Deficits in orofacial sensorimotor function in Parkinson's disease

Sensorimotor regulation of facial expression - An untouched frontier

Facial expression is a critical form of nonverbal social communication which promotes emotional exchange and affiliation among humans. Facial expressions are generated via precise contraction of the facial muscles, guided by sensory feedback. While the neural pathways underlying facial motor control are well characterized in humans and primates, it remains unknown how tactile and proprioceptive information reaches these pathways to guide facial muscle contraction. Thus, despite the importance of facial expressions for social functioning, little is known about how they are generated as a unique sensorimotor behavior. In this review, we highlight current knowledge about sensory feedback from the face and how it is distinct from other body regions. We describe connectivity between the facial sensory and motor brain systems, and call attention to the other brain systems which influence facial expression behavior, including vision, gustation, emotion, and interoception. Finally, we petition for more research on the sensory basis of facial expressions, asserting that incomplete understanding of sensorimotor mechanisms is a barrier to addressing atypical facial expressivity in clinical populations.

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

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

The Feel of Speech: Multisystem and Polymodal Somatosensation in Speech Production

PURPOSE

The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production.

METHOD

The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience.

RESULTS AND CONCLUSIONS

The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders.

A Preliminary Study of Voluntary Cough Motor Performance and Learning With Skill Training and Biofeedback

PURPOSE

Sensorimotor cough skill training (CST) has been shown to improve cough strength, as well as facilitate changes during training (i.e., motor performance) and generalization to untrained tasks (i.e., motor learning). However, there is a gap in our understanding of the effects of voluntary CST (without sensory stimuli) on motor performance and learning. Furthermore, the contribution of physiologic factors, such as lung volume, a driver of cough strength in healthy adults, and treatment-specific factors, such as biofeedback, remains unexamined.

METHOD

Twenty individuals with Parkinson's disease (PD) completed pre- and post-CST single voluntary, sequential voluntary, and reflex cough testing. Participants were randomized to biofeedback or no biofeedback groups. They completed one CST session involving 25 trials of voluntary coughs, with the treatment target set 25% above baseline peak flow. Participants were instructed to "cough hard" to exceed the target. In the biofeedback group, participants received direct visualization of the target line in real time.

RESULTS

Cough peak flow showed positive improvements in motor performance (β = .02; 95% credible interval [CI]: 0.01, 0.03) and learning (β = .26; 95% CI: 0.03, 0.47). Changes in lung volume from pre- to post-CST did not predict treatment response. No differences in treatment response were detected between the biofeedback groups.

CONCLUSIONS

A single session of voluntary CST improved voluntary cough motor performance and learning. Although lung volume increased during CST, changes to lung volume did not predict treatment response. These findings demonstrate the potential of voluntary CST to improve motor performance and motor learning among individuals with PD and cough dysfunction.

SUPPLEMENTAL MATERIAL AND OPEN SCIENCE FORM

https://doi.org/10.23641/asha.25447444.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Altered parabrachial nucleus nociceptive processing may underlie central pain in Parkinson's disease

The presence of central neuropathic pain in Parkinson's disease suggests that the brain circuits that allow us to process pain could be dysfunctional in the disorder. However, there is to date no clear pathophysiological mechanism to explain these symptoms. In this work, we present evidence that the dysfunction of the subthalamic nucleus and/or substantia nigra pars reticulata may impact nociceptive processing in the parabrachial nucleus (PBN), a low level primary nociceptive structure in the brainstem, and induce a cellular and molecular neuro-adaptation in this structure. In rat models of Parkinson's disease with a partial dopaminergic lesion in the substantia nigra compacta, we found that the substantia nigra reticulata showed enhanced nociceptive responses. Such responses were less impacted in the subthalamic nucleus. A total dopaminergic lesion produced an increase in the nociceptive responses as well as an increase of the firing rate in both structures. In the PBN, inhibited nociceptive responses and increased expression of GABA_A receptors were found following a total dopaminergic lesion. However, neuro-adaptations at the level of dendritic spine density and post-synaptic density were found in both dopaminergic lesion groups. These results suggest that the molecular changes within the PBN following a larger dopaminergic lesion, such as increased GABA_A expression, is a key mechanism to produce nociceptive processing impairment, whilst other changes may protect function after smaller dopaminergic lesions. We also propose that these neuro-adaptations follow increased inhibitory tone from the substantia nigra pars reticulata and may represent the mechanism generating central neuropathic pain in Parkinson's disease.

Idiopathic Parkinson's disease and chronic pain in the era of deep brain stimulation: a systematic review and meta-analysis

OBJECTIVE

Pain is the most common nonmotor symptom of Parkinson's disease (PD) and is often undertreated. Deep brain stimulation (DBS) effectively mitigates the motor symptoms of this multisystem neurodegenerative disease; however, its therapeutic effect on nonmotor symptoms, especially pain, remains inconclusive. While there is a critical need to help this large PD patient population, guidelines for managing this significant disease burden are absent. Herein, the authors systematically reviewed the literature and conducted a meta-analysis to study the influence of traditional (subthalamic nucleus [STN] and globus pallidus internus [GPi]) DBS on chronic pain in patients with PD.

METHODS

The authors performed a systematic review of the literature and a meta-analysis following PRISMA guidelines. Risk of bias was assessed using the levels of evidence established by the Oxford Centre for Evidence-Based Medicine. Inclusion criteria were articles written in English, published in a peer-reviewed scholarly journal, and about studies conducting an intervention for PD-related pain in no fewer than 5 subjects.

RESULTS

Twenty-six studies were identified and included in this meta-analysis. Significant interstudy heterogeneity was detected (Cochran's Q test p < 0.05), supporting the use of the random-effects model. The random-effects model estimated the effect size of DBS for the treatment of idiopathic pain as 1.31 (95% CI 0.84-1.79). The DBS-on intervention improved pain scores by 40% as compared to the control state (preoperative baseline or DBS off).

CONCLUSIONS

The results indicated that traditional STN and GPi DBS can have a favorable impact on pain control and improve pain scores by 40% from baseline in PD patients experiencing chronic pain. Further trials are needed to identify the subtype of PD patients whose pain benefits from DBS and to identify the mechanisms by which DBS improves pain in PD patients.

Clinical Efficacy and Dosing of Vibrotactile Coordinated Reset Stimulation in Motor and Non-motor Symptoms of Parkinson's Disease: A Study Protocol

Enhanced neuronal synchronization of the subthalamic nucleus (STN) is commonly found in PD patients and corresponds to decreased motor ability. Coordinated reset (CR) was developed to decouple synchronized states causing long lasting desynchronization of neural networks. Vibrotactile CR stimulation (vCR) was developed as non-invasive therapeutic that delivers gentle vibrations to the fingertips. A previous study has shown that vCR can desynchronize abnormal brain rhythms within the sensorimotor cortex of PD patients, corresponding to sustained motor relief after 3 months of daily treatment. To further develop vCR, we created a protocol that has two phases. Study 1, a double blinded randomized sham-controlled study, is designed to address motor and non-motor symptoms, sensorimotor integration, and potential calibration methods. Study 2 examines dosing effects of vCR using a remote study design. In Study 1, we will perform a 7-month double-blind sham-controlled study including 30 PD patients randomly placed into an active vCR or inactive (sham) vCR condition. Patients will receive stimulation for 4 h a day in 2-h blocks for 6 months followed by a 1-month pause in stimulation to assess long lasting effects. Our primary outcome measure is the Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III off medication after 6 months of treatment. Secondary measures include a freezing of gait (FOG) questionnaire, objective motor evaluations, sensorimotor electroencephalography (EEG) results, a vibratory temporal discrimination task (VTDT), non-motor symptom evaluations/tests such as sleep, smell, speech, quality of life measurements and Levodopa Equivalent Daily Dose (LEDD). Patients will be evaluated at baseline, 3, 6, and 7 months. In the second, unblinded study phase (Study 2), all patients will be given the option to receive active vCR stimulation at a reduced dose for an additional 6 months remotely. The remote MDS-UPDRS part III off medication will be our primary outcome measure. Secondary measures include sleep, quality of life, objective motor evaluations, FOG and LEDD. Patients will be evaluated in the same time periods as the first study. Results from this study will provide clinical efficacy of vCR and help validate our investigational vibrotactile device for the purpose of obtaining FDA clearance. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT04877015.

Speech and Language Therapy for Voice Problems in Parkinson's Disease: A Meta-Analysis

Patients with Parkinson's disease (PD) commonly have speech and voice problems that affect their functional communication and that are not sensitive to pharmacological or neurosurgical treatments. The authors aimed to evaluate the effects of speech and language therapies (SLTs) on dysphonia in patients with PD by analyzing data from published randomized controlled trials (RCTs). Studies in English and Chinese that were related to speech and language treatment for patients with PD were retrieved from PubMed, Embase, Chinese National Knowledge Infrastructure, China Science and Technology Journal Database, Chinese Biomedical Literature Database, and Wanfang Database. On the basis of exclusion criteria, 391 records identified through the search were reduced to 10 studies that included 230 patients in the treatment groups and 205 patients in the control groups. A meta-analysis of data from the 10 studies was performed to examine the effects of SLTs on dysphonia in patients with PD. SLTs increased sound pressure level during sustained phonation, reading of the Rainbow Passage, and monologue 6 months after treatment, enhanced semitone standard deviation during reading of the Rainbow Passage more than 12 months after treatment, and reduced Voice Handicap Index scores among patients with PD with dysphonia problems at least 3 months after treatment. These findings demonstrate the efficacy of SLTs, especially Lee Silverman Voice Treatment, in increasing vocal loudness and functional communication among patients with PD. Further RCTs with large samples and multicenter participation are needed to validate the long-term effects and the efficacy of SLTs among patients with severe PD.

How far can I reach? The perception of upper body action capabilities in Parkinson's disease

Successful interaction within the environment is contingent upon one’s ability to accurately perceive the extent over which they can successfully perform actions, known as action boundaries. Healthy young adults are accurate in estimating their action boundaries and can flexibly update them to accommodate stable changes in their action capabilities. However, there are conditions in which motor abilities are subject to variability over time such as in Parkinson’s disease (PD). PD impairs the ability to perform actions and can lead to variability in perceptual-motor experience, but the effect on the perceptions of their action boundaries remains unknown. This study investigated the influence of altered perceptual-motor experience during PD, on the perceptions of action boundaries for reaching, grasping, and aperture passing. Thirty participants with mild-to-moderate idiopathic PD and 26 healthy older adults provided estimates of their reaching, grasping, and aperture-passing ability. Participants’ estimates were compared with their actual capabilities. There was no evidence that individuals with PD’s perceptions were less accurate than those of healthy controls. Furthermore, there was some evidence for more conservative estimates than seen in young healthy adults in reaching (both groups) and aperture passing (PD group). This suggests that the ability to judge action capabilities is preserved in mild to moderate PD.

Speech Intensity Response to Altered Intensity Feedback in Individuals With Parkinson's Disease

Purpose Hypophonia (low speech intensity) is the most common speech symptom experienced by individuals with Parkinson's disease (IWPD). Previous research suggests that, in IWPD, there may be abnormal integration of sensory information for motor production of speech intensity. In the current study, intensity of auditory feedback was systematically manipulated (altered in both positive and negative directions) during sensorimotor conditions that are known to modulate speech intensity in everyday contexts in order to better understand the role of auditory feedback for speech intensity regulation. Method Twenty-six IWPD and 24 neurologically healthy controls were asked to complete the following tasks: converse with the experimenter, start vowel production, and read sentences at a comfortable loudness, while hearing their own speech intensity randomly altered. Altered intensity feedback conditions included 5-, 10-, and 15-dB reductions and increases in the feedback intensity. Speech tasks were completed in no noise and in background noise. Results IWPD displayed a reduced response to the altered intensity feedback compared to control participants. This reduced response was most apparent when participants were speaking in background noise. Specific task-based differences in responses were observed such that the reduced response by IWPD was most pronounced during the conversation task. Conclusions The current study suggests that IWPD have abnormal processing of auditory information for speech intensity regulation, and this disruption particularly impacts their ability to regulate speech intensity in the context of speech tasks with clear communicative goals (i.e., conversational speech) and speaking in background noise.

Functional characterization of extrinsic tongue muscles in the Pink1-/- rat model of Parkinson disease

Parkinson disease (PD) is associated with speech and swallowing difficulties likely due to pathology in widespread brain and nervous system regions. In post-mortem studies of PD, pathology has been reported in pharyngeal and laryngeal nerves and muscles. However, it is unknown whether PD is associated with neuromuscular changes in the tongue. Prior work in a rat model of PD (Pink1-/-) showed oromotor and swallowing deficits in the premanifest stage which suggested sensorimotor impairments of these functions. The present study tested the hypothesis that Pink1-/- rats show altered tongue function coinciding with neuromuscular differences within tongue muscles compared to wildtype (WT). Male Pink1-/- and WT rats underwent behavioral tongue function assays at 4 and 6 months of age (n = 7–8 rats per group), which are time points early in the disease. At 6 months, genioglossus (GG) and styloglossus (SG) muscles were analyzed for myosin heavy chain isoforms (MyHC), α-synuclein levels, myofiber size, centrally nucleated myofibers, and neuromuscular junction (NMJ) innervation. Pink1-/- showed greater tongue press force variability, and greater tongue press forces and rates as compared to WT. Additionally, Pink1-/- showed relative increases of MyHC 2a in SG, but typical MyHC profiles in GG. Western blots revealed Pink1-/- had more α-synuclein protein than WT in GG, but not in SG. There were no differences between Pink1-/- and WT in myofiber size, centrally-nucleated myofibers, or NMJ innervation. α-synuclein protein was observed in nerves, NMJ, and vessels in both genotypes. Findings at these early disease stages suggest small changes or no changes in several peripheral biological measures, and intact motor innervation of tongue muscles. Future work should evaluate these measures at later disease stages to determine when robust pathological peripheral change contributes to functional change, and what CNS deficits cause behavioral changes. Understanding how PD affects central and peripheral mechanisms will help determine therapy targets for speech and swallowing disorders.

Treating Speech Movement Hypokinesia in Parkinson's Disease: Does Movement Size Matter?

Purpose

This study evaluates the effects of a novel speech therapy program that uses a verbal cue and gamified augmented visual feedback regarding tongue movements to address articulatory hypokinesia during speech in individuals with Parkinson's disease (PD).

Method

Five participants with PD participated in an ABA single-subject design study. The treatment aimed to increase tongue movement size using a combination of a verbal cue and augmented visual feedback and was conducted in 10 45-min sessions over 5 weeks. The presence of visual feedback was manipulated during treatment. Articulatory working space of the tongue was the primary outcome measure and was examined during treatment and in cued and uncued sentences pre- and posttreatment. Changes in speech intelligibility in response to a verbal cue pre- and posttreatment were also examined.

Results

During treatment, 4/5 participants showed a beneficial effect of visual feedback on tongue articulatory working space. At the end of the treatment, they used larger tongue movements when cued, relative to their pretreatment performance. None of the participants, however, generalized the effect to the uncued sentences. Speech intelligibility of cued sentences was judged as superior posttreatment only in a single participant.

Conclusions

This study demonstrated that using an augmented visual feedback approach is beneficial, beyond a verbal cue alone, in addressing articulatory hypokinesia in individuals with PD. An optimal degree of articulatory expansion might, however, be required to elicit a speech intelligibility benefit.

Speech disorders in Parkinson's disease: pathophysiology, medical management and surgical approaches

The prevalence of speech disorders among individuals with Parkinson's disease (PD) has been reported to be as high as 89%. Speech impairment in PD results from a combination of motor and nonmotor deficits. The production of speech depends upon the coordination of various motor activities: respiration, phonation, articulation, resonance and prosody. A speech disorder is defined as impairment in any of its inter-related components. Despite the high prevalence of speech disorders in PD, only 3–4% receive speech treatment. Treatment modalities include pharmacological intervention, speech therapy, surgery, deep brain stimulation and vocal fold augmentation. Although management of Parkinsonian dysarthria is clinically challenging, speech treatment in PD should be part of a multidisciplinary approach to patient care in this disease.

Beyond Dopamine: GABA, Glutamate, and the Axial Symptoms of Parkinson Disease

Introduction: The axial symptoms of Parkinson disease (PD) include difficulties with balance, posture, speech, swallowing, and locomotion with freezing of gait, as well as axial rigidity. These axial symptoms impact negatively on quality of life for many patients, yet remain poorly understood. Dopaminergic treatments typically have little effect on the axial symptoms of PD, suggesting that disruptions in other neurotransmitter systems beyond the dopamine system may underlie these symptoms. The purpose of the present study was to examine the relationship between the axial symptoms of PD and GABA and glutamate levels quantified with magnetic resonance spectroscopy.

Methods: The participant group included 20 patients with PD and 17 healthy control participants. Water-scaled GABA and Glx (glutamate + glutamine) concentrations were derived from GABA-edited MEGA-PRESS spectra acquired from the left basal ganglia and prefrontal cortex, and additional water-scaled Glx concentrations were acquired from standard PRESS spectra acquired from the pons. Spectra were analyzed with LCModel. The axial symptoms of PD were evaluated from subscales of the Unified Parkinson's Disease rating scale (MDS-UPDRS).

Results: PD patients demonstrated significantly higher GABA levels in the basal ganglia, which correlated with the degree of gait disturbance. Basal ganglia Glx levels and prefrontal GABA and Glx levels did not differ significantly between patient and control groups, but within the PD group prefrontal Glx levels correlated negatively with difficulties turning in bed. Results from an exploratory subgroup analysis indicate that the associations between GABA, Glx, and axial symptoms scores are typically more prominent in akinetic-rigid patients than in tremor-dominant patients.

Conclusion: Alterations in GABAergic and glutamatergic neurotransmission may contribute to some of the axial symptoms of PD.

Swallowing impairment in neurologic disorders: the role of videofluorographic swallowing study

Patients with neurologic diseases almost inevitably develop various degrees of swallowing disorders during their life. Dysphagia is one of the main negative prognostic factors in this class of patients, leading to severe morbidity (i.e. aspiration pneumonia, dehydration, malnutrition, and life quality deterioration) and to a noticeable increase in public health spending. Videofluorographic swallowing study is considered the gold standard technique for swallowing impairment assessment. It is aimed at early identification of the risk of aspiration, definition of the kind and grade of dysphagia, and an indication to suspend oral nutrition and adopt other feeding strategies, and define when the patient is able to return to physiological nutrition. Every radiologist should be familiar with the main videofluorographic swallowing features in neurological patients, not only because early diagnosis of deglutition disorders widely improves their prognosis, but also because customising feeding strategies has a great impact on patients' quality of life.

Sentence-Level Movements in Parkinson's Disease: Loud, Clear, and Slow Speech

PURPOSE

To further understand the effect of Parkinson's disease (PD) on articulatory movements in speech and to expand our knowledge of therapeutic treatment strategies, this study examined movements of the jaw, tongue blade, and tongue dorsum during sentence production with respect to speech intelligibility and compared the effect of varying speaking styles on these articulatory movements.

METHOD

Twenty-one speakers with PD and 20 healthy controls produced 3 sentences under normal, loud, clear, and slow speaking conditions. Speech intelligibility was rated for each speaker. A 3-dimensional electromagnetic articulograph tracked movements of the articulators. Measures included articulatory working spaces, ranges along the first principal component, average speeds, and sentence durations.

RESULTS

Speakers with PD demonstrated significantly smaller jaw movements as well as shorter than normal sentence durations. Between-speaker variation in movement size of the jaw, tongue blade, and tongue dorsum was associated with speech intelligibility. Analysis of speaking conditions revealed similar patterns of change in movement measures across groups and articulators: larger than normal movement sizes and faster speeds for loud speech, increased movement sizes for clear speech, and larger than normal movement sizes and slower speeds for slow speech.

CONCLUSIONS

Sentence-level measures of articulatory movements are sensitive to both disease-related changes in PD and speaking-style manipulations.

Differences between Subjective and Objective Assessment of Speech Deficiency in Parkinson Disease

OBJECTIVES

This study aims to establish the frequency at which patients with Parkinson disease subjectively assess the intensity of their speech disorders, factors that the patients believe determine the severity of their vocal impairment, and how their subjective self-assessment of vocal impairment by means of the Voice Handicap Index compares with the objective evaluation of the performance of the articulatory organs by means of Frenchay Dysarthria Assessment.

MATERIALS AND METHODS

The methods used Voice Handicap Index, Frenchay Dysarthria Assessment, and the Hoehn and Yahr scale.

RESULTS

Positive correlation was found between the subjective assessment of the performance of the speech organs and the impaired differentiation of lip movements and tongue sideways movements, impaired saliva control, dysfunction of the soft palate, and the pitch. Negative correlation was found between the subjective assessment of the severity of speech disorder, breathing at rest, and sentence comprehension.

CONCLUSIONS

Although we observed correlation between the subjective perception of certain speech disorders of patients with Parkinson disease and the objective assessment carried out by means of the Frenchay Dysarthria Assessment scale, the subjects did not believe the disorders had a significant impact on the quality of speech. Negative results of an examination do not necessarily reflect the subjective perception of the decline in the functioning of the articulatory organs. It should be assumed that lack of correlation between the subjective perception measured using Voice Handicap Index and the objective Frenchay Dysarthria-based assessment of the performance of the articulatory organs may result from a good adaptation to the progressive changes.

Human subthalamic oscillatory dynamics following somatosensory stimulation

OBJECTIVE

Electrical median nerve somatosensory stimulation leads to a distinct modulation of cortical oscillations. Initial high frequency and gamma augmentation, as well as modulation of beta and alpha oscillations have been reported. We aimed at investigating the involvement of the subthalamic nucleus in somatosensory processing by means of local field potential recordings, since recordings during passive movements and peripheral somatosensory stimulation have suggested a prominent role.

METHODS

Recordings of subthalamic neuronal activity following median nerve stimulation in 11 Parkinson's disease patients were performed. Time-frequency analysis from 1 to 500 Hz was averaged and analyzed.

RESULTS

Several oscillatory components in response to somatosensory stimulation were revealed in the time-frequency analysis: (I) prolonged increase in alpha band power, followed by attenuation; (II) initial suppression of power followed by a subsequent rebound in the beta band; (III) early broad-frequency increase in gamma band power; (IV) and sustained increase of 160 Hz frequency oscillations throughout the trial.

CONCLUSIONS

These results further corroborate the involvement of the subthalamic nucleus in somatosensory processing.

SIGNIFICANCE

The present results not only support the notion of somatosensory processing in the subthalamic nucleus. Moreover, an improvement of somatosensory processing during subthalamic deep brain stimulation in Parkinson's disease might be accounted for by enhancement of prevailing high frequency oscillations.

Reduced protein expressions of cytomembrane GABAARβ3 at different postnatal developmental stages of rats exposed prenatally to valproic acid

Decreased inhibition plays an extremely important role in pathogenesis of autism spectrum disorder (ASD). Therefore, we aimed to determine whether expression levels of the γ-aminobutyric acid type A receptor β3 subunit (GABAARβ3), K+-Cl- cotransporter 2 (KCC2), and Na+-K+-Cl- cotransporter 1 (NKCC1) related to inhibition transmission are changed in a sodium valproate-induced rat model of ASD. Decreased expression levels of membrane GABAARβ3 (m-GABAARβ3) and KCC2 as well as increased endocytosis of GABAARs were found in the model group. However, there were no significant differences in expression of total GABAARβ3 and NKCC1 between the control and model groups. In addition, we observed growth retardation, impaired spatial memory, limited exploration, increased anxiety, and reduced sociability in the model group. These results suggest alterations in m-GABAARβ3 levels, KCC2 levels, and trafficking of GABAARs in rats prenatally exposed to valproic acid and advance our understanding of the pathogenesis of ASD.

Game-Based Augmented Visual Feedback for Enlarging Speech Movements in Parkinson's Disease

PURPOSE

The purpose of this pilot study was to demonstrate the effect of augmented visual feedback on acquisition and short-term retention of a relatively simple instruction to increase movement amplitude during speaking tasks in patients with dysarthria due to Parkinson's disease (PD).

METHOD

Nine patients diagnosed with PD, hypokinetic dysarthria, and impaired speech intelligibility participated in a training program aimed at increasing the size of their articulatory (tongue) movements during sentences. Two sessions were conducted: a baseline and training session, followed by a retention session 48 hr later. At baseline, sentences were produced at normal, loud, and clear speaking conditions. Game-based visual feedback regarding the size of the articulatory working space (AWS) was presented during training.

RESULTS

Eight of nine participants benefited from training, increasing their sentence AWS to a greater degree following feedback as compared with the baseline loud and clear conditions. The majority of participants were able to demonstrate the learned skill at the retention session.

CONCLUSIONS

This study demonstrated the feasibility of augmented visual feedback via articulatory kinematics for training movement enlargement in patients with hypokinesia due to PD.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5116840.

The Effect of Dopaminergic Medication on Joint Kinematics during Haptic Movements in Individuals with Parkinson's Disease

This study examined whether altered joint angular motion during haptic exploration could account for a decline in haptic sensitivity in individuals with PD by analyzing joint position data during haptic exploration of a curved contour. Each participant's hand was passively moved by a robotic arm along the edges of a virtual box (5 cm × 15 cm) with a curved left wall. After each trial, participants indicated whether the contour was curved or straight. Visual, auditory, and tactile cues were occluded, and an electrogoniometer recorded shoulder and elbow joint angles during each trial. The PD group in the OFF state had a higher mean detection threshold (4.67 m⁻¹) than the control group (3.06 m⁻¹). Individuals with PD in the OFF state also had a significantly greater magnitude of shoulder abduction than those in the ON state (p = 0.003) and a smaller magnitude of elbow flexion than those in the ON state or compared to the control group (both p < 0.001). These findings suggest that individuals with PD employ joint configurations that may contribute to haptic insensitivity. Dopamine replacement therapy improved joint configurations during haptic exploration in patients with PD, suggesting a role for dopaminergic dysfunction in PD-related haptic insensitivity.

Speech production and sensory impairment in mild Parkinson's disease

Little is known about speech-related sensory systems and the link to speech in Parkinson's disease (PD). This study investigates auditory and somatosensory acuity and their association to speech in PD, using /s/ and /ʃ/ as speech targets. Ten adults with mild PD and ten age- and gender-matched healthy participants performed three tasks. In the auditory task, participants discriminated three aperiodic sounds acoustically modified from /s/ and /ʃ/ and differing in spectral shapes. In the tactile task, they judged the orientation of a dome-shaped grating probe gently touching their tongue tip. Measures of auditory and tactile acuity were determined based on participants' responses. For the production task, participants read a passage and eight sentences with /s/- and /ʃ/-initial words; acoustic contrast between the two sibilants was measured using difference between the average first spectral moments of /s/ and /ʃ/. The PD participants showed reduced auditory acuity of spectral sibilant contrast and reduced tactile acuity of the tongue tip. For speech production, the PD group showed smaller sibilant contrast in the sentence readings, but the difference was not statistically significant. Correlation analyses showed significant correlations between tactile acuity and sibilant contrast for the PD group, but not for auditory task.

Coordination of Tongue Pressure and Jaw Movement in Mastication

The tongue plays an important role in mastication and swallowing by its contact with the hard palate. Using an experimental palatal plate with 7 pressure sensors, and recording jaw movement using mandibular kinesiography, we assessed, in healthy subjects, the coordination of tongue and jaw movements during the entire masticatory sequence of solids, by measuring tongue pressure against the hard palate. Tongue pressure appeared during the occlusal phase, reached a peak near the start of opening, and disappeared during opening. Specific patterns in order, duration, and magnitude of tongue pressure were seen at the 7 pressure sensors in each chewing stroke. Magnitude and duration were significantly larger in the late stage of chewing (8 strokes before initial swallowing) than in the early stage (until 8 strokes after starting mastication). The normal pattern of tongue contact against the hard palate, control of tongue activity, and coordination with jaw movement during mastication is described.

Autophonic loudness perception in Parkinson's disease

The relationship between the intensity and loudness of self-generated (autophonic) speech remains invariant despite changes in auditory feedback, indicating that non-auditory processes contribute to this form of perception. The aim of the current study was to determine if the speech perception deficit associated with Parkinson's disease may be linked to deficits in such processes. Loudness magnitude estimates were obtained from parkinsonian and non-parkinsonian subjects across four separate conditions: self-produced speech under normal, perturbed, and masked auditory feedback, as well as auditory presentation of pre-recorded speech (passive listening). Slopes and intercepts of loudness curves were compared across groups and conditions. A significant difference in slope was found between autophonic and passive-listening conditions for both groups. Unlike control subjects, parkinsonian subjects' magnitude estimates under auditory masking increased in variability and did not show as strong a shift in intercept values. These results suggest that individuals with Parkinson's disease rely on auditory feedback to compensate for underlying deficits in sensorimotor integration important in establishing and regulating autophonic loudness.

Swallowing disturbances in the corticobasal syndrome

OBJECTIVES

To determine the characteristics of swallowing and speech disturbances in patients with corticobasal syndrome (CBS) compared to healthy controls, and whether a subjective swallowing questionnaire, the NIH-Speech Pathology swallowing questionnaire (NIH-SQ), can predict swallowing impairment.

METHODS

Twenty-four consecutive CBS patients underwent a swallowing assessment comprised of the NIH-SQ, ultrasound swallow study (US) and modified barium swallow (MBS) study. Healthy controls (n = 28) completed the NIH-SQ and the US.

RESULTS

Ninety-six percent of the patients with CBS reported at least one complaint in the NIH-SQ, 59% had abnormal dry swallow duration and 10% abnormal wet swallow duration. Twenty-three patients with CBS had some abnormality on the MBS. The MBS category "piecemeal deglutition" (excessive lingual gestures causing multiple swallows required to clear a single bolus) was characteristic of CBS patients. No aspiration was detected. No NIH-SQ cutoff score or combination of subjective complaints predicted an abnormal MBS. Fifty-two percent of the patients had speech apraxia.

CONCLUSIONS

Swallowing and speech disturbances are common in patients with CBS and differ from those previously reported in patients with PSP syndrome. Piecemeal deglutition and speech apraxia are characteristic features of our CBS patients. Although the NIH-SQ cannot predict the results of the more objective MBS in this population, it characterizes the patients' major subjective swallowing complaints.

Point pressure sensitivity in early stage Parkinson's disease

A number of sensory changes occur in the earliest stages of Parkinson's disease (PD), some of which precede the expression of the classic motor phenotype by years (e.g., olfactory dysfunction). Whether point pressure sensitivity (PPS), a cutaneous measure of light touch mediated by myelinated Aβ fibers, is altered in early PD is not clear. Prior studies on this point are contradictory and are based on non-forced-choice threshold tests that confound the sensitivity measure with the response criterion. While α-synuclein pathology, a defining feature of PD, is present in the skin of PD patients, it is restricted to unmyelinated nerve fibers, suggesting PPS may be spared in this disease. We determined PPS thresholds using a state-of-the-art forced-choice staircase threshold test paradigm in 29 early stage PD patients and 29 matched controls at 11 body sites: the center of the forehead and the left and right forearms, index fingers, palms, medial soles of the feet, and plantar halluces. The patients were tested, in counterbalanced sessions, both on and off dopamine-related medications (DRMs). PPS was not influenced by PD and did not correlate with DRM l-DOPA equivalents, scores on the Unified Parkinson's Disease Rating Scale, side of the major motor disturbances, or SPECT imaging of the striatal dopamine transporter, as measured by technetium-99m TRODAT. However, PPS thresholds were lower on the left than on the right side of the body (p=0.008) and on the upper extremities relative to the toes and feet (ps<0.0001). Positive correlations were evident among the thresholds obtained across all body sectors, even though disparate regions of the body differed in terms of absolute sensitivity. This study indicates that PPS is not influenced in early stage PD regardless of whether patients are on or off DRMs.

Loudness perception and speech intensity control in Parkinson's disease

The aim of this study was to examine loudness perception in individuals with hypophonia and Parkinson's disease. The participants included 17 individuals with hypophonia related to Parkinson's disease (PD) and 25 age-equivalent controls. The three loudness perception tasks included a magnitude estimation procedure involving a sentence spoken at 60, 65, 70, 75 and 80 dB SPL, an imitation task involving a sentence spoken at 60, 65, 70, 75 and 80 dB SPL, and a magnitude production procedure involving the production of a sentence at five different loudness levels (habitual, two and four times louder and two and four times quieter). The participants with PD produced a significantly different pattern and used a more restricted range than the controls in their perception of speech loudness, imitation of speech intensity, and self-generated estimates of speech loudness. The results support a speech loudness perception deficit in PD involving an abnormal perception of externally generated and self-generated speech intensity.

LEARNING OUTCOMES

Readers will recognize that individuals with hypophonia related to Parkinson's disease may demonstrate a speech loudness perception deficit involving the abnormal perception of externally generated and self-generated speech intensity.

Multiple factors are involved in the dysarthria associated with Parkinson's disease: a review with implications for clinical practice and research

PURPOSE

Motor speech abnormalities are highly common and debilitating in individuals with idiopathic Parkinson's disease (IPD). These abnormalities, collectively termed hypokinetic dysarthria (HKD), have been traditionally attributed to hypokinesia and bradykinesia secondary to muscle rigidity and dopamine deficits. However, the role of rigidity and dopamine in the development of HKD is far from clear. The purpose of the present study was to offer an alternative view of the factors underlying HKD.

METHOD

The authors conducted an extensive, but not exhaustive, review of the literature to examine the evidence for the traditional view versus the alternative view.

RESULTS

The review suggests that HKD is a highly complex and variable phenomenon including multiple factors, such as scaling and maintaining movement amplitude and effort; preplanning and initiation of movements; internal cueing; sensory and temporal processing; automaticity; emotive vocalization; and attention to action (vocal vigilance). Although not part of the dysarthria, nonmotor factors, such as depression, aging, and cognitive-linguistic abnormalities, are likely to contribute to the overall speech symptomatology associated with IPD.

CONCLUSION

These findings have important implications for clinical practice and research.

Airway somatosensory deficits and dysphagia in Parkinson's disease

BACKGROUND

Individuals with Parkinson's disease (PD) often experience substantial impairment of swallow control, and are typically unaware of the presence or severity of their impairments suggesting that these individuals may also experience airway sensory deficits. However, the degree to which impaired swallow function in PD may relate to airway sensory deficits has yet to be formally tested.

OBJECTIVE

The purpose of this study was to examine whether airway sensory function is associated with swallow impairment in PD.

METHODS

Eighteen PD participants and 18 healthy controls participated in this study and underwent endoscopic assessment of airway somatosensory function, endoscopic assessment of swallow function, and clinical ratings of swallow and disease severity.

RESULTS

PD participants exhibited abnormal airway somatosensory function and greater swallow impairment compared with healthy controls. Swallow and sensory deficits in PD were correlated with disease severity. Moreover, PD participants reported similar self-rated swallow function as healthy controls, and swallow deficits were correlated with sensory function suggesting an association between impaired sensory function and poor self-awareness of swallow deficits in PD.

CONCLUSIONS

These results suggest that control of swallow is influenced by airway somatosensory function, that swallow-related deficits in PD are related to abnormal somatosensation, and that swallow and airway sensory function may degrade as a function of disease severity. Therefore, the basal ganglia and related neural networks may play an important role to integrate airway sensory input for swallow-related motor control. Furthermore, the airway deficits observed in PD suggest a disintegration of swallow-related sensory and motor control.

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

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

Sensorimotor adaptation of speech in Parkinson's disease

The basal ganglia are involved in establishing motor plans for a wide range of behaviors. Parkinson's disease (PD) is a manifestation of basal ganglia dysfunction associated with a deficit in sensorimotor integration and difficulty in acquiring new motor sequences, thereby affecting motor learning. Previous studies of sensorimotor integration and sensorimotor adaptation in PD have focused on limb movements using visual and force-field alterations. Here, we report the results from a sensorimotor adaptation experiment investigating the ability of PD patients to make speech motor adjustments to a constant and predictable auditory feedback manipulation. Participants produced speech while their auditory feedback was altered and maintained in a manner consistent with a change in tongue position. The degree of adaptation was associated with the severity of motor symptoms. The patients with PD exhibited adaptation to the induced sensory error; however, the degree of adaptation was reduced compared with healthy, age-matched control participants. The reduced capacity to adapt to a change in auditory feedback is consistent with reduced gain in the sensorimotor system for speech and with previous studies demonstrating limitations in the adaptation of limb movements after changes in visual feedback among patients with PD.

Striatal dopamine loss and discriminative sensory dysfunction in Parkinson's disease

OBJECTIVES

Patients with Parkinson's disease (PD) have higher-order discriminative sensory dysfunction including prolonged somesthetic temporal discrimination threshold (sTDT). We studied the effect of striatal dopamine loss on the prolongation of sTDT and also studied the impact of prolonged sTDT values on the various parkinsonian motor deficits.

MATERIALS AND METHODS

In 30 patients with PD, the severity of parkinsonian motor deficits was evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores during levodopa off and on periods. The UPDRS motor subscores were calculated, representing bradykinesia, rigidity, tremor, and axial motor deficits. During levodopa off and on periods, the sTDT value of each index finger was studied. Using [(18) F]-N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane (FPCIT) positron emission tomography studies, caudate and putaminal dopamine transporter uptake levels were measured. Multiple regression analysis covariated with age was used for statistical analysis.

RESULTS

During the off period, the striatal FPCIT uptake levels had an impact on the sTDT values (P < 0.01). The sTDT values had an impact on the UPDRS subscores for axial motor deficits (P < 0.05), but had no impact on those for bradykinesia, rigidity, and tremor. The sTDT values as well as UPDRS total motor scores and all UPDRS subscores were improved by a single oral levodopa treatment.

CONCLUSIONS

Striatal dopamine deficiency and consequent basal ganglia dysfunction may prolong sTDT, and higher-order discriminative sensory dysfunction seems to contribute in part to the development of axial motor deficits in patients with PD.

Tone discrimination as a window into acoustic perceptual deficits in Parkinson's disease

PURPOSE

Deficits in auditory perception compromise a range of linguistic processes in persons with Parkinson's disease (PD), including speech perception and sensitivity to affective and linguistic prosody. An unanswered question is whether this deficit exists not only at the level of speech perception, but also at a more pervasive level of auditory perception. It is possible that PD produces a selective impairment in the perception of a salient acoustic feature such as frequency, amplitude, or duration.

METHOD

Auditory perception in persons with PD was investigated using a tone discrimination task where clients ( N = 12) and age-matched controls ( N = 15) made same/different judgments for pairs of pure tones that were factorially varied by acoustic feature (i.e., frequency, amplitude, or duration) crossed with perceptual distance (i.e., close vs. far).

RESULTS

Relative to healthy age-matched controls, persons with PD showed marked impairment in tone discrimination. Persons with PD showed an acoustic feature by perceptual distance interaction that was characterized by deficits in detecting frequency and amplitude differences for perceptually near tones.

CONCLUSION

These results suggest that persons with PD show a reduced ability to notice change in frequency and amplitude as compared to normal older adults. More generally, these findings implicate a frontal-striatal contribution to auditory perception.

Tongue force and tongue motility are differently affected by unilateral vs bilateral nigrostriatal dopamine depletion in rats

In addition to its cardinal symptoms of bradykinesia, muscle rigidity, resting tremor and postural disturbances, Parkinson's disease (PD) also affects orolingual motor function. Orolingual motor deficits can contribute to dysphagia, which increases morbidity and mortality in this population. Previous preclinical studies describing orolingual motor deficits in animal models of PD have focused on unilateral nigrostriatal dopamine (DA) depletion. In this study we compared the effects of unilateral vs bilateral 6-hydroxydopamine (6-OHDA)-induced DA depletion in rats trained to lick water from an isometric force-sensing disc. Rats received either unilateral or bilateral 6-OHDA into the medial forebrain bundle and were tested for four weeks post-lesion. Dependent variables included task engagement (the number of licks per session), tongue force (mean and maximum), and tongue motility (the number of licks per second). While both lesion groups exhibited decreased tongue force output, tongue motility deficits were present in only the group that received unilateral nigrostriatal DA depletion. Task engagement was not significantly diminished by 6-OHDA. Analysis of striatal DA tissue content revealed that DA depletion was ∼97% in the unilateral group and ∼90% in the bilateral group. These results suggest that while nigrostriatal DA depletion affects tongue force output, deficits in tongue motility may instead result from a functional imbalance in neural pathways affecting this midline structure.

Dopamine alters tactile perception in Parkinson's disease

BACKGROUND

Abnormal somatosensory processing may contribute to motor impairments observed in Parkinson's disease (PD). Dopaminergic medications have been shown to alter somatosensory processing such that tactile perception is improved. In PD, it remains unclear whether the temporal sequencing of tactile stimuli is altered and if dopaminergic medications alter this perception.

METHODS

Somatosensory tactile perception was investigated using temporal order judgment in patients with Parkinson's disease on and off dopaminergic medications and in aged-matched healthy controls. Measures of temporal order judgment were acquired using computer controlled stimulation to digits 2 and 3 on the right hand and subjects were required to determine which stimuli occurred first. Two experimental tasks were compared, temporal order judgment without and with synchronization whereby digits 2 and 3 were vibrated synchronously in advance of the temporal order judgment sequence of stimuli.

RESULTS

Temporal order judgment in PD patients of and on medications were similar to controls. Temporal order judgment preceded by synchronous vibration impaired tactical acuity in controls and in PD patients off medications to similar degrees, but this perceptual impairment by synchronous vibration was not present in PD patients on medications.

CONCLUSIONS

These findings suggest that dopamine in PD reduces cortico-cortical connectivity with SI and this leads to changes in tactical sensitivity.

Altered brain activation and connectivity in early Parkinson disease tactile perception

BACKGROUND AND PURPOSE

Deficits in tactile perception are common in patients with PD. However, the neural mechanisms have not been previously reported in the early stages. This study aims to investigate how the brain activity and connectivity changed under tactile perception at early Parkinsonian state by using functional MR imaging.

MATERIALS AND METHODS

Twenty-one patients with early PD and 22 age- and sex-matched controls were recruited and scanned under a passive tactile stimulation task. Within-group and between-group activation maps were acquired, and regions of interest were defined according to the group-comparison result. This was followed by a functional connectivity analysis based on the graph theory.

RESULTS

We found that in the PD group, bilateral sensorimotor cortex was hypoactive during the task, whereas the hyperactive regions were mainly in bilateral prefrontal cortex, bilateral cerebellum, and contralateral striatum. There was a significant decrease of total connectivity degree in ipsilateral SMA in PD, which was negatively correlated with the Unified Parkinson's Disease Rating Scale score. Furthermore, the connection strengths among the areas of prefrontal cortex, striatum, and cerebellum were increased.

CONCLUSIONS

This study illustrated that early PD was associated with not only altered brain activation but also changed functional connectivity in tactile perception. The most significant impairment was in SMA, whereas striato-prefrontal and cerebello-prefrontal loops may play a compensatory role in early PD tactile function.

Regional alterations of brain microstructure in Parkinson's disease using diffusion tensor imaging

This study tested the hypothesis that diffusion tensor imaging can detect alteration in microscopic integrity of white matter and basal ganglia regions known to be involved in Parkinson's disease (PD) pathology. It was also hypothesized that there is an association between diffusion abnormality and PD severity and subtype. Diffusion tensor imaging at 4 Tesla was obtained in 12 PD and 20 control subjects, and measures of fractional anisotropy and mean diffusivity were evaluated using both region-of-interest and voxel-based methods. Movement deficits and subtypes in PD subjects were assessed using the Motor Subscale (Part III) of the Unified Parkinson's Disease Rating Scale. Reduced fractional anisotropy (P < .05, corrected) was found in PD subjects in regions related to the precentral gyrus, substantia nigra, putamen, posterior striatum, frontal lobe, and the supplementary motor areas. Reduced fractional anisotropy in the substantia nigra correlated (P < .05, corrected) with the increased rating scale motor scores. Significant spatial correlations between fractional anisotropy alterations in the putamen and other PD-affected regions were also found in the context of PD subtypes index analysis. Our data suggest that microstructural alterations detected with diffusion tensor might serve as a potential biomarker for PD.

Rhythmic movement in Parkinson's disease: effects of visual feedback and medication state

Previous studies examining discrete movements of Parkinson's disease (PD) patients have found that in addition to performing movements that were slower than those of control participants, they exhibit specific deficits in movement coordination and in sensorimotor integration required to accurately guide movements. With medication, movement speed was normalized, but the coordinative aspects of movement were not. This led to the hypothesis that dopaminergic medication more readily compensates for intensive aspects of movement (such as speed), than for coordinative aspects (such as coordination of different limb segments) (Schettino et al., Exp Brain Res 168:186-202, 2006). We tested this hypothesis on rhythmic, continuous movements of the forearm. In our task, target peak speed and amplitude, availability of visual feedback, and medication state (on/off) were varied. We found, consistent with the discrete-movement results, that peak speed (intensive aspect) was normalized by medication, while accuracy, which required coordination of speed and amplitude modulation (coordinative aspect), was not normalized by dopaminergic treatment. However, our findings that amplitude, an intensive aspect of movement, was also not normalized by medication, suggests that a simple pathway gain increase does not act to remediate all intensive aspects of movement to the same extent. While it normalized movement peak speed, it did not normalize movement amplitude. Furthermore, we found that when visual feedback was not available, all participants (PD and controls) made faster movements. The effects of dopaminergic medication and availability of visual feedback on movement speed were additive. The finding that movement speed uniformly increased both in the PD and the control groups suggests that visual feedback may be necessary for calibration of peak speed, otherwise underestimated by the motor control system.