Performance Of Fine Motor Tasks Research Articles

Pinch Strength Measurements in Adolescents With Pediatric Multiple Sclerosis.

Multiple sclerosis (MS) is a degenerative disease with typical onset between 20 and 50 years of age. An increase in MS cases has been found in the adolescent US population. Adolescents require fine motor manipulation skills for their functional and academic performance. Deficits in the major components of manipulation skills may result in insufficient function. This study examined the 2-point, 3-point, and lateral pinch strength of adolescents diagnosed as having MS. Seventy-four adolescents, 37 with a diagnosis of relapsing-remitting MS and a control group of 37 age-matched peers, participated in this study. Data on 2-point, 3-point, and lateral pinch strength in both hands were collected using a pinch meter. Analyses of covariance were used to describe differences across the 2 groups, and effect sizes (Cohen d) were calculated by finding the mean difference between the study groups divided by the pooled SD. A significant difference was found in the 2-point pinch strength of the right hand of participants with pediatric MS compared with age- and sex-matched control participants. There were no significant differences in 2-point pinch strength of the left hand or in 3-point or lateral pinch strength of the right and left hands. Pinch grasp strength was differentially affected in adolescents with MS. Pinch strength should be assessed and considered in adolescents with MS for a better understanding of their functional performance of fine motor tasks in activities of daily living and academics.

The Influence of Caffeine Consumption and the Polymorphisms of DRD2 and ADORA2A Genes on Fine Motor Task Performance

Caffeine is the most commonly used psychoactive drug and has been associated with increased attention, focus and motor activity through adenosine receptor (ADORA2A) antagonism. ADORA2A and DRD2 are co‐localized in the central nervous system and blocking the adenosine receptor has been show to act as a dopamine receptor (DRD2) agonist which influence focus and motor tasks. Finally, single nucleotide polymorphisms of ADORA2A varies in response to caffeine which may influence the dopamine response.PURPOSEThe purpose of this study was to determine the influence of caffeine as well as the effects of the adenosine (ADORA2A) and dopamine (DRD2) polymorphisms during unilateral and bilateral motor tasks.METHODSThirty‐four subjects (age: 18‐23) were recruited and gave informed consent to participate in the study. An oral bolus of caffeine (CAF), 5mg•kg‐1, or placebo (PLA), maltodextrin, was given in a double‐blind, randomized, and counterbalanced design 60 min prior to testing. The Purdue Pegboard Test (PPT) was used to assess the unilateral movements by placing pegs with the right hand and left hand; this was coded for dominant and non‐dominant. Bilateral movements were also assessed with PPT by placing pegs with both hands and during a peg/washer/collar assembly task. Buccal cells were obtained using a 0.9% NaCl mouth rinse, spun down, and lysed via proteinase k. DNA was extracted using QiAmp Mini spin columns with amplification and allelic discrimination for ADORA2A (rs5751876) and DRD2 (rs1800497) obtained via One‐Step qPCR. All samples were run in duplicate with negative and positive controls. Data was analyzed using a 2 (condition) x 2 (SNP) with repeated measures for each subset of the PPT and a 2 (condition) x 2 (ADORA2A) x 2 (DRD2) with repeated measures to for each subset to find the interaction of ADORA2A and DRD2, p<0.05)RESULTSFor the ADORA2A SNP, the main effect of caffeine demonstrated a significant increase in performance for each unilateral task from placebo to caffeine trials, dominant hand (16.4+1.6 to 17.4, p<0.01), non‐dominant hand, (15.8+1.8 to 16.0, p<0.05) and combined (45.5+4.3 to 46.2, p<0.05). No difference was found for the bilateral movements. ADORA2A interaction effects demonstrated that TT genotype scored better under the caffeine condition, 15.8+1.9 to 16.2+ 0.8 for placebo and caffeine respectively. For DRD2, there were no significant differences in the main effects or interaction effects. The 3‐way ANOVA, condition x ADORA2A x DRD2, demonstrated no significant differences for the main effects or interaction effects.DISCUSSIONA bolus of caffeine improved performance for the test subset scores that involved unilateral movements but had no influence on scores for bilateral movements. The reduction in performance could be due to slower reaction times or neural coupling to coordinate movements between the limbs during bilateral movements. The increased performance in the non‐dominant hand for the TT genotype may be due to the increased sensitivity of this specific SNP to caffeine. While not significant, variations in responses to caffeine were observed when assessing task performance by grouped ADORA2A/DRD2 polymorphisms and the possible combinations. One grouping, TC/CC:AG/AA, demonstrated negative response to caffeine, whereas two other groupings (TT:GG, TC/CC:GG) demonstrated positive responses to caffeine. Further research and an increased sample size will help demonstrate the specific SNP interactions.

Optimizing Motor Learning: Difficulty Manipulation Combined with Feedback- Frequency Enhance Under-Time-Pressure Fine-Motor-Coordination Skill Acquisition and Retention

Improving acquisition and retention of new motor skills is of great importance. This study investigated the effects of progressive task difficulty manipulation (TD), combined with varying knowledge of results frequencies (KR) on performance accuracy and consistency when learning novel fine motor coordination tasks, and examined relationships between novel fine motor task performance and executive function (EF), working memory (WM), and perceived difficulty (PD). Thirty-six, right-handed, novice physical-education students (age = 10.72 ± 0.89 years) participated; participants were separated into three groups, receiving varying KR frequency (100%KR, 50%KR, and 33%KR). For each group, distance to the target was increased progressively (2 m, 2.37 m, and 3.56 m) to obtain three difficulty levels. We assessed performance during test sessions (pretest, post-test, Retention1 and Retention2) under free (FC) and time pressure (TPC) conditions. Results revealed that under FC, 100%KR improved significantly. Results revealed significant linear improvements in accuracy for 50%KR and 33%KR under TPC. New findings indicate that the association between TD and KR (50%KR) may provide more appropriate cognitive loads compared to 33%KR and 100%KR groups. These have implications for practitioners because, while strategies are clearly necessary for improving learning, the efficacy of the process appears to be based on the characteristics of the learners.

Trait Energy and Fatigue Modify the Effects of Caffeine on Mood, Cognitive and Fine-Motor Task Performance: A Post-Hoc Study.

Multiple studies suggest that genetic polymorphisms influence the neurocognitive effects of caffeine. Using data collected from a double-blinded, within-participants, randomized, cross-over design, this study examined the effects of trait (long-standing pre-disposition) mental and physical energy and fatigue to changes in moods (Profile of Mood Survey-Short Form (POMS-SF), state mental and physical energy and fatigue survey), cognitive (serial subtractions of 3 (SS3) and 7 (SS7)), and fine-motor task (nine-hole peg test) performance after consuming a caffeinated beverage and a non-caffeinated placebo. Results indicate that trait mental and physical fatigue and mental energy modified the effects of caffeine on vigor, tension-anxiety, physical, and mental fatigue. Additionally, we report that those who were high trait physical and mental fatigue and low-trait mental energy reported the greatest benefit of caffeine on the SS3 and SS7, while those who were high trait mental and physical fatigue reported the greatest benefit of consuming caffeine on fine-motor task performance. The results of our study suggest that trait mental and physical fatigue and mental energy modify the acute effects of caffeine among a group of healthy, young adults and should be measured and controlled for by researchers who choose to study the effects of caffeine on acute moods and cognitive and fine-motor task performance.

Effects of Viewing Cute Pictures on Quiet Eye Duration and Fine Motor Task Performance.

We investigated if viewing cute pictures could improve fine motor skills and prolong quiet eye (QE) duration. QE is a gaze phenomenon, and its duration (i.e., the period between fixation onset preceding a critical movement and fixation offset) is thought to represent attention control. As it has been reported that QE duration is longer for expert athletes than for novice athletes in various sports and becomes shorter even for experts who choke under pressure during games, resulting in performance deterioration, QE prolongation is important to prevent choking under pressure. Separately, several studies have confirmed that viewing cute pictures can induce focal attention, thus improving performance in fine motor tasks. We hypothesized that viewing cute pictures may modulate attention control and prolong QE duration. We also tested if the beneficial effects of viewing cute pictures could be obtained in a high-pressure situation in which participant performance was evaluated by an experimenter. We used a fine-motor task requiring participants to use a pair of tweezers to remove 12 small pieces from holes in a game board. We randomly assigned participants to either the baby-animal pictures group or the adult-animal pictures group, based on pictures viewed prior to the task. Participants executed the task in a pre-test, post-test, and pressure test. In both the post-test and the pressure test, participants viewed seven photographs of either baby animals or adult animals before execution of the task. In accordance with previous research, task precision increased after viewing pictures of baby animals in both the post-test and pressure test. Furthermore, QE duration was also prolonged after viewing cute pictures in the post-test, but not in the pressure test. Neither performance improvement nor QE prolongation was found after viewing pictures of adult animals. These results suggested that simply viewing cute pictures could prolong QE duration without pressure and might provide a beneficial effect on performance, even in a high-pressure situation.

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.

Repetitive Transcranial Magnetic Stimulation Enhances Recovery in Central Cord Syndrome Patients.

ObjectiveTo investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on neurological and functional recovery in patients with central cord syndrome (CCS) involving the upper extremities between the treated and non-treated sides of the treated group and whether the outcomes are comparable to that of the untreated control group.MethodsNineteen CCS patients were treated with high-frequency (20 Hz) rTMS over the motor cortex for 5 days. The stimulation side was randomly selected, and all the subjects received conventional occupational therapy during the rTMS-treatment period. Twenty CCS patients who did not receive rTMS were considered as controls. Clinical assessments, including those by the International Standard for Neurological Classification of Spinal Cord Injury, the Jebsen-Taylor Hand Function Test, and the O'Connor Finger Dexterity Test were performed initially and followed up for 1 month after rTMS treatment or 5 weeks after initial assessments.ResultsThe motor scores for upper extremities were increased and the number of improved cases was greater for the treated side in rTMS-treated patients than for the non-treated side in rTMS-treated patients or controls. The improved cases for writing time and score measured on the Jebsen-Taylor Hand Function Test were also significantly greater in number on the rTMS-treated side compared with the non-treated side and controls. There were no adverse effects during rTMS therapy or the follow-up period.ConclusionThe results of the application of high-frequency rTMS treatment to CCS patients suggest that rTMS can enhance the motor recovery and functional fine motor task performance of the upper extremities in such individuals.

Don't Make Me Angry! A Psychophysiological Examination of the Anger–Performance Relationship in Intermediate and Elite Fencers

We aimed to identify the effect of state-anger on precision, speed, and power components of performance during fencing attacks. We conducted a laboratory-based, single-case research experiment to test the fine motor task performance of two experienced and two elite-level fencers under two emotional states: anger and emotion-neutral. We assessed anger via psychophysiological and self-report measures, and we induced anger via a brief imagery intervention. Through the use of an innovative design, which included multiple measures of change, we showed that anger had a consistent negative effect on precision but an inconsistent relationship with response time and muscle activity. The current research design and protocol offer a novel and in-depth method for examining the specific relationships between affective states, emotions, and the complexities that underpin performance. The specific effects of anger on performance were multifarious, complex, and inconsistent. Nonetheless, the results tend to indicate that anger facilitates reaction time and debilitates performance, and these effects were clearer for the most elite performers. The effects of anger on performance are clearly complex, so it would be rather premature to make any suggestions for future practice at this point. Nonetheless, the clearer findings with the elite fencers indicate that researchers will likely yield the most fruitful insights by examining the effects of emotion of performance in elite performers.

Three-dimensional assessment of postural tremor during goal-directed aiming.

The performance of fine motor tasks which require a degree of precision can be negatively affected by physiological tremor. This study examined the effect of different aiming positions on anterior-posterior (AP), medial-lateral (ML) and vertical (VT) postural tremor. Participants were required to aim a mock handgun at a target located in front of them at eye level. Changes in AP, ML and VT tremor from the forearm and gun barrel were assessed as a function of limb (i.e., whether one or both arms were used) and upper arm position (elbow bent or extended). Tremor was recorded using triaxial accelerometers. Results showed that, across all tasks, the ML and VT tremor for any point was characterized by two frequency peaks (between 1-4 and 8-12Hz) with amplitude increasing from proximal (forearm) to distal (gun barrel). Interestingly, irrespective of the posture adopted, ML accelerations were of greater amplitude than VT oscillations. AP oscillations were markedly smaller compared to VT and ML tremor, did not display consistent frequency peaks, and were not altered by the arm conditions. Altering the aiming posture resulted in changes in VT and ML tremor amplitude, with oscillations being greater when using a single arm as compared to when two arms were used together. Similarly, tremor amplitude was reduced when the task was performed with the elbow bent compared to the straight arm condition. Overall, these results highlight that ML oscillations make as significant a contribution to the overall tremor dynamics as those observed in the VT direction. However, the origin of ML tremor is not simply the product of voluntary adjustments to maintain aim on the target, but also exhibits features similar to the neural generated 8-12-Hz tremor seen under postural conditions.

P107. Disturbed fine motor performance is associated with altered structure and perfusion of the motor system in schizophrenia

Introduction Motor symptoms are an integral part of the clinical presentation of schizophrenia and disturbances of fine motor function are frequent. However, only limited knowledge exists on the neural correlates of fine motor skills in schizophrenia. We implemented a complex fine motor task to test associations with whole brain gray matter (GM) volume as well as cerebral blood flow (CBF). We aimed to investigate whether patients with difficulties of fine motor performance would show structural and cerebral blood flow alterations in the motor loop. Methods In total 42 schizophrenia patients (59.5% men, mean age=38.6±11.4) diagnosed according to DSM-V underwent MR-neuroimaging. All patients but four received antipsychotic treatment. Parkinsonism was assessed using the motor part of the Unified Parkinson Disease Rating Scale (UPDRS). Fine motor skills were assessed using the coin rotation task. The task is to rotate a coin (.5 swiss francs) using three fingers of the left hand (thumb, index, middle) through serial 180-degree turns as rapidly as possible. Deficits are indicated by the reduced number of half turns and coin drops. We processed structural images using standard SPM8 procedures, in particular voxel-based morphometry (VBM) toolbox. Resting state CBF was measured by arterial spin labeling (ASL). ASL data was analyzed with our custom written MATLAB programs (Federspiel et al., 2006; Walther et al., 2011). The main emphasis was to explore the effect of task performance on GM volume and CBF. Correlations of task performance (mean=10.7±4.1) and GM volume (covariates total intracranial volume and UPDRS) as well as CBF (covariate UPDRS) were calculated. A threshold of p - uncorr 0.001 (min. cluster size=17: equivalent to a map-wise false positive rate of alpha Results We found significant correlations of coin rotation scores and GM volume in the bilateral pre-supplementary motor area (pre-SMA) extending to the SMA, in the left primary motor cortex, the right superior frontal gyrus, bilateral the cerebellum and the left putamen. The pre-SMA cluster survived family wise error correction at cluster level. Significant correlations of CBF and the coin rotation scores were detected in the right SMA, the left primary motor cortex and in the right superior frontal gyrus (Area Fp1), the left inferior frontal gyrus and the right precuneus. Two clusters survived family wise error correction: right superior frontal gyrus and the left inferior frontal gyrus. Discussion Difficulties of fine motor task performance were associated with structural gray matter volume reduction in the motor loop, particularly in cortical motor control areas. In addition fine motor function in schizophrenia patients was linked with cerebral blood flow. These findings were corrected for parkinsonism. In sum, the results argue for specific alterations of the motor system in schizophrenia as source of impaired fine motor function beyond parkinsonism.

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.

Investigating Human Performance in a Virtual Reality Haptic Simulator as Influenced by Fidelity and System Latency

The objective of this study was to demonstrate the utility of an established model of human motor behavior for assessing the fidelity of a virtual reality (VR) and haptic-based simulation for fine motor task performance. This study was also to serve as a basis for formulating general performance-based simulator-design guidelines toward balancing perceived realism with simulator limitations, such as latency resulting from graphic and haptic renderings. A low-fidelity surgical simulator was developed as an example VR for study, and user performance was tested in a simplified tissue-cutting task using a virtual scalpel. The observed aspect of the simulation included a discrete-movement task under different system-lag conditions and settings of task difficulty. Results revealed user performance in the VR to conform with Fitts' law of motor behavior and for performance to degrade with increasing task difficulty and system time lag. In general, the findings of this work support predictions on human performance under various simulator-design conditions using an established model of motor-control behavior and formulation of human-performance-based simulator-design principles.

Associations among Strength, Steadiness, and Hand Function across the Adult Life Span

Age-related differences in force steadiness have been extensively examined and used as an index of motor function. However, the functional relevance of steadiness remains unclear. The aim here was to evaluate the relations among hand strength, steadiness, and function across the adult life span. Seventy-five adults (45 women; 18-89 yr) performed three strength, two steadiness, and four functional tests with both hands. Strength was measured during index finger abduction, precision pinch, and handgrip, and steadiness was measured during index finger abduction and precision pinch. Functional tests included the Grooved Pegboard test, the game Operation™, a scissor task, and a tracing task. Moderate correlations were observed between both steadiness tasks and performance on the Grooved Pegboard test (R(2) = 0.57 and R(2) = 0.46, respectively) and Operation™ (R(2) = -0.47 and R(2) = -0.57, respectively). The relation between measures of steadiness and hand function suggests that the physiological mechanisms responsible for differences in steadiness also contribute to differences in the performance of fine motor tasks with the hand.

Variability of Precision Pinch Movements Caused by Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) impairs the performance of fine motor tasks of the hand, leading to clumsiness. Precision pinch by the thumb and index finger is a frequent task that requires the fine control of each digit as well as the coordination of the 2 digits. The purpose of this study was to examine the performance of precision pinch movements impaired by CTS. Sixteen CTS subjects and 16 gender- and age-matched control subjects were instructed to repetitively perform the precision pinch movement with the thumb and index finger. A marker-based motion analysis method was used to obtain the kinematic data of the thumb and index finger during the precision pinch movements. Pinch performance was quantified by the variability of tip positions, joint angles, and tip distance at the pinch closures in the repeated movements. The CTS subjects performed the precision pinch movements less consistently compared with performance of the control subjects. The inconsistency was demonstrated by the increased variability of the tip positions of the 2 digits and the joint angles of the index finger. However, the variability of thumb joint angles was not significantly different between the 2 groups. The tip-to-tip distance, an indicator of thumb and index finger coordination, was relatively reproducible for both groups. Still, the CTS subjects showed a 50% greater variability of the tip distance compared with that of the control subjects. Carpal tunnel syndrome impairs the performance of precision pinch movement as indicated by the increased variability. The results correlate with the observed clumsiness or lack of dexterity for patients with CTS.

DESEMPENHO EM TAREFA MOTORA FINA SOB DIFERENTES CONDIÇÕES DE PRÁTICA

Aiming at investigating the effects of the practice types on a Fine Motor Task performance by undergraduate students of both sexes 48 subjects were randomly submitted to the following methodological protocol: Group A - pretest, mental practice, postest; Group B - pretest, physical practice, postest; Group C - pretest, mental practice in addition to physical practice, postest; Group D - pretest followed by postest. The data been colleted by means of two measures: the time spent and the number of errors made in the accomplishment of the task. The number of errors made was analysed by nonparametric statistics Kruskal-Wallis probe and Wilcoxon and U of Mann-Whitney all of which with a pre established significance level of p <= 0,05. The results indicated that the mental practice in addition to physical practice and physical practice in itself have obtained the best scores, in the number of errors made as well as in the time spent on the task.

Chronic intragastric administration of gamma-butyrolactone produces physical dependence in baboons

Abuse of gamma-hydroxybutyrate (GHB) and its precursors is a public health concern. Gamma-butyrolactone (GBL) is found in commercially available products and, when ingested, is metabolized to GHB. The goal was to evaluate the physical dependence potential and behavioral effects of GBL. Vehicle and then GBL were administered continuously (24 h per da y) in baboons (Papio anubis, n=5) via intragastric catheters. GBL dosing was initiated at 100 mg/kg/day and then progressively increased stepwise by increments of 100 mg/kg to a final dose of 600 mg/kg. The number of food pellets earned, fine-motor task performance, and observed behaviors were used as dependent measures. Precipitated withdrawal was evaluated after administration of GABA-B and benzodiazepine receptor antagonists during chronic GBL dosing (400-600 mg/kg). Spontaneous withdrawal was evaluated after discontinuation of chronic GBL 600 mg/kg. Blood GHB levels were determined during chronic dosing of each GBL dose by isotope dilution assay. Chronic GBL dose-dependently decreased food-maintained behavior, disrupted performance on the fine-motor task, and produced signs of sedation and muscle relaxation. The GABA-B antagonist SGS742 [56 mg/kg, intramuscular (IM)] precipitated a withdrawal syndrome, whereas the benzodiazepine antagonist flumazenil (5 mg/kg, IM) produced little or no effect. Signs of physical dependence were also demonstrated when chronic GBL dosing was discontinued. Analysis of plasma indicated GBL was metabolized to GHB; levels were 825 to 1,690 micromol l(-1) GHB and 2,430 to 3,785 micromol l(-1) GHB after week 1 of 400 and 600 mg/kg/day, respectively. These data indicate that, like GHB, chronic GBL dosing produced physical dependence that likely involved the GABA-B receptor.

Phase‐dependent and task‐dependent modulation of stretch reflexes during rhythmical hand tasks in humans

Phase-dependent and task-dependent modulation of reflexes has been extensively demonstrated in leg muscles during locomotory activity. In contrast, the modulation of reflex responses of hand muscles during rhythmic movement is poorly documented. The objective of this study was to determine whether comparable reflex modulation occurs in muscles controlling finger motions during rhythmic, fine-motor tasks akin to handwriting. Twelve healthy subjects performed two rhythmic tasks while reflexes were evoked by mechanical perturbations applied at various phases of each task. Electromyograms (EMGs) were recorded from four hand muscles, and reflexes were averaged during each task relative to the movement phase. Stretch reflexes in all four muscles were found to be modulated in amplitude with respect to the phase of the rhythmic tasks, and also to vary distinctly with the tasks being conducted. The extent and pattern of reflex modulation differed between muscles in the same task, and between tasks for the same muscle. Muscles with a primary role in each task showed a higher correlation between reflex response and background EMG than other muscles. The results suggest that the modulation patterns observed may reflect optimal strategies of central-peripheral interactions in controlling the performance of fine-motor tasks. As with comparable studies on locomotion, the phase-dependency of the stretch reflexes implies a dynamically fluctuating role of proprioceptive feedback in the control of the hand muscles. The clear task-dependency is also consistent with a dynamic interaction of sensory feedback and central programming, presumably adapted to facilitate the successful performance of the different fine-motor tasks.

Behavioral and Morphological Comparison of Two Nonhuman Primate Models of Huntington’s Disease

OBJECTIVE Huntington’s disease is a progressive neurodegenerative disease characterized by movement disorder, cognitive deterioration, and selective striatal degeneration. No effective treatment exists, and thus stable primate models could aid in the development of novel therapies. METHODS Two primate models of Huntington’s disease were analyzed: bilateral stereotactic intrastriatal injections of quinolinic acid (QA), and daily systemic intramuscular administration of 3-nitropropionic acid (3-NP) for up to 8 weeks in male Cebus apella monkeys. The animals’ behavior was evaluated before, during, and 3 months after administration of the neurotoxin. Magnetic resonance imaging scans of the brain were obtained before and after treatment. RESULTS Frontal cognitive function as evaluated by object retrieval-detour task test demonstrated a marked deterioration in successful responses, with an increase in barrier reaches in both groups. No significant change in performance of fine motor tasks was observed. QA-treated animals displayed hyperactivity at night. Animals in both groups demonstrated abnormal posture, and the 3-NP-treated group showed spontaneous and apomorphine-induced dystonia and dyskinesia. The QA-treated group displayed large areas of increased signal on T2-weighted images in the caudate and putamen bilaterally. Treatment with 3-NP resulted in smaller lesions. Immunohistochemistry and morphometric analyses revealed that both groups had lesions in the striatum. A large area of neuronal loss with glial sparing was observed in the QA-treated group, including the caudate and putamen bilaterally. The 3-NP-treated group displayed smaller lesions restricted to the dorsolateral putamen. CONCLUSION These results suggest that both QA and 3-NP induce behavioral and morphological features that resemble the juvenile and akinetic-rigid variants of Huntington’s disease, with the group with 3-NP-induced lesions displaying smaller lesions and spontaneous dyskinesia.

Essential Tremor Entrains Rapid Voluntary Movements

The effect of essential tremor on the timing of rapid wrist flexion was examined in 10 patients with moderate to severe disability. The mean reaction time and motor time of the patients did not differ from the mean values of 10 healthy age- and sex-matched controls. The latencies of the triphasic agonist and antagonist EMG bursts did not differ between patients and controls. The initiation of movement was time-locked to the tremor cycle in all patients. The initial agonist muscle activation occurred in phase with the rhythmic bursts of EMG, but the onset of rapid wrist flexion occurred when the momentum of essential tremor opposed the volitional movement. Essential tremor has subtle effects on motor control that transcend oscillation per se. These effects probably contribute to the impaired performance of fine motor tasks in patients with advanced disease.