiliar non-dance subjects, respectively. That KMI of a complex dance sequence relative to everyday, non-dance movements recruits greater cognitive resources suggests it may be a more powerful tool in driving neural plasticity of action networks, especially among the elderly and those with movement disorders.

Changes in neural circuitry associated with depression at pre-clinical, pre-motor and early motor phases of Parkinson's disease

Although Parkinson's Disease (PD) is mostly considered a motor disorder, it can present at early stages as a non-motor pathology. Among the non-motor clinical manifestations, depression shows a high prevalence and can be one of the first clinical signs to appear, even a decade before the onset of motor symptoms. Here, we review the evidence of early dysfunction in neural circuitry associated with depression in the context of PD, focusing on pre-clinical, pre-motor and early motor phases of the disease. In the pre-clinical phase, structural and functional changes in the substantia nigra, basal ganglia and limbic structures are already observed. Some of these changes are linked to motor compensation mechanisms while others correspond to pathological processes common to PD and depression and thus could underlie the appearance of depressive symptoms during the pre-motor phase. Studies of the early motor phase (less than five years post diagnosis) reveal an association between the extent of damage in different monoaminergic systems and the appearance of emotional disorders. We propose that the limbic loop of the basal ganglia and the lateral habenula play key roles in the early genesis of depression in PD. Alterations in the neural circuitry linked with emotional control might be sensitive markers of the ongoing neurodegenerative process and thus may serve to facilitate an early diagnosis of this disease. To take advantage of this, we need to improve the clinical criteria and develop biomarkers to identify depression, which could be used to determine individuals at risk to develop PD.

Prefrontal Markers and Cognitive Performance Are Dissociated during Progressive Dopamine Lesion

Dopamine is thought to directly influence the neurophysiological mechanisms of both performance monitoring and cognitive control-two processes that are critically linked in the production of adapted behaviour. Changing dopamine levels are also thought to induce cognitive changes in several neurological and psychiatric conditions. But the working model of this system as a whole remains untested. Specifically, although many researchers assume that changing dopamine levels modify neurophysiological mechanisms and their markers in frontal cortex, and that this in turn leads to cognitive changes, this causal chain needs to be verified. Using longitudinal recordings of frontal neurophysiological markers over many months during progressive dopaminergic lesion in non-human primates, we provide data that fail to support a simple interaction between dopamine, frontal function, and cognition. Feedback potentials, which are performance-monitoring signals sometimes thought to drive successful control, ceased to differentiate feedback valence at the end of the lesion, just before clinical motor threshold. In contrast, cognitive control performance and beta oscillatory markers of cognitive control were unimpaired by the lesion. The differing dynamics of these measures throughout a dopamine lesion suggests they are not all driven by dopamine in the same way. These dynamics also demonstrate that a complex non-linear set of mechanisms is engaged in the brain in response to a progressive dopamine lesion. These results question the direct causal chain from dopamine to frontal physiology and on to cognition. They imply that biomarkers of cognitive functions are not directly predictive of dopamine loss.

Patients' Views on a Combined Action Observation and Motor Imagery Intervention for Parkinson's Disease

Background. Action observation and motor imagery activate neural structures involved in action execution, thereby facilitating movement and learning. Although some benefits of action observation and motor imagery have been reported in Parkinson's disease (PD), methods have been based on stroke rehabilitation and may be less suitable for PD. Moreover, previous studies have focused on either observation or imagery, yet combining these enhances effects in healthy participants. The present study explores the feasibility of a PD-specific home-based intervention combining observation, imagery, and imitation of meaningful everyday actions. Methods. A focus group was conducted with six people with mild to moderate PD and two companions, exploring topics relating to the utility and feasibility of a home-based observation and imagery intervention. Results. Five themes were identified. Participants reported their experiences of exercise and use of action observation and motor imagery in everyday activities, and the need for strategies to improve movement was expressed. Motivational factors including feedback, challenge, and social support were identified as key issues. The importance of offering a broad range of actions and flexible training was also highlighted. Conclusions. A home-based intervention utilising action observation and motor imagery would be useful and feasible in mild to moderate PD.

Body Constraints on Motor Simulation in Autism Spectrum Disorders

Developmental data suggested that mental simulation skills become progressively dissociated from overt motor activity across development. Thus, efficient simulation is rather independent from current sensorimotor information. Here, we tested the impact of bodily (sensorimotor) information on simulation skills of adolescents with Autism Spectrum Disorders (ASD). Typically-developing (TD) and ASD participants judged laterality of hand images while keeping one arm flexed on chest or while holding both arms extended. Both groups were able to mentally simulate actions, but this ability was constrained by body posture more in ASD than in TD adolescents. The strong impact of actual body information on motor simulation implies that simulative skills are not fully effective in ASD individuals.

Human behavioral assessments in current research of Parkinson's disease

Parkinson's disease (PD) is traditionally classified as a movement disorder because patients mainly complain about motor symptoms. Recently, non-motor symptoms of PD have been recognized by clinicians and scientists as early signs of PD, and they are detrimental factors in the quality of life in advanced PD patients. It is crucial to comprehensively understand the essence of behavioral assessments, from the simplest measurement of certain symptoms to complex neuropsychological tasks. We have recently reviewed behavioral assessments in PD research with animal models (Asakawa et al., 2016). As a companion volume, this article will systematically review the behavioral assessments of motor and non-motor PD symptoms of human patients in current research. The major aims of this article are: (1) promoting a comparative understanding of various behavioral assessments in terms of the principle and measuring indexes; (2) addressing the major strengths and weaknesses of these behavioral assessments for a better selection of tasks/tests in order to avoid biased conclusions due to inappropriate assessments; and (3) presenting new concepts regarding the development of wearable devices and mobile internet in future assessments. In conclusion we emphasize the importance of improving the assessments for non-motor symptoms because of their complex and unique mechanisms in human PD brains.

The Extrastriate Body Area Computes Desired Goal States during Action Planning

How do object perception and action interact at a neural level? Here we test the hypothesis that perceptual features, processed by the ventral visuoperceptual stream, are used as priors by the dorsal visuomotor stream to specify goal-directed grasping actions. We present three main findings, which were obtained by combining time-resolved transcranial magnetic stimulation and kinematic tracking of grasp-and-rotate object manipulations, in a group of healthy human participants (N = 22). First, the extrastriate body area (EBA), in the ventral stream, provides an initial structure to motor plans, based on current and desired states of a grasped object and of the grasping hand. Second, the contributions of EBA are earlier in time than those of a caudal intraparietal region known to specify the action plan. Third, the contributions of EBA are particularly important when desired and current object configurations differ, and multiple courses of actions are possible. These findings specify the temporal and functional characteristics for a mechanism that integrates perceptual processing with motor planning.

Lateral occipitotemporal cortex (LOTC) activity is greatest while viewing dance compared to visualization and movement: learning and expertise effects

The lateral occipitotemporal cortex (LOTC) is comprised of subregions selectively activated by images of human bodies (extrastriate body area, EBA), objects (lateral occipital complex, LO), and motion (MT+). However, their role in motor imagery and movement processing is unclear, as are the influences of learning and expertise on its recruitment. The purpose of our study was to examine putative changes in LOTC activation during action processing following motor learning of novel choreography in professional ballet dancers. Subjects were scanned with functional magnetic resonance imaging up to four times over 34 weeks and performed four tasks: viewing and visualizing a newly learned ballet dance, visualizing a dance that was not being learned, and movement of the foot. EBA, LO, and MT+ were activated most while viewing dance compared to visualization and movement. Significant increases in activation were observed over time in left LO only during visualization of the unlearned dance, and all subregions were activated bilaterally during the viewing task after 34 weeks of performance, suggesting learning-induced plasticity. Finally, we provide novel evidence for modulation of EBA with dance experience during the motor task, with significant activation elicited in a comparison group of novice dancers only. These results provide a composite of LOTC activation during action processing of newly learned ballet choreography and movement of the foot. The role of these areas is confirmed as primarily subserving observation of complex sequences of whole-body movement, with new evidence for modification by experience and over the course of real world ballet learning.

A third-person perspective on co-speech action gestures in Parkinson's disease

A combination of impaired motor and cognitive function in Parkinson's disease (PD) can impact on language and communication, with patients exhibiting a particular difficulty processing action verbs. Co-speech gestures embody a link between action and language and contribute significantly to communication in healthy people. Here, we investigated how co-speech gestures depicting actions are affected in PD, in particular with respect to the visual perspective—or the viewpoint – they depict. Gestures are closely related to mental imagery and motor simulations, but people with PD may be impaired in the way they simulate actions from a first-person perspective and may compensate for this by relying more on third-person visual features. We analysed the action-depicting gestures produced by mild-moderate PD patients and age-matched controls on an action description task and examined the relationship between gesture viewpoint, action naming, and performance on an action observation task (weight judgement). Healthy controls produced the majority of their action gestures from a first-person perspective, whereas PD patients produced a greater proportion of gestures produced from a third-person perspective. We propose that this reflects a compensatory reliance on third-person visual features in the simulation of actions in PD. Performance was also impaired in action naming and weight judgement, although this was unrelated to gesture viewpoint. Our findings provide a more comprehensive understanding of how action-language impairments in PD impact on action communication, on the cognitive underpinnings of this impairment, as well as elucidating the role of action simulation in gesture production.

Gray matter correlates of dopaminergic degeneration in Parkinson's disease: A hybrid PET/MR study using (18) F-FP-CIT

Dopaminergic degeneration is a hallmark of Parkinson's disease (PD), which causes various symptoms affected by corticostriatal circuits. So far, the relationship between cortical changes and dopamine loss in the striatum is unclear. Here, we evaluate the gray matter (GM) changes in accordance with striatal dopaminergic degeneration in PD using hybrid PET/MR. Sixteen patients with idiopathic PD underwent (18) F-FP-CIT PET/MR. To measure dopaminergic degeneration in PD, binding ratio (BR) of dopamine transporter in striatum was evaluated by (18) F-FP-CIT. Voxel-based morphometry (VBM) was used to evaluate GM density. We obtained voxelwise correlation maps of GM density according to the striatal BR. Voxel-by-voxel correlation between BR maps and GM density maps was done to evaluate region-specific correlation of striatal dopaminergic degeneration. There was a trend of positive correlation between striatal BR and GM density in the cerebellum, parahippocampal gyri, and frontal cortex. A trend of negative correlation between striatal BR and GM density in the medial occipital cortex was found. Voxel-by-voxel correlation revealed that the positive correlation was mainly dependent on anterior striatal BR, while posterior striatal BR mostly showed negative correlation with GM density in occipital and temporal cortices. Decreased GM density related to anterior striatal dopaminergic degeneration might demonstrate degeneration of dopaminergic nonmotor circuits. Furthermore, the negative correlation could be related to the motor circuits of posterior striatum. Our integrated PET/MR study suggests that the widespread structural progressive changes in PD could denote the cortical functional correlates of the degeneration of striatal dopaminergic circuits. Hum Brain Mapp 37:1710-1721, 2016. © 2016 Wiley Periodicals, Inc.

When I am (almost) 64: The effect of normal ageing on implicit motor imagery in young elderlies

Motor imagery (M.I.) is a cognitive process in which movements are mentally evoked without overt actions. Behavioral and fMRI studies show a decline of explicit M.I. ability (e.g., the mental rehearsal of finger oppositions) with normal ageing: this decline is accompanied by the recruitment of additional cortical networks. However, none of these studies investigated behavioral and the related fMRI ageing modifications in implicit M.I. tasks, like the hand laterality task (HLT). To address this issue, we performed a behavioral and fMRI study: 27 younger subjects (mean age: 31 years) and 29 older subjects (mean age: 61 years) underwent two event-related design fMRI experiments. In the HLT, participants were asked to decide whether a hand rotated at different angles was a left or right hand. To test the specificity of any age related difference in the HLT, we used a letter rotation task as a control experiment: here subjects had to decide whether rotated letters were presented in a standard or a mirror orientation. We did not find any group difference in either behavioral task; however, we found significant additional neural activation in the elderly group in occipito-temporal regions: these differences were stronger for the HLT rather than for the LRT with group by task interactions effects in right occipital cortices. We interpret these results as evidence of compensatory processes associated with ageing that permit a behavioral performance comparable to that of younger subjects. This process appears to be more marked when the task specifically involves motor representations, even when these are implicitly evoked.

Action Observation and Motor Imagery: Innovative Cognitive Tools in the Rehabilitation of Parkinson's Disease

Parkinson's disease (PD) is characterized by a progressive impairment of motor skills with deterioration of autonomy in daily living activities. Physiotherapy is regarded as an adjuvant to pharmacological and neurosurgical treatment and may provide small and short-lasting clinical benefits in PD patients. However, the development of innovative rehabilitation approaches with greater long-term efficacy is a major unmet need. Motor imagery (MI) and action observation (AO) have been recently proposed as a promising rehabilitation tool. MI is the ability to imagine a movement without actual performance (or muscle activation). The same cortical-subcortical network active during motor execution is engaged in MI. The physiological basis of AO is represented by the activation of the "mirror neuron system." Both MI and AO are involved in motor learning and can induce improvements of motor performance, possibly mediated by the development of plastic changes in the motor cortex. The review of available evidences indicated that MI ability and AO feasibility are substantially preserved in PD subjects. A few preliminary studies suggested the possibility of using MI and AO as parts of rehabilitation protocols for PD patients.

Task-rest modulation of basal ganglia connectivity in mild to moderate Parkinson's disease

Parkinson's disease (PD) is associated with abnormal synchronization in basal ganglia-thalamo-cortical loops. We tested whether early PD patients without demonstrable cognitive impairment exhibit abnormal modulation of functional connectivity at rest, while engaged in a task, or both. PD and healthy controls underwent two functional MRI scans: a resting-state scan and a Stroop Match-to-Sample task scan. Rest-task modulation of basal ganglia (BG) connectivity was tested using seed-to-voxel connectivity analysis with task and rest time series as conditions. Despite substantial overlap of BG-cortical connectivity patterns in both groups, connectivity differences between groups had clinical and behavioral correlates. During rest, stronger putamen-medial parietal and pallidum-occipital connectivity in PD than controls was associated with worse task performance and more severe PD symptoms suggesting that abnormalities in resting-state connectivity denote neural network dedifferentiation. During the executive task, PD patients showed weaker BG-cortical connectivity than controls, i.e., between caudate-supramarginal gyrus and pallidum-inferior prefrontal regions, that was related to more severe PD symptoms and worse task performance. Yet, task processing also evoked stronger striatal-cortical connectivity, specifically between caudate-prefrontal, caudate-precuneus, and putamen-motor/premotor regions in PD relative to controls, which was related to less severe PD symptoms and better performance on the Stroop task. Thus, stronger task-evoked striatal connectivity in PD demonstrated compensatory neural network enhancement to meet task demands and improve performance levels. fMRI-based network analysis revealed that despite resting-state BG network compromise in PD, BG connectivity to prefrontal, premotor, and precuneus regions can be adequately invoked during executive control demands enabling near normal task performance.