Parkinsonian patients reduce their stroke size with increased processing demands

Parkinson's disease diagnosis using deep learning: A bibliometric analysis and literature review

Parkinson's Disease (PD) is a progressive neurodegenerative illness triggered by decreased dopamine secretion. Deep Learning (DL) has gained substantial attention in PD diagnosis research, with an increase in the number of published papers in this discipline. PD detection using DL has presented more promising outcomes as compared with common machine learning approaches. This article aims to conduct a bibliometric analysis and a literature review focusing on the prominent developments taking place in this area. To achieve the target of the study, we retrieved and analyzed the available research papers in the Scopus database. Following that, we conducted a bibliometric analysis to inspect the structure of keywords, authors, and countries in the surveyed studies by providing visual representations of the bibliometric data using VOSviewer software. The study also provides an in-depth review of the literature focusing on different indicators of PD, deployed approaches, and performance metrics. The outcomes indicate the firm development of PD diagnosis using DL approaches over time and a large diversity of studies worldwide. Additionally, the literature review presented a research gap in DL approaches related to incremental learning, particularly in relation to big data analysis.

Can jaw position affect the fine motor activity of the hand during writing?

BACKGROUND

Jaw and neck systems have been shown to be functionally related and changes in either system can modulate gross motor functions, such as posture control. It remains to be seen if any change in jaw position can affect fine motor skills. The objective of this study was to determine the effect of resting, open and clenched jaw positions on various handwriting parameters while standing on firm and unstable surfaces.

METHODS

Handwriting samples were collected from 36 healthy male participants (age, 15-35 years) using a digitizer tablet (WACOM Intuos 4) with noninking pen in the resting, open and clenched jaw positions while standing on firm and unstable surfaces. The measured handwriting parameters included duration, vertical size, horizontal size, absolute size, average absolute velocity, and absolute jerk. Recordings and analyses were performed using NeuroScript MovAlyzeR software.

RESULTS

All handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces. However, based on statistical analyses, there were no significant differences in the handwriting parameters among three jaw positions on both surfaces (p > .05).

CONCLUSION

This study revealed that all handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces, showing that change in the jaw motor system may potentially affect the fine motor skills. However, on statistical analysis, there was no significant effect of 3 studied jaw positions on fine motor skills as seen on gross motor skills among healthy individuals.

Biometric handwriting analysis to support Parkinson's Disease assessment and grading

BACKGROUND

Handwriting represents one of the major symptom in Parkinson's Disease (PD) patients. The computer-aided analysis of the handwriting allows for the identification of promising patterns that might be useful in PD detection and rating. In this study, we propose an innovative set of features extracted by geometrical, dynamical and muscle activation signals acquired during handwriting tasks, and evaluate the contribution of such features in detecting and rating PD by means of artificial neural networks.

METHODS

Eleven healthy subjects and twenty-one PD patients were enrolled in this study. Each involved subject was asked to write three different patterns on a graphic tablet while wearing the Myo Armband used to collect the muscle activation signals of the main forearm muscles. We have then extracted several features related to the written pattern, the movement of the pen and the pressure exerted with the pen and the muscle activations. The computed features have been used to classify healthy subjects versus PD patients and to discriminate mild PD patients from moderate PD patients by using an artificial neural network (ANN).

RESULTS

After the training and evaluation of different ANN topologies, the obtained results showed that the proposed features have high relevance in PD detection and rating. In particular, we found that our approach both detect and rate (mild and moderate PD) with a classification accuracy higher than 90%.

CONCLUSIONS

In this paper we have investigated the representativeness of a set of proposed features related to handwriting tasks in PD detection and rating. In particular, we used an ANN to classify healthy subjects and PD patients (PD detection), and to classify mild and moderate PD patients (PD rating). The implemented and tested methods showed promising results proven by the high level of accuracy, sensitivity and specificity. Such results suggest the usability of the proposed setup in clinical settings to support the medical decision about Parkinson's Disease.

Dynamic Handwriting Analysis for Neurodegenerative Disease Assessment: A Literary Review

Studying the effects of neurodegeneration on handwriting has emerged as an interdisciplinary research topic and has attracted considerable interest from psychologists to neuroscientists and from physicians to computer scientists. The complexity of handwriting, in fact, appears to be sensitive to age-related impairments in cognitive functioning; thus, analyzing handwriting in elderly people may facilitate the diagnosis and monitoring of these impairments. A large body of knowledge has been collected in the last thirty years thanks to the advent of new technologies which allow researchers to investigate not only the static characteristics of handwriting but also especially the dynamic aspects of the handwriting process. The present paper aims at providing an overview of the most relevant literature investigating the application of dynamic handwriting analysis in neurodegenerative disease assessment. The focus, in particular, is on Parkinon’s disease (PD) and Alzheimer’s disease (AD), as the two most widespread neurodegenerative disorders. More specifically, the studies taken into account are grouped in accordance with three main research questions: disease insight, disease monitoring, and disease diagnosis. The net result is that dynamic handwriting analysis is a powerful, noninvasive, and low-cost tool for real-time diagnosis and follow-up of PD and AD. In conclusion of the paper, open issues still demanding further research are highlighted.

Repetitive finger movement and circle drawing in persons with Parkinson's disease

Little is known regarding how repetitive finger movement performance impacts other fine motor control tasks, such as circle drawing, in persons with Parkinson's disease (PD). Previous research has shown that impairments in repetitive finger movements emerge at rates near to and above 2 Hz in most persons with PD. Thus, the purpose of this study was to compare circle drawing performance in persons with PD that demonstrate impairment in repetitive finger movement and those that do not. Twenty-two participants with PD and twelve healthy older adults completed the study. Only participants with PD completed the repetitive finger movement task. From the kinematic data for the repetitive finger movement task, participants were grouped into Hasteners and Non-Hasteners. Participants with PD and the healthy older adults completed a series of circle drawing tasks at two different target sizes (1 cm and 2 cm) and three pacing conditions (Self-paced, 1.25 Hz, and 2.5 Hz). Kinematic and electromyography data were recorded and compared between groups. Results revealed that, in general, persons with PD demonstrate impairments in circle drawing and associated electromyography activity compared to healthy older adults. Moreover, persons with PD that hasten during repetitive finger movements demonstrate significantly increased movement rate during circle drawing, while those persons with PD that do not hasten demonstrate a significant increase in width variability. This suggests that differing motor control mechanisms may play a role in the performance of fine motor tasks in persons with PD. Continued research is needed to better understand differences in circle drawing performance among persons with PD to inform future development of patient-centered treatments.

Effects of Concurrent Manual Task Performance on Connected Speech Acoustics in Individuals With Parkinson Disease

Purpose Prior investigations suggest that simultaneous performance of more than 1 motor-oriented task may exacerbate speech motor deficits in individuals with Parkinson disease (PD). The purpose of the current investigation was to examine the extent to which performing a low-demand manual task affected the connected speech in individuals with and without PD. Method Individuals with PD and neurologically healthy controls performed speech tasks (reading and extemporaneous speech tasks) and an oscillatory manual task (a counterclockwise circle-drawing task) in isolation (single-task condition) and concurrently (dual-task condition). Results Relative to speech task performance, no changes in speech acoustics were observed for either group when the low-demand motor task was performed with the concurrent reading tasks. Speakers with PD exhibited a significant decrease in pause duration between the single-task (speech only) and dual-task conditions for the extemporaneous speech task, whereas control participants did not exhibit changes in any speech production variable between the single- and dual-task conditions. Conclusions Overall, there were little to no changes in speech production when a low-demand oscillatory motor task was performed with concurrent reading. For the extemporaneous task, however, individuals with PD exhibited significant changes when the speech and manual tasks were performed concurrently, a pattern that was not observed for control speakers. Supplemental Material https://doi.org/10.23641/asha.8637008.

A Kinematic Study of Progressive Micrographia in Parkinson's Disease

Progressive micrographia is decrement in character size during writing and is commonly associated with Parkinson's disease (PD). This study has investigated the kinematic features of progressive micrographia during a repetitive writing task. Twenty-four PD patients with duration since diagnosis of <10 years and 24 age-matched controls wrote the letter “e” repeatedly. PD patients were studied in defined off states, with scoring of motor function on the Unified Parkinson's Disease Rating Scale Part III. A digital tablet captured x-y coordinates and ink-pen pressure. Customized software recorded the data and offline analysis derived the kinematic features of pen-tip movement. The average size of the first and the last five letters were compared, with progressive micrographia defined as >10% decrement in letter stroke length. The relationships between dimensional and kinematic features for the control subjects and for PD patients with and without progressive micrographia were studied. Differences between the initial and last letter repetitions within each group were assessed by Wilcoxon signed-rank test, and the Kruskal-Wallis test was applied to compare the three groups. There are five main conclusions from our findings: (i) 66% of PD patients who participated in this study exhibited progressive micrographia; (ii) handwriting kinematic features for all PD patients was significantly lower than controls (p < 0.05); (iii) patients with progressive micrographia lose the normal augmentation of writing speed and acceleration in the x axis with left-to-right writing and show decrement of pen-tip pressure (p = 0.034); (iv) kinematic and pen-tip pressure profiles suggest that progressive micrographia in PD reflects poorly sustained net force; and (v) although progressive micrographia resembles the sequence effect of general bradykinesia, we did not find a significant correlation with overall motor disability, nor with the aggregate UPDRS-III bradykinesia scores for the dominant arm.

Handwriting training in Parkinson's disease: A trade-off between size, speed and fluency

BACKGROUND

In previous work, we found that intensive amplitude training successfully improved micrographia in Parkinson's disease (PD). Handwriting abnormalities in PD also express themselves in stroke duration and writing fluency. It is currently unknown whether training changes these dysgraphic features.

OBJECTIVE

To determine the differential effects of amplitude training on various hallmarks of handwriting abnormalities in PD.

METHODS

We randomized 38 right-handed subjects in early to mid-stage of PD into an experimental group (n = 18), receiving training focused at improving writing size during 30 minutes/day, five days/week for six weeks, and a placebo group (n = 20), receiving stretch and relaxation exercises at equal intensity. Writing skills were assessed using a touch-sensitive tablet pre- and post-training, and after a six-week retention period. Tests encompassed a transfer task, evaluating trained and untrained sequences, and an automatization task, comparing single- and dual-task handwriting. Outcome parameters were stroke duration (s), writing velocity (cm/s) and normalized jerk (i.e. fluency).

RESULTS

In contrast to the reported positive effects of training on writing size, the current results showed increases in stroke duration and normalized jerk after amplitude training, which were absent in the placebo group. These increases remained after the six-week retention period. In contrast, velocity remained unchanged throughout the study.

CONCLUSION

While intensive amplitude training is beneficial to improve writing size in PD, it comes at a cost as fluency and stroke duration deteriorated after training. The findings imply that PD patients can redistribute movement priorities after training within a compromised motor system.

The kinematics of handwriting movements as expression of cognitive and sensorimotor impairments in people with multiple sclerosis

Handwriting is an important activity of daily living, which requires sensorimotor and cognitive skills that could deteriorate in presence of neurological diseases. Handwriting impairments are common in people with multiple sclerosis (PwMS). Aims of the present study were to characterize handwriting movement features of PwMS in comparison with those of healthy adults, and to evaluate the relationship between kinematic parameters of handwriting movements and the results of the assessment of cognitive and motor domains. A new handwriting evaluation methodology was applied to quantify handwriting features of 19 PwMS and 22 age-matched healthy controls who were required to write a sentence on a digitizing tablet. Kinematic parameters of the sentence and of the strokes were used to evaluate handwriting performance. PwMS showed an altered handwriting kinematics with respect to healthy controls: higher movement duration, fragmented velocity profile and higher jerk. Furthermore, motor abilities and cognitive status of PwMS were related to handwriting parameters in accordance with the evidence that MS is a multifactorial disease affecting different domains. These results suggested that the proposed methodology might be a valuable tool to quantitatively assess handwriting impairments and the efficacy of handwriting treatments in PwMS.

Handwriting Analysis in Parkinson's Disease: Current Status and Future Directions

BACKGROUND

The majority of patients with Parkinson's disease (PD) have handwriting abnormalities. Micrographia (abnormally small letter size) is the most commonly reported and easily detectable handwriting abnormality in patients with PD. However, micrographia is perhaps the tip of the iceberg representing the handwriting abnormalities in PD. Digitizing tablet technology, which has evolved over the last 2 decades, has made it possible to study the pressure and kinematic features of handwriting. This has resulted in a surge of studies investigating graphomotor impairment in patients with PD.

METHODS

The objectives of this study were to review the evolution of the kinematic analysis of handwriting in PD and to provide an overview of handwriting abnormalities observed in PD along with future directions for research in this field. Articles for review were searched from the PubMed and SCOPUS databases.

RESULTS

Digitizing tablet technologies have resulted in a shift of focus from the analysis of only letter size to the analysis of several kinematic features of handwriting. Studies based on the kinematic analysis of handwriting have revealed that patients with PD may have abnormalities in velocity, fluency, and acceleration in addition to micrographia. The recognition of abnormalities in several kinematic parameters of handwriting has given rise to the term PD dysgraphia. In addition, certain kinematic properties potentially may be helpful in distinguishing PD from other parkinsonian disorders.

CONCLUSION

The journey from micrographia to PD dysgraphia is indeed a paradigm shift. Further research is warranted to gain better insight into the graphomotor impairments in PD and their clinical implications.

Evaluation of Handwriting Movement Kinematics: From an Ecological to a Magnetic Resonance Environment

Writing is a means of communication which requires complex motor, perceptual, and cognitive skills. If one of these abilities gets lost following traumatic events or due to neurological diseases, handwriting could deteriorate. Occupational therapy practitioners provide rehabilitation services for people with impaired handwriting. However, to determine the effectiveness of handwriting interventions no studies assessed whether the proposed treatments improved the kinematics of writing movement or had an effect at the level of the central nervous system. There is need to find new quantitative methodologies able to describe the behavioral and the neural outcomes of the rehabilitative interventions for handwriting. In the present study we proposed a combined approach that allowed evaluating the kinematic parameters of handwriting movements, acquired by means of a magnetic resonance-compatible tablet, and their neural correlates obtained simultaneously from a functional magnetic resonance imaging examination. Results showed that the system was reliable in term of reproducibility of the kinematic data during a test/re-test procedure. Further, despite the modifications with respect to an ecological writing movement condition, the kinematic parameters acquired inside the MR-environment were descriptive of individuals’ movement features. At last, the imaging protocol succeeded to show the activation of the cerebral regions associated with the production of writing movement in healthy people. From these findings, this methodology seems to be promising to evaluate the handwriting movement deficits and the potential alterations in the neural activity in those individuals who have handwriting difficulties. Finally, it would provide a mean to quantitatively assess the effect of a rehabilitative treatment.

Graphical Tasks to Measure Upper Limb Function in Patients With Parkinson's Disease: Validity and Response to Dopaminergic Medication

The most widely used method to assess motor functioning in Parkinson's disease (PD) patients is the unified Parkinson's disease rating scale-III (UPDRS-III). The UPDRS-III has limited ability to detect subtle changes in motor symptoms. Alternatively, graphical tasks can be used to provide objective measures of upper limb motor dysfunction. This study investigated the validity of such graphical tasks to assess upper limb function in PD patients and their ability to detect subtle changes in performance. Fourteen PD patients performed graphical tasks before and after taking dopaminergic medication. Graphical tasks included figure tracing, writing, and a modified Fitts' task. The Purdue pegboard test was performed to validate these graphical tasks. Movement time (MT), writing size, and the presence of tremor were assessed. MT on the graphical tasks correlated significantly with performance on the Purdue pegboard test (Spearman's ρ > 0.65; p < 0.05). MT decreased significantly after the intake of dopaminergic medication. Tremor power decreased after taking dopaminergic medication in most PD patients who suffered from tremor. Writing size did not correlate with performance on the Purdue pegboard test, nor did it change after taking medication. Our set of graphical tasks is valid to assess upper limb function in PD patients. MT proved to be the most useful measure for this purpose. The response on dopaminergic medication was optimally reflected by an improved MT on the graphical tasks in combination with a decreased tremor power, whereas writing size did not respond to dopaminergic treatment.

Neural correlates underlying micrographia in Parkinson's disease

Micrographia is a common symptom in Parkinson's disease, which manifests as either a consistent or progressive reduction in the size of handwriting or both. Neural correlates underlying micrographia remain unclear. We used functional magnetic resonance imaging to investigate micrographia-related neural activity and connectivity modulations. In addition, the effect of attention and dopaminergic administration on micrographia was examined. We found that consistent micrographia was associated with decreased activity and connectivity in the basal ganglia motor circuit; while progressive micrographia was related to the dysfunction of basal ganglia motor circuit together with disconnections between the rostral supplementary motor area, rostral cingulate motor area and cerebellum. Attention significantly improved both consistent and progressive micrographia, accompanied by recruitment of anterior putamen and dorsolateral prefrontal cortex. Levodopa improved consistent micrographia accompanied by increased activity and connectivity in the basal ganglia motor circuit, but had no effect on progressive micrographia. Our findings suggest that consistent micrographia is related to dysfunction of the basal ganglia motor circuit; while dysfunction of the basal ganglia motor circuit and disconnection between the rostral supplementary motor area, rostral cingulate motor area and cerebellum likely contributes to progressive micrographia. Attention improves both types of micrographia by recruiting additional brain networks. Levodopa improves consistent micrographia by restoring the function of the basal ganglia motor circuit, but does not improve progressive micrographia, probably because of failure to repair the disconnected networks.

From micrographia to Parkinson's disease dysgraphia

Micrographia, an abnormal reduction in writing size, is a specific behavioral deficit associated with Parkinson's disease (PD). In recent years, the availability of graphic tablets has made it possible to study micrographia in unprecedented detail. Consequently, a growing number of studies show that PD patients also exhibit impaired handwriting kinematics. Is micrographia still the most characteristic feature of PD-related handwriting deficits? To answer this question, we identified studies that investigated handwriting in PD, either with conventional pencil-and-paper measures or with graphic tablets, and we reported their findings on key spatiotemporal and kinematic variables. We found that kinematic variables (velocity, fluency) differentiate better between control participants and PD patients, and between off- and on-treatment PD patients, than the traditional measure of static writing size. Although reduced writing size is an important feature of PD handwriting, the deficit is not restricted to micrographia stricto sensu. Therefore, we propose the term PD dysgraphia, which encompasses all deficits characteristic of Parkinsonian handwriting. We conclude that the computerized analysis of handwriting movements is a simple and useful tool that can contribute to both diagnosis and follow-up of PD.

The effects of shift work and time of day on fine motor control during handwriting

Handwriting is an elaborate and highly automatised skill relying on fine motor control. In laboratory conditions handwriting kinematics are modulated by the time of day. This study investigated handwriting kinematics in a rotational shift system and assessed whether similar time of day fluctuations at the work place can be observed. Handwriting performance was measured in two tasks of different levels of complexity in 34 shift workers across morning (6:00-14:00), evening (14:00-22:00) and night shifts (22:00-6:00). Participants were tested during all three shifts in 2-h intervals with mobile testing devices. We calculated average velocity, script size and writing frequency to quantify handwriting kinematics and fluency. Average velocity and script size were significantly affected by the shift work schedule with the worst performance during morning shifts and the best performance during evening shifts. Our data are of high economic relevance as fine motor skills are indispensable for accurate and effective production at the work place.

PRACTITIONER SUMMARY

Handwriting is one of the most complex fine motor skills in humans, which is frequently performed in daily life. In this study, we tested handwriting repeatedly at the work place in a rotational shift system. We found slower handwriting velocity and reduced script size during morning shifts.

Standardized handwriting to assess bradykinesia, micrographia and tremor in Parkinson's disease

Objective

To assess whether standardized handwriting can provide quantitative measures to distinguish patients diagnosed with Parkinson's disease from age- and gender-matched healthy control participants.

Design

Exploratory study. Pen tip trajectories were recorded during circle, spiral and line drawing and repeated character ‘elelelel’ and sentence writing, performed by Parkinson patients and healthy control participants. Parkinson patients were tested after overnight withdrawal of anti-Parkinsonian medication.

Setting

University Medical Center Groningen, tertiary care, the Netherlands.

Participants

Patients with Parkinson's disease (n = 10; mean age 69.0 years; 6 male) and healthy controls (n = 10; mean age 68.1 years; 6 male).

Interventions

Not applicable.

Main Outcome Measures

Movement time and velocity to detect bradykinesia and the size of writing to detect micrographia. A rest recording to investigate the presence of a rest-tremor, by frequency analysis.

Results

Mean disease duration in the Parkinson group was 4.4 years and the patients were in modified Hoehn-Yahr stages 1–2.5. In general, Parkinson patients were slower than healthy control participants. Median time per repetition, median velocity and median acceleration of the sentence task and median velocity of the elel task differed significantly between Parkinson patients and healthy control participants (all p<0.0014). Parkinson patients also wrote smaller than healthy control participants and the width of the ‘e’ in the elel task was significantly smaller in Parkinson patients compared to healthy control participants (p<0.0014). A rest-tremor was detected in the three patients who were clinically assessed as having rest-tremor.

Conclusions

This study shows that standardized handwriting can provide objective measures for bradykinesia, tremor and micrographia to distinguish Parkinson patients from healthy control participants.

Signal-to-noise velocity peaks difference: a new method for evaluating the handwriting movement fluency in children with dysgraphia

This study evaluated handwriting movement dysfluency related to dysgraphia. A new variable, the Signal-to-Noise velocity peaks difference (SNvpd), was proposed to describe abnormal velocity fluctuations in cursive handwriting. This variable was compared to two variables most frequently used variables for assessing handwriting fluency. This comparison was carried out for three different groups, children with dysgraphia, proficient children, and adults, all of whom wrote the same single word. The adults were taken as the reference. Results revealed that, of the three variables studied, the SNvpd proved most efficient in discriminating children with dysgraphia, and that furthermore, it had the significant advantage of facilitating the localization of dysfluency peaks within a word. Our results also showed that the movement dysfluency of children with dysgraphia was specific to certain letters. In light of these results, we discuss the methodological and theoretical relevance of this new variable to the analysis of handwriting movement with the aim of characterizing dysgraphia.

SEPARATING PARKINSONIAN PATIENTS FROM NORMAL PERSONS USING HANDWRITING FEATURES

Parkinson's disease (PD) is a widespread progressive neural degenerative disease. Patients encounter problems in carrying out ordinary voluntary movements such as gaiting and writing. Effects of tremor, rigidity, and bradykinesia are seen in writing. Since the diagnosis of PD is based on the presence of cardinal symptoms, therefore voluntary movements like writing could be helpful as an indicator in this process. Handwriting analysis can be a suitable method to separate patients from normal individuals. We recorded handwriting data from 17 normal and 13 PD subjects, and then used mathematical analysis in order to extract proper features. At the end of the study, we used these selected features in a classifier. We achieved 93.89% accuracy in the test phase. Hence, this tool may be aid in the diagnosing of both PD and suspected PD individuals in the early stages of the disease.

Repetitive transcranial magnetic stimulation improves handwriting in Parkinson's disease

Background. Parkinson disease (PD) is characterized by hypometric movements resulting from loss of dopaminergic neurons in the substantia nigra. PD leads to decreased activation of the supplementary motor area (SMA); the net result of these changes is a poverty of movement. The present study determined the impact of 5 Hz repetitive transcranial magnetic stimulation (rTMS) over the SMA on a fine motor movement, handwriting (writing cursive “l”s), and on cortical excitability, in individuals with PD. Methods. In a cross-over design, ten individuals with PD were randomized to receive either 5 Hz or control stimulation over the SMA. Immediately following brain stimulation right handed writing was assessed. Results. 5 Hz stimulation increased vertical size of handwriting and diminished axial pressure. In addition, 5 Hz rTMS significantly decreased the threshold for excitability in the primary motor cortex. Conclusions. These data suggest that in the short term 5 Hz rTMS benefits functional fine motor task performance, perhaps by altering cortical excitability across a network of brain regions. Further, these data may provide the foundation for a larger investigation of the effects of noninvasive brain stimulation over the SMA in individuals with PD.

Impaired endogenously evoked automated reaching in Parkinson's disease

Intended reaches triggered by exogenous targets often coexist with spontaneous, automated movements that are endogenously activated. It has been posited that Parkinson's disease (PD) primarily impairs automated movements, but it is unknown to what extent this may affect multijoint/limb control, particularly when patients are off their dopaminergic medications. Here we tested nine human patients with PD while off dopaminergic medication versus nine age-matched normal controls (NCs). Participants performed intentional reaches forward to a target in a dark room and then transitioned back to their initial posture. Upon target flash, three forms of guidance were used: (1) memory with eyes closed, (2) continuous target vision only, and (3) vision of their moving finger only. The trajectories of their arm joints were measured and their joint velocities decomposed into the (intended) task-relevant and the (spontaneous) task-incidental degrees of freedom (DOF). We also measured the balance between these two subsets of DOF as these movements unfolded. In PD patients we found that the incidental DOF values were abnormally variable during the retracting movements and prevailed over the task-relevant DOF values. By contrast, their forward intentional motions were abnormally dominated by the task-relevant components. Moreover, the patients abruptly transitioned between voluntary and automated modes of joint control, and, unlike NCs, the type of visual guidance differentially affected their postural trajectories. These findings lend support to an emerging view that there is a loss of automated control in PD patients that contributes to impairments in voluntary control, and that basal ganglia-cortical circuits are critical for the maintenance and balance of multijoint control.

Micrographia and related deficits in Parkinson's disease: a cross-sectional study

OBJECTIVES

To determine the prevalence and clinical features associated with micrographia in Parkinson's Disease (PD).

SETTING

This study was conducted at a Movement Disorders clinic located in a Veteran Administration Hospital.

PARTICIPANTS

PD subjects were included only if they satisfied UK Parkinson's Disease Society criteria for diagnosis. Subjects with history of severe tremors, dystonia, dyskinesia, strokes, peripheral neuropathy and dementia were excluded.

DESIGN

This was a case-control study where PD subjects were prospectively enrolled and their demographics, Hoehn & Yahr stage, Unified Parkinson's Disease Rating Scale and Mini Mental Status examination (MMSE) scores were recorded. All subjects were specifically asked for micrographia on history and the handwritings were quantitatively documented. Bradykinesia was determined by history and quantified by a finger tap, Purdue pegboard and a timed walk test. Similarly, hypophonia was determined by history and the volume of speech quantified using a decibel meter. Controls were enrolled for validation of handwriting test scores and decibel meter recordings.

PRIMARY OUTCOME MEASURES

Prevalence of micrographia in the PD cohort and the clinical factors that correlate with micrographia.

RESULTS

68 subjects with PD were enrolled (68 men; mean age 72.3 years). Micrographia was identified in 63.2% of the cohort on verbal history and in 50% of the cohort when the handwriting test was used for ascertainment. Micrographia ascertained on history correlated significantly with disease severity (Hoehn & Yahr stage), motor impairment (Unified Parkinson's Disease Rating Scale), cognitive impairment (MMSE) and both bradykinesia and hypophonia determined by history and quantitative testing. Micrographia on handwriting test correlated with age (p=0.02), MMSE testing (p=0.04), hypophonia by history (p=0.01) and bradykinesia by quantitative testing (p=0.04).

CONCLUSION

Micrographia was found in nearly half of the PD cohort. Disease severity and impaired cognition were important clinical correlates. Micrographia had a significant relationship with bradykinesia and hypophonia, suggesting a possible overlap in their pathophysiology.

Auditory instructional cues benefit unimanual and bimanual drawing in Parkinson's disease patients

The present study investigated performance of unimanual and bimanual anti-phase and in-phase upper limb line drawing using three different types of cues. Fifteen Parkinson's disease (PD) patients, 15 elderly, and 15 young adults drew lines away from and towards their body on a tabletop every 1000 ms for 30 s under three different cueing conditions: (1) verbal ('up', 'down'); (2) auditory (high tone, low tone); (3) visual (target line switched from top to bottom). PD patients had larger and more variable amplitudes which may be related to the finding that they also produced more curvilinear movements than young and elderly adults. Consistent with previous research, when compared to the elderly and young adult group PD patients produced a mean relative phase which deviated more from the instructed coordination modes and they showed larger variability of relative phase in bimanual coordination, especially in anti-phase conditions. For all groups, auditory and verbal cues resulted in lower coefficient of variance of cycle time, lower variability of amplitude and lower variability of relative phase than visual cues. The benefit of auditory cues may be related to the timing nature of the task or factors related to the auditory cues (e.g., reduced attentional demands, more kinesthetic focus).

Computerized kinematic analysis of the clock drawing task in elderly people with mild major depressive disorder: an exploratory study

BACKGROUND

Developments in data collection technology enable evaluation of kinematic characteristics of the drawing process. We examined the clock drawing task in elderly patients with mild Major Depressive Disorder (MDD), assessed the relative importance of kinematic measures that differentiate the groups and analyzed associations between computerized measures, and the cognitive and depression status of the study groups.

METHODS

The participants comprised 20 elderly people with mild MDD and 20 matched controls. Both groups performed a clock drawing task using a computerized system. Kinematic measures included: number of segments drawn, performance time, pressure implemented towards the drawing surface, and pen azimuth. Three representative spatial characteristics were analyzed per segments drawn on the paper: height, width and length. The clock drawing tasks were blindly scored with Freedman's method. Cognitive state was quantified using the Mini-mental State Examination (MMSE) and depression with the Geriatric Depression Scale (GDS).

RESULTS

Freedman's method found no between-group differences. Pressure and azimuth measures and spatial measures of segments height, width and length were significantly lower in the mild MDD group, while the number of paper segments and performance time did not differ. The azimuth measure correlated with the GDS score, and pressure with the MMSE and the GDS scores. Spatial measures did not correlate with either the MMSE or GDS. Pressure, segment width and length, azimuth and segment height allowed correct classification of 81.1% of the participants.

CONCLUSIONS

A computerized system focusing on the clock drawing task might be sensitive to altered performance among elderly people with mild MDD.

Handwriting process variables among elderly people with mild Major Depressive Disorder: a preliminary study

BACKGROUND AND AIMS

Despite evidence of cognitive impairment and difficulties in performing daily activities among elderly people with major depression, studies implementing objective performance-based evaluation of functional deficits in this patient population are scarce. With the aid of a computerized device we examined functional handwriting performance among elderly patients with mild Major Depressive Disorder (MDD) in comparison with controls.

METHODS

Participants were 20 elderly participants with mild MDD and 20 matched controls. Both groups performed four functional writing tasks with a computerized system. Kinematic measures were: in-air time per stroke (temporal), stroke width (spatial), pressure applied (pressure).

RESULTS

A MANOVA yielded statistically significant between-groups differences for the four writing tasks across the temporal, spatial and pressure measures. A univariate ANOVA revealed that the significance was due to differences between mild MDD and controls on the pressure measure in all four tasks. Moderately significant correlations were found in all tasks between in-air time and pressure while writing and the GDS score, and between the in-air time of three tasks (except writing one's name) and the Mini-Mental State Examination (MMSE) score. Handwriting pressure, and temporal and spatial measures of the task of writing one's name allowed us to classify 84.2% of the participants correctly.

CONCLUSIONS

Computerized evaluation of handwriting, a daily task, was found to be sensitive to altered performance among participants with mild MDD, and was correlated with cognitive impairment and depression status. The theoretical importance and practical implications of handwriting process measures are discussed.

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.

Alzheimer's disease and mild cognitive impairment deteriorate fine movement control

Sensory-motor dysfunctions are often associated with Alzheimer's disease (AD) or mild cognitive impairment (MCI). This study suggests that deterioration in fine motor control and coordination characterizes sensory-motor deficiencies of AD and MCI. Nine patients with a clinical diagnosis of probable AD, 9 amnestic MCI subjects and 10 cognitively normal controls performed four types of handwriting movement on a digitizer. Movement time and smoothness were analyzed between the groups and across the movement patterns. Kinematic profiles were also compared among the groups. AD and MCI patients demonstrated slower, less smooth, less coordinated, and less consistent handwriting movements than their healthy counterparts. The theoretical relevance and practical implications of fine motor tasks, such as these movements involved in handwriting, are discussed relative to the deteriorated sensory-motor system of AD and MCI patients.

The forces behind the words: development of the kinetic pen

This paper describes the creation of a Kinetic Pen capable of measuring the six-component force and torque that each of four individual contacts applies to the pen during writing. This was done by staggering the mounting of the four sensors along the long axis of the pen and having an extended arm run from the sensor to the grip site, preventing a clustering of the sensors where the digit tips meet while grasping. The implications of this tool allow handwriting studies to be expanded from two-dimensional pen-tip kinematics to three-dimensional dynamics at each contact point between the hand and pen.

A computational neuroanatomy for motor control

The study of patients to infer normal brain function has a long tradition in neurology and psychology. More recently, the motor system has been subject to quantitative and computational characterization. The purpose of this review is to argue that the lesion approach and theoretical motor control can mutually inform each other. Specifically, one may identify distinct motor control processes from computational models and map them onto specific deficits in patients. Here we review some of the impairments in motor control, motor learning and higher-order motor control in patients with lesions of the corticospinal tract, the cerebellum, parietal cortex, the basal ganglia, and the medial temporal lobe. We attempt to explain some of these impairments in terms of computational ideas such as state estimation, optimization, prediction, cost, and reward. We suggest that a function of the cerebellum is system identification: to build internal models that predict sensory outcome of motor commands and correct motor commands through internal feedback. A function of the parietal cortex is state estimation: to integrate the predicted proprioceptive and visual outcomes with sensory feedback to form a belief about how the commands affected the states of the body and the environment. A function of basal ganglia is related to optimal control: learning costs and rewards associated with sensory states and estimating the "cost-to-go" during execution of a motor task. Finally, functions of the primary and the premotor cortices are related to implementing the optimal control policy by transforming beliefs about proprioceptive and visual states, respectively, into motor commands.

Withdrawal of visual feedback improves micrographia in Parkinson's disease

Micrographia is a common, often presenting feature of Parkinson's disease. We assessed a simple writing paradigm in 40 PD patients "off" medications, 40 different PD patients "on" medications, and 64 age- and sex-matched controls. Patients wrote "Today is a nice day" with both eyes open and eyes closed to assess the effects of visual withdrawal (eyes closure). The order (eyes open vs. eyes closed) was alternated. In the "off" medicine group, eye closure increased the writing length by 14.0 +/- 10.1% (P < 0.05) from a mean of 69.1 to 77.7 mm [range -14% to +73%]. The percentage increase was larger in the 20 subjects with the smallest baseline writing size (worse micrographia), compared to the 20 with relatively larger writing (19.5% vs. 7.9%, P < 0.05). Neither the "on" medicine group, nor the control group changed. Simple eye closure significantly increased writing size in "off" PD patients to a similar or greater amount as levodopa. This data suggests that micrographia is not a pure motor hypokinetic feature but is affected by PD similar to other superlearned tasks such as walking. Furthermore, some patients have adapted this simple eye closing strategy when writing, especially signatures.

Impairment of complex upper limb motor function in de novo Parkinson's disease

The aim of the present study was to evaluate complex upper limb motor function in newly diagnosed, untreated Parkinson's disease (PD) patients. Four different unimanual upper limb motor tasks were applied to 13 newly diagnosed, untreated PD patients and 13 age- and sex-matched controls. In a handwriting task, PD patients had significantly reduced sentence length and writing velocity, and decreasing letter height in the course of writing. Furthermore, PD patients performed an aiming task slower with than without target, and showed increased transposition in a pointing task. The results of this study extend previous observations of impaired complex upper limb movements to newly diagnosed, untreated PD patients.

Reaching and grasping phenotypes in the mouse (Mus musculus): a characterization of inbred strains and mutant lines

Skilled movements, such as reaching and grasping, have classically been considered as originating in the primate lineage. For this reason, the use of rodents to investigate the genetic and molecular machinery of reaching and grasping has been limited in research. A few studies in rodents have now shown that these movements are not exclusive to primates. Here we present a new test, the Mouse Reaching and Grasping (MoRaG) performance scale, intended to help researchers in the characterization of these motor behaviors in the mouse. Within the MoRaG test battery we identified early phenotypes for the characterization of motor neurone (Tg[SOD1-G93A](dl)1Gur mice) and neurodegenerative (TgN(HD82Gln)81Dbo transgenic mice) disease models in addition to specific motor deficits associated with aging (C3H/HeH inbred strain). We conclude that the MoRaG test can be used to further investigate complex neuromuscular, neurological, neurodegenerative and behavioral disorders. Moreover, our study supports the validity of the mouse as a model for reaching and grasping studies.

Flanker compatibility effects in patients with Parkinson's disease: impact of target onset delay and trial-by-trial stimulus variation

Parkinson's disease (PD) patients and healthy controls were administered a flanker task that consisted of the presentation of colored targets and distractors. Participants were required to attend to the center target and identify its color. The stimulus displays were either congruent (i.e., the target and flankers were the same color) or incongruent. The time between the onset of the flanker and the target color (the target onset delay) was either short or long. Results indicated that PD patients and controls did not differ in the magnitude of the flanker effect within individual trials in that both groups demonstrated a typical flanker effect at the short target onset delay and neither group demonstrated a flanker effect at the longer delay. However, when performance was examined on a trial-by-trial basis, PD patients demonstrated a slowing of reaction time relative to controls when having to make the same response across consecutive trials at longer inter-trial intervals when the flankers were incongruent across consecutive trials and the display on the second of two trials was incongruent. These results indicate that PD patients are impaired in inhibiting the distractors over an extended delay and that this deficit may impact motor responding in these patients, suggesting that the basal ganglia contribute to the interface of attention and action.

Differentiation between external and internal cuing: an fMRI study comparing tracing with drawing

Externally cued movement is thought to preferentially involve cerebellar and premotor circuits whereas internally generated movement recruits basal ganglia, pre-supplementary motor cortex (pre-SMA) and dorsolateral prefrontal cortex (DLPFC). Tracing and drawing are exemplar externally and internally guided actions and Parkinson's patients and cerebellar patients show deficits in tracking and drawing, respectively. In this study we aimed to examine this external/internal distinction in healthy subjects using functional imaging. Ten healthy subjects performed tracing and drawing of simple geometric shapes using pencil and paper while in a 3-T fMRI scanner. Results indicated that compared to tracing, drawing generated greater activation in the right cerebellar crus I, bilateral pre-SMA, right dorsal premotor cortex and right frontal eye field. Tracing did not recruit any additional activation compared to drawing except in striate and extrastriate visual areas. Therefore, drawing recruited areas more frequently associated with cognitively challenging tasks, attention and memory, but basal ganglia and cerebellar activity did not differentiate tracing from drawing in the hypothesised manner. As our paradigm was of a simple, repetitive and static design, these results suggest that the task familiarity and the temporal nature of visual feedback in tracking tasks, compared to tracing, may be important contributing factors towards the degree of cerebellar involvement. Future studies comparing dynamic with static external cues and visual feedback may clarify the role of the cerebellum and basal ganglia in the visual guidance of drawing actions.

On the genesis of unilateral micrographia of the progressive type

We report a patient who, following a focal ischemic lesion of the left basal ganglia, developed right hand micrographia characterised by progressive reduction of letter size during writing (progressive micrographia). The patient did not show relevant cognitive impairments, but achieved pathological scores in tests for verbal fluency, and cognitive flexibility and monitoring. A systematic investigation of the writing performances demonstrated that micrographia showed a clear length effect in whatever writing style or task, while it was not observed in drawing, or in left hand writing to a comparable extent. Right hand progressive micrographia was not affected by a concurrent motor and cognitive load; instead, switching between two kinds of allographic responses and presenting one letter at a time in copying tasks reduced severity of micrographia significantly. These findings support the view that progressive micrographia in our patient could be ascribed to a defect in regulating the motor output on the basis of self-generated strategies. This conclusion would be consistent with neuroimaging evidence about the role of the basal ganglia in the control of motor sequencing, and could suggest that progressive micrographia might be associated with specific executive defects.

Quantitative measurement of handwriting in the assessment of drug-induced parkinsonism

Monitoring drug-induced side effects is especially important for patients who undergo treatment with antipsychotic medications, as these drugs often produce extrapyramidal side effects (EPS) resulting in movement abnormalities similar to parkinsonism. Scientists have developed several objective laboratory tests to measure and research drug-induced movement disorders, but equipment and tests are complex and costly and have not become accepted in large-scale, multi-site clinical trials. The goals of this study were to test whether a simple handwriting measure can discriminate between individuals with psychotropic-induced parkinsonism, Parkinson's disease, and healthy individuals, and to examine some of the psychometric properties of the measure. We examined pen movement kinematics during cursive writing of a standard word in 13 patients with idiopathic Parkinson's disease (PD), 10 schizophrenia patients with drug-induced parkinsonism (SZ), and 12 normal healthy control participants (NC). Participants were instructed to write the word "hello" in cursive twice, at three vertical height scales. Software was used for data acquisition and analysis of vertical stroke velocities, velocity scaling, and smoothness. There were four important results from this study: (1) both SZ patients with drug-induced EPS and PD participants exhibited impaired movement velocities and velocity scaling; (2) performance on the velocity scaling measure distinguished drug-induced EPS from normal with 90% accuracy; (3) SZ, but not PD participants displayed abnormalities in movement smoothness; and (4) there was a positive correlation between age and magnitude of the velocity scaling deficit in PD participants. This study demonstrates that kinematic analyses of pen movements during handwriting may be useful in detecting and monitoring subtle changes in motor control related to the adverse effects of psychotropic medications.

Brain dopamine and kinematics of graphomotor functions

Three experiments were performed in an attempt to achieve a better understanding of the effect of dopamine on handwriting. In the first experiment, kinematic aspects of handwriting movements were compared between healthy participants and patients with Parkinson's disease (PD) on their usual dopaminergic treatment and following withdrawal of dopaminergic medication. In the second experiment, the writing performance of healthy participants with a hyperechogenicity of the substantia nigra as detected by transcranial sonography (TCS) was compared with the performance of healthy participants with low echogenicity of the substantia nigra. The third experiment examined the effect of central dopamine reduction on kinematic aspects of handwriting movements in healthy adults using acute phenylalanine and tyrosine depletion (APTD). A digitising tablet was used for the assessment of handwriting movements. Participants were asked to perform a simple writing task. Movement time, distance, velocity, acceleration and measures of fluency of handwriting movements were measured. The kinematic analysis of handwriting movements revealed that alterations of central dopaminergic neurotransmission adversely affect movement execution during handwriting. In comparison to the automatic processing of handwriting movements displayed by control participants, participants with an altered dopaminergic neurotransmission shifted from an automatic to a controlled processing of movement execution. Central dopamine appears to be of particular importance with regard to the automatic execution of well-learned movements.

Movement precues in planning and execution of aiming movements in Parkinson's disease

Two experiments tested how changing a planned movement affects movement initiation and execution in idiopathic Parkinson's disease (PD) patients. In Experiment 1, PD patients, elderly controls, and young adults performed discrete aiming movements to one of two targets on a digitizer. A precue (80% valid cue and 20% invalid cue of all trials) reflecting the subsequent movement direction was presented prior to the imperative stimulus. All groups produced slower reaction times (RTs) to the invalid precue condition. Only the subgroup of patients with slowest movement time showed a significant prolongation of movement for the invalid condition. This suggests that, in the most impaired patients, modifying a planned action also affects movement execution. In Experiment 2, two-segment aiming movements were used to increase the demand on movement planning. PD patients and elderly controls underwent the two precue conditions (80% valid, 20% invalid). Patients exhibited longer RTs than the controls. RT was similarly increased for the invalid condition in both groups. The patients, however, exhibited longer movement times, lower peak velocities, and higher normalized jerk scores of the first segment in the invalid condition compared to the valid condition. Conversely, the controls showed no difference between the valid and invalid cue conditions. Thus, PD patients demonstrated substantially pronounced movement slowness and variability when required to change a planned action. The results from both experiments suggest that modifying a planned action may continue beyond the initiation phase into the execution phase in PD patients.

Antiparkinson medications improve agonist activation but not antagonist inhibition during sequential reaching movements

The execution of sequential arm movements is critical to activities of daily living such as eating and grooming. It is known that movement sequences are bradykinetic in people with Parkinson's disease (PD) and that antiparkinson medications improve the speed of movement sequences. However, it is unclear how muscle activity is modulated during sequential movements and what effect antiparkinson medications have on muscle modulation. We studied subjects with PD and age- and gender-matched control subjects making sequential reaching movements. Subjects with PD were tested before and after their morning dose of antiparkinson medications (levodopa and/or dopamine agonists). We examined the effect of antiparkinson medications on the modulation of muscle activity (i.e., the ability to activate and inhibit each muscle throughout the course of a sequence). Results showed that the group with PD, before medication, moved more slowly and modulated muscle activity poorly compared to the control group. Antiparkinson medications improved movement speed as expected, although sequential movements remained slower than normal even after medication. Medication improved the ability to activate agonist muscle activity but did not improve the ability to inhibit antagonist activity. Instead, antagonist activity was also increased, resulting in minimal improvements in muscle modulation during sequential reaching movements.

Post graphemic impairments of writing: the case of micrographia

Micrographia (MG), an acquired impairment of writing characterized by diminution of letter size, coupled with slowing and loss of accuracy, is most frequently observed in the course of degenerative disease of basal ganglia, such as Parkinson's Disease. Only a few cases of MG without concomitant extrapyramidal signs have been described, mostly following vascular lesion of the left basal ganglia. In this article we report an isolated pattern of MG following an extensive traumatic cerebral lesion centered in the left basal ganglia. The nature of this impairment is analyzed according to a cognitive model of writing and interpreted as a specific example of peripheral dysgraphia.

The effect of Parkinson's disease on the control of multi-segmental coordination

An experiment was designed to test whether or not Parkinson's disease (PD) patients were able to maintain endpoint kinematic patterns in a prehension task involving movement of the torso. Nine PD patients and nine healthy controls were asked to reach for and grasp a full cup of water that was either covered or uncovered and placed beyond the reach of the outstretched arm. An OPTOTRAK (Northern Digital) 3-dimensional motion analysis system was used to capture the movement of four markers placed on the arm, hand, and torso. The results indicated the Parkinson's patients had a decreased ability to maintain the kinematics of the end effector. The PD patients were also found to be impaired in terms of their ability to synchronize the arm, hand, and torso. More specifically, although the elderly controls seemed to employ a strategy of increasing the involvement of the torso when reaching to grasp the uncovered cup, no such strategy was observed in the PD patients. Collectively, the results suggest that the multi-joint synergies observed in the elderly controls, which help preserve relatively consistent endpoint trajectories, are disrupted in Parkinson's patients.

Parkinson's disease patients undershoot target size in handwriting and similar tasks

OBJECTIVES

Previous research suggested that people with Parkinson's disease are able to increase handwriting stroke size up to 1.5 cm without an increase of stroke duration; whereas age matched individuals in normal health are able to modulate stroke size without changes in stroke duration for sizes up to 2 cm. This study was designed to test this finding by examining whether sizes larger than 1.5 cm show different relationships with stroke duration for patients with Parkinson's disease as compared with age matched controls.

METHODS

The study included 13 subjects with Parkinson's disease and 13 age matched controls. Participants were required to write a cursive "llllllll" pattern, or a cursive "lililili" pattern without the dots, at a comfortable speed and also as fast as possible, in five different sizes (1.0, 1.5, 2.0, 3.0, and 5.0 cm). The participants wrote with a ballpoint pen on a digitiser tablet. The target pattern was displayed at its required size on a screen, but disappeared as soon as the pen touched the surface of the digitiser tablet. Online visual monitoring of the hand was prevented by a cover over the digitiser. After each trial, the recorded movement of the tip of the pen was displayed with two lines to indicate whether the size requirement had been met. The writing conditions were presented in random order and consisted of 12 trials for each participant.

RESULTS

The results demonstrated that stroke size and duration produced by the participants with Parkinson's disease were independently modulated up to 1.5 cm; sizes over 1.5 cm resulted in progressive undershooting by patients with Parkinson's disease (PD). It was also shown that these participants modulated acceleration measures inefficiently as compared with controls.

CONCLUSIONS

The findings suggest that individuals with Parkinson's disease writing at speed produce inadequate stroke sizes when these should equal or exceed 1.5 cm.