Disorders Of Motor Control Research Articles

EP 1. Brain activity after acute left hemispheric stroke in imitation and tool associated actions

Background Apraxia, a disorder of higher motor control, frequently leads to impaired tool use or imitation capacities due to left hemispheric lesions. However, despite similar lesion size or location, patients present with different apraxic deficits thus different early reorganization mechanism may be assumed. To understand the impaired praxis network after stroke on a functional level, we correlated behavioral performance in imitation and tool use tasks with activation patterns in fMRI of 47 acute left-hemispheric stroke patients. Methods A cohort of 47 acute stroke patients (mean age 63.5 years ± SD 13.6; 13 female) with first ever embolic stroke in the left arteria cerebri media territory were tested for deficits in imitation of meaningless hand and finger postures and tool associated actions (pantomime of tool use, imitation of tool use, actual tool use). Testing was performed mean 4.8 days ± SD 2.9 post stroke. FMRI was acquired during presentation of video sequences of tool-associated actions viewed from a first-person perspective. Voxel wise linear regression analyses for task scores only and with lesion volume as covariate as well as group differences for categorized behavioral performance (deficit vs. no deficit) were calculated to analyze activity associated with behavioral performance in tool use and meaningless imitation. Analyses were performed using GLMflex. Results are presented on a p Results Intact imitation of meaningless postures was associated with activation in the left middle occipital gyrus as well as in the left superior temporal lobe in linear regression analyses and categorical group differences (deficit vs. no deficit). Tool associated tasks correlated with activation in the left supramarginal gyrus and superior temporal lobe without occipital activation. For group differences in pantomime of tool use (deficit vs. no deficit) an additional activation for patients with low behavioral performance could be found in the posterior middle temporal gyrus. Conclusion For intact imitation of meaningless postures and tool associated actions, specific left hemispheric activation patterns in the acute phase after stroke could be determined. These areas are commonly associated to the left hemispheric praxis network. While intact imitation of meaningless gestures seems to rely on intact left middle occipital gyrus for visual analysis of the presented movement tool associated actions rather seem to rely on integrity of the supramarginal gyrus, known to store movement engrams. Patients with deficits in pantomime of tool use additionally show activation of posterior middle temporal gyrus for semantic movement information. These mechanisms possibly can be interpreted as early compensatory effort.

Vowel reduction across tasks for male speakers of American English.

This study examined acoustic variation of vowels within speakers across speech tasks. The overarching goal of the study was to understand within-speaker variation as one index of the range of normal speech motor behavior for American English vowels. Ten male speakers of American English performed four speech tasks including citation form sentence reading with a clear-speech style (clear-speech), citation form sentence reading (citation), passage reading (reading), and conversational speech (conversation). Eight monophthong vowels in a variety of consonant contexts were studied. Clear-speech was operationally defined as the reference point for describing variation. Acoustic measures associated with the conventions of vowel targets were obtained and examined. These included temporal midpoint formant frequencies for the first three formants (F1, F2, and F3) and the derived Euclidean distances in the F1-F2 and F2-F3 planes. Results indicated that reduction toward the center of the F1-F2 and F2-F3 planes increased in magnitude across the tasks in the order of clear-speech, citation, reading, and conversation. The cross-task variation was comparable for all speakers despite fine-grained individual differences. The characteristics of systematic within-speaker acoustic variation across tasks have potential implications for the understanding of the mechanisms of speech motor control and motor speech disorders.

Alien Hand, Restless Brain: Salience Network and Interhemispheric Connectivity Disruption Parallel Emergence and Extinction of Diagonistic Dyspraxia.

Diagonistic dyspraxia (DD) is by far the most spectacular manifestation reported by sufferers of acute corpus callosum (CC) injury (so-called “split-brain”). In this form of alien hand syndrome, one hand acts at cross purposes with the other “against the patient’s will”. Although recent models view DD as a disorder of motor control, there is still little information regarding its neural underpinnings, due to widespread connectivity changes produced by CC insult, and the obstacle that non-volitional movements represent for task-based functional neuroimaging studies. Here, we studied patient AM, the first report of DD in patient with complete developmental CC agenesis. This unique case also offers the opportunity to study the resting-state connectomics of DD in the absence of diffuse changes subsequent to CC injury or surgery. AM developed DD following status epilepticus (SE) which resolved over a 2-year period. Whole brain functional connectivity (FC) was compared (Crawford-Howell [CH]) to 16 controls during the period of acute DD symptoms (Time 1) and after remission (Time 2). Whole brain graph theoretical models were also constructed and topological efficiency examined. At Time 1, disrupted FC was observed in inter-hemispheric and intra-hemispheric right edges, involving frontal superior and midline structures. Graph analysis indicated disruption of the efficiency of salience and right frontoparietal (FP) networks. At Time 2, after remission of diagnostic dyspraxia symptoms, FC and salience network changes had resolved. In sum, longitudinal analysis of connectivity in AM indicates that DD behaviors could result from disruption of systems that support the experience and control of volitional movements and the ability to generate appropriate behavioral responses to salient stimuli. This also raises the possibility that changes to large-scale functional architecture revealed by resting-state functional magnetic resonance imaging (fMRI) (rs-fMRI) may provide relevant information on the evolution of behavioral syndromes in addition to that provided by structural and task-based functional imaging.

Efek Aquatic Aerobic Activity Terhadap Perkembangan Kemampuan Basic Motor Control, Gross Motor Dan Occupational Performance Skills Pada Anak Cerebral Palsy (CP)

Abstract: Aquatic Aerobic Activity, Land Based Activity, Motor Control. Cerebral palsy (CP) is characterized by sensorimotor disorders of motor control (gross motors and fine motor) as well as posture. Aquatic aerobic activity is designed to give sensorimotor stimulation through a series of activities undertaken in the pool. Indicators of sensorimotor function improvement in CP can be evaluated through changes in the motion control capabilities, basic motor control in the setting of functional posture, and the ability to perform functional activities. The purpose of this study was to examine the effect of aerobic aquatic activity towards the development of motor abilities, basic motor control, and occupational performance skills in children with CP. The study design was performed according to quasi-experimental design with control group pretest-posttest design. The study population was patients with CP that received rehabilitation treatment in occupational therapy unit YPAC Surakarta. Sampling using quota sampling with a sample size of 30 people. Analysis of data using paired samples t-test, Wilcoxon and Mann-Whitney using SPSS version 16.0. The average value of the change scores Bobath Chart and GMFM post-intervention aquatic aerobic activity amounted to 4.07 and 7.33, while the post-intervention land-based activity amounted to 0.80 and 1.53. The test results paired sample t-test for Bobath Chart scores and GMFM scores before and after intervention showed p-value <0.05. The results of the comparative analysis showed a significant difference (p-value <0.05) between the changes Bobath Chart scores and GMFM scores between the intervention group aquatic aerobic activity with land-based activity. Performance and satisfaction scores increased by 0.13 and 0.47 (aquatic aerobic activity) and 0.07 & 0.27 (land-based activity). Aquatic Aerobic Activity results in significant effect towards basic motor control, gross motor and occupational performance skills in children with CP.

Age-related disorders of sleep and motor control in the rat models of functionally distinct cholinergic neuropathology

We studied the impact of aging during sleep in the rat models of Alzheimer's (AD) and Parkinson's (PD) disease cholinergic neuropathology to determine the possible different and earlier onset of age-related sleep disorder during the neurodegenerative diseases vs. healthy aging.We used the bilateral nucleus basalis (NB) and pedunculopontine tegmental nucleus (PPT) lesioned rats as the in vivo models of functionally distinct cholinergic neuropathology, and we followed the impact of aging on sleep architecture, the electroencephalographic (EEG) microstructure and motor control across sleep/wake states.Our results have shown for the first time that the earliest signs of aging during distinct cholinergic neuropathology were expressed through a different and topographically specific EEG microstructure during rapid eye movement sleep (REM). EEG delta amplitude attenuation within the sensorimotor cortex (SMCx) during REM was the earliest sign of aging in the NB lesion. EEG sigma amplitude augmentation within the motor cortex (MCx) during REM was the earliest sign of aging in the PPT lesion. In addition, aging was differently expressed through the SMCx drive alterations, but it was commonly expressed through the MCx drive alterations during all sleep/wake states.Our study provided evidence of distinct REM sleep disorders and sleep state related cortical drives as the signs of aging onset during functionally distinct cholinergic neuropathologies (NB lesion vs. PPT lesion).

Постинсультная спастичность

Spasticity is a common complication of stroke that results in impairments and limitations in performance of activities and participation. Although it is an important problem, spasticity, defined as velocity-dependent muscle overactivity, is only one component of the upper motor neuron syndrome (UMNS). It is often related to other motor impairments, such as weakness, and disordered motor control, which magnify the functional impact of spasticity. The mere presence of spasticity is not enough reason to initiate treatment. A thoughtful assessment of the clinical picture and functional impairment is the first step in establishing a management strategy, followed by treatment goal setting. Patient engagement in goal setting is an important component of a collaborative management with the clinician. Various pharmacologic and surgical interventions have been used for a different clinical situations and indications with varying outcomes. The related evidence is presented, and specific practice recommendations are provided.

Trunk Impairment Scale -TIS precise tool for evaluating trunk motor deficit of stroke patients

Abstract Stroke causes impairment of brain function resulting in the disorder of motor control of the trunk. Assessment of the movement of a patient with hemiparesis poses many difficulties and limitations. A standard clinical neurological diagnosis does not provide an accurate assessment in terms of trunk deficit. This is the reason for the relatively small and insufficient monitoring of motor changes in patients. Post stroke assessment of the trunk is still insufficient despite the fact that disorders are a common problem in patients with stroke. Trunk function has been identified as an important early predictor of functional outcome after stroke. Trunk Impairment Scale-TIS is the only well-validated tool to examine a patient with hemiparesis taking into account qualitative and quantitative assessment of the trunk deficit. This scale consists of three subscales: static balance in sitting, dynamic balance sitting and coordination. TIS assesses existing compensation during motor tasks. The scale was translated into Polish and pre-adapted to clinical practice The scale supports clinical reasoning in terms of structure and function, body disorders and activity limitations of patients after stroke It appears that the introduction of scale in the clinical study for patients with stroke hemiplegia may not only affect the expansion of detailed documentation of motor deficits, but to support planning and carrying out appropriate (suitable) physiotherapy strategies.

Commentary: Noradrenaline and Dopamine Neurons in the Reward/Effort Trade-off: A Direct Electrophysiological Comparison in Behaving Monkeys.

Commentary: Noradrenaline and Dopamine Neurons in the Reward/Effort Trade-off: A Direct Electrophysiological Comparison in Behaving Monkeys.

Motor control investigation of dystonic cerebral palsy: A pilot study of passive knee trajectory.

The purpose of this study is to better understand dystonia in CP and be able to objectively distinguish between individuals who experience spasticity, dystonia, or a combination of these conditions while evaluating the effect of 2Hz vestibular stimulation. Selected outcome measures included knee ROM, angular velocity and acceleration and all measures increased post vestibular stimulation; these results are indications of a possible reduction in the level of disability. The current investigation also identified an unexpected and unique behavior of the knee in children with dystonic cerebral palsy (CP) that was noticed while administering the Pendulum Knee Drop test (PKD) at approximately 0.4 rad (a mid-angle between full extension and zero vertical). There was a catch-like phenomenon at the described mid-angle in dystonic individuals. These results may suggest that dystonia is not a velocity dependent hypersensitivity of reflexes, but may include position dependent muscle reflexes and co-contractions. This reinforces the need for a more precise objective measure or perhaps a modified measure such as a mid-angle PKD test. Furthermore, based on the results obtained through the modified technique, beneficial alterations can be made to the form of treatment such as: robotic therapy or physical therapy that specifically accommodates the unique motor control disorder in individuals with dystonic CP.

Limb apraxia and the "affordance competition hypothesis".

Limb apraxia, a disorder of higher order motor control, has long been a challenge for clinical assessment and understanding (Leiguarda and Marsden, 2000). The deficits originally described in limb apraxia (Liepmann, 1920) have been classified by the nature of the errors made by the patients leading to, namely, ideational and ideomotor apraxia. The dual stream hypothesis (Goodale and Milner, 1992) has been used to explain these categories: ideational apraxia is thought to relate to a deficit in the concept of a movement (coded in the ventral stream). Patients have difficulty using objects, sequencing actions to interact with them or pantomiming their use. Ideomotor apraxia, on the other hand, is thought to arise from problems in the accurate implementation of movements within the dorsal stream. One of the limitations on understanding apraxia is the failure by the clinical literature to draw on knowledge of the factors determining actions in the environment. Here we emphasize the role of affordance. There is much recent work indicating that our responses to stimuli are strongly influenced by the actions that the objects “afford”, based on their physical properties and the intentions of the actor (e.g., Tucker and Ellis, 1998). The concept of affordance, originally suggested by Gibson (1979) has been incorporated in a recent model of interactive behavior that draws from findings in non-human primates, namely the “affordance competition hypothesis” (Cisek, 2007). This postulates that interactive behavior arises by a process of competition between possible actions elicited by the environment. In this paper we argue that “affordance competition” may play a role in apraxia. We review evidence that at least some aspects of apraxia may reflect an abnormal sensitivity to competition when multiple affordances are present (Riddoch et al., 1998) and/or a poor ability to exert cognitive control over this competition when it occurs. This framework suggests a new way of conceptualizing deficits in apraxia which invites further investigations in the field.

Recasting brain-machine interface design from a physical control system perspective.

With the goal of improving the quality of life for people suffering from various motor control disorders, brain-machine interfaces provide direct neural control of prosthetic devices by translating neural signals into control signals. These systems act by reading motor intent signals directly from the brain and using them to control, for example, the movement of a cursor on a computer screen. Over the past two decades, much attention has been devoted to the decoding problem: how should recorded neural activity be translated into the movement of the cursor? Most approaches have focused on this problem from an estimation standpoint, i.e., decoders are designed to return the best estimate of motor intent possible, under various sets of assumptions about how the recorded neural signals represent motor intent. Here we recast the decoder design problem from a physical control system perspective, and investigate how various classes of decoders lead to different types of physical systems for the subject to control. This framework leads to new interpretations of why certain types of decoders have been shown to perform better than others. These results have implications for understanding how motor neurons are recruited to perform various tasks, and may lend insight into the brain’s ability to conceptualize artificial systems.

Relationship between subthalamic nucleus neuronal activity and electrocorticogram is altered in the R6/2 mouse model of Huntington's disease.

Neural synchrony between the subthalamic nucleus (STN) and cortex is critical for proper information processing in basal ganglia circuits. Using in vivo extracellular recordings in urethane-anaesthetized mice, we demonstrate that single units and local field potentials from the STN exhibit oscillatory entrainment to low-frequency (0.5-4Hz) rhythms when the cortex is in a synchronized state. Here we report novel findings in the R6/2 transgenic mouse model of Huntington's disease (HD) by demonstrating that STN activity is reduced and less phase-locked to cortical low-frequency oscillations. The spectral power of low-frequency oscillations in ECoG recordings of R6/2 mice is diminished while the spectral power of higher frequencies is augmented and such altered cortical patterning could lead to decreased synchrony in corticosubthalamic circuits. Our data establish that cortical entrainment of STN neural activity is disrupted in R6/2 mice and may be one of the mechanisms contributing to disordered motor control in HD. Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder in which impairments in the processing of information between the cortex and basal ganglia are fundamental to the onset and progression of the HD phenotype. The corticosubthalamic hyperdirect pathway plays a pivotal role in motor selection and blockade of neuronal activity in the subthalamic nucleus (STN) results in a hyperkinetic movement syndrome, similar to the HD phenotype. The aim of the present study was to examine the relationship between neuronal activity in the STN and cortex in an animal model of HD. We performed in vivo extracellular recordings in the STN to measure single-unit activity and local field potentials in the R6/2 transgenic mouse model of HD. These recordings were obtained during epochs of simultaneously acquired electrocorticogram (ECoG) in discrete brain states representative of global cortical network synchronization or desynchronization. Cortically patterned STN neuronal activity was less phase-locked in R6/2 mice, which is likely to result in less efficient coding of cortical inputs by the basal ganglia. In R6/2 mice, the power of the ECoG in lower frequencies (0.5-4Hz) was diminished while the power expressed in higher frequencies (13-100Hz) was increased. In addition, the spontaneous activity of STN neurons in R6/2 mice was reduced and neurons exhibited a more irregular firing pattern. Glutamatergic STN neurons provide the major excitatory drive to the output nuclei of the basal ganglia and altered discharge patterns could lead to aberrant basal ganglia output and disordered motor control in HD.

Accuracy and Precision of a Custom Camera-Based System for 2-D and 3-D Motion Tracking During Speech and Nonspeech Motor Tasks

PURPOSE Studying normal or disordered motor control requires accurate motion tracking of the effectors (e.g., orofacial structures). The cost of electromagnetic, optoelectronic, and ultrasound systems is prohibitive for many laboratories and limits clinical applications. For external movements (lips, jaw), video-based systems may be a viable alternative, provided that they offer high temporal resolution and submillimeter accuracy. METHOD The authors examined the accuracy and precision of 2-D and 3-D data recorded with a system that combines consumer-grade digital cameras capturing 60, 120, or 240 frames per second (fps), retro-reflective markers, commercially available computer software (APAS, Ariel Dynamics), and a custom calibration device. RESULTS Overall root-mean-square error (RMSE) across tests was 0.15 mm for static tracking and 0.26 mm for dynamic tracking, with corresponding precision (SD) values of 0.11 and 0.19 mm, respectively. The effect of frame rate varied across conditions, but, generally, accuracy was reduced at 240 fps. The effect of marker size (3- vs. 6-mm diameter) was negligible at all frame rates for both 2-D and 3-D data. CONCLUSION Motion tracking with consumer-grade digital cameras and the APAS software can achieve submillimeter accuracy at frame rates that are appropriate for kinematic analyses of lip/jaw movements for both research and clinical purposes.

A89: The Relationship Between Benign Joint Hypermobility Syndrome and Developmental Coordination Disorders in Children

Background/Purpose:Benign joint hypermobility syndrome (BJHS) is a heritable connective tissue disorder, which is characterised by excessive joint flexibility and musculoskeletal dysfunction.In childhood, BJHS has been linked clinically with disorders of motor control, however the association remains poorly characterised and the extent to which this reflects developmental variation remains uncertain. A systematic review found reduced lower limb joint proprioception in those with BJHS compared with non‐hypermobile cohorts with possible implications on co‐ordination.The purpose of this study was to examine baseline data from an interventional study of BJHS in childhood to assess the relationship between joint hypermobility and motor control.Methods:The study subjects included 119 children between the ages of 5 and 16 years. All had documented joint hypermobility (assessed by a paediatric rheumatologist) and musculoskeletal pain or dysfunction. Motor ability was assessed using the norm‐referenced Movement Assessment Battery for Children 2 (M‐ABC 2); a validated tool that identifies developmental coordination disorder. The assessment covers three domains: 1. Manual Dexterity 2. Ball Skills /throwing catching skills 3. Static and Dynamic Balance.The test contains eight activities for three age groups: 3–6 years; 7–10 years and 11–16 years.Total standard scores and percentiles were calculated using a standard scoring system.Children with age‐corrected scores falling below the 15th percentile were defined as having movement difficulty. Those that score below 5th Centile were classified as having significant movement difficulty.The child's functioning, including pain and wellbeing was assessed using the Childhood Health Assessment Questionnaire (CHAQ) which is a validated parent questionnaire for the use in children with juvenile idiopathic arthritis but was modified for use in this study.Results:Among the children with BJHS that were assessed, 32.8% scored ≤15 percentile on the M‐ABC (p<0.001). 18.4% scored less than or equal to 5% on the M‐ABC, suggesting they have significant movement difficulty. Movement difficulty was commoner in males (40%) than females (25%). The prevalence of movement difficulty was higher in younger subjects when compared with older children with BJHS (5 to 8 years = 41%; 9 to 12 years: 29%; 13 to 16: 19%). There was no correlation between degree of hypermobility and level of pain. The CHAQ score showed a moderate inverse correlation to the level of motor difficulty (r = −0.4186, R‐squared = 0.175, p < 0.01).Conclusion:Movement difficulty is a common independent component of BJHS in childhood. An evaluation of motor function needs to be included as part of the assessment of all children with BJHS and may merit targeted intervention as its presence represents a lower quality of functioning. Further research is needed into children with BJHS and movement difficulty, who may benefit from targeted interventions.

Oral-diadochokinesis rates across languages: English and Hebrew norms

Oro-facial and speech motor control disorders represent a variety of speech and language pathologies. Early identification of such problems is important and carries clinical implications. A common and simple tool for gauging the presence and severity of speech motor control impairments is oral-diadochokinesis (oral-DDK). Surprisingly, norms for adult performance are missing from the literature. The goals of this study were: (1) to establish a norm for oral-DDK rate for (young to middle-age) adult English speakers, by collecting data from the literature (five studies, N=141); (2) to investigate the possible effect of language (and culture) on oral-DDK performance, by analyzing studies conducted in other languages (five studies, N=140), alongside the English norm; and (3) to find a new norm for adult Hebrew speakers, by testing 115 speakers. We first offer an English norm with a mean of 6.2syllables/s (SD=.8), and a lower boundary of 5.4syllables/s that can be used to indicate possible abnormality. Next, we found significant differences between four tested languages (English, Portuguese, Farsi and Greek) in oral-DDK rates. Results suggest the need to set language and culture sensitive norms for the application of the oral-DDK task world-wide. Finally, we found the oral-DDK performance for adult Hebrew speakers to be 6.4syllables/s (SD=.8), not significantly different than the English norms. This implies possible phonological similarities between English and Hebrew. We further note that no gender effects were found in our study. We recommend using oral-DDK as an important tool in the speech language pathologist's arsenal. Yet, application of this task should be done carefully, comparing individual performance to a set norm within the specific language.Learning outcomes: Readers will be able to: (1) identify the Speech-Language Pathologist assessment process using the oral-DDK task, by comparing an individual performance to the present English norm, (2) describe the impact of language on oral-DDK performance, and (3) accurately detect Hebrew speakers’ patients using this tool.

Absent movement‐related cortical potentials in children with primary motor stereotypies

The underlying pathophysiologic mechanism for complex motor stereotypies in children is unknown, with hypotheses ranging from an arousal to a motor control disorder. Movement-related cortical potentials (MRCPs), representing the activation of cerebral areas involved in the generation of movements, precede and accompany self-initiated voluntary movements. The goal of this study was to compare cerebral activity associated with stereotypies to that seen with voluntary movements in children with primary complex motor stereotypies. Electroencephalographic (EEG) activity synchronized with video recording was recorded in 10 children diagnosed with primary motor stereotypies and 7 controls. EEG activity related to stereotypies and self-paced arm movements were analyzed for presence or absence of early or late MRCP, a steep negativity beginning about 1 second before the onset of a voluntary movement. Early MRCPs preceded self-paced arm movements in 8 of 10 children with motor stereotypies and in 6 of 7 controls. Observed MRCPs did not differ between groups. No MRCP was identified before the appearance of a complex motor stereotypy. Unlike voluntary movements, stereotypies are not preceded by MRCPs. This indicates that premotor areas are likely not involved in the preparation of these complex movements and suggests that stereotypies are initiated by mechanisms different from voluntary movements. Further studies are required to determine the site of the motor control abnormality within cortico-striatal-thalamo-cortical pathways and to identify whether similar findings would be found in children with secondary stereotypies.

Speech Science: Technique, Concept, Theory

The purpose of this paper is to outline a history and a possible future of speech science as a discipline. Two major and sometimes opposing views of speech science are discussed. One view is inspired by Stetson's work, and holds that study of speech movements is most likely to reveal the essentials of speech motor control. The other view regards the speech acoustic signal as part of the control mechanism; in this view, movements and the signals produced by them are intertwined as part of the control mechanism. The importance of understanding these two views of speech science is in the application of speech science skills to clinical disorders of speech motor control. The paper uses motor speech disorders as an example of how the two views can be joined empirically and theoretically for a maximally productive application of speech science to an understanding of disorders of speech motor control.

Apraxia.

The term apraxia refers to 'higher level' disorders of motor control. Apraxia differs from other motor symptoms of unilateral brain damage by the bilaterality of symptoms following unilateral lesions. Lesions causing apraxia are located predominantly in the left hemisphere and apraxia is frequently, although not invariably, associated with aphasia. Examination for apraxia traditionally assesses imitation of gestures, performance of communicative gestures on command, and use of tools and objects. It has, however, been amply demonstrated that these three domains can be affected more or less independently from each other. This review discusses current topics of research and controversy from each of these domains concentrating on questions that are relevant for determining the border between motor and cognitive mechanisms underlying apraxic errors. For imitation, the proposal of a direct link from perception to motor execution is confronted with the hypothesis that body part coding is interpolated between perception and motor replication of gestures. Discussion of communicative gestures concentrates on pantomime of tool use and argues that pantomime is not equivalent to reproduction of the motor programs of actual tool use but that pantomimes are created by selection and combination of distinctive features of the object and its use. For tool use the boundary between visuo-motor coordination and knowledge about tool use is addressed by discussion of the selection of grips for use or for transport of tools. WIREs Cogn Sci 2013, 4:453-462. doi: 10.1002/wcs.1241 For further resources related to this article, please visit the WIREs website. The author has declared no conflicts of interest for this article.

Contribution of hip joint proprioception to static and dynamic balance in cerebral palsy: a case control study

BackgroundBalance problems are common in cerebral palsy (CP) but etiology is often uncertain. The classic Romberg test compares ability to maintain standing with eyes open versus closed. Marked instability without vision is a positive test and generally indicates proprioceptive loss. From previous work showing diminished hip joint proprioception in CP, we hypothesized that static and dynamic balance without vision (positive Romberg) would be compromised in CP.MethodsForce plate sway and gait velocity data were collected using 3D motion capture on 52 participants, 19 with diplegic CP, 13 with hemiplegic CP, and 20 without disability. Center of mass (COM) and center or pressure (COP) velocity, excursion, and differences between COM and COP in AP and ML directions were computed from static standing trials with eyes open and closed. Mean gait velocity with and without dribble glasses was compared. Hip joint proprioception was quantified as the root mean square of magnitude of limb positioning errors during a hip rotation task with and without view of the limb. Mixed model repeated measures analysis of variance (ANOVA) was performed with condition as within-subject (EO, EC) and group as between-subject factors (hemiplegia, diplegia, controls). Sway characteristics and gait speed were correlated with proprioception values.ResultsGroups with CP had greater sway in standing with eyes open indicating that they had poorer balance than controls, with the deficit relatively greater in the ML compared to AP direction. Contrary to our hypothesis, the decrement with eyes closed did not differ from controls (negative Romberg); however, proprioception error was related to sway parameters particularly for the non-dominant leg. Gait speed was related to proprioception values such that those with worse proprioception tended to walk more slowly.ConclusionsPostural instability is present even in those with mild CP and is yet another manifestation of their motor control disorder, the specific etiology of which may vary across individuals in this heterogeneous diagnostic category.

Evidence for Altered Basal Ganglia-Brainstem Connections in Cervical Dystonia

BackgroundThere has been increasing interest in the interaction of the basal ganglia with the cerebellum and the brainstem in motor control and movement disorders. In addition, it has been suggested that these subcortical connections with the basal ganglia may help to coordinate a network of regions involved in mediating posture and stabilization. While studies in animal models support a role for this circuitry in the pathophysiology of the movement disorder dystonia, thus far, there is only indirect evidence for this in humans with dystonia.Methodology/Principal FindingsIn the current study we investigated probabilistic diffusion tractography in DYT1-negative patients with cervical dystonia and matched healthy control subjects, with the goal of showing that patients exhibit altered microstructure in the connectivity between the pallidum and brainstem. The brainstem regions investigated included nuclei that are known to exhibit strong connections with the cerebellum. We observed large clusters of tractography differences in patients relative to healthy controls, between the pallidum and the brainstem. Tractography was decreased in the left hemisphere and increased in the right hemisphere in patients, suggesting a potential basis for the left/right white matter asymmetry we previously observed in focal dystonia patients.Conclusions/SignificanceThese findings support the hypothesis that connections between the basal ganglia and brainstem play a role in the pathophysiology of dystonia.