The influence of mental and motor load on handwriting movements in parkinsonian patients

Bilateral Transfer of a Visuomotor Task in Different Workspace Configurations

Bilateral transfer occurs when a learned behavior transfers from one (group of) effectors(s) to another. Researchers investigating bilateral transfer of a visuomotor adaptation task between limbs used across workspaces have observed divergent results. This study assessed whether bilateral transfer of a visuomotor adaptation task changes with workspace configuration manipulation. Ninety-six right-handed young adults were assigned to one of three workspace locations, i.e., ipsilateral, contralateral, and central. Within each workspace were two retention groups (RRR/LLL) and two bilateral transfer groups (RLR/LRL). Performance before and after training was collected to determine direct and after-effects. We observed an asymmetric transfer of pathlength (left to right) but no ensuing after-effect. However, the transfer of movement time and normalized jerk was symmetric in the contralateral workspace. These findings showed differences in the pattern of bilateral transfer asymmetry in the different workspace configurations, which was parameter specific.

Leveraging the Potential of Digital Technology for Better Individualized Treatment of Parkinson's Disease

Recent years have witnessed a strongly increasing interest in digital technology within medicine (sensor devices, specific smartphone apps) and specifically also neurology. Quantitative measures derived from digital technology could provide Digital Biomarkers (DMs) enabling a quantitative and continuous monitoring of disease symptoms, also outside clinics. This includes the possibility to continuously and sensitively monitor the response to treatment, hence opening the opportunity to adapt medication pathways quickly. In addition, DMs may in the future allow early diagnosis, stratification of patient subgroups and prediction of clinical outcomes. Thus, DMs could complement or in certain cases even replace classical examiner-based outcome measures and molecular biomarkers measured in cerebral spinal fluid, blood, urine, saliva, or other body liquids. Altogether, DMs could play a prominent role in the emerging field of precision medicine. However, realizing this vision requires dedicated research. First, advanced data analytical methods need to be developed and applied, which extract candidate DMs from raw signals. Second, these candidate DMs need to be validated by (a) showing their correlation to established clinical outcome measures, and (b) demonstrating their diagnostic and/or prognostic value compared to established biomarkers. These points again require the use of advanced data analytical methods, including machine learning. In addition, the arising ethical, legal and social questions associated with the collection and processing of sensitive patient data and the use of machine learning methods to analyze these data for better individualized treatment of the disease, must be considered thoroughly. Using Parkinson's Disease (PD) as a prime example of a complex multifactorial disorder, the purpose of this article is to critically review the current state of research regarding the use of DMs, discuss open challenges and highlight emerging new directions.

A new scheme for the automatic assessment of Alzheimer's disease on a fine motor task with Transfer Learning. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:3823-3829. [PMID: 34892068 DOI: 10.1109/embc46164.2021.9630539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We present a new scheme for Alzheimer's Disease (AD) automatic assessment, based on Archimedes spiral, drawn on a digitizing tablet. We propose to enrich spiral images generated from the raw sequence of pen coordinates with dynamic information (pressure, altitude, velocity) represented with a semi-global encoding in RGB images. By exploiting Transfer Learning, such hybrid images are given as input to a deep network for an automatic high-level feature extraction. Experiments on 30 AD patients and 45 Healthy Controls (HC) showed that the hybrid representations allow a considerable improvement of classification performance, compared to those obtained on raw spiral images. We reach, with SVM classifiers, an accuracy of 79% with pressure, 76% with velocity, and 70.5% with altitude. The analysis with PCA of internal features of the deep network, showed that dynamic information included in images explain a much higher amount of variance compared to raw images. Moreover, our study demonstrates the need for a semi-global description of dynamic parameters, for a better discrimination of AD and HC classes. This description allows uncovering specific trends on the dynamics for both classes. Finally, combining the decisions of the three SVMs leads to 81.5% of accuracy.Clinical Relevance- This work proposes a decision-aid tool for detecting AD at an early stage, based on a non-invasive simple graphic task, executed on a Wacom digitizer. This task can be considered in the battery of usual clinical tests.

Tracking the Costs of Clear and Loud Speech: Interactions Between Speech Motor Control and Concurrent Visuomotor Tracking

Purpose Prior work has demonstrated that competing tasks impact habitual speech production. The purpose of this investigation was to quantify the extent to which clear and loud speech are affected by concurrent performance of an attention-demanding task. Method Speech kinematics and acoustics were collected while participants spoke using habitual, loud, and clear speech styles. The styles were performed in isolation and while performing a secondary tracking task. Results Compared to the habitual style, speakers exhibited expected increases in lip aperture range of motion and speech intensity for the clear and loud styles. During concurrent visuomotor tracking, there was a decrease in lip aperture range of motion and speech intensity for the habitual style. Tracking performance during habitual speech did not differ from single-task tracking. For loud and clear speech, speakers retained the gains in speech intensity and range of motion, respectively, while concurrently tracking. A reduction in tracking performance was observed during concurrent loud and clear speech, compared to tracking alone. Conclusions These data suggest that loud and clear speech may help to mitigate motor interference associated with concurrent performance of an attention-demanding task. Additionally, reductions in tracking accuracy observed during concurrent loud and clear speech may suggest that these higher effort speaking styles require greater attentional resources than habitual speech.

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.

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.

Characterization of the fine motor problems in patients with cognitive dysfunction - A computerized handwriting analysis

This study proposed a new technology to assess the accuracy of Chinese handwriting by comparing every stroke movement between a template model and a handwritten script. It tested the feasibility of a computerized evaluation in the parameterization of the handwriting deterioration caused by impaired cognitive function. This study recruited 22 participants with Alzheimer's disease (AD) and 14 with amnestic mild cognitive impairment (aMCI); 18 age- and gender-matched healthy elderly individuals made up the health control. The graphomotor tasks included drawing four straight lines (vertical, horizontal, and two diagonal) as well as writing Chinese words with simple vertical, horizontal and diagonal strokes. The temporal and spatial data were calculated to measure the motor coordination. The results in geographic drawing tests reveal significant differences among the three groups in task accuracy and movement fluency, especially in nonequivalent and wrist movements. The accuracy control of the graphic drawing in the AD and aMCI groups was significantly lower than that for the subjects in the normal group. These two groups also showed longer pauses in stroke movement with the handwriting tasks. The handwriting accuracy in the AD and aMCI groups was found to be significantly different from that of the subjects in the normal group. The results of this study can be used as an indicative reference for early detection of AD or aMCI, an objective evaluation for the effectiveness of interventions, and an assessment of disease progression.

Interrelations between cognitive dysfunction and motor symptoms of Parkinson's disease: behavioral and neural studies

Parkinson's disease (PD) is characterized by a range of motor symptoms. Besides the cardinal symptoms (tremor, bradykinesia/akinesia, and rigidity), PD patients also show other motor deficits, including gait disturbance, speech deficits, and impaired handwriting. However, along with these key motor symptoms, PD patients also experience cognitive deficits in attention, executive function, working memory, and learning. Recent evidence suggests that these motor and cognitive deficits of PD are not completely dissociable, as aspects of cognitive dysfunction can impact motor performance in PD. In this article, we provide a review of behavioral and neural studies on the associations between motor symptoms and cognitive deficits in PD, specifically akinesia/bradykinesia, tremor, gait, handwriting, precision grip, and speech production. This review paves the way for providing a framework for understanding how treatment of cognitive dysfunction, for example cognitive rehabilitation programs, may in turn influence the motor symptoms of PD.

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.

Validity and reliability of a new tool to evaluate handwriting difficulties in Parkinson's disease

BACKGROUND

Handwriting in Parkinson's disease (PD) features specific abnormalities which are difficult to assess in clinical practice since no specific tool for evaluation of spontaneous movement is currently available.

OBJECTIVE

This study aims to validate the 'Systematic Screening of Handwriting Difficulties' (SOS-test) in patients with PD.

METHODS

Handwriting performance of 87 patients and 26 healthy age-matched controls was examined using the SOS-test. Sixty-seven patients were tested a second time within a period of one month. Participants were asked to copy as much as possible of a text within 5 minutes with the instruction to write as neatly and quickly as in daily life. Writing speed (letters in 5 minutes), size (mm) and quality of handwriting were compared. Correlation analysis was performed between SOS outcomes and other fine motor skill measurements and disease characteristics. Intrarater, interrater and test-retest reliability were assessed using the intraclass correlation coefficient (ICC) and Spearman correlation coefficient.

RESULTS

Patients with PD had a smaller (p = 0.043) and slower (p<0.001) handwriting and showed worse writing quality (p = 0.031) compared to controls. The outcomes of the SOS-test significantly correlated with fine motor skill performance and disease duration and severity. Furthermore, the test showed excellent intrarater, interrater and test-retest reliability (ICC > 0.769 for both groups).

CONCLUSION

The SOS-test is a short and effective tool to detect handwriting problems in PD with excellent reliability. It can therefore be recommended as a clinical instrument for standardized screening of handwriting deficits in PD.

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.

Limb Dominance and Its Effects on the Benefits of Intralimb Transfer of Learning: A Visuomotor Aiming Task

Research has attempted to address what characteristics benefit from transfer of learning; however, it is still unclear which characteristics are effector dependent or independent. Furthermore, it is not clear if intralimb transfer shows, similarly to interlimb transfer, an asymmetry of benefits between the upper limbs. The purpose of the current study is to examine if effector independence effects emerge, as observed in interlimb transfer studies, when transfer to new effector group within the same limb occurs, and whether the pattern of intralimb transfer benefits differ between the limbs. Our results suggest that a visuomotor task transfers within both limbs, even though the transfer benefits within the limbs seem to differ. This was supported by more transfer occurring in the dominant limb than the nondominant limb. Potential control mechanisms used for intralimb transfer are discussed.

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.

Coordination deficits during trunk-assisted reach-to-grasp movements in Parkinson's disease

The present study investigated how Parkinson's disease (PD) affects temporal coordination among the trunk, arm, and fingers during trunk-assisted reach-to-grasp movements. Seated participants with PD and healthy controls made prehensile movements. During the reach to the object, the involvement of the trunk was altered based on the instruction; the trunk was not involved, moved forward (flexion), or moved backward (extension) in the sagittal plane. Each of the trunk movements was combined with an extension or flexion motion of the arm during the reach. For the transport component, the individuals with PD substantially delayed the onset of trunk motion relative to that of arm motion in conditions where the trunk was moved in the direction opposite from the arm reaching toward the object. At the same time, variability of intervals between the onsets and intervals between the velocity peaks of the trunk and wrist movements was increased. The magnitudes of the variability measures were significantly correlated with the severity of PD. Regarding the grasp component, the individuals with PD delayed the onset of finger movements during reaching. These results imply that PD impairs temporal coordination between the axial and distal body segments during goal-directed skilled actions. When there is a directional discrepancy between the trunk and wrist motions, individuals with PD appear to prioritize wrist motion that is tied to the task goal over the trunk motion. An increase in disease severity magnifies the coordination deficits.

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.

Movement trajectory smoothness is not associated with the endpoint accuracy of rapid multi-joint arm movements in young and older adults

The minimum variance theory proposes that motor commands are corrupted by signal-dependent noise and smooth trajectories with low noise levels are selected to minimize endpoint error and endpoint variability. The purpose of the study was to determine the contribution of trajectory smoothness to the endpoint accuracy and endpoint variability of rapid multi-joint arm movements. Young and older adults performed arm movements (4 blocks of 25 trials) as fast and as accurately as possible to a target with the right (dominant) arm. Endpoint accuracy and endpoint variability along with trajectory smoothness and error were quantified for each block of trials. Endpoint error and endpoint variance were greater in older adults compared with young adults, but decreased at a similar rate with practice for the two age groups. The greater endpoint error and endpoint variance exhibited by older adults were primarily due to impairments in movement extent control and not movement direction control. The normalized jerk was similar for the two age groups, but was not strongly associated with endpoint error or endpoint variance for either group. However, endpoint variance was strongly associated with endpoint error for both the young and older adults. Finally, trajectory error was similar for both groups and was weakly associated with endpoint error for the older adults. The findings are not consistent with the predictions of the minimum variance theory, but support and extend previous observations that movement trajectories and endpoints are planned independently.

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.

Co-variation between graphic pattern stability and attentional cost: a clue for the difficulty to produce handwritten traces

Attentional cost incurred for generating handwritten graphic patterns was investigated using a classic dual-task procedure, in which a concurrent reaction time (RT) task was used as an index of the attentional cost incurred by the primary graphic task. Eight right-handed adults had to trace graphic patterns, characterized by a 0°, 45°, 90°, 135° or 180° relative phase and corresponding to shapes ranging from lines to ellipses to circles, while responding by a key press as fast as possible to an auditory signal. The results evidenced a strong and significant correlation between the stability of the produced pattern and the associated attentional cost. The amplitude of the minor and major axes of the produced ellipsoids decreased with the increase of movement frequency, as expected by nonlinear models of oscillatory pattern generation. These findings pave the way to the study for the (coordinative) processes for letter (mal)formation in cursive handwriting.

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.

A computerized multidimensional measurement of mental workload via handwriting analysis

The goal of this study was to test the effect of mental workload on handwriting behavior and to identify characteristics of low versus high mental workload in handwriting. We hypothesized differences between handwriting under three different load conditions and tried to establish a profile that integrated these indicators. Fifty-six participants wrote three numerical progressions of varying difficulty on a digitizer attached to a computer so that we could evaluate their handwriting behavior. Differences were found in temporal, spatial, and angular velocity handwriting measures, but no significant differences were found for pressure measures. Using data reduction, we identified three clusters of handwriting, two of which differentiated well according to the three mental workload conditions. We concluded that handwriting behavior is affected by mental workload and that each measure provides distinct information, so that they present a comprehensive indicator of mental workload.

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.

Biased wrist and finger coordination in Parkinsonian patients during performance of graphical tasks

Handwriting impairments in Parkinson's disease (PD) have been associated with micrographia, i.e. diminished letter size. However, dyscoordination of the wrist and fingers may also contribute to handwriting deterioration in PD. To investigate this hypothesis, right-handed PD patients and controls were tested in performance of three types of cyclic wrist and finger movements: drawing of two lines and a circle. The line drawing was performed with either simultaneous flexion and extension of the wrist and fingers (equivalent pattern resulting in a right-tilted line) or with wrist flexion/extension accompanied with finger extension/flexion (nonequivalent pattern resulting in a left-tilted line). Circle drawing required a specific phase difference between wrist and finger motions. Movements were performed with an inkless pen on a digitizer-tablet at two frequency levels. Consistent deformations of the circle into right-tilted ovals and lower variability in equivalent compared with nonequivalent lines revealed preference to produce right-tilted shapes. This preference became more apparent with increased movement speed and it was amplified in PD patients. Analysis revealed that the circle deformation emerged mainly due to reduction in relative phase, while wrist and finger amplitudes remained unchanged. The results suggest that PD causes deficit characterized by strong tendency to produce certain coordination patterns between wrist and finger motions. This deficit may significantly contribute to handwriting impairments in PD by reducing the dexterity in the production of the variety of shapes of the cursive letters. Furthermore, the deficiency revealed in wrist and finger coordination may represent a more general deficit affecting control of various multi-joint movements in 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.

Movement structure in young and elderly adults during goal-directed movements of the left and right arm

Elderly adults often exhibit performance deficits during goal-directed movements of the dominant arm compared with young adults. Recent studies involving hemispheric lateralization have provided evidence that the dominant and non-dominant hemisphere-arm systems are specialized for controlling different movement parameters and that hemispheric specialization may be reduced during normal aging. The purpose was to examine age-related differences in the movement structure for the dominant (right) and non-dominant (left) during goal-directed movements. Young and elderly adults performed 72 aiming movements as fast and as accurately as possible to visual targets with both arms. The findings suggest that previous research utilizing the dominant arm can be generalized to the non-dominant arm because performance was similar for the two arms. However, as expected, the elderly adults showed shorter relative primary submovement lengths and longer relative primary submovement durations, reaction times, movement durations, and normalized jerk scores compared to the young adults.

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.

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.

Micrographia on free writing versus copying tasks in idiopathic Parkinson's disease

BACKGROUND

Only a few studies have reported on the frequency of micrographia in idiopathic Parkinson's disease (IPD), and the definition of micrographia in these studies was based simply on the visual inspection of the patients' free writing.

OBJECTIVES

We investigated the frequency of consistent (CM) and progressive (PM) micrographia by quantifying the patients' copying of a target letter or figure.

METHODS

Seventy-five IPD patients and 30 sex/age matched healthy controls were assigned the tasks of free writing and letter/figure copying. CM was defined by the average size of the letter or figure written or copied by the patients below the controls' mean-2SD. PM was defined by the slope of reduction in size as a function of the serial positioning of the letters/figures below the mean-2SD of the controls.

RESULTS

In the free writing, of 75 patients, only one met the criteria for the definition of CM and two met the criteria for the definition of PM definition. In contrast, letter/figure copying tasks identified 33 (44%) patients with CM and 19 (25%) with PM.

CONCLUSION

Our study suggests that the prior definition of CM or PM by visual inspection in free writing task is less valid, and that the definition of CM and PM, based on the letter/figure copying tasks rather than free writing tests, could be more objective.

Discrete and dynamic scaling of the size of continuous graphic movements of parkinsonian patients and elderly controls

OBJECTIVES

To systematically investigate the ability of Parkinson's disease patients to discretely and dynamically scale the size of continuous movements and to assess the impact of movement size on outcome variability.

METHODS

Ten patients with Parkinson's disease (mean age 72 years) were compared with 12 healthy elderly controls (mean age 70 years). The subjects wrote with a stylus on a graphics tablet. In experiment 1 they drew circles, matching the size of five target circles ranging in magnitude from a radius of 0.5 cm up to 2.5 cm. In experiment 2 they drew spirals with a radius of at least 2 cm. In both experiments the drawings were initially performed as accurately as possible then as fast and accurately as possible.

RESULTS

In both experiments the patients and controls drew at a similar speed. The within trial variability of the pen trajectory was greater for patients than controls, and increased disproportionately with the size of the movement. When the emphasis was on size rather than variability (circles), the patients' drawing movements were the same size as controls. When the emphasis was on accuracy of pen trajectory (that is, minimum variability) rather than size (spirals), the patients' drawing movements were smaller than controls.

CONCLUSIONS

The movements made by Parkinson's disease patients are hypometric partly as an adaptive strategy used to reduce movement variability. This strategy is used primarily when the requirement to make accurate movements outweighs the need to make large movements.

Parkinsonian patients reduce their stroke size with increased processing demands

Parkinson's disease (PD) patients often show reductions in writing size (micrographia) as the length of the text they produce increases. The cause for these reductions in stroke size are not well understood. Reductions in stroke size could be associated with either concurrent processing demands that result from the coordination and control of fingers, wrist, and arm during writing and the processing of future words or increased extension of the wrist joint as the execution of the writing progresses to the right across the page, resulting in increased stiffness in the pen-limb system. Parkinson's patients and elderly controls wrote phrases of different lengths with target patterns in various serial positions. When the number of words to be written increased, PD patients reduced their stroke size of the initial target pattern, while the elderly controls did not reduce their stroke size. There was no systematic change in stroke size of the second pattern as function of serial position. This result suggests that PD patients reduce the size of their handwriting strokes when concurrent processing load increases.