A connectivity model of the anatomic substrates underlying ideomotor apraxia: A meta-analysis of functional neuroimaging studies.

BACKGROUND: Patients with ideomotor apraxia (IMA) present with selective impairments in higher-order motor cognition and execution without damage to any motor or sensory pathways. Although extensive research has been conducted to determine the regions of interest (ROIs) underlying these unique impairments, previous models are heterogeneous and may be further clarified based on their structural connectivity, which has been far less described. OBJECTIVE: The goal of this research is to propose an anatomically concise network model for the neurophysiologic basis of IMA, specific to the voluntary pantomime, imitation and tool execution, based on intrinsic white matter connectivity. METHODS: We utilized meta-analytic software to identify relevant ROIs in ideomotor apraxia as reported in the literature based on functional neuroimaging data with healthy participants. After generating an activation likelihood estimation (ALE) of relevant ROIs, cortical parcellations overlapping the ALE were used to construct an anatomically precise model of anatomic substrates using the parcellation scheme outlined by the Human Connectome Project (HCP). Deterministic tractography was then performed on 25 randomly selected, healthy HCP subjects to determine the structural connectivity underlying the identified ROIs. RESULTS: 10 task-based fMRI studies met our inclusion criteria and the ALE analysis demonstrated 6 ROIs to constitute the IMA network: SCEF, FOP4, MIP, AIP, 7AL, and 7PC. These parcellations represent a fronto-parietal network consisting mainly of intra-parietal, U-shaped association fibers (40%) and long-range inferior fronto-occipital fascicle (IFOF) fibers (50%). These findings support previous functional models based on dual-stream motor processing. CONCLUSION: We constructed a preliminary model demonstrating the underlying structural interconnectedness of anatomic substrates involved in higher-order motor functioning which is seen impaired in IMA. Our model provides support for previous dual-stream processing frameworks discussed in the literature, but further clarification is necessary with voxel-based lesion studies of IMA to further refine these findings.

A pilot study of fascia Bowen therapy for 8-11 year-old boys with developmental coordination disorder.

BACKGROUND: Developmental coordination disorder (DCD), also known as dyspraxia, is a disorder emerging in childhood characterised by motor skill impairments. The motor difficulties often produce negative effects in other areas of life, such as poor self-esteem and reduced social interactions. One treatment used for DCD is fascia Bowen therapy, which involves stimulating the fascia tissues of the body using finger and thumb rolling movements over the skin to improve overall muscle movement. However, no studies to date have been reported testing the effectiveness of fascia Bowen in DCD. METHODS: The present pilot study tested the effectiveness of 6 weeks of fascia Bowen in 10 boys aged 8-11 years with DCD. None of the boys had ever received treatment in any form before this study. Motor skills were assessed using the Movement Assessment Battery for Children-2 (MABC-2) and the DCD questionnaire, and psycho-social functioning was measured using the Self-Perception Profile, Spence Social Skills Questionnaire, and Strengths and Difficulties Questionnaire. All measures of interest were assessed before and after the therapy. RESULTS: Results showed significant improvement in motor function post-intervention, with 60% of the children no longer clinically being classified as having a movement difficulty on the MABC-2. However, no significant improvements were seen in psycho-social measures, at least within the short time-frame of the therapy in the current study. CONCLUSIONS: The current pilot study revealed improvements in motor functioning after fascia Bowen therapy, across both performance and questionnaire measures, but that these improvements did not extend to wider areas of life. Further research in DCD is needed to test the effectiveness of fascia Bowen in larger studies with expanded ages and both genders over longer periods, including the generalisation of results of these longer interventions to different areas of life beyond motor ability.

Parietal Involvement in Constructional Apraxia as Measured Using the Pentagon Copying Task.

Deficits in copying ("constructional apraxia") is generally defined as a multifaceted deficit. The exact neural correlates of the different types of copying errors are unknown. To assess whether the different categories of errors on the pentagon drawing relate to different neural correlates, we examined the pentagon drawings of the MMSE in persons with subjective cognitive complaints, mild cognitive impairment, or early dementia due to Alzheimer's disease. We adopted a qualitative scoring method for the pentagon copy test (QSPT) which categorizes different possible errors in copying rather than the dichotomous categories "correct" or "incorrect." We correlated (regional) gray matter volumes with performance on the different categories of the QSPT. Results showed that the total score of the QSPT was specifically associated with parietal gray matter volume and not with frontal, temporal, and occipital gray matter volume. A more fine-grained analysis of the errors reveals that the intersection score and the number of angles share their underlying neural correlates and are associated with specific subregions of the parietal cortex. These results are in line with the idea that constructional apraxia can be attributed to the failure to integrate visual information correctly from one fixation to the next, a process called spatial remapping.

Motor experience influences object knowledge.

An object's perceived readiness-for-action (e.g., its size, the degree of rotation from its canonical position, the user's viewpoint) can influence semantic knowledge retrieval. Yet, the organization of object knowledge may also be affected by body-specific sensorimotor experiences. Here, we investigated whether people's history of performing motor actions with their hands influences the knowledge they store and retrieve about graspable objects. We compared object representations between healthy right- and left-handers (Experiment 1), and between unilateral stroke patients, whose motor experience was changed by impairment of either their right or left hand (Experiment 2). Participants saw pictures of graspable everyday items with the handles oriented toward either the left or right hand, and they generated the type of grasp they would employ (i.e., clench or pinch) when using each object, responding orally. In both experiments, hand dominance and object orientation interacted to predict response times. In Experiment 1, judgments were fastest when objects were oriented toward the right hand in right-handers, but not in left-handers. In Experiment 2, judgments were fastest when objects were oriented toward the left hand in patients who had lost the use of their right hand, even though these patients were right-handed prior to brain injury. Results suggest that at least some aspects of object knowledge are determined by motor experience, and can be changed by new patterns of motor experience. People with different bodily characteristics, who interact with objects in systematically different ways, form correspondingly different neurocognitive representations of the same common objects. (PsycINFO Database Record

A critical review of closing-in.

When performing complex actions, like graphic copying or imitation of gestures, some patients may perform these actions very close to, or directly on the top of the model. This peculiar behavior, known as closing-in, is the focus of the present literature review, which will provide a critical picture of the research in this field, highlighting the difficulties in defining and assessing closing-in and the contrasting results about the nature and the characteristics of this phenomenon. Most importantly, we will discuss the 2 hypotheses proposed to explain closing-in, namely the compensation and the attraction account, in light of the most recent work. This critical review will provide substantial evidence that closing-in represent a primitive default tendency in which movements are attracted toward the focus of attention. On the other hand, the possibility that this interpretation might not be fully exhaustive and that different components of closing-in might exist will also be discussed. (PsycINFO Database Record

Improving ideomotor limb apraxia by electrical stimulation of the left posterior parietal cortex.

Limb apraxia, a deficit of planning voluntary gestures, is most frequently caused by damage to the left hemisphere, where, according to an influential neurofunctional model, gestures are planned, before being executed through the motor cortex of the hemisphere contralateral to the acting hand. We used anodal transcranial direct current stimulation delivered to the left posterior parietal cortex (PPC), the right motor cortex (M1), and a sham stimulation condition, to modulate the ability of six left-brain-damaged patients with ideomotor apraxia, and six healthy control subjects, to imitate hand gestures, and to perform skilled hand movements using the left hand. Transcranial direct current stimulation delivered to the left PPC reduced the time required to perform skilled movements, and planning, but not execution, times in imitating gestures, in both patients and controls. In patients, the amount of decrease of planning times brought about by left PPC transcranial direct current stimulation was influenced by the size of the parietal lobe damage, with a larger parietal damage being associated with a smaller improvement. Of interest from a clinical perspective, left PPC stimulation also ameliorated accuracy in imitating hand gestures in patients. Instead, transcranial direct current stimulation to the right M1 diminished execution, but not planning, times in both patients and healthy controls. In conclusion, by using a transcranial stimulation approach, we temporarily improved ideomotor apraxia in the left hand of left-brain-damaged patients, showing a role of the left PPC in planning gestures. This evidence opens up novel perspectives for the use of transcranial direct current stimulation in the rehabilitation of limb apraxia.

Progression of limb apraxia in corticobasal syndrome: neuropychological and functional neuroimaging report of a case series.

The current study described the progression of limb apraxia in seven corticobasal syndrome patients through a comprehensive battery, including both gesture production tasks and conceptual tool/action knowledge tasks. The examination of the behavioral and neuroimaging (SPECT) data revealed two patient subgroups. One group consisted of patients with preserved conceptual tool/action knowledge, relatively mild gesture production and neuropsychological deficits with few significantly hypoperfused regions of interest. The other group consisted of those whose conceptual tool/action knowledge and general cognition eventually deteriorated and who were quite severely affected in their gesture production performance. These patients were characterized by bilateral hypoperfusion in parietal regions and in one case bilateral anterior cingulate regions.

Cognitive performance is impaired in coeliac patients on gluten free diet: a case-control study in patients older than 65 years of age.

INTRODUCTION: Retrospective studies and case reports suggest an association between coeliac disease and impaired cognitive function. AIM: To evaluate functional and cognitive performances in coeliac disease vs. control patients older than 65 years. METHOD: Eighteen coeliac disease patients (75±4 years, group A) on gluten free diet since 5.5±3 years and 18 age-sex matched controls (76±4 years, group B) were studied using a battery of neuropsychological tests. Results of functional and cognitive tests are expressed as "row scores" and as "equivalent scores" by relating "raw scores" to reference rank categories. RESULTS: Barthel Index of functional performance was similar in the 2 groups. "Raw score" was significantly lower in coeliac disease than controls for Mini Mental Test Examination (p=0.02), Trail Making Test (p=0.001), Semantic Fluency (p=0.03), Digit Symbol Test (p=0.007), Ideo-motor apraxia (p<0.001) and Bucco-facial apraxia (p<0.002). "Equivalent score" was also lower in coeliac disease than controls for Semantic memory (p<0.01) and for Ideo-motor apraxia (p=0.007). CONCLUSION: Cognitive performance is worse in elderly coeliac disease than control patients, despite prolonged gluten avoidance in coeliacs. Awareness on the increasing phenomenon of late-onset coeliac disease is important to minimize diagnostic delay and prolonged exposure to gluten that may adversely and irreversibly affect cognitive function.

Gesture comprehension, knowledge and production in Alzheimer's disease.

BACKGROUND AND PURPOSE: Although apraxia is a typical consequence of Alzheimer's disease (AD), the profile of apraxic impairments is still subject to debate. Here, we analysed apraxia components in patients with AD with mild-to-moderate or moderately severe dementia. METHODS: Thirty-one patients were included. We first evaluated simple gestures, that is, the imitation of finger and hand configurations, symbolic gestures (recognition, production on verbal command and imitation), pantomimes (recognition, production on verbal command, imitation and production with the object), general knowledge and complex gestures (tool-object association, function-tool association, production of complex actions and knowledge about action sequences). Tests for dementia (Mini Mental State Examination and the Dementia Rating Scale), language disorders, visual agnosia and executive function were also administered. RESULTS: Compared with controls, patients showed significant difficulties (P ≤ 0.01) in subtests relating to simple gestures (except for the recognition and imitation of symbolic gestures). General knowledge about tools, objects and action sequences was less severely impaired. Performance was frequently correlated with the severity of dementia. Multiple-case analyses revealed that (i) the frequency of apraxia depended on the definition used, (ii) ideomotor apraxia was more frequent than ideational apraxia, (iii) conceptual difficulties were slightly more frequent than production difficulties in the early stage of AD and (iv) difficulties in gesture recognition were frequent (especially for pantomimes). CONCLUSION: Patients with AD can clearly show gesture apraxia from the mild-moderate stage of dementia onwards. Recognition and imitation disorders are relatively frequent (especially for pantomimes). We did not find conceptual difficulties to be the main problem in early-stage AD.

Dyspraxia series: part one. At sixes and sevens.

Developmental Co-ordination Disorder (DCD), also known as Dyspraxia in the UK, is a common disorder affecting motor co-ordination in children and for many continues into adulthood. This condition is formally recognised by international organisations including the World Health Organisation. DCD is distinct from other motor disorders such as cerebral palsy and stroke. The range of intellectual ability is in line with the general population. Individuals may vary in how their difficulties present. The co-ordination difficulties may affect participation and functioning of everyday life skills in education, work and employment. Children may present with difficulties in writing, typing, riding a bike, self care tasks, and recreational activities. In adulthood many of these difficulties will continue, as well as learning new skills at home and work such as planning, organisation, driving a car and DIY.

A new approach to rhythm cueing of cognitive functions: the case of ideomotor apraxia.

Although positive effects of rhythm cueing on motor control in neurologic disorders are known, no studies have yet focused on patients suffering from impaired programming of complex actions. One patient suffering from ideomotor apraxia (a potentially ideal experimental paradigm to test the effect of rhythm on high-level motor control) underwent two rehabilitation training sets differing only for the presence or absence of rhythm cueing. Both sets of training increased the patient's proficiency, but rhythm cueing was significantly more effective, during the training as well as during the post-training uncued test. Ideomotor apraxia represents an effective model to test the effects of rhythm on high-level motor control.

Disorders of the perceptual-motor system.

The study of patients with movement disorders provides insight into both the functional organization and the neural substrates of the perceptual-motor system. By and large, we feel this source of information has been underutilized within the basic science of motor control. To begin to address this shortcoming, this chapter reviews three disorders of the perceptual-motor system (disorders of the body schema, optic ataxia, and ideomotor apraxia) and illustrates how the study of these disorders can inform central issues within the field of motor control. These issues include (1) the need for the perceptual-motor system to maintain a representation of the body's current configuration in order to produce movements, (2) the use of visual information in movement production, (3) the coordinate frame in which movements are controlled, (4) the distinction between movement planning and online correction, and (5) the role of the parietal cortex in action. In the conclusion, we discuss several limitations of studying patients with movement disorders as well as suggest that greater communication is needed between researchers in the basic science of motor control and clinicians developing treatments for movement disorders.

A model-based approach to understanding apraxia in Corticobasal Syndrome.

Limb apraxia is a neurological disorder of higher cognitive function characterized by an inability to perform purposeful skilled movements and not attributable to an elementary sensorimotor dysfunction or comprehension difficulty. Corticobasal Syndrome (CBS) is an akinetic rigid syndrome with asymmetric onset and progression with at least one basal ganglia feature (rigidity, limb dystonia or myoclonus) and one cortical feature (limb apraxia, alien hand syndrome or cortical sensory loss). Even though limb apraxia is highly prevalent in CBS (70-80%), very few studies have examined the performance of CBS patients on praxis measures in detail. This review aims to (1) briefly summarize the clinical, neuroanatomical and pathological findings in CBS, (2) briefly outline what limb apraxia is and how it is assessed, (3) to comprehensively review the literature on limb apraxia in CBS to date and (4) to briefly summarize the literature on other forms of apraxia, such as limb-kinetic apraxia and buccofacial apraxia. Overall, the goal of the review is to bring a model-based perspective to the findings available in the literature to date on limb apraxia in CBS.

Progressive asymmetric apraxic agraphia.

BACKGROUND/OBJECTIVES: Patients with apraxic agraphia cannot correctly form the letters needed to write words but can correctly spell words orally. Apraxic agraphia (AA) is often associated with ideomotor apraxia and most commonly induced by stroke, but can be associated with degenerative diseases. In degenerative diseases, asymmetrical apraxic agraphia (AAA) has rarely been reported as one of the presenting features. The purpose of this report is to describe a case series of 3 patients who presented with an AAA, and also to elucidate some of the cognitive mechanisms of this disorder. METHODS/RESULTS: These patients, who were not aphasic or alexic, developed agraphia as one of their earliest reported symptoms. They also demonstrated an asymmetrical ideomotor apraxia. Their agraphia was characterized by the inability to form letters, with the preserved ability to orally spell. To learn if this disorder was being caused by a loss of spatial-movement representations versus an impairment of implementation, one patient was asked to determine if gestures made by the examiner were correct or incorrect, and also to image the structure of letters. He performed poorly on both these tests and he also demonstrated an asymmetrical agraphesthesia. CONCLUSIONS: These patients' AAA might be the beginning of the corticobasal degeneration syndrome, but future studies will have to examine the brain pathology associated with AAA. Our patient's poor performance on pantomime recognition and imagery suggests that his apraxia is related to a deterioration of his graphemic and transitive spatial movement representations. The recognition of numbers written on the hand with eyes closed might also depend on having intact movement representations and his asymmetrical agraphesthesia might also be related to his AAA.

Ideomotor limb apraxia in Huntington's disease: a case-control study.

INTRODUCTION: Ideomotor limb apraxia is the disturbance of planning and of execution of motor activity,which is not caused by a dysfunction of the motor or sensory nervous system. Apraxia is a diagnostic criterion in dementialike Alzheimer's disease. However, this symptom may also occur in dementia with subcortical lesions like Huntington's disease (HD), a hereditary, devastating neurodegenerative disease leading to neurological and psychiatric dysfunction. The aim of our study is to determine the correlation between the occurrence of ideomotor limb apraxia and neuropsychological deficits in HD. METHODS: To assess the correlation between apraxia and neuropsychological abilities in HD, 41 patients with HD and 33 age- and sex-matched controls were examined. The De Renzi test for apraxia and an apraxia test battery containing tests of i) imitation of meaningless gestures of hands, ii) imitation of meaningless gestures of fingers, iii) performance of meaningful gestures on demand, and iv) pantomime of tool use were used to assess apraxia. Moreover, neuropsychological function was rated by the Mini Mental State Examination (MMSE), the Rey Complex Figure Memory Test, the Trail Making Test A and B, the California Verbal Learning Test (German version), the Stroop Color and Word Test, the Controlled Oral Word Association Test, and the Mehrfachwahl- Wortschatz-Intelligenztest for measuring verbal intelligence. Motor function was assessed in all HD patients by the Unified HD Rating Scale (UHDRS), rating oculomotor and orolingual function, fine motor tasks, parkinsonism, dystonia, chorea and statics and gait. RESULTS: Apraxic HD patients showed worse results than non-apraxic HD patients in three items of the Rey Complex Figure Memory Test (Organisation, short-term and longterm memory), but not in other assessed neuropsychological tests. In assessment of meaningful gestures on demand 39.3% of HD patients were apraxic, in assessment of pantomime of tool use 67.9% of HD patients showed apraxia. Patients with HD showed highly significant worse results than controls in the De Renzi test, in hands' and fingers' imitation, in performance of gestures on demand, in pantomime of tool use and every neuropsychological test except for the test measuring verbal intelligence. Apraxic HD patients showed worse results than non-apraxic HD patients in the UHDRS total motor score and the score for oculomotor function. CONCLUSION: This is the largest study on apraxia in HD. Ideomotor limb apraxia is a common sign in HD patients, occurring in a high percentage. In contrast to the opinion of several authors, occurrence of apraxia in HD is independent from neuropsychological decline and the severity of most neurological symptoms.

Interactions between perception and action programming: evidence from visual extinction and optic ataxia.

We report a series of 7 experiments examining the interaction between visual perception and action programming, contrasting 2 neuropsychological cases: a case of visual extinction and a case with extinction and optic ataxia. The patients had to make pointing responses to left and right locations, whilst identifying briefly presented shapes. Different patterns of performance emerged with the two cases. The patient with "pure" extinction (i.e., extinction without optic ataxia) showed dramatic effects of action programming on perceptual report. Programming an action to the ipsilesional side increased extinction (on 2-item trials) and tended to induce neglect (on 1-item trials); this was ameliorated when the action was programmed to the contralesional side. Separable effects of using the contralesional hand and pointing to the contralesional side were apparent. In contrast, the optic ataxic patient showed few effects of congruency between the visual stimulus and the action, but extinction when an action was programmed. This effect was particularly marked when actions had to be made to peripheral locations, suggesting that it reflected reduced resources to stimuli. These effects all occurred using stimulus exposures that were completed well before actions were effected. The data demonstrate interactions between action programming and visual perception. Programming an action to the affected side with the contralesional limb reduces "pure" extinction because attention is coupled to the end point of the action. However, in a patient with deficient visuo-motor coupling (optic ataxia), programming an action can increase a spatial deficit by recruiting resources away from perceptual processing. The implications for models of perception and action are discussed.

Retrieval by a patient with apraxia of sensorimotor information from visually presented objects.

Motor representations are reported to be implicitly evoked when one observes manipulatable objects (action potentiation). The relationship was examined between action potentiation and pantomime deficit in apraxia. Participants responded to line drawings of manipulatable objects with either the left or right hand, according to the color of the stimulus. In normal participants (N= 10, four women, six men, M age = 28.5 yr., SD = 5.6), responses were faster when the orientation of the stimulus was compatible with the response-hand grasp. However, the apraxic patient did not exhibit this compatibility effect. On a control task in which a nonobject (circle) was presented, all participants exhibited the compatibility effect. These results indicated that the apraxic patient was impaired in evoking motor representation associated with objects. Thus, in some cases, apraxic disorders may be attributable to a deficit in retrieving object-specific information for manipulation.

Neuropsychological evidence for a strategic control of multiple routes in imitation.

Previous studies have suggested that imitators can reproduce known gestures shown by a model using a semantic, indirect route, and novel gestures using a sublexical, direct route. In the present study we aimed at testing the validity of such a dual-route model of action imitation. Patients with either left-brain damage (LBD) or right-brain damage (RBD) were tested on an action imitation task. Actions were either meaningful (n = 20) or meaningless (n = 20), and were presented in an intermingled list and, on a different day, in separate lists. We predicted that, in the mixed condition, patients would use a direct route to imitate meaningful and meaningless actions, as it allows the imitation of both action types. In the blocked condition, patients were expected to select the semantic route for meaningful actions and the direct route for meaningless actions. As hypothesized, none of the 32 patients showed dissociations between imitation of meaningful and meaningless actions in the mixed presentation. In contrast, eight patients showed a dissociation between imitation of meaningful actions and imitation of meaningless actions in the blocked presentation. Moreover, two of these patients showed a classical double dissociation between the imitation of the two action types. Results were interpreted in support of the validity of a dual-route model for explaining action imitation. We argue that the decrease in imitation of meaningful actions, relative to meaningless actions, is caused by a damage of the semantic route, and that the decline in imitation of meaningless actions, relative to meaningful actions, is produced by a breakdown of the direct route. The brain areas that were lesioned in all six LBD patients who showed a dissociation were in the superior temporal gyrus and the angular gyrus, whereas the two RBD subjects had common lesions of the pallidum and of the putamen. The brain structures affected in our patients with selective apraxia are consistent with those reported before in other neuropsychological reports. They are also in agreement with areas found activated in imaging studies in which the neural mechanisms underlying imitation were examined.

'Directional apraxia': a unitary account of mirror writing following brain injury or as found in normal young children.

Mirror writing refers to the production of individual letters, whole words or sentences in reverse direction. Unintentional mirror writing has been observed in young children and brain-damaged people and interpreted as the manifestation of different cognitive impairments. We report on a mirror writing patient following left hemisphere stroke and the mirror writing phenomena in one sample of children learning to write. We propose a unitary account of mirror writing as the unavailability of the appropriate movement direction representation, either because the right configuration has yet to be specified fully (children learning to write) or because of its damage (acquired brain injury). For this reason, we propose that the lack of directional information relevant to writing be labelled 'directional apraxia'.