FMRI correlates of apraxia in Parkinson's disease patients OFF medication

Finger dexterity measured by the Grooved Pegboard test indexes Parkinson's motor severity in a tremor-independent manner

Fine motor impairments are frequent complaints in people with Parkinson's disease (PD). While they may develop at an early stage of the disease, they become more problematic as the disease progresses. Tremors and fine motor symptoms may seem related, but evidence suggests two distinct phenomena. The purpose of our study was to investigate the relationships between fine motor skills and clinical characteristics of PD patients. We hypothesized worse fine motor skills to be associated with greater motor severity that is independent of tremor. We measured fine motor abilities using the Grooved Pegboard test (GPT) in each hand separately and collected clinical and demographics data in a cohort of 82 persons with PD. We performed regression analyses between GPT scores and a range of outcomes: motor severity, time from diagnosis, age and tremors. We also explored similar associations using finger and hand dexterity scores from a standardized PD rating scale. Our results indicate that scores on the GPT for each hand, as measures of manual dexterity, are associated with motor severity and time from diagnosis. The presence of tremors was not a confounding factor, as hypothesized, but age was associated with GPT scores for the dominant hand. Motor severity was also associated with hand and finger dexterity as measured by single items from the clinical Parkinson's rating scale. These findings suggest that the GPT to be useful tool for motor severity assessments of people with PD.

First evidence of long-term effects of transcranial pulse stimulation (TPS) on the human brain

Background

With the high spatial resolution and the potential to reach deep brain structures, ultrasound-based brain stimulation techniques offer new opportunities to non-invasively treat neurological and psychiatric disorders. However, little is known about long-term effects of ultrasound-based brain stimulation. Applying a longitudinal design, we comprehensively investigated neuromodulation induced by ultrasound brain stimulation to provide first sham-controlled evidence of long-term effects on the human brain and behavior.

Methods

Twelve healthy participants received three sham and three verum sessions with transcranial pulse stimulation (TPS) focused on the cortical somatosensory representation of the right hand. One week before and after the sham and verum TPS applications, comprehensive structural and functional resting state MRI investigations and behavioral tests targeting tactile spatial discrimination and sensorimotor dexterity were performed.

Results

Compared to sham, global efficiency significantly increased within the cortical sensorimotor network after verum TPS, indicating an upregulation of the stimulated functional brain network. Axial diffusivity in left sensorimotor areas decreased after verum TPS, demonstrating an improved axonal status in the stimulated area.

Conclusions

TPS increased the functional and structural coupling within the stimulated left primary somatosensory cortex and adjacent sensorimotor areas up to one week after the last stimulation. These findings suggest that TPS induces neuroplastic changes that go beyond the spatial and temporal stimulation settings encouraging further clinical applications.

Impaired Hand Dexterity Function in a Non-human Primate Model with Chronic Parkinson's Disease

Symptoms of Parkinson’s disease (PD) caused by loss of dopaminergic neurons are accompanied by movement disorders, including tremors, rigidity, bradykinesia, and akinesia. Non-human primate (NHP) models with PD play an essential role in the analysis of PD pathophysiology and behavior symptoms. As impairments of hand dexterity function can affect activities of daily living in patients with PD, research on hand dexterity function in NHP models with chronic PD is essential. Traditional rating scales previously used in the evaluation of animal spontaneous behavior were insufficient due to factors related to subjectivity and passivity. Thus, experimentally designed applications for an appropriate apparatus are necessary. In this study, we aimed to longitudinally assess hand dexterity function using hand dexterity task (HDT) in NHP-PD models. To validate this assessment, we analyzed the alteration in Parkinsonian tremor signs and the functionality of presynaptic dopaminergic neuron using positron emission tomography imaging of dopamine transporters in these models. In addition, a significant inverse correlation between HDT and DAT level was identified, but no local bias was found. The correlation with intention tremor signs was lower than the resting tremor. In conclusion, the evaluation of HDT may reflect behavioral symptoms of NHP-PD models. Furthermore, HDT was effectively used to experimentally distinguish intention tremors from other tremors.

Starting to Talk at Age 10 Years: Lessons About the Acquisition of English Speech Sounds in a Rare Case of Severe Congenital But Remediated Motor Disease of Genetic Origin

Purpose This study was conducted to observe speech development in a child whose onset of oral communication was extremely delayed. In rare cases, children are born with physical limitations that temporarily interfere with speech sound production. Whether the development of speech sound production follows the same trajectory as that in typical children at younger ages is not well understood. Method We present a child who was wheelchair-bound and communicated nearly exclusively via augmentative and alternative communication devices due to severe congenital motor disease and generalized hypotonia. At age 10 years, her condition improved dramatically with medication after a mutation in a dopamine-related gene was discovered, and she switched entirely to oral communication. Observation of speech development was based on chart reviews, video recordings, and direct testing at age 15 years. Results At age 4 years, the participant's attempts at speech showed a small phoneme inventory consisting of early-acquired phonemes and large numbers of common phonological processes. Following the medical intervention at age 10 years, mastery of velars occurred after age 12 years and mastery of liquids was still incomplete at age 15 years. Conclusions Findings are consistent with general growth trends in speech sound acquisition that are independent of chronological age. Theoretical considerations regarding the role of motor control in the invariant order of speech sound acquisition are posited, specifically regarding articulatory building blocks. Clinical recommendations include interprofessional management of children with complex motor disease and referrals to genetics professionals in the care of such children.

Impaired finger dexterity and nigrostriatal dopamine loss in Parkinson's disease

Impaired finger dexterity occurs in Parkinson's disease (PD) and has been considered a limb-kinetic apraxia associated with primary sensory cortical dysfunction. To study the role of nigrostriatal dopamine loss and elementary parkinsonian motor deficits in impaired finger dexterity of PD. Thirty-two right-handed untreated PD patients and 30 right-handed healthy controls were included. All patients underwent [¹⁸F] FP-CIT positron emission tomography studies. We examined the associations among unilateral coin rotation (CR) score, Unified Parkinson's Disease Rating Scale (UPDRS) subscores for bradykinesia and rigidity of the corresponding arm, and contralateral regional striatal dopamine transporter (DAT) uptake. We also measured the effect of oral levodopa dose on CR scores and UPDRS subscores. PD patients performed worse than controls on the CR task. Unilateral arm UPDRS bradykinesia scores were associated with DAT uptake in the contralateral putamen. The left CR score was associated with left arm bradykinesia and rigidity scores and DAT uptake in the right posterior putamen, whereas no such associations were found for the right CR score. There was a significant effect of handedness on the association of putamen DAT uptake with CR scores, but not with UPDRS subscores. An oral levodopa challenge improved CR scores and UPDRS subscores on both sides. Impaired finger dexterity in PD is related to elementary parkinsonian motor deficits and nigrostriatal dopamine loss. Impaired dominant hand dexterity associated with nigrostriatal dopamine loss seems to be compensated to some extent by the dominant cerebral cortex specialized for controlling precise finger movements.

Deficient supplementary motor area at rest: Neural basis of limb kinetic deficits in Parkinson's disease

Parkinson's disease (PD) patients frequently suffer from limb kinetic apraxia (LKA) affecting quality of life. LKA denotes an impairment of precise and independent finger movements beyond bradykinesia, which is reliably assessed by coin rotation (CR) task. BOLD fMRI detected activation of a left inferior parietal-premotor praxis network in PD during CR. Here, we explored which network site is most critical for LKA using arterial spin labeling (ASL). Based on a hierarchical model, we hypothesized that LKA would predominantly affect the functional integrity of premotor areas including supplementary motor areas (SMA). Furthermore, we suspected that for praxis function with higher demand on temporal-spatial processing such as gesturing, inferior parietal lobule (IPL) upstream to premotor areas would be essential. A total of 21 PD patients and 20 healthy controls underwent ASL acquisition during rest. Behavioral assessment outside the scanner involved the CR, finger tapping task, and the test of upper limb apraxia (TULIA). Whole-brain analysis of activity at rest showed a significant reduction of CR-related perfusion in the left SMA of PD. Furthermore, the positive correlation between SMA perfusion and CR, seen in controls, was lost in patients. By contrast, TULIA was significantly associated with the perfusion of left IPL in both patients and controls. In conclusion, the findings suggest that LKA in PD are linked to an intrinsic disruption of the left SMA function, which may only be overcome by compensatory network activation. In addition, gestural performance relies on IPL which remains available for functional recruitment in early PD.

Effect of Subthalamic Deep Brain Stimulation on Upper Limb Dexterity in Patients with Parkinson Disease

OBJECTIVE

The efficacy of deep brain stimulation (DBS) of the subthalamic nucleus (STN) on dexterity remains controversial despite its recognition as an effective strategy for Parkinson disease. The present study investigated the efficacy of STN-DBS for ameliorating bradykinesia and dexterity compared with dopaminergic medications.

METHODS

Part III of the Unified Parkinson's Disease Rating Scale was used for the evaluation of bradykinesia, whereas the Purdue Pegboard Test and the Box and Block test were selected for dexterity.

RESULTS

Our findings indicate that bradykinesia is significantly improved with both DBS and dopaminergic medication, whereas dexterity is improved only with DBS. Dopaminergic medication did not show a satisfactory efficacy on dexterity, and there was little synergistic effect of dopaminergic medication and STN-DBS for improving dexterity associated with Parkinson disease.

CONCLUSIONS

Our results suggest that DBS is potentially more effective than dopaminergic medications for improving dexterity. The disparities in efficacy for bradykinesia and dexterity between DBS and dopaminergic medication hint at the potential mechanisms of STN-DBS. We speculate that DBS follows at least 2 different mechanisms for improving parkinsonian symptoms: 1) the dopaminergic system, primarily for the improvement of bradykinesia and 2) the nondopaminergic system, for the improvement of dexterity. This hypothesis requires further verification and investigation.

Altered praxis network underlying limb kinetic apraxia in Parkinson's disease - an fMRI study

Parkinson's disease (PD) patients frequently suffer from dexterous deficits impeding activities of daily living. There is controversy whether impaired fine motor skill may stem from limb kinetic apraxia (LKA) rather than bradykinesia. Based on classical models of limb praxis LKA is thought to result when premotor transmission of time-space information of skilled movements to primary motor representations is interrupted. Therefore, using functional magnetic resonance imaging (fMRI) we tested the hypothesis that dexterous deficits in PD are associated with altered activity and connectivity in left parieto-premotor praxis network. Whole-brain analysis of fMRI activity during a task for LKA (coin rotation) showed increased activation of superior and inferior parietal lobule (SPL, IPL) and ventral premotor cortex (vPM) in PD patients compared to controls. For bradykinesia (assessed by finger tapping) a decreased fMRI activity could be detected in patients. Additionally, psychophysical interaction analysis showed increased functional connectivity between IPL and the posterior hippocampi in patients with PD. By contrast, functional connectivity to the right dorsolateral prefrontal cortex was decreased in patients with PD compared to controls.

In conclusion, our data demonstrates that dexterous deficits in PD were associated with enhanced fMRI activation of the left praxis network upstream to primary motor areas, mirroring a neural correlate for the behavioral dissociation of LKA and bradykinesia. Furthermore, the findings suggest that patients recruit temporal areas of motor memory as an attempt to compensate for impaired motor skills. Finally, dysexecutive function may contribute to the deficit.

•

Impaired dexterity is related to a defective praxis network in PD.

•

The findings support the concept of an underlying limb kinetic apraxia.

•

Recruitment of temporal areas may reflect compensatory recall of motor engrams.

•

Dysexecutive control in PD may contribute to impaired motor skill.

F-wave and motor-evoked potentials during motor imagery and observation in apraxia of Parkinson disease

INTRODUCTION

The amplitudes of F-waves and motor-evoked potentials (MEPs) increase during imagination or active motor performance. The aim of this study was to investigate F-wave and MEP facilitation during assessment of apraxia.

METHODS

Eight Parkinson disease (PD) patients with apraxia, 11 patients without apraxia, and 8 healthy volunteers were enrolled. F-waves and MEPs were recorded during 4 states (resting, imagination, observation, and active movement).

RESULTS

The mean amplitude of the F-waves increased significantly during imagination and active movement as compared with at rest in healthy individuals (P = 0.028) and in the nonapraxia group (P = 0.005). PD patients with apraxia did not have similar facilitation. The mean amplitude of the MEPs also showed a similar loss of facilitation in PD with apraxia.

CONCLUSIONS

Loss of facilitation during the preparation for movement is closely related to the "gold standard" clinical praxis battery. This study provides additional support and a potential electrophysiological assessment method for apraxia in PD.

Limb apraxia in neurodegenerative disorders

SUMMARY Apraxia is a cognitive-motor disorder affecting gestural communication and tool use, and is seen in various neurodegenerative disorders. Apraxia is a major feature of the corticobasal syndrome associated with nonlevodopa-responsive, typically asymmetric parkinsonism. Mild apraxia may also be seen in Parkinson’s disease, at least in later stages of the disease. Furthermore, patients with Alzheimer’s disease or posterior cortical atrophy are prone to develop apraxia during their disease course. However, apraxia may be difficult to dissect from other motor (e.g., dystonia and bradykinesia in corticobasal syndrome) or cognitive (e.g., dysexecutive or semantic memory deficits in Alzheimer’s disease) dysfunction. Therefore, the ecological significance of apraxia in neurodegenerative disorders may not always be obvious. Although treatment protocols for apraxia have been developed in stroke, there is little information on the management of apraxia in neurodegenerative disorders. Owing to their progressive nature, benefits from therapeutic interventions are certainly limited, although some capacity of motor learning may be preserved, at least in earlier disease stages. In advanced cases, management of apraxia should focus on compensatory measures, for instance, on adapting the patient’s environment to their needs, particularly when related to safety and comfort.

Measures of fine motor skills in people with tremor disorders: appraisal and interpretation

People with Parkinson's disease, essential tremor, or other movement disorders involving tremor have changes in fine motor skills that are among the hallmarks of these diseases. Numerous measurement tools have been created and other methods devised to measure such changes in fine motor skills. Measurement tools may focus on specific features - e.g., motor skills or dexterity, slowness in movement execution associated with parkinsonian bradykinesia, or magnitude of tremor. Less obviously, some tools may be better suited than others for specific goals such as detecting subtle dysfunction early in disease, revealing aspects of brain function affected by disease, or tracking changes expected from treatment or disease progression. The purpose of this review is to describe and appraise selected measurement tools of fine motor skills appropriate for people with tremor disorders. In this context, we consider the tools' content - i.e., what movement features they focus on. In addition, we consider how measurement tools of fine motor skills relate to measures of a person's disease state or a person's function. These considerations affect how one should select and interpret the results of these tools in laboratory and clinical contexts.

Validity of the finger tapping test in Parkinson's disease, elderly and young healthy subjects: is there a role for central fatigue?

OBJECTIVE

The main goal of this work is to evaluate the validity of the finger tapping test (FT) to detect alterations in rhythm formation.

METHODS

We use FT to study the alterations in motor rhythm in three different groups: Parkinson's patients, elderly healthy controls, and young healthy control subjects (HY). The test was performed in COMFORT and FAST tapping modes and repeated on two different days.

RESULTS

For the variables analyzed (frequency and variability) both modes were repeatable in all groups. Also, intra-class correlation coefficients showed excellent levels of consistency between days. The test clearly differentiated the groups in both FAST and COMFORT modes. However, when fatigue was analyzed, a decrease in the tapping frequency was observed in HY during the FAST mode only. The amplitude of motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) was early-potentiated but not delayed-depressed, both for COMFORT and FAST modes. This suggests that fatigue was not of cortico-spinal origin. Other forms of central fatigue are discussed.

CONCLUSIONS

FT at FAST mode is not a valid test to detect differences in rhythm formation across the groups studied; fatigue is a confounding variable in some groups if the test is performed as fast as possible.

SIGNIFICANCE

COMFORT mode is recommended in protocols including the FT for evaluating rhythm formation.

Accounting for movement increases sensitivity in detecting brain activity in Parkinson's disease

Parkinson's disease (PD) is manifested by motor impairment, which may impede the ability to accurately perform motor tasks during functional magnetic resonance imaging (fMRI). Both temporal and amplitude deviations of movement performance affect the blood oxygenation level-dependent (BOLD) response. We present a general approach for assessing PD patients' movement control employing simultaneously recorded fMRI time series and behavioral data of the patients' kinematics using MR-compatible gloves. Twelve male patients with advanced PD were examined with fMRI at 1.5T during epoch-based visually paced finger tapping. MR-compatible gloves were utilized online to quantify motor outcome in two conditions with or without dopaminergic medication. Modeling of individual-level brain activity included (i) a predictor consisting of a condition-specific, constant-amplitude boxcar function convolved with the canonical hemodynamic response function (HRF) as commonly used in fMRI statistics (standard model), or (ii) a custom-made predictor computed from glove time series convolved with the HRF (kinematic model). Factorial statistics yielded a parametric map for each modeling technique, showing the medication effect on the group level. Patients showed bilateral response to levodopa in putamen and globus pallidus during the motor experiment. Interestingly, kinematic modeling produced significantly higher activation in terms of both the extent and amplitude of activity. Our results appear to account for movement performance in fMRI motor experiments with PD and increase sensitivity in detecting brain response to levodopa. We strongly advocate quantitatively controlling for motor performance to reach more reliable and robust analyses in fMRI with PD patients.

Virtual reality as a tool for evaluation of repetitive rhythmic movements in the elderly and Parkinson's disease patients

This work presents an immersive Virtual Reality (VR) system to evaluate, and potentially treat, the alterations in rhythmic hand movements seen in Parkinson's disease (PD) and the elderly (EC), by comparison with healthy young controls (YC). The system integrates the subjects into a VR environment by means of a Head Mounted Display, such that subjects perceive themselves in a virtual world consisting of a table within a room. In this experiment, subjects are presented in 1(st) person perspective, so that the avatar reproduces finger tapping movements performed by the subjects. The task, known as the finger tapping test (FT), was performed by all three subject groups, PD, EC and YC. FT was carried out by each subject on two different days (sessions), one week apart. In each FT session all subjects performed FT in the real world (FT(REAL)) and in the VR (FT(VR)); each mode was repeated three times in randomized order. During FT both the tapping frequency and the coefficient of variation of inter-tap interval were registered. FT(VR) was a valid test to detect differences in rhythm formation between the three groups. Intra-class correlation coefficients (ICC) and mean difference between days for FT(VR) (for each group) showed reliable results. Finally, the analysis of ICC and mean difference between FT(VR) vs FT(REAL), for each variable and group, also showed high reliability. This shows that FT evaluation in VR environments is valid as real world alternative, as VR evaluation did not distort movement execution and detects alteration in rhythm formation. These results support the use of VR as a promising tool to study alterations and the control of movement in different subject groups in unusual environments, such as during fMRI or other imaging studies.

Diffusion tensor imaging in Alzheimer's disease and dementia with Lewy bodies

White matter changes have been investigated in Alzheimer's disease (AD) in a number of studies using diffusion imaging. Fewer studies have investigated dementia with Lewy bodies (DLB). We used diffusion-weighted magnetic resonance imaging (MRI) and high-resolution (0.3 mm in-plane) coronal 3T MRI of the medial temporal lobe in 16 subjects with AD, 16 with DLB and 16 similarly aged healthy subjects. We found increased mean diffusivity in the temporal lobe of AD, and reduced fractional anisotropy (FA) in a small cluster in the right postcentral gyrus region in the DLB group. Mean FA in this cluster correlated with UPDRS (Unified Parkinson's Disease Rating Scale) motor score. We had previously reported reduced visibility in the AD group of a dark appearing layer of the hippocampus in the high-resolution images. In an SPM analysis on all subjects, there were significant clusters of reduced FA in the corpus callosum, fornix and stria terminalis that correlated with the visual rating of the hippocampus. These results suggest that changes to the hippocampus are associated with structural changes to the white matter fibres of the hippocampus output, and that changes in motor function are associated with changes in white matter underlying somatosensory cortex.

Impaired finger dexterity in Parkinson's disease is associated with praxis function

A controversial concept suggests that impaired finger dexterity in Parkinson's disease may be related to limb kinetic apraxia that is not explained by elemental motor deficits such as bradykinesia. To explore the nature of dexterous difficulties, the aim of the present study was to assess the relationship of finger dexterity with ideomotor praxis function and parkinsonian symptoms. Twenty-five patients with Parkinson's disease participated in the study. Their left and right arms were tested independently. Testing was done in an OFF and ON state as defined by a modified version of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Finger dexterity was assessed by a coin rotation (CR) task and ideomotor praxis using a novel test of upper limb apraxia (TULIA), in which the patients were requested to imitate and pantomime 48 meaningless, as well as communicative and tool-related gestures. Coin rotation significantly correlated with TULIA irrespective of the motor state and arm involved, but not with the MDS-UPDRS. This association was significantly influenced by Hoehn and Yahr stage. The strong association of finger dexterity with praxis function but not the parkinsonian symptoms indicates that impaired finger dexterity in Parkinson's disease may be indeed apraxic in nature, yet, predominantly in advanced stages of the disease when cortical pathology is expected to develop. The findings are discussed within a cognitive-motor model of praxis function.