Limb Apraxias: The Influence of Higher Order Perceptual and Semantic Deficits in Motor Recovery After Stroke.

Stroke is a leading cause of disability worldwide. Limb apraxia is a group of higher order motor disorders associated with greater disability and dependence after stroke. Original neuropsychology studies distinguished separate brain pathways involved in perception and action, known as the dual stream hypothesis. This framework has allowed a better understanding of the deficits identified in Limb Apraxia. In this review, we propose a hierarchical organization of this disorder, in which a distinction can be made between several visuomotor pathways that lead to purposeful actions. Based on this, executive apraxias (such as limb kinetic apraxia) cause deficits in executing fine motor hand skills, and intermediate apraxias (such as optic ataxia and tactile apraxia) cause deficits in reaching to grasp and manipulating objects in space. These disorders usually affect the contralesional limb. A further set of disorders collectively known as limb apraxias include deficits in gesture imitation, pantomime, gesture recognition, and object use. These deficits are due to deficits in integrating perceptual and semantic information to generate complex movements. Limb apraxias are usually caused by left-hemisphere lesions in right-handed stroke patients, affecting both limbs. The anterior- to posterior-axis of brain areas are disrupted depending on the increasing involvement of perceptual and semantic processes with each condition. Lower-level executive apraxias are linked to lesions in the frontal lobe and the basal ganglia, while intermediate apraxias are linked to lesions in dorso-dorsal subdivisions of the dorsal fronto-parietal networks. Limb apraxias can be caused by lesions in both dorsal and ventral subdivisions including the ventro-dorsal stream and a third visuomotor pathway, involved in body schema and social cognition. Rehabilitation of these disorders with behavioral therapies has aimed to either restore perceptuo-semantic deficits or compensate to overcome these deficits. Further studies are required to better stratify patients, using modern neurophysiology and neuroimaging techniques, to provide targeted and personalized therapies for these disorders in the future.

A fist bump in a political meeting? The influence of social context on affordance selection.

Historically, understanding human cognition such as action processing has been a challenging issue in cognitive neuropsychology and the more we know about cognition, the more we shape it as a complex, multi-determined phenomenon that is embedded in a social context. The present study aimed at understanding how the social context could influence affordance selection. We hypothesized that affordance selection would be modulated by social context and that a given hand configuration would be considered appropriate or not, as a function of the presence or absence of social context. Twenty-six healthy participants were asked to judge the appropriateness of three variants of 10 hand-object interactions based on photographs presented with or without a visual, social context. In our results, hand configurations were intrinsically acceptable or not, but this effect was modulated by the social context. A three-step model of the influence of social context on affordance selection was proposed, according to which selection depends on social norms, in the form of social knowledge and social context analysis.

Effects of limb apraxia intervention in patients with stroke: A meta-analysis of randomized controlled trials.

OBJECTIVE: Limb apraxia, a complication of stroke, causes difficulties in performing activities of daily living (ADL). To date, there are no studies on the effectiveness of limb apraxia interventions. We conducted a meta-analysis to assess the effectiveness of limb apraxia interventions in reducing its severity and improving ADL. METHODS: We conducted a search of randomized controlled trials (RCTs) related to limb apraxia till December 2021 using the databases of PubMed, Embase, CINAHL, and the Cochrane Library. We measured the outcome variables in the subgroups of total apraxia (TA), ideational apraxia (IA), ideomotor apraxia (IMA), and ADL. The Physiotherapy Evidence Database (PEDro) scale was used to assess the quality. RESULTS: Five RCTs were selected, and of the 310 participants, 155 were in the experimental and 155 in the control group. A random-effects model was used for the effect size distribution. The limb apraxia intervention methods included gesture and strategy training (three and two studies, respectively). The effect sizes of the outcome variables in the subgroups were small for the TA and IA, with 0.475 (95% confidence interval [CI]: -0.151-1.102; p = 0.137) and 0.289 (95% CI: -0.144-0.722; p = 0.191), respectively. IMA had a medium effect size of 0.731 (95% CI: -0.062-1.525; p = 0.071), not statistically significant, whereas ADL effect size was small and statistically significant, 0.416 (95% CI: 0.159-0.673; p = 0.002). CONCLUSIONS: Gesture and strategy training had statistically significant effects on ADL as limb apraxia interventions. Therefore, the effectiveness of the apraxia interventions needs to be further evaluated through continuous RCTs.

Treating limb apraxia via action semantics: a preliminary study.

Limb apraxia is evident in approximately 50% of patients after left hemisphere cerebral vascular accident (LCVA) and increases disability and caregiver dependence. Individuals with apraxia exhibit abnormalities in spatio-temporal aspects of gesture production and/or in knowledge of tool-related actions (action semantics). This preliminary study of three LCVA participants aimed to (i) explore the efficacy of a novel Action Network Treatment (ANT) that focused on improving the semantic association between tool actions and other types of tool knowledge, an intervention inspired by successful semantic network treatments in aphasia (e.g., Edmonds et al., 2009), and (ii) explore whether there are individuals with apraxia who benefit from ANT relative to a version of a comparatively well-studied existing apraxia treatment (Smania et al., 2006; Smania et al., 2000) that shapes gesture via focus on practicing the spatio-temporal aspects of gesture production (Tool Use Treatment or TUT). One participant demonstrated treatment benefits from both ANT and TUT, while another only benefited from TUT. These findings indicate that our novel semantic network strengthening approach to gesture training may be efficacious in at least some individuals with apraxia, and provide a foundation for future study of the characteristics of people with apraxia who benefit from each approach.

A combined therapy for limb apraxia and related anosognosia.

Left hemisphere stroke frequently leads to limb apraxia, a disorder that has been reported to impact independence in daily life and rehabilitation success. Nonetheless, there is a shortcoming in research and availability of applicable trainings. Further, to date, anosognosia for limb apraxia has largely been neglected. Therefore, we developed a Naturalistic Action Therapy that trains object selection and application with an errorless learning approach and which includes supported self-evaluation. The current study presents the results of two stroke patients participating in the training. The procedure entailed two baseline and one post-training sessions including standardized limb apraxia and anosognosia assessments as well as 18 naturalistic action tasks. The training consisted of 15 sessions during which 4-6 of the 18 naturalistic action tasks (e.g., pour water into a glass, make a phone call) were trained. Both patients showed improvement in trained and untrained tasks as well as in standardized apraxia and anosognosia assessments. Training effects appeared strongest for the trained items. The procedure is documented in detail and easy to administer and thus may have the potential to be applied by relatives. The results of this pilot-study are promising and suggest that the approach is suitable for further evaluation.

Limb Apraxia: a Disorder of Learned Skilled Movement.

PURPOSE OF REVIEW: This chapter focuses on limb apraxia, a cognitive-motor disorder of learned skilled movement, and the nature of the spatiotemporal errors that disrupt movement sequences. RECENT FINDINGS: A cognitive model that attempts to reconcile conceptual and preparatory aspects of the motor program with perceptual and kinematic features will be discussed. An update on the localization of the praxis network will be provided. In addition, a long-held view that limb apraxia does not have ecological relevance will be disputed in the context of studies that have shown that limb apraxia (i) is one of the most important predictors of increased caregiver burden and (ii) is associated with impaired activities of daily living in post-stroke patients. This review summarizes current screening tools and the few randomized clinical controlled treatment studies to date. Limb apraxia is underdiagnosed and very few therapeutic options are available. Cognitive process models should be used to inform future controlled multi-modal treatment strategies.

Critical Motor Involvement in Prediction of Human and Non-biological Motion Trajectories.

OBJECTIVES: Adaptive interaction with the environment requires the ability to predict both human and non-biological motion trajectories. Prior accounts of the neurocognitive basis for prediction of these two motion classes may generally be divided into those that posit that non-biological motion trajectories are predicted using the same motor planning and/or simulation mechanisms used for human actions, and those that posit distinct mechanisms for each. Using brain lesion patients and healthy controls, this study examined critical neural substrates and behavioral correlates of human and non-biological motion prediction. METHODS: Twenty-seven left hemisphere stroke patients and 13 neurologically intact controls performed a visual occlusion task requiring prediction of pantomimed tool use, real tool use, and non-biological motion videos. Patients were also assessed with measures of motor strength and speed, praxis, and action recognition. RESULTS: Prediction impairment for both human and non-biological motion was associated with limb apraxia and, weakly, with the severity of motor production deficits, but not with action recognition ability. Furthermore, impairment for human and non-biological motion prediction was equivalently associated with lesions in the left inferior parietal cortex, left dorsal frontal cortex, and the left insula. CONCLUSIONS: These data suggest that motor planning mechanisms associated with specific loci in the sensorimotor network are critical for prediction of spatiotemporal trajectory information characteristic of both human and non-biological motions. (JINS, 2017, 23, 171-184).

The Neuropsychology of Movement and Movement Disorders: Neuroanatomical and Cognitive Considerations.

This paper highlights major developments over the past two to three decades in the neuropsychology of movement and its disorders. We focus on studies in healthy individuals and patients, which have identified cognitive contributions to movement control and animal work that has delineated the neural circuitry that makes these interactions possible. We cover advances in three major areas: (1) the neuroanatomical aspects of the "motor" system with an emphasis on multiple parallel circuits that include cortical, corticostriate, and corticocerebellar connections; (2) behavioral paradigms that have enabled an appreciation of the cognitive influences on the preparation and execution of movement; and (3) hemispheric differences (exemplified by limb praxis, motor sequencing, and motor learning). Finally, we discuss the clinical implications of this work, and make suggestions for future research in this area. (JINS, 2017, 23, 768-777).

A Cognitive Overview of Limb Apraxia.

Since the first studies on limb apraxia carried out by Hugo Liepmann more than a century ago, research interests focused on the way humans process manual gestures by assessing gesture production after patients suffered neurologic deficits. Recent reviews centered their attention on deficits in gesture imitation or processing object-related gestures, namely pantomimes and transitive gestures, thereby neglecting communicative/intransitive gestures. This review will attempt to reconcile limb apraxia in its entirety. To this end, the existing cognitive models of praxis processing that have been designed to account for the complexity of this disorder will be taken into account, with an attempt to integrate in these models the latest findings in the studies of limb apraxia, in particular on meaningful gestures. Finally, this overview questions the very nature of limb apraxia when other cognitive deficits are observed.

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.

The effect of goals and vision on movements: a case study of optic ataxia and limb apraxia.

Normally we can perform a variety of goal-directed movements effortlessly. However, damage to the parietal cortex may dramatically reduce this ability, giving rise to optic ataxia and limb apraxia. Patients with optic ataxia show clear misreaches towards targets when presented in the peripheral visual field, whereas limb apraxia refers to the inability to use common tools or to imitate simple gestures. In the present paper we describe the case of a left-brain damaged patient, who presented both symptoms. We systematically investigated both spatial and temporal parameters of his movements, when asked to reach and grasp common objects to move (Experiment 1) or to use them (Experiment 2), presented either in the central or peripheral visual field. Different movement parameters changed in relation to the goal of the task (grasp to move vs. grasp to use), reflecting a normal modulation of the movement to accomplish tasks with different goals. On the other hand, grip aperture appeared to be more affected from both task goal and viewing condition, with a specific decrement observed when CF was asked to use objects presented peripherally. On the contrary, a neat effect of the viewing condition was observed in the spatial distribution of the end-points of the movements, and of the horizontal end point in particular, which were shifted towards the fixation point when reaching towards peripheral targets. We hypothesized that optic ataxia and limb apraxia have a differential effect on the patient's performance. The specific presence of optic ataxia would have an effect on the movement trajectory, but both symptoms might interact and influence the grasping component of the movement. As a 'cognitive side of motor control impairment', the presence of limb apraxia may have increased the task demands in grasping to use the objects thus exacerbating optic ataxia.

Clinical and MRI characterization of apraxic syndrome in corticobasal degeneration: A single-case study.

Objective: To identify the cortical and subcortical distribution of atrophy and the disorganization of white matter bundles underlying the apraxic disorders in a patient with corticobasal degeneration (CBD). Method: Patient underwent appropriate neuropsychological tasks aimed at identifying the nature of the apraxic disorder and morphometric structural MRI with whole-brain voxel-wise analysis. Results: Progressive limbkinetic apraxia (LKA) with onset in the right upper limb with subsequent extension to the limbs, trunk, orofacial district, and eye movements was documented, associated with element of ideomotor apraxia (IMA). The MRI study showed grey matter atrophy extending to much of the frontal cortex bilaterally, including the precentral cortex, and into the inferior parietal regions. Caudate and putamen were involved on the left. Significant clusters of white matter atrophy were found in the bilateral superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF) and corpus callosum (CC). Sensory evoked potentials (SEPs) and motor evoked potentials (MEPs) were normal. Conclusion: Previous observations in CBD indicate lack of inhibitory control from the sensory to the primary motor cortex with dysfunctional frontoparietal and cortico-motoneuron projections. Our neuroimaging data are partially consistent with these observations suggesting that the apraxic disorder in our patient might be produced by the disconnection of the primary motor cortex from the parietal areas that prevents selection and control of muscle movements, in the presence of preserved cortico-motoneuron as demonstrated by normal PEM. Apraxic disorders in CBD are high-level deficits of movement control that spare the motoneuron.

A preliminary study of white matter disconnections underlying deficits in praxis in left hemisphere stroke patients.

Limb apraxia is a higher-order motor disorder often occurring post-stroke, which affects skilled actions. It is assessed through tasks involving gesture production or pantomime, recognition, meaningless gesture imitation, complex figure drawing, single and multi-object use. A two-system model for the organisation of actions hypothesizes distinct pathways mediating praxis deficits via conceptual, 'indirect', and perceptual 'direct' routes to action. Traditional lesion- symptom mapping techniques have failed to identify these distinct routes. We assessed 29 left hemisphere stroke patients to investigate white matter disconnections on deficits of praxis tasks from the Birmingham Cognitive Screening. White matter disconnection maps derived from patients' structural T1 lesions were created using a diffusion-weighted healthy participant dataset acquired from the human connectome project (HCP). Initial group-level regression analyses revealed significant disconnection between occipital lobes via the splenium of the corpus callosum and involvement of the inferior longitudinal fasciculus in meaningless gesture imitation deficits. There was a trend of left fornix disconnection in gesture production deficits. Further, voxel-wise Bayesian Crawford single-case analyses performed on two patients with the most severe meaningless gesture imitation and meaningful gesture production deficits, respectively, confirmed distinct posterior interhemispheric disconnection, for the former, and disconnections between temporal and frontal areas via the fornix, rostrum of the corpus callosum and anterior cingulum, for the latter. Our results suggest distinct pathways associated with perceptual and conceptual deficits akin to 'direct' and 'indirect' action routes, with some patients displaying both. Larger studies are needed to validate and elaborate on these findings, advancing our understanding of limb apraxia.

Recovery of gestures for persons with severe non-fluent aphasia and limb apraxia: A long-term follow-up study.

Persons with severe non-fluent aphasia would benefit from using gestures to substitute for their absent powers of speech. The use of gestures, however, is challenging for persons with aphasia and concomitant limb apraxia. Research on the long-term recovery of gestures is scant, and it is unclear whether gesture performance can show recovery over time. This study evaluated the recovery of emblems and tool use pantomimes of persons with severe non-fluent aphasia and limb apraxia after a left hemisphere stroke. The Florida Apraxia Screening Test-Revised (FAST-R) was used for measurements. The test includes 30 gestures to be performed (i) after an oral request, (ii) with the aid of a pictorial cue, or (iii) as an imitation. The gestures were rated on their degree of comprehensibility. The comprehensibility of gestures after an oral request improved significantly in five out of seven participants between the first (1-3 months after the stroke) and the last (3 years after) examination. Improvement continued for all five in the period between six months and three years. The imitation model did improve the comprehensibility of gestures for all participants, whereas the pictorial cue did so just slightly. The skill of producing gestures can improve even in the late phase post-stroke. Because of this potential, we suggest that gesture training should be systematically included in the rehabilitation of communication for persons with severe non-fluent aphasia.

Gesture profiles distinguish primary progressive aphasia variants.

Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. There are three main variants of PPA - semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) - that can be challenging to distinguish. Limb praxis may also be affected in PPA, but it is unclear whether different variants of PPA are associated with differences in gesture production. Prior research with neurotypical individuals indicates that the left temporal lobe is a critical locus of manipulable object and hand posture representations. Moreover, when imitating gestures, individuals whose strokes include the left temporal lobe show reduced benefit of gesture meaning and disproportionate impairment in hand posture as compared to arm kinematics. We tested the hypothesis that svPPA - who typically exhibit primarily temporal lobe atrophy - would differentially show these expected patterns of gesture imitation performance. Nineteen participants with PPA completed meaningful and meaningless gesture imitation tasks, and performance was scored for hand posture and arm kinematics accuracy. Generalized logistic mixed-effect regression models controlling for dementia severity showed overall benefits from gesture meaning, and greater impairments in hand posture than arm kinematics. We also found that svPPA participants were the most impaired in gesture imitation overall. Critically, there was also a significant three-way interaction of group, meaning, and gesture component: only svPPA participants showed relative impairments of hand posture for meaningful gestures as well as meaningless gestures. Thus, unlike lvPPA and nfvPPA, the hand postures of svPPA failed to benefit from gesture meaning. This research extends prior findings on the role of the temporal lobe in hand posture representations associated with manipulable objects, and is the first to indicate that there may be distinct gesture imitation patterns as a function of PPA variant. Characterizing componential gesture deficits in PPA may help to inform differential diagnosis, compensatory communication strategies, and cognitive praxis models of PPA.

Shared and distinct routes in speech and gesture imitation: Evidence from stroke.

Dual-route models of high-level (praxis) actions distinguish between an "indirect" semantic route mediating meaningful gesture imitation, and a "direct" sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct route mediating non-word repetition. Although aphasia and limb apraxia frequently co-occur following left-hemisphere cerebrovascular accident (LCVA), it is unclear which aspects of these functional-neuroanatomic dual-route architectures are shared across praxis and language domains. This study focused on gesture imitation to test the hypothesis that semantic information (and portions of the indirect route) are shared across domains, whereas two distinct dorsal routes mediate sensory-motor mapping. Forty chronic LCVA and 17 neurotypical controls completed semantic memory and language tasks and imitated 3 types of gesture stimuli: (1) labeled/"named" meaningful, (2) unnamed meaningful, and (3) meaningless gestures. The comparison of accuracy between meaningless versus unnamed meaningful gestures examined the benefits of semantic information, while the comparison of unnamed meaningful versus named meaningful imitation examined additional benefits of linguistic cueing. Mixed-effects models examined group by task interaction effects on gesture ability. We found that for patients with LCVA, unnamed meaningful gestures were imitated more accurately than meaningless gestures, suggesting that semantic information was beneficial, but there was no benefit of labeling. Reduced benefit of semantic information on gesture accuracy was associated with lesions to inferior frontal and posterior temporal regions as well as semantic memory performance on a pictorial (non-gesture) task. In contrast, there was no relationship between meaningless gesture imitation and nonword repetition, indicating that measures of direct route performance are not associated across language and action. These results provide preliminary evidence that portions of the indirect semantic route are shared across the language and action domains, while two direct sensory-motor mapping routes mediate word repetition and gesture imitation.

The Impact of Upper Limb Apraxia on General and Domain-Specific Self-Efficacy in Post-Stroke Patients.

BACKGROUND: Upper limb apraxia (ULA) is a neurological syndrome characterized by the inability to perform purposeful movements. ULA could impact individuals' perceptions, including perceived self-efficacy. The aim of this study is to investigate whether ULA is related to general self-efficacy and self-efficacy for managing symptoms in post-stroke patients. METHODS: A cross-sectional study was conducted involving 82 post-stroke patients. Regression analyses were implemented using a stepwise model including seven dimensions of ULA: imitation (non-symbolic, intransitive, and transitive), pantomime (non-symbolic, intransitive, and transitive), and dimension of apraxic performance in activities of daily living. These dimensions were independent variables, while general self-efficacy and symptom management self-efficacy dimensions were dependent variables. RESULTS: The findings revealed that intransitive imitation accounted for 14% of the variance in general self-efficacy and 10% of self-efficacy for managing emotional symptoms. Transitive imitation explained 10% of the variance in self-efficacy for managing global symptoms and 5% for social-home integration symptoms. The combination of intransitive imitation, non-symbolic pantomime, and alterations in activities of daily living performance associated with ULA explained 24% of the variance in cognitive self-efficacy. CONCLUSIONS: Hence, ULA dimensions seem to be related to the levels of general perceived self-efficacy and self-efficacy for managing symptoms among post-stroke patients.

Single-case disconnectome lesion-symptom mapping: Identifying two subtypes of limb apraxia.

Influential theories of skilled action posit that distinct cognitive mechanisms and neuroanatomic substrates support meaningless gesture imitation and tool use pantomiming, and poor performance on these tasks are hallmarks of limb apraxia. Yet prior research has primarily investigated brain-behavior relations at the group level; thus, it is unclear whether we can identify individuals with isolated impairments in meaningless gesture imitation or tool use pantomiming whose performance is associated with a distinct neuroanatomic lesion profile. The goal of this study was to test the hypothesis that individuals with disproportionately worse performance in meaningless gesture imitation would exhibit cortical damage and white matter disconnection in left fronto-parietal brain regions, whereas individuals with disproportionately worse performance in tool use pantomiming would exhibit cortical damage and white matter disconnection in left temporo-parietal brain regions. Fifty-eight participants who experienced a left cerebrovascular accident took part in a meaningless gesture imitation task, a tool use pantomiming task, and a T1 structural MRI. Two participants were identified who had relatively small lesions and disproportionate impairments on one task relative to the other, as well as below-control-level performance on one task and not the other. Using these criteria, one participant was disproportionately impaired at meaningless gesture imitation, and the other participant was disproportionately impaired at pantomiming tool use. Graph theoretic analysis of each participant's structural disconnectome demonstrated that disproportionately worse meaningless gesture imitation performance was associated with disconnection among the left inferior parietal lobule, the left superior parietal lobule, and the left middle and superior frontal gyri, whereas disproportionately worse tool use pantomiming performance was associated with disconnection between left temporal and parietal regions. Our results demonstrate that relatively focal lesions to specific portions of the Tool Use Network can be associated with distinct limb apraxia subtypes.

The challenge of apraxia: Toward an operational definition?

The diagnosis of limb apraxia relies mainly on exclusion criteria (e.g., elementary motor or sensory deficits, aphasia). Due to the diversity of apraxia definitions and assessment methods, patients may or may not show apraxia depending on the chosen assessment method or theory, making the definition of apraxia somewhat arbitrary. As a result, "apraxia" may be diagnosed in patients with different cognitive impairments. Based on a quantitative and critical review of the literature, it is argued that this situation has its roots in the evolution from a task-based approach (i.e., the use of gold standard tests to detect apraxia) toward a process-based approach, namely, the deconstruction of the conceptual or production systems of action into multiple cognitive processes: language, executive functions, working memory, semantic memory, body schema, body image, visual-spatial skills, social cognition, visual-kinesthetic engrams, manipulation knowledge, technical reasoning, structural inference, and categorical apprehension. The coexistence of both approaches in the current literature is a major challenge that stands in the way of a scientific definition of apraxia. As a step toward a solution, we suggest to focus on symptoms, and on two complementary definition criteria (in addition with traditional exclusion criteria): Specificity (i.e., is apraxia explained by the alteration of cognitive processes specifically dedicated to gesture production?), and consistency (i.e., is the gesture production impairment consistent across tasks?). Two categories of limb apraxia are proposed: symptomatic apraxia (i.e., gesture production deficits that are secondary to more general cognitive impairments) and idiopathic apraxia (i.e., gesture production deficits that can be observed in isolation). It turns out that the only apraxia subtype that fulfills exclusion, specificity, and consistency criteria is limb-kinetic apraxia. A century after Liepmann's demonstration of the autonomy of apraxia toward language, the autonomy of this syndrome toward the rest of cognition remains an open question, while it poses new challenges to apraxia studies.