Hand rhythmic tapping and timing in Parkinson's disease

Premotor cortical beta synchronization and the network neuromodulation of externally paced finger tapping in Parkinson's disease

Parkinson's disease (PD) is characterized by the disruption of repetitive, concurrent and sequential motor actions due to compromised timing-functions principally located in cortex-basal ganglia (BG) circuits. Increasing evidence suggests that motor impairments in untreated PD patients are linked to an excessive synchronization of cortex-BG activity at beta frequencies (13-30 Hz). Levodopa and subthalamic nucleus deep brain stimulation (STN-DBS) suppress pathological beta-band reverberation and improve the motor symptoms in PD. Yet a dynamic tuning of beta oscillations in BG-cortical loops is fundamental for movement-timing and synchronization, and the impact of PD therapies on sensorimotor functions relying on neural transmission in the beta frequency-range remains controversial. Here, we set out to determine the differential effects of network neuromodulation through dopaminergic medication (ON and OFF levodopa) and STN-DBS (ON-DBS, OFF-DBS) on tapping synchronization and accompanying cortical activities. To this end, we conducted a rhythmic finger-tapping study with high-density EEG-recordings in 12 PD patients before and after surgery for STN-DBS and in 12 healthy controls. STN-DBS significantly ameliorated tapping parameters as frequency, amplitude and synchrony to the given auditory rhythms. Aberrant neurophysiologic signatures of sensorimotor feedback in the beta-range were found in PD patients: their neural modulation was weaker, temporally sluggish and less distributed over the right cortex in comparison to controls. Levodopa and STN-DBS boosted the dynamics of beta-band modulation over the right hemisphere, hinting to an improved timing of movements relying on tactile feedback. The strength of the post-event beta rebound over the supplementary motor area correlated significantly with the tapping asynchrony in patients, thus indexing the sensorimotor match between the external auditory pacing signals and the performed taps. PD patients showed an excessive interhemispheric coherence in the beta-frequency range during the finger-tapping task, while under DBS-ON the cortico-cortical connectivity in the beta-band was normalized. Ultimately, therapeutic DBS significantly ameliorated the auditory-motor coupling of PD patients, enhancing the electrophysiological processing of sensorimotor feedback-information related to beta-band activity, and thus allowing a more precise cued-tapping performance.

Which factors modulate spontaneous motor tempo? A systematic review of the literature

Intentionally or not, humans produce rhythmic behaviors (e.g., walking, speaking, and clapping). In 1974, Paul Fraisse defined rhythmic behavior as a periodic movement that obeys a temporal program specific to the subject and that depends less on the conditions of the action (p. 47). Among spontaneous rhythms, the spontaneous motor tempo (SMT) corresponds to the tempo at which someone produces movements in the absence of external stimuli, at the most regular, natural, and pleasant rhythm for him/her. However, intra- and inter-individual differences exist in the SMT values. Even if several factors have been suggested to influence the SMT (e.g., the age of participants), we do not yet know which factors actually modulate the value of the SMT. In this context, the objectives of the present systematic review are (1) to characterize the range of SMT values found in the literature in healthy human adults and (2) to identify all the factors modulating the SMT values in humans. Our results highlight that (1) the reference value of SMT is far from being a common value of 600 ms in healthy human adults, but a range of SMT values exists, and (2) many factors modulate the SMT values. We discuss our results in terms of intrinsic factors (in relation to personal characteristics) and extrinsic factors (in relation to environmental characteristics). Recommendations are proposed to assess the SMT in future research and in rehabilitative, educative, and sport interventions involving rhythmic behaviors.

The effect of standing posture on amplitude and variability of postural tremor in Parkinson’s disease

INTRODUCTION

This study examined whether altering body position (i.e., sitting or standing) affected the dynamics of physiological tremor for healthy older adults and persons with Parkinson's disease (PD). It was also of interest to determine how consistent the tremor was for both groups as determined by examining changes in within-subject variability of tremor amplitude, regularity and frequency.

METHODS

Ten Parkinsonian participants (65.1±3.2 yrs.) and twelve elderly persons (71.2±2.6 yrs.) participated in this study. Tremor was collected from the index finger and hand segments using lightweight accelerometers during the performance of a bilateral pointing task. Persons performed the pointing task in a standing or sitting position.

RESULTS

As expected, the tremor for the PD persons was greater in magnitude (mean RMS, peak power), more regular (lower SampEn), and more inconsistent from trial-to-trial (increased intra-individual variability, IIV) than the tremor recorded for the elderly. Further, when assessed during standing, the magnitude of the tremor for all individuals (elderly and PD) was greater, more variable, and less complex compared to the tremor when assessed during the sitting posture. The only measure which did not change within each group was the frequency of the major tremor peak which remained consistent, showing no significant change between limbs or as a function of the posture adopted.

CONCLUSION

The findings revealed that tremor increased in amplitude and decreased in regularity for all individuals was assessed when standing compared to sitting. It is likely that these increases were task-related, reflecting the increased physical demands of performing the task when standing rather than being driven by specific age- or disease-related changes in the mechanisms underlying tremorgenesis. Further, the tremor for the PD individuals tended to be more variable from trial-by-trial in terms of both amplitude and regularity as compared to the elderly persons. Interestingly, the only tremor metric which showed no change within each group was the frequency of the major tremor peak which was consistent within both groups irrespective of the posture adopted.

Cross-frequency phase-amplitude coupling in repetitive movements in patients with Parkinson's disease

Bradykinesia is a cardinal motor symptom in Parkinson’s disease (PD), the pathophysiology of which is not fully understood. We analyzed the role of cross-frequency coupling of oscillatory cortical activity in motor impairment in patients with PD and healthy controls. High-density EEG signals were recorded during various motor activities and at rest. Patients performed a repetitive finger-pressing task normally, but were slower than controls during tapping. Phase-amplitude coupling (PAC) between β (13–30 Hz) and broadband γ (50–150 Hz) was computed from individual EEG source signals in the premotor, primary motor, and primary somatosensory cortices, and the primary somatosensory complex. In all four regions, averaging the entire movement period resulted in higher PAC in patients than in controls for the resting condition and the pressing task (similar performance between groups). However, this was not the case for the tapping tasks where patients performed slower. This suggests the strength of state-related β-γ PAC does not determine Parkinsonian bradykinesia. Examination of the dynamics of oscillatory EEG signals during motor transitions revealed a distinctive motif of PAC rise and decay around press onset. This pattern was also present at press offset and slow tapping onset, linking such idiosyncratic PAC changes to transitions between different movement states. The transition-related PAC modulation in patients was similar to controls in the pressing task but flattened during slow tapping, which related to normal and abnormal performance, respectively. These findings suggest that the dysfunctional evolution of neuronal population dynamics during movement execution is an important component of the pathophysiology of Parkinsonian bradykinesia.

NEW & NOTEWORTHY Our findings using noninvasive EEG recordings provide evidence that PAC dynamics might play a role in the physiological cortical control of movement execution and may encode transitions between movement states. Results in patients with Parkinson’s disease suggest that bradykinesia is related to a deficit of the dynamic regulation of PAC during movement execution rather than its absolute strength. Our findings may contribute to the development of a new concept of the pathophysiology of bradykinesia.

Frequency of hand movements as a possible diagnostic tool for parkinsonian bradykinesia. Proposal of a simple bedside test

BACKGROUND

Bradykinesia, dysrhythmia, and decrement in hand movements (HM) are core symptoms of Parkinson's disease (PD). The maximal rate of repetitive rhythm-preserving HM can be a diagnostic tool for PD bradykinesia.

OBJECTIVES

To improve the clinical diagnosis of bradykinesia by identifying the frequencies at which rhythmic HM become irregular in PD patients compared to healthy age-matched controls.

METHOD

Forty PD patients and 16 controls were asked to alternately perform left and right hand movements following the rate of a metronome with sound stimulation beginning at 85 beats per minute (BPM) and increasing in increments of 15 BPM up to 355 BPM. The rhythm of the HM for each rate was assessed visually, and the threshold frequency at which the subject could no longer rhythmically continue HM was measured by the metronome. The increasing rates of HM until reaching that threshold were compared between patients with PD and controls.

RESULTS

The mean rates of a metronome in PD vs. healthy subjects were 173.3 ± 42.0 vs. 248.8 ± 48.5 BPM (p < 0.001) and 164.8 ± 34.2 vs. 241.2 ± 40.1 BPM (p < 0.001) for the dominant and non-dominant hands, respectively. The areas under the ROC curve were 0.929 [95%CI: (0.86-0.99)] for the dominant hand and 0.947 [95%CI: (0.88-1.0)] for the non-dominant hand. The BMP score cut-off value was 208 (sensitivity 72.7%, specificity 100%) for the dominant hand and 206 (sensitivity 87.5%, specificity 95%) for the non-dominant hand.

CONCLUSIONS

The proposed test quantified the frequencies of rhythmic HMs in PD patients vs. controls and improved the diagnosis of bradykinesia in PD patients.

The relation between falls risk and movement variability in Parkinson's disease

Falls are a major health concern for older adults with Parkinson's disease (PD). This study was designed to examine differences in falls risk and its relation to changes in the average and variability (i.e. intra-individual variability) of reaction time (RT), finger tapping, standing balance and walking between healthy older adults and persons with PD. Thirty-nine adults with PD (70.0 ± 8.1 years) and 29 healthy older adults (66.8 ± 10.4 years) participated in this study. Falls risk (using the physiological profile assessment), gait, RT, balance and tapping responses were assessed for all persons. Results demonstrated that individuals with PD exhibited a greater risk of falling coupled with a general slowing of motor function covering declines in walking, RT and finger tapping. In addition, the movement responses of the PD group were more variable than the healthy older adults. Correlation results revealed group differences with regards to the neuromotor measures which were significantly correlated with falls risk. For the PD group, gait measures were highly correlated with their falls risk while, for the healthy older adults, falls risk was linked to balance measures even though PD persons had increased sway. Overall, persons with PD were at greater falls risk, moved slower and with increased variability compared to the healthy older adults. Further, while there are some similarities between the two groups in terms of those measures related to falls risk, there were also several differences which highlight that persons with PD can have different risk factors for falling compared to healthy adults of similar age.

Quantifying upper limb motor impairment in people with Parkinson's disease: a physiological profiling approach

BACKGROUND

Upper limb motor impairments, such as slowness of movement and difficulties executing sequential tasks, are common in people with Parkinson's disease (PD).

OBJECTIVE

To evaluate the validity of the upper limb Physiological Profile Assessment (PPA) as a standard clinical assessment battery in people with PD, by determining whether the tests, which encompass muscle strength, dexterity, arm stability, position sense, skin sensation and bimanual coordination can (a) distinguish people with PD from healthy controls, (b) detect differences in upper limb test domains between "off" and "on" anti-Parkinson medication states and (c) correlate with a validated measure of upper limb function.

METHODS

Thirty-four participants with PD and 68 healthy controls completed the upper limb PPA tests within a single session.

RESULTS

People with PD exhibited impaired performance across most test domains. Based on validity, reliability and feasibility, six tests (handgrip strength, finger-press reaction time, 9-hole peg test, bimanual pole test, arm stability, and shirt buttoning) were identified as key tests for the assessment of upper limb function in people with PD.

CONCLUSIONS

The upper limb PPA provides a valid, quick and simple means of quantifying specific upper limb impairments in people with PD. These findings indicate clinical assessments should prioritise tests of muscle strength, unilateral movement and dexterity, bimanual coordination, arm stability and functional tasks in people with PD as these domains are the most commonly and significantly impaired.

Comparison of Spontaneous Motor Tempo during Finger Tapping, Toe Tapping and Stepping on the Spot in People with and without Parkinson's Disease

OBJECTIVE

Spontaneous motor tempo (SMT), observed in walking, tapping and clapping, tends to occur around 2 Hz. Initiating and controlling movement can be difficult for people with Parkinson's (PWP), but studies have not identified whether PWP differ from controls in SMT. For community-based interventions, e.g. dancing, it would be helpful to know a baseline SMT to optimize the tempi of cued activities. Therefore, this study compared finger tapping (FT), toe tapping (TT) and stepping 'on the spot' (SS) in PWP and two groups of healthy controls [age-matched controls (AMC) and young healthy controls (YHC)], as SMT is known to change with age.

METHODS

Participants (PWP; n = 30, AMC; n = 23, YHC; n = 35) were asked to tap or step on the spot at a natural pace for two trials lasting 40 seconds. The central 30 seconds were averaged for analyses using mean inter-onset intervals (IOI) and coefficient of variation (CoV) to measure rate and variability respectively.

RESULTS

PWP had faster SMT than both control groups, depending on the movement modality: FT, F(2, 87) = 7.92, p < 0.01 (PWP faster than YHC); TT, F(2, 87) = 4.89, p = 0.01 (PWP faster than AMC); and SS, F(2, 77) = 3.26, p = 0.04 (PWP faster than AMC). PWP had higher CoV (more variable tapping) than AMC in FT only, F(2, 87) = 4.10, p = 0.02.

CONCLUSION

This study provides the first direct comparison of SMT between PWP and two control groups for different types of movements.

RESULTS

suggest SMT is generally faster in PWP than control groups, and more variable when measured with finger tapping compared to stepping on the spot.

Double-Tap Interaction as an Actuation Mechanism for On-Demand Cueing in Parkinson's Disease

Freezing of Gait (FoG) is one of the most debilitating symptoms of Parkinson’s disease and is an important contributor to falls. When the management of freezing episodes cannot be achieved through medication or surgery, non-pharmacological methods, such as cueing, have emerged as effective techniques, which ameliorates FoG. The use of On-Demand cueing systems (systems that only provide cueing stimuli during a FoG episode) has received attention in recent years. For such systems, the most common method of triggering the onset of cueing stimuli, utilize autonomous real-time FoG detection algorithms. In this article, we assessed the potential of a simple double-tap gesture interaction to trigger the onset of cueing stimuli. The intended purpose of our study was to validate the use of double-tap gesture interaction to facilitate Self-activated On-Demand cueing. We present analyses that assess if PwP can perform a double-tap gesture, if the gesture can be detected using an accelerometer’s embedded gestural interaction recognition function and if the action of performing the gesture aggravates FoG episodes. Our results demonstrate that a double-tap gesture may provide an effective actuation method for triggering On-Demand cueing. This opens up the potential future development of self-activated cueing devices as a method of On-Demand cueing for PwP and others.

Bipolar oscillations between positive and negative mood states in a computational model of Basal Ganglia

Bipolar disorder is characterized by mood swings-oscillations between manic and depressive states. The swings (oscillations) mark the length of an episode in a patient's mood cycle (period), and can vary from hours to years. The proposed modeling study uses decision making framework to investigate the role of basal ganglia network in generating bipolar oscillations. In this model, the basal ganglia system performs a two-arm bandit task in which one of the arms (action responses) leads to a positive outcome, while the other leads to a negative outcome. We explore the dynamics of key reward and risk related parameters in the system while the model agent receives various outcomes. Particularly, we study the system using a model that represents the fast dynamics of decision making, and a module to capture the slow dynamics that describe the variation of some meta-parameters of fast dynamics over long time scales. The model is cast at three levels of abstraction: (1) a two-dimensional dynamical system model, that is a simple two variable model capable of showing bistability for rewarding and punitive outcomes; (2) a phenomenological basal ganglia model, to extend the implications from the reduced model to a cortico-basal ganglia setup; (3) a detailed network model of basal ganglia, that incorporates detailed cellular level models for a more realistic understanding. In healthy conditions, the model chooses positive action and avoids negative one, whereas under bipolar conditions, the model exhibits slow oscillations in its choice of positive or negative outcomes, reminiscent of bipolar oscillations. Phase-plane analyses on the simple reduced dynamical system with two variables reveal the essential parameters that generate pathological 'bipolar-like' oscillations. Phenomenological and network models of the basal ganglia extend that logic, and interpret bipolar oscillations in terms of the activity of dopaminergic and serotonergic projections on the cortico-basal ganglia network dynamics. The network's dysfunction, specifically in terms of reward and risk sensitivity, is shown to be responsible for the pathological bipolar oscillations. The study proposes a computational model that explores the effects of impaired serotonergic neuromodulation on the dynamics of the cortico basal ganglia network, and relates this impairment to abstract mood states (manic and depressive episodes) and oscillations of bipolar disorder.

Music and Metronomes Differentially Impact Motor Timing in People with and without Parkinson's Disease: Effects of Slow, Medium, and Fast Tempi on Entrainment and Synchronization Performances in Finger Tapping, Toe Tapping, and Stepping on the Spot Tasks

Introduction

Rhythmic auditory stimulation (RAS) has successfully helped regulate gait for people with Parkinson's disease. However, the way in which different auditory cues and types of movements affect entrainment, synchronization, and pacing stability has not been directly compared in different aged people with and without Parkinson's. Therefore, this study compared music and metronomes (cue types) in finger tapping, toe tapping, and stepping on the spot tasks to explore the potential of RAS training for general use.

Methods

Participants (aged 18–78 years) included people with Parkinson's (n = 30, Hoehn and Yahr mean = 1.78), older (n = 26), and younger adult controls (n = 36), as age may effect motor timing. Timed motor production was assessed using an extended synchronization-continuation task in cue type and movement conditions for slow, medium, and fast tempi (81, 116, and 140 mean beats per minute, respectively).

Results

Analyses revealed main effects of cue and movement type but no between-group interactions, suggesting no differences in motor timing between people with Parkinson's and controls. Music supported entrainment better than metronomes in medium and fast tempi, and stepping on the spot enabled better entrainment and less asynchrony, as well as more stable pacing compared to tapping in medium and fast tempi. Age was not confirmed as a factor, and no differences were observed in slow tempo.

Conclusion

This is the first study to directly compare how different external auditory cues and movement types affect motor timing. The music and the stepping enabled participants to maintain entrainment once the external pacing cue ceased, suggesting endogenous mechanisms continued to regulate the movements. The superior performance of stepping on the spot suggests embodied entrainment can occur during continuous movement, and this may be related to emergent timing in tempi above 600 ms. These findings can be applied therapeutically to manage and improve adaptive behaviours for people with Parkinson's.

Deficits in tapping accuracy and variability in tremor patients

Background

The basal ganglia and cerebellum are brain structures involved in movement initiation, execution and termination. They are thought to be involved in the tremor generation and movement deficits in Parkinson’s disease (PD) and essential tremor (ET). Especially in PD, maintaining cyclic movement, such as walking or tapping can be significantly disturbed. Providing external cues improves timing of these movements in PD but its effect on ET has not yet been studied in depth. The aim of this study is to evaluate the usefulness of a bimanual tapping task as a tool during clinical decision making.

Method

Hand movements and tremor was recorded using accelerometers and EMG (m. extensor carpi ulnaris) from PD and ET patients and healthy controls during a bimanual tapping task as a way to distinguish PD from ET. All subjects performed the tapping task at two different frequencies, 2 Hz and 4 Hz, with and without the presence of auditory cues.

Results

No significant intra-group differences were found in the patient groups. Acceleration data revealed significantly less accurate tapping and more variable tapping in PD than in ET and healthy controls. ET subjects tapped less accurate and with a greater variability than healthy controls during the 4 Hz tapping task. Most interestingly the tapping accuracy improved in PD patients when kinetic tremor was recorded with EMG during the task.

Conclusion

Providing ET and PD patients with an external cue results in different tapping performances between patient groups and healthy controls. Furthermore, the findings suggest that kinetic tremor in PD enables patients to perform the task with a greater accuracy. So far this has not been shown in other studies.

Repetitive Finger Movement and Dexterity Tasks in People With Parkinson’s Disease

BACKGROUND. Little is known regarding how repetitive finger movement performance, an assessment of bradykinesia (slowness of movement), is related to fine-motor dexterity tasks in people with Parkinson’s disease (PD).

OBJECTIVE. This pilot study examined the relationship between the performance of fine-motor dexterity tasks and repetitive finger movement in people with PD.

METHOD. Forty-six participants with PD completed an acoustically cued repetitive finger movement task (1–3 Hz). Movement amplitude, movement rate difference, and coefficient of variation were obtained for each tone rate. Participants also completed a buttoning and Purdue pegboard assembly task. Buttoning time and number of assemblies were recorded.

RESULTS. A significant association was found between movement rate difference and movement rate difference coefficient of variation and buttoning performance in which higher movement rate and higher variability were associated with slower buttoning times. No significant associations between any of the repetitive finger movement outcome measures and Purdue pegboard assembly performance were revealed.

CONCLUSION. Changes in movement amplitude and movement rate may influence fine-motor dexterity tasks differently. Thus, it is important to consider the quantitative assessment of both movement rate and movement amplitude because they may indicate differential clinical applications in the treatment of people with PD.

When motor control gets out of hand: Speeding up triggers freezing in the upper limb in Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) can suffer from sudden movement arrests during upper limb tasks. The current study investigated a test to assess freezing of the upper limbs (FOUL) at two speed conditions to improve the sensitivity of FOUL detection.

METHODS

Forty-nine patients with PD and 10 age-matched controls (HC) performed a freezing-provoking writing task, requiring up- and down-stroke writing at varying sizes in-between visual target zones indicating funnel-shapes on a touch-sensitive tablet. They performed five trials at their preferred speed, referred to as the Normal Funnel Task (NFT) and five trials at maximum speed, referred to as the Fast Funnel Task (FFT), in a random order.

RESULTS

Based on a combination of kinematic criteria and video analysis, 183 FOUL episodes were detected in 24 participants (23 PD, 1 HC). The number of patients with FOUL, number of FOUL episodes and percentage time frozen were significantly higher during FFT than NFT. Most FOUL episodes occurred during writing at small (51.6%) and decreasing size (36.3%). Additionally, FOUL outcomes significantly correlated with the Montreal Cognitive Assessment and New Freezing of Gait Questionnaire.

CONCLUSION

As FOUL is more prevalent under higher task demands, these data offer support for the "threshold model", previously proposed to provide insight in freezing of gait (FOG) and underscoring the presupposed link between FOG and FOUL. As well, this study may provide a novel paradigm to assess FOUL in both laboratory and clinical settings.

Effects of Galvanic Vestibular Stimulation on Upper and Lower Extremities Motor Symptoms in Parkinson's Disease

As a neurodegenerative movement disorder, Parkinson’s disease (PD) is commonly characterized by motor symptoms such as resting tremor, rigidity, bradykinesia, and balance and postural impairments. While the main cause of PD is still not clear, it is shown that the basal ganglia loop, which has a role in adjusting a planned movement execution through fine motor control, is altered during this disease and contributes toward the manifested motor symptoms. Galvanic vestibular stimulation (GVS) is a non-invasive technique to influence the vestibular system and stimulate the motor system. This study explores how the motor symptoms of upper and lower extremities in PD are instantly affected by vestibular stimulation. In this regard, direct current GVS was applied to 11 individuals with PD on medication while they were performing two sets of experiments: (1) Instrumented Timed Up and Go (iTUG) test and (2) finger tapping task. The performance of participants was recorded with accelerometers and cameras for offline processing of data. Several outcome measures including coefficient of variation of the step duration, gait phase, phase coordination index, tapping score, and the number and duration of manual motor blocks (MMBs) were considered for objective quantifying of performance. Results showed that almost all of considered outcome measures were improved with the application of GVS and that the improvement in the coefficient of variation of the step duration, the tapping score, and the number of MMBs was statistically significant (p-value < 0.05). The results of this study suggest that GVS can be used to alleviate some of the common motor symptoms of PD. Further research is required to fully characterize the effects of GVS and determine its efficacy in the long term.

Does the Clock Tick Slower or Faster in Parkinson's Disease? - Insights Gained From the Synchronized Tapping Task

The rhythm of the internal clock is considered to be determined by the basal ganglia, with some studies suggesting slower internal clock in Parkinson's disease (PD). However, patients may also show motor hastening when they walk (festination) or are engaged in repetitive tapping, indicating faster ticking of the internal clock. Is the internal clock slower or faster in PD? The purpose of this study was to answer this question, i.e., how fast and slow a rhythm they can synchronize with, especially with reference to the limit of sensorimotor synchronization or temporal integration, representing the threshold of slower pace they can entrain into their motor actions, which is known to lie between 2 and 3 s in normal subjects but not yet studied in PD. We employed a synchronized tapping task that required subjects to tap the key in synchrony with repetitive tones at fixed interstimulus intervals (ISI) between 200 and 4800 ms. Twenty normal subjects and sixteen PD patients were enrolled, who were classified into early and advanced PD groups by UPDRS-III (early: 15 or less, advanced: more than 15). The ISI at which the response changes from synchronizing with the tones to lagging behind them was considered to be the limit of temporal integration. Early PD patients responded ahead of the tones (negative asynchrony), which became more apparent with repeated tapping. This suggested "faster" ticking clock even in the presence of the pacing tones. In normal subjects, the limit of temporal integration was around 2-3 s: below this, subjects could synchronize with the tones, while above it they had difficulty in synchronization. In early PD patients, the limit of temporal integration was significantly longer than in normal subjects, pointing to their enhanced ability to synchronize also with slower paces of tones, but advanced PD patients had significantly shortened limits, suggesting that advanced patients lost this ability. In conclusion, the limit of temporal integration is initially longer but gets shorter as the disease progresses. It can be explained by the hastening of the internal clock at the earlier stages of PD, followed by the loss of temporal integration.

Quantitative assessment of finger tapping characteristics in mild cognitive impairment, Alzheimer's disease, and Parkinson's disease

BACKGROUND

Fine motor impairments are common in neurodegenerative disorders, yet standardized, quantitative measurements of motor abilities are uncommonly used in neurological practice. Thus, understanding and comparing fine motor abilities across disorders have been limited.

OBJECTIVES

The current study compared differences in finger tapping, inter-tap interval, and variability in Alzheimer's disease (AD), Parkinson's disease (PD), mild cognitive impairment (MCI), and healthy older adults (HOA).

METHODS

Finger tapping was measured using a highly sensitive light-diode finger tapper. Total number of finger taps, inter-tap interval, and intra-individual variability (IIV) of finger tapping was measured and compared in AD (n = 131), PD (n = 63), MCI (n = 46), and HOA (n = 62), controlling for age and sex.

RESULTS

All patient groups had fine motor impairments relative to HOA. AD and MCI groups produced fewer taps with longer inter-tap interval and higher IIV compared to HOA. The PD group, however, produced more taps with shorter inter-tap interval and higher IIV compared to HOA.

CONCLUSIONS

Disease-specific changes in fine motor function occur in the most common neurodegenerative diseases. The findings suggest that alterations in finger tapping patterns are common in AD, MCI, and PD. In addition, the present results underscore the importance of motor dysfunction even in neurodegenerative disorders without primary motor symptoms.

Freezing during tapping tasks in patients with advanced Parkinson's disease and freezing of gait

Introduction

Parkinson’s disease patients with freezing of gait also experience sudden motor blocks (freezing) during other repetitive motor tasks. We assessed the proportion of patients with advanced PD and freezing of gait who also displayed segmental “freezing” in tapping tasks.

Methods

Fifteen Parkinson’s disease patients with freezing of gait were assessed. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients performed repetitive tapping movements (as described in the MDS-UPDRS task) with the hands or the feet in the presence or absence of a metronome set to 4 Hz. Movements were recorded with a video motion system. The primary endpoint was the occurrence of segmental freezing in these tapping tasks. The secondary endpoints were (i) the relationship between segmental episodic phenomena and FoG severity, and (ii) the reliability of the measurements.

Results

For the upper limbs, freezing was observed more frequently with a metronome (21% of trials) than without a metronome (5%). For the lower limbs, the incidence of freezing was higher than for the upper limbs, and was again observed more frequently in the presence of an auditory cue (47%) than in its absence (14%).

Conclusion

Although freezing of the lower limbs was easily assessed during an MDS-UPDRS task with a metronome, it was not correlated with the severity of freezing of gait (as evaluated during a standardized gait trajectory). Only this latter was a reliable measurement in patients with advanced Parkinson’s disease.

Freezing/festination during motor tasks in early-stage Parkinson's disease: A prospective study

BACKGROUND

Parkinsonian patients have a tendency to speed up during repetitive motor tasks (festination) and to experience sudden motor blocks (freezing). In this article, we prospectively studied the appearance and progression of these phenomena in 30 early-stage PD patients.

METHODS

A total of 30 controls and early-stage PD patients were assessed in the "off-drug" condition at baseline and 2 years later. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients also performed diadochokinetic tasks with 3 different effectors (repetitive, antiphase movements for the hands and feet, and repetitive syllable production for the orofacial effector) at frequencies ranging from 1 to 7 Hz (in random order). The primary endpoint was the occurrence of freezing and festination.

RESULTS

At baseline, freezing was observed in 6.5% of the trials in PD patients (43% of the patients) and 2.3% of the trials in controls, and festination was observed in 5.7% of the trials in patients (53% of the patients) and 0.8% of the trials in controls. These proportions were slightly higher in patients 2 years later. None of the patients presented freezing of gait at baseline, but 2 displayed this condition 2 years later. These phenomena occurred more frequently for the limb effectors than for the orofacial effector. Freezing and festination were associated with the akinetic-rigid subtype, although tremor-dominant patients displayed greater rhythm variability outside episodes.

CONCLUSION

Freezing and festination of the upper and lower limbs are observed soon after the diagnosis of PD and may be early biomarkers for disease progression. © 2016 International Parkinson and Movement Disorder Society.

DEVELOPMENT OF ARDUINO-BASED HAND DYNAMOMETER ASSISTIVE DEVICE

The aim of this study is to develop a hand dynamometer that can act as a rehabilitation device by acquiring quantified data to enhance the power of hand grip strength. On the whole, patient that suffers from the hand injury is directly exposed to intricacy when performing daily task. Therefore, many hand aids have been developed to overcome the problem. A typical hand assistive device is able to measure the hand grip strength, which eventually increases its functionality. Like hand dynamometer, it is used for regular screening of hand grip strength and also for the preliminary and ongoing assessment of patients with hand dysfunction or trauma. Strain gauge-based system transducer acts as the measurement system together with Arduino microcontroller for the instrumentation, communication and controlling applications. The integration of strain gauges with a transducer is called a load cell which also made up the overall of force sensor to obtain readings from the hand grip movement. Microcontroller will further use this information to store and analyze data in the SD card. The percentage difference observed between hands across the sample of 25 subjects support the 10% rule. An overall 10.74% difference was found when combined dominant and non-dominant hand strength scores for all subjects were observed.

Impact of Auditory Context on Executed Motor Actions

The auditory and motor systems are strongly coupled, as is evident in the specifically tight motor synchronization that occurs in response to regularly occurring auditory cues compared with cues of other modalities. Timing of rhythmic action is known to rely on multiple neural centers including the cerebellum and the basal-ganglia which have access to both motor cortical and spinal circuitries. To date, however, there is little information on the motor mechanisms that operate during preparation and execution of rhythmic vs. non-rhythmic movements. We measured acceleration profile and muscle activity while subjects performed tapping movements in response to auditory cues. We found that when tapping at random intervals there was a higher variability of both acceleration profile and muscle activity during motor preparation compared to rhythmic tapping. However, the specific rhythmic context (cued, self-paced, or syncopation) did not affect the motor parameters of the executed taps. Finally, during entrainment we found a gradual as opposed to episodic change in low-level motor parameters (i.e., preparatory muscle activity) that was strongly correlated with changes in high-level parameters (i.e., shift in the reaction time to negative asynchrony). These findings suggest that motor entrainment involves not only adjusting the timing of movement but also modifying parameters that are related to its production. These changes in motor output were insensitive to the specifics of the rhythmic cue: although it took subjects different times to become entrained to different types of rhythmic cues, the motor actions produced once entrainment was obtained were indistinguishable. These findings suggest that motor entrainment involves not only adjusting the timing of movement but also modifying parameters related to its production. The reduced variability of muscle activity during the preparatory period could be one mechanism used by the motor system to enhance the accuracy of motor timing.

Predictive timing functions of cortical beta oscillations are impaired in Parkinson's disease and influenced by L-DOPA and deep brain stimulation of the subthalamic nucleus

Cortex-basal ganglia circuits participate in motor timing and temporal perception, and are important for the dynamic configuration of sensorimotor networks in response to exogenous demands. In Parkinson's disease (PD) patients, rhythmic auditory stimulation (RAS) induces motor performance benefits. Hitherto, little is known concerning contributions of the basal ganglia to sensory facilitation and cortical responses to RAS in PD. Therefore, we conducted an EEG study in 12 PD patients before and after surgery for subthalamic nucleus deep brain stimulation (STN-DBS) and in 12 age-matched controls. Here we investigated the effects of levodopa and STN-DBS on resting-state EEG and on the cortical-response profile to slow and fast RAS in a passive-listening paradigm focusing on beta-band oscillations, which are important for auditory–motor coupling. The beta-modulation profile to RAS in healthy participants was characterized by local peaks preceding and following auditory stimuli. In PD patients RAS failed to induce pre-stimulus beta increases. The absence of pre-stimulus beta-band modulation may contribute to impaired rhythm perception in PD. Moreover, post-stimulus beta-band responses were highly abnormal during fast RAS in PD patients. Treatment with levodopa and STN-DBS reinstated a post-stimulus beta-modulation profile similar to controls, while STN-DBS reduced beta-band power in the resting-state. The treatment-sensitivity of beta oscillations suggests that STN-DBS may specifically improve timekeeping functions of cortical beta oscillations during fast auditory pacing.

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High density EEG investigation in patients with PD before and after STN-DBS surgery

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Resting state EEG: altered spectral composition following STN-DBS

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Rhythmic auditory stimulation (RAS): absence of pre-stimulus beta activity in PD

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Fast RAS: normalization of beta (13–30 Hz) activities by L-DOPA and STN-DBS

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Altered beta modulation profile may contribute to timekeeping deficits in PD.

Motor automaticity in Parkinson's disease

Bradykinesia is the most important feature contributing to motor difficulties in Parkinson's disease (PD). However, the pathophysiology underlying bradykinesia is not fully understood. One important aspect is that PD patients have difficulty in performing learned motor skills automatically, but this problem has been generally overlooked. Here we review motor automaticity associated motor deficits in PD, such as reduced arm swing, decreased stride length, freezing of gait, micrographia and reduced facial expression. Recent neuroimaging studies have revealed some neural mechanisms underlying impaired motor automaticity in PD, including less efficient neural coding of movement, failure to shift automated motor skills to the sensorimotor striatum, instability of the automatic mode within the striatum, and use of attentional control and/or compensatory efforts to execute movements usually performed automatically in healthy people. PD patients lose previously acquired automatic skills due to their impaired sensorimotor striatum, and have difficulty in acquiring new automatic skills or restoring lost motor skills. More investigations on the pathophysiology of motor automaticity, the effect of L-dopa or surgical treatments on automaticity, and the potential role of using measures of automaticity in early diagnosis of PD would be valuable.

Digitomotography in Parkinson's disease: a cross-sectional and longitudinal study

Motor symptoms in Parkinson’s disease (PD) are usually assessed with semi-quantitative tests such as the Unified PD Rating Scale (UPDRS) which are limited by subjectivity, categorical design, and low sensitivity. Particularly bradykinesia as assessed e.g. with speeded index finger tapping exhibits low validity measures. This exploratory study set out to (i) assess whether force transducer-based objective and quantitative analysis of motor coordination in index finger tapping is able to distinguish between PD patients and controls, and (ii) assess longitudinal changes. Sixteen early-stage and 17 mid-stage PD patients as well as 18 controls were included in the cross-sectional part of the study; thirteen, 16 and 16 individuals of the respective groups agreed in a reassessment 12 months later. Frequency, force, rhythmicity, regularity and laterality of speeded and metronome paced tapping were recorded by digitomotography using a quantitative motor system ("Q-Motor"). Analysis of cross-sectional data revealed most consistent differences between PD patients and controls in variability of tap performance across modalities assessed. Among PD patients, variability of taps and the ability to keep a given rhythm were associated with UPDRS motor and finger tapping scores. After 12 months, laterality parameters were reduced but no other parameters changed significantly. This data suggests that digitomotography provides quantitative and objective measures capable to differentiate PD from non-PD in a small cohort, however, the value of the assessment to track PD progression has to be further evaluated in larger cohorts of patients.

Effects of STN DBS and auditory cueing on the performance of sequential movements and the occurrence of action tremor in Parkinson's disease

Background

Parkinson’s disease (PD) patients show a higher ability to perform repetitive movements when they are cued by external stimuli, suggesting that rhythmic synchronization with an auditory timekeeper can be achieved in the absence of intact basal ganglia function. Deep brain stimulation (DBS) is another therapeutic method that improves movement performance in PD and may suppress or enhance action tremor. However, the combined effect of these therapies on action tremor has not been studied yet. In this pilot study, we thus test the effect of both DBS in the subthalamic nucleus (STN) and auditory cueing on movement performance and action tremor.

Methods

7 PD patients treated with (bilateral) STN DBS were asked to move one hand or foot between two dots, separated by 30 cm as indicated on the table or the floor. The movement frequency was dictated by a metronome with a frequency in the range of 1.6 to 4.8 Hz. Each test was repeated three times for each extremity, with different stimulation settings applied during each repetition. The power spectral density patterns of recorded movements were studied. Tremor intermittency was taken into account by classifying each 2-second window of the recorded angular velocity signals as a tremor or non-tremor window. By determining the phase locking value it was tested whether movement or tremor was synchronized with the auditory cue.

Results

While action tremor presence or absence did not affect the level of synchronization of the movement signal with the auditory cue for the different metronome frequencies, the number of extremities showing action tremor was significantly reduced under external cueing conditions in combination with DBS. In this respect the cueing frequencies of 1.6 and 4.8 Hz showed similar effects, suggesting that the frequency of the cueing signal is not that critical.

Conclusion

The combination of deep brain stimulation and auditory cueing, which both are proposed to involve the activation of cerebellar circuits, shows an enhanced action tremor reduction in Parkinson’s disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-0003-11-135) contains supplementary material, which is available to authorized users.

Contributions of the Basal Ganglia to Temporal Processing: Evidence from Parkinson’s Disease

The motor and perceptual timing deficits documented in patients with Parkinson’s disease (PD) have heavily influenced the theory that the basal ganglia play an important role in temporal processing. This review is a systematic exploration of the findings from behavioural and neuroimaging studies of motor and perceptual timing in PD. In particular, we consider the influence of a variety of task factors and of patient heterogeneity in explaining the mixed results. We also consider the effect of basal ganglia dysfunction on the non-temporal cognitive factors that contribute to successful motor and perceptual timing. Although there is convincing evidence from PD that the basal ganglia are critical to motor and perceptual timing, further work is needed to characterize the precise contribution of this complex structure to temporal processing.

Motor and perceptual timing in Parkinson's disease

Neuroimaging has been a powerful tool for understanding the neural architecture of interval timing. However, identifying the critical brain regions engaged in timing was initially driven by investigation of human patients and animals. This chapter draws on the important contribution that the study of patients with Parkinson's disease (PD) has made in identifying the basal ganglia as a key component of motor and perceptual timing. The chapter initially describes the experimental tasks that have been critical in PD (and non-PD) timing research before systematically discussing the results from behavioural studies. This is followed by a critique of neuroimaging studies that have given insight into the pattern of neural activity during motor and perceptual timing in PD. Finally, discussion of the effects of medical and surgical treatment on timing in PD enables further evaluation of the role of dopamine in interval timing.

Automatic and objective assessment of alternating tapping performance in Parkinson's disease

This paper presents the development and evaluation of a method for enabling quantitative and automatic scoring of alternating tapping performance of patients with Parkinson's disease (PD). Ten healthy elderly subjects and 95 patients in different clinical stages of PD have utilized a touch-pad handheld computer to perform alternate tapping tests in their home environments. First, a neurologist used a web-based system to visually assess impairments in four tapping dimensions ('speed', 'accuracy', 'fatigue' and 'arrhythmia') and a global tapping severity (GTS). Second, tapping signals were processed with time series analysis and statistical methods to derive 24 quantitative parameters. Third, principal component analysis was used to reduce the dimensions of these parameters and to obtain scores for the four dimensions. Finally, a logistic regression classifier was trained using a 10-fold stratified cross-validation to map the reduced parameters to the corresponding visually assessed GTS scores. Results showed that the computed scores correlated well to visually assessed scores and were significantly different across Unified Parkinson's Disease Rating Scale scores of upper limb motor performance. In addition, they had good internal consistency, had good ability to discriminate between healthy elderly and patients in different disease stages, had good sensitivity to treatment interventions and could reflect the natural disease progression over time. In conclusion, the automatic method can be useful to objectively assess the tapping performance of PD patients and can be included in telemedicine tools for remote monitoring of tapping.

The pattern of striatal dopaminergic denervation explains sensorimotor synchronization accuracy in Parkinson's disease

The basal ganglia are thought to play a critical role in duration perception and production. However, experimental evidence for impaired temporal processing in Parkinson's disease (PD) patients is mixed. This study examined the association between striatal dopaminergic denervation in PD patients and sensorimotor synchronization. Twenty-eight mild-to-moderate stage PD patients synchronized finger taps to tone sequences of either 500 ms, 1000 ms or 1500 ms time intervals while ON levodopa (l-DOPA) or placebo pill (on separate test days) with the index finger of their more and less affected hands. We measured the accuracy and variability of synchronization. In a separate session, patients underwent (11)C-dihydrotetrabenazine ((11)C-DTBZ) PET scanning to measure in vivo striatal dopaminergic denervation. Patients were less accurate synchronizing to the 500 ms target time interval, compared to the 1000 ms and 1500 ms time intervals, but neither medication state nor hand affected accuracy; medication state, hand nor the target time interval affected synchronization variability. Regression analyses revealed no strong relationships between synchronization accuracy or variability and striatal dopaminergic denervation. We performed a cluster analysis on the degree of dopaminergic denervation to determine whether patient subgroup differences underlie our results. Three patient subgroups showed behavioral differences in synchronization accuracy, but not variability, paralleling their pattern of denervation. These findings provide further evidence for the role of the basal ganglia and dopamine in duration production and suggest that the degree of striatal dopaminergic denervation may explain the heterogeneity of performance between PD patients on the sensorimotor synchronization task.

Is DOPA-Responsive Hypokinesia Responsible for Bimanual Coordination Deficits in Parkinson's Disease?

Bradykinesia is a well-documented DOPA-responsive clinical feature of Parkinson’s disease (PD). While amplitude deficits (hypokinesia) are a key component of this slowness, it is important to consider how dopamine influences both the amplitude (hypokinesia) and frequency components of bradykinesia when a bimanually coordinated movement is required. Based on the notion that the basal ganglia are associated with sensory deficits, the influence of dopaminergic replacement on sensory feedback conditions during bimanual coordination was also evaluated. Bimanual movements were examined in PD and healthy comparisons in an unconstrained three-dimensional coordination task. PD were tested “off” (overnight withdrawal of dopaminergic treatment) and “on” (peak dose of dopaminergic treatment), while the healthy group was evaluated for practice effects across two sessions. Required cycle frequency (increased within each trial from 0.75 to 2 Hz), type of visual feedback (no vision, normal vision, and augmented vision), and coordination pattern (symmetrical in-phase and non-symmetrical anti-phase) were all manipulated. Overall, coordination (mean accuracy and standard deviation of relative phase) and amplitude deficits during bimanual coordination were confirmed in PD participants. In addition, significant correlations were identified between severity of motor symptoms as well as bradykinesia to greater coordination deficits (accuracy and stability) in PD “off” group. However, even though amplitude deficits (hypokinesia) improved with dopaminergic replacement, it did not improve bimanual coordination performance (accuracy or stability) in PD patients from “off” to “on.” Interestingly, while coordination performance in both groups suffered in the augmented vision condition, the amplitude of the more affected limb of PD was notably influenced. It can be concluded that DOPA-responsive hypokinesia contributes to, but is not directly responsible for bimanual coordination impairments in PD. It is likely that bimanual coordination deficits in PD are caused by the combination of dopaminergic system dysfunction as well as other neural impairments that may be DOPA-resistant or related to non-dopaminergic pathways.

Which Aspects of Postural Control Differentiate between Patients with Parkinson's Disease with and without Freezing of Gait?

This exploratory study aimed to identify which aspects of postural control are able to distinguish between subgroups of patients with Parkinson's disease (PD) and controls. Balance was tested using static and dynamic posturography. Freezers (n = 9), nonfreezers (n = 10), and controls (n = 10) stood on a movable force platform and performed 3 randomly assigned tests: (1) sensory organization test (SOT) to evaluate the effective use of sensory information, (2) motor control test (MCT) to assess automatic postural reactions in response to platform perturbations, and (3) rhythmic weight shift test (RWS) to evaluate the ability to voluntarily move the center of gravity (COG) mediolaterally and anterior-posteriorly (AP). The respective outcome measures were equilibrium and postural strategy scores, response strength and amplitude of weight shift. Patients were in the “on” phase of the medication cycle. In general, freezers performed similarly on SOT and MCT compared to nonfreezers. Freezers showed an intact postural strategy during sensory manipulations and an appropriate response to external perturbations. However, during voluntary weight shifting, freezers showed poorer directional control compared to nonfreezers and controls. This suggests that freezers have adequate automatic postural control and sensory integration abilities in quiet stance, but show specific directional control deficits when weight shifting is voluntary.

Comparing kinematic changes between a finger-tapping task and unconstrained finger flexion-extension task in patients with Parkinson's disease

Repetitive finger tapping is a well-established clinical test for the evaluation of parkinsonian bradykinesia, but few studies have investigated other finger movement modalities. We compared the kinematic changes (movement rate and amplitude) and response to levodopa during a conventional index finger-thumb-tapping task and an unconstrained index finger flexion-extension task performed at maximal voluntary rate (MVR) for 20 s in 11 individuals with levodopa-responsive Parkinson's disease (OFF and ON) and 10 healthy age-matched controls. Between-task comparisons showed that for all conditions, the initial movement rate was greater for the unconstrained flexion-extension task than the tapping task. Movement rate in the OFF state was slower than in controls for both tasks and normalized in the ON state. The movement amplitude was also reduced for both tasks in OFF and increased in the ON state but did not reach control levels. The rate and amplitude of movement declined significantly for both tasks under all conditions (OFF/ON and controls). The time course of rate decline was comparable for both tasks and was similar in OFF/ON and controls, whereas the tapping task was associated with a greater decline in MA, both in controls and ON, but not OFF. The findings indicate that both finger movement tasks show similar kinematic changes during a 20-s sustained MVR, but that movement amplitude is less well sustained during the tapping task than the unconstrained finger movement task. Both movement rate and amplitude improved with levodopa; however, movement rate was more levodopa responsive than amplitude.

Modeling accuracy and variability of motor timing in treated and untreated Parkinson's disease and healthy controls

Parkinson’s disease (PD) is characterized by difficulty with the timing of movements. Data collected using the synchronization–continuation paradigm, an established motor timing paradigm, have produced varying results but with most studies finding impairment. Some of this inconsistency comes from variation in the medication state tested, in the inter-stimulus intervals (ISI) selected, and in changeable focus on either the synchronization (tapping in time with a tone) or continuation (maintaining the rhythm in the absence of the tone) phase. We sought to re-visit the paradigm by testing across four groups of participants: healthy controls, medication naïve de novo PD patients, and treated PD patients both “on” and “off” dopaminergic medication. Four finger tapping intervals (ISI) were used: 250, 500, 1000, and 2000 ms. Categorical predictors (group, ISI, and phase) were used to predict accuracy and variability using a linear mixed model. Accuracy was defined as the relative error of a tap, and variability as the deviation of the participant’s tap from group predicted relative error. Our primary finding is that the treated PD group (PD patients “on” and “off” dopaminergic therapy) showed a significantly different pattern of accuracy compared to the de novo group and the healthy controls at the 250-ms interval. At this interval, the treated PD patients performed “ahead” of the beat whilst the other groups performed “behind” the beat. We speculate that this “hastening” relates to the clinical phenomenon of motor festination. Across all groups, variability was smallest for both phases at the 500-ms interval, suggesting an innate preference for finger tapping within this range. Tapping variability for the two phases became increasingly divergent at the longer intervals, with worse performance in the continuation phase. The data suggest that patients with PD can be best discriminated from healthy controls on measures of motor timing accuracy, rather than variability.

Aspects of speech rate and regularity in Parkinson's disease

The hypokinetic dysarthria of Parkinson's disease (PD) has been defined as a multidimensional impairment leading to abnormalities in speech breathing, phonation, articulation and prosody. The aspect of prosody can be subdivided into further dimensions, as for example stress and accentuation, intonation variability and speech rate and regularity. According to available data from literature and findings of our own published studies, the present review illuminates the concept that inconstancies of speech fluency in PD are characterized by modifications of the arrangement of speech pauses and by a tendency of pace acceleration in the course of the performance. Furthermore, on the level of single utterances, Parkinsonian speakers feature significant difficulties to steadily repeat single syllables without accelerating or slowing down the pace as we were able to show in a series of published investigations. Evidence from literature and our own work justifies the hypothesis that the characteristic abnormalities in speech articulatory rate and regularity might serve as a marker of disease progression in PD.

Instability of syllable repetition as a marker of disease progression in Parkinson's disease: a longitudinal study

Parkinsonian speakers show a tendency to articulatory acceleration and have difficulties to keep the steady pace of repeated syllables. The aim of this study was to analyse the stability of motor speech performance based upon a syllable repetition paradigm during the course of disease to find a potential marker of disease progression in Parkinson's disease (PD). 58 patients with PD and 35 controls were tested and re-tested after at least 12 months (mean: 33.40/range: 12-88). In the PD group, motor impairment was similar at first and second visit. Participants had to repeat the syllable /pa/ in a self chosen steady pace. Percental coefficient of variance (COV) of interval length was measured for description of pace stability throughout the performance. Percental pace acceleration (%PA) was based upon a comparison of the speed of syllable repetition in the first and second half of the task. Patients with PD showed a significant elevation of COV and %PA indicating an instability of syllable repetition and a tendency to pace acceleration in the course of performing. Furthermore, in the PD group, COV and %PA showed a significant deterioration from first to second examination. Instability of steady syllable repetition in PD shows characteristic changes during the course of the disease, but no correlation with general motor impairment. Therefore, the underlying mechanism may be independent from dopaminergic deficits. The potential role of impaired syllable repetition as a marker of non-dopaminergic disease progression in PD needs validation by further studies.

A home environment test battery for status assessment in patients with advanced Parkinson's disease

A test battery for assessing patient state in advanced Parkinson's disease, consisting of self-assessments and motor tests, was constructed and implemented on a hand computer with touch screen in a telemedicine setting. The aim of this work was to construct an assessment device, applicable during motor fluctuations in the patient's home environment. Selection of self-assessment questions was based on questions from an e-diary, previously used in a clinical trial. Both un-cued and cued tapping tests and spiral drawing tests were designed for capturing upper limb stiffnes, slowness and involuntary movements. The patient interface gave an audible signal at scheduled response times and was locked otherwise. Data messages in an XML-format were sent from the hand unit to a central server for storage, processing and presentation. In tapping tests, speed and accuracy were calculated and in spiral tests, standard deviation of frequency filtered radial drawing velocity was calculated. An overall test score, combining repeated assessments of the different test items during a test period, was defined based on principal component analysis and linear regression. An evaluation with two pilot patients before and after receiving new types of treatments was performed. Compliance and usability was assessed in a clinical trial (65 patients with advanced Parkinson's disease) and correlations between different test items and internal consistency were investigated. The test battery could detect treatment effect in the two pilot patients, both in self-assessments, tapping tests' results and spiral scores. It had good patient compliance and acceptable usability according to nine nurses. Correlation analysis showed that tapping results provided different information as compared to diary responses. Internal consistency of the test battery was good and learning effects in the tapping tests were small.

Effect of movement frequency on repetitive finger movements in patients with Parkinson's disease

Performance of repetitive hand movements in patients with Parkinson's disease (PD) is characterized by slowness, reduced movement amplitude, and hesitation or arrests in ongoing movement. Currently, the factors and mechanisms contributing to impaired performance of these types of movement remain poorly understood. This study examined the effects of movement frequency and medication on the performance of unconstrained index finger flexion movements in patients with PD and matched control subjects. Movements were synchronized with an auditory tone as the frequency of the tone was increased from 1 to 3 Hz in 0.25 Hz increments. Movement performance was quantified based upon finger kinematics and electromyography (EMG) recorded from the index finger flexors and extensors. The principal finding was that patients with PD showed a dramatic reduction in movement amplitude, an increase in movement frequency, and a loss of phase when the movement frequency reached or exceeded 2 Hz. This deficit was not significantly improved with medications. In contrast, all control subjects could synchronize to 3 Hz. These findings show that movement frequency is a major determinant of hypokinesia during repetitive movements and may contribute to hesitations and movement arrest during clinical testing of bradykinesia in the upper limb of patients with PD.

Hypometria and bradykinesia during drawing movements in individuals with Parkinson's disease

To address the hypothesis that Parkinson's disease (PD) patients have deficits in controlling acceleration, a drawing task was used in which target size, frequency, and weight of pen were manipulated. In accordance with previous results, it was found that, relative to controls, PD patients produced movements at the required frequency, but moved significantly slower, produced less acceleration, and drew smaller-than-required stroke sizes. This resulted in smaller-than-required movement amplitudes, suggesting that hypometria and bradykinesia in drawing and/or handwriting are related. Patients were found to perform similarly to controls when the target size was 1 cm. However, their performance became more dissimilar at greater stroke lengths. In addition to the aforementioned effects it was found that movement amplitude error was less when the pen was 20 times heavier than the normal pen and that the increased load may dampen abnormal limb-stiffness characteristics induced by PD.

Upper limb movement interruptions are correlated to freezing of gait in Parkinson's disease

Freezing of gait (FOG) in patients with Parkinson's disease (PD) is a common problem of unknown origin, which possibly reflects a general motor control deficit. We investigated the relationship between the frequency of freezing episodes during gait and during a bimanual task in control and subjects with PD with and without FOG. Group differences in spatiotemporal characteristics were also examined as well as the effects of visual cueing. Twenty patients with PD in the off-phase of the medication cycle and five age-matched controls performed a repetitive drawing task in an anti-phase pattern on a digitizer tablet. The task was offered at two different speeds (comfortable and maximal) and two different amplitudes (small and large) with and without visual cueing. The results showed that freezing episodes in the upper limbs occurred in only 10.4% of patient trials and that their occurrence was correlated with FOG scores (Spearman's rho = 0.64). Overall, few spatiotemporal differences were found between freezers, non-freezers and controls, except for an overshooting of the target amplitude in controls. Effects of visual cueing were largely similar in all groups, except for the variability of relative phase, which decreased in non-freezers and controls, and was unaffected in freezers. Despite the fact that general motor differences between subgroups were small, freezing episodes were manifest during a bimanual repetitive upper limb task and were correlated to FOG. Further study into upper limb movement breakdown is warranted to understand the parallel deficits that lead up to FOG.