Facets of Pantomime.

OBJECTIVES: Exploring the nature of defective pantomime in apraxia. METHODS: Critical review of behavioral associations and dissociations between defective pantomime, imitation of gestures, and real tool use. Analysis of congruencies between crucial lesions for pantomime, imitation, and tool use. RESULTS: There are behavioral double dissociations between pantomime and imitation, and their cerebral substrates show very little overlap. Whereas defective pantomime is bound to temporal and inferior frontal lesions, imitation is mainly affected by parietal lesions. Pantomime usually replicates the motor actions of real use but on scrutiny there are important differences between the movements of real use and of pantomime that cast doubt on the assumption that pantomime is produced by the same motor programs as actual use. A more plausible proposal posits that pantomime is a communicative gesture that uses manual actions for conveying information about objects and their use. The manual actions are constructed by selection and combination of distinctive features of tools and actions. They frequently include replications of characteristic motor actions of real use, but the main criterion for selection and modification of features is the comprehensibility of the gestures rather than the accurate replication of the motor actions of real use. CONCLUSIONS: Pantomime of tool use is a communicative gesture rather than a replication of the motor actions of real use. (JINS, 2017, 23, 121-127).

The ventral fiber pathway for pantomime of object use.

The current concept of a dual loop system of brain organization predicts a domain-general dual-pathway architecture involving dorsal and ventral fiber connections. We investigated if a similar dichotomy of brain network organization applies for pantomime (P) and imitation of meaningless gestures (I). Impairments of these tasks occur after left hemispheric brain lesions causing apraxia. Isolated impairments and double-dissociations point towards an anatomical segregation. Frontal and parietal areas seem to contribute differently. A special role of the inferior frontal gyrus and underlying fiber pathways was suggested recently. Using a combined fMRI/DTI-approach, we compared the fiber pathway architecture of left hemispheric frontal, temporal and parietal network components of pantomime and imitation. Thereby, we separated object effects from pantomime-specific effects. P and I both engage a fronto-temporo-parietal network of cortical areas interconnected by a dorsal fiber system (superior longitudinal fascicle) for direct sensory-motor interactions. The pantomime-specific effect additionally involved the triangular part of the inferior frontal gyrus, the middle temporal gyrus, the inferior parietal cortex and the intraparietal sulcus, interconnected by ventral fibers of the extreme capsule, likely related to higher-order conceptual and semantic operations. We discuss this finding in the context of the dual loop model and recent anatomical concepts.

Apraxia in left-handers.

In typical right-handed patients both apraxia and aphasia are caused by damage to the left hemisphere, which also controls the dominant right hand. In left-handed subjects the lateralities of language and of control of the dominant hand can dissociate. This permits disentangling the association of apraxia with aphasia from that with handedness. Pantomime of tool use, actual tool use and imitation of meaningless hand and finger postures were examined in 50 consecutive left-handed subjects with unilateral hemisphere lesions. There were three aphasic patients with pervasive apraxia caused by left-sided lesions. As the dominant hand is controlled by the right hemisphere, they constitute dissociations of apraxia from handedness. Conversely there were also three patients with pervasive apraxia caused by right brain lesions without aphasia. They constitute dissociations of apraxia from aphasia. Across the whole group of patients dissociations from handedness and from aphasia were observed for all manifestations of apraxia, but their frequency depended on the type of apraxia. Defective pantomime and defective tool use occurred rarely without aphasia, whereas defective imitation of hand, but not finger, postures was more frequent after right than left brain damage. The higher incidence of defective imitation of hand postures in right brain damage was mainly due to patients who had also hemi-neglect. This interaction alerts to the possibility that the association of right hemisphere damage with apraxia has to do with spatial aptitudes of the right hemisphere rather than with its control of the dominant left hand. Comparison with data from right-handed patients showed no differences between the severity of apraxia for imitation of hand or finger postures, but impairment on pantomime of tool use was milder in apraxic left-handers than in apraxic right-handers. This alleviation of the severity of apraxia corresponded with a similar alleviation of the severity of aphasia as manifested by a lower proportion of left-handed patients with global aphasia.

Speech and Nonspeech Parameters in the Clinical Assessment of Dysarthria: A Dimensional Analysis.

Nonspeech (or paraspeech) parameters are widely used in clinical assessment of speech impairment in persons with dysarthria (PWD). Virtually every standard clinical instrument used in dysarthria diagnostics includes nonspeech parameters, often in considerable numbers. While theoretical considerations have challenged the validity of these measures as markers of speech impairment, only a few studies have directly examined their relationship to speech parameters on a broader scale. This study was designed to investigate how nonspeech parameters commonly used in clinical dysarthria assessment relate to speech characteristics of dysarthria in individuals with movement disorders. Maximum syllable repetition rates, accuracies, and rates of isolated and repetitive nonspeech oral-facial movements and maximum phonation times were compared with auditory-perceptual and acoustic speech parameters. Overall, 23 diagnostic parameters were assessed in a sample of 130 patients with movement disorders of six etiologies. Each variable was standardized for its distribution and for age and sex effects in 130 neurotypical speakers. Exploratory Graph Analysis (EGA) and Confirmatory Factor Analysis (CFA) were used to examine the factor structure underlying the diagnostic parameters. In the first analysis, we tested the hypothesis that nonspeech parameters combine with speech parameters within diagnostic dimensions representing domain-general motor control principles. In a second analysis, we tested the more specific hypotheses that diagnostic parameters split along effector (lip vs. tongue) or functional (speed vs. accuracy) rather than task boundaries. Our findings contradict the view that nonspeech parameters currently used in dysarthria diagnostics are congruent with diagnostic measures of speech characteristics in PWD.

Tool use without a tool: kinematic characteristics of pantomiming as compared to actual use and the effect of brain damage.

Movement goals and task mechanics differ substantially between actual tool use and corresponding pantomimes. In addition, apraxia seems to be more severe during pantomime than during actual tool use. Comparisons of these two modes of action execution using quantitative methods of movement analyses are rare. In the present study, repetitive scooping movements with a ladle from a bowl into a plate were recorded and movement kinematics was analyzed. Brain-damaged patients using their ipsilesional hand and healthy control subjects were tested in three conditions: pantomime, demonstration with the tool only, and actual use in the normal context. Analysis of the hand trajectories during the transport component revealed clear differences between the tasks, such as slower actual use and moderate deficits in patients with left brain damage (LBD). LBD patients were particularly impaired in the scooping component: LBD patients with apraxia exhibited reduced hand rotation at the bowl and the plate. The deficit was most obvious during pantomime but actual use was also affected, and reduced hand rotation was consistent across conditions as indicated by strong pair-wise correlations between task conditions. In healthy control subjects, correlations between movement parameters were most evident between the pantomime and demonstration conditions but weak in correlation pairs involving actual use. From these findings and published neuroimaging evidence, we conclude that for a specific tool-use action, common motor schemas are activated but are adjusted and modified according to the actual task constraints and demands. An apraxic LBD individual can show a deficit across all three action conditions, but the severity can differ substantially between conditions.

Anticipatory scaling of grip forces when lifting objects of everyday life.

The ability to predict and anticipate the mechanical demands of the environment promotes smooth and skillful motor actions. Thus, the finger forces produced to grasp and lift an object are scaled to the physical properties such as weight. While grip force scaling is well established for neutral objects, only few studies analyzed objects known from daily routine and none studied grip forces. In the present study, eleven healthy subjects each lifted twelve objects of everyday life that encompassed a wide range of weights. The finger pads were covered with force sensors that enabled the measurement of grip force. A scale registered load forces. In a control experiment, the objects were wrapped into paper to prevent recognition by the subjects. Data from the first lift of each object confirmed that object weight was anticipated by adequately scaled forces. The maximum grip force rate during the force increase phase emerged as the most reliable measure to verify that weight was actually predicted and to characterize the precision of this prediction, while other force measures were scaled to object weight also when object identity was not known. Variability and linearity of the grip force-weight relationship improved for time points reached after liftoff, suggesting that sensory information refined the force adjustment. The same mechanism seemed to be involved with unrecognizable objects, though a lower precision was reached. Repeated lifting of the same object within a second and third presentation block did not improve the precision of the grip force scaling. Either practice was too variable or the motor system does not prioritize the optimization of the internal representation when objects are highly familiar.

Nonverbal Semantics Test (NVST)-A Novel Diagnostic Tool to Assess Semantic Processing Deficits: Application to Persons with Aphasia after Cerebrovascular Accident.

Assessment of semantic processing capacities often relies on verbal tasks which are, however, sensitive to impairments at several language processing levels. Especially for persons with aphasia there is a strong need for a tool that measures semantic processing skills independent of verbal abilities. Furthermore, in order to assess a patient's potential for using alternative means of communication in cases of severe aphasia, semantic processing should be assessed in different nonverbal conditions. The Nonverbal Semantics Test (NVST) is a tool that captures semantic processing capacities through three tasks-Semantic Sorting, Drawing, and Pantomime. The main aim of the current study was to investigate the relationship between the NVST and measures of standard neurolinguistic assessment. Fifty-one persons with aphasia caused by left hemisphere brain damage were administered the NVST as well as the Aachen Aphasia Test (AAT). A principal component analysis (PCA) was conducted across all AAT and NVST subtests. The analysis resulted in a two-factor model that captured 69% of the variance of the original data, with all linguistic tasks loading high on one factor and the NVST subtests loading high on the other. These findings suggest that nonverbal tasks assessing semantic processing capacities should be administered alongside standard neurolinguistic aphasia tests.

Different left brain regions are essential for grasping a tool compared with its subsequent use.

Tool use engages a left hemispheric network including frontal, temporal and parietal regions. Patients with left brain lesions (LBD patients) exhibit deficits when demonstrating use of a single tool (apraxia). When attempting to use a tool, some apraxic patients show errors in the preceding grasping movement. Forty-two LBD patients and 18 healthy controls grasped individual tools and demonstrated their typical use. For patients with a tool use impairment (22), lesion analysis revealed a large area of overlap in the left hemisphere, mainly in the supramarginal gyrus (SMG). For patients with erroneous grasping (12), the lesion overlay showed overlaps in the left frontal and parietal cortices, especially in the inferior frontal gyrus (IFG) and the angular gyrus (ANG). However, contrasting lesions associated with impaired grasping versus tool use impairments reveal little overlap, limited to the inferior parietal cortex. Presumably the left IFG is involved in selection processes in the context of tool use, such as choosing a functional or non-functional grasping movement depending on the task and the online information about the tool's structure and orientation. The ANG might provide this grasp related information, which is relevant for the specific action. The contribution of the SMG to tool use involves more general principals, such as integrating online and learned tool use information into the action plan for the use movement.

Therapy to improve gestural expression in aphasia: a controlled clinical trial.

OBJECTIVES: To assess whether production of communicative gestures can be ameliorated by therapy, to explore factors that might influence individual variability of therapeutic success and to find out whether therapy effects generalize to unpractised gestures. SETTING: Hospital department specializing in rehabilitation of patients with neuropsychological disorders. SUBJECTS: Twenty-three consecutive severely aphasic patients received therapy; ten were tested repeatedly without interpolated therapy. DESIGN: Twenty-four communicative gestures were divided into three sets of eight gestures. In the therapy group one set was practised during each of three consecutive periods and after that period changes in proficiency were assessed for all three sets. Comparisons were made between changes of practised and unpractised gestures during each therapy period within the therapy group, and between changes of unpractised gestures in the therapy group, and the changes brought forward by repeated testing in the control group. INTERVENTIONS: Therapy was centred on familiarizing patients with the communicative functions of gestures and on improving the spatial precision of their gestures. MAIN MEASURE: Scoring of gestures considered their accuracy and the necessity of assistance. RESULTS: Therapy led to substantial improvement of practised gestures. There was also improvement of unpractised gestures which was significantly smaller than that of practised gestures but greater than the improvement induced by repeated testing in the control group. CONCLUSIONS: In view of the limited generalization, gesture therapy should concentrate on gestures that are relevant for communication in daily living of the individual patients.

Grasping tools: effects of task and apraxia.

In patients with apraxia the ability to access tool-use-knowledge and to integrate it into a movement plan is frequently disturbed. The present study investigated potential differences between a 'transport'- and a 'use'-task as well as the influence of apraxia on the preceding grasping movement, when the tool is presented with its handle pointing away from the participant. 20 controls, 10 patients with right brain damage (RBD-group) and 17 patients with left brain damage (LBD-group) were tested. 10 LBD-patients were classified as moderately to severely apraxic according to erroneous demonstration of tool-use. Participants were asked to grasp the tool and either to demonstrate its typical 'use' or to 'transport' it into a container. Functional grasp, which enables comfortable use, was distinguished from non-functional grasp. The results showed that task-content influences the way to grasp an object. Apart from some LBD-patients, nearly all participants produced 100% functional grasps during the 'use'-task. Additionally inappropriate non-functional grasping has always been followed by apraxic tool-use behaviour. Compared to the 'use'-task in the 'transport'-task, functional grasping was significantly reduced in all groups. Our results imply that grasping a tool is specific to a task. Selection of the grasp type seems to be determined by individual weighting of several factors, including knowledge about the function of the object, structural tool characteristics, biomechanical costs of the movement, and previous experience. In general perception and integration of tool-structure plus specific tool-related functional knowledge are necessary for its use and might be processed synchronously. Patients with apraxic tool-use may fail to access any of these information resources.

A network underlying human higher-order motor control: Insights from machine learning-based lesion-behaviour mapping in apraxia of pantomime.

Neurological patients with apraxia of pantomime provide us with a unique opportunity to study the neural correlates of higher-order motor function. Previous studies using lesion-behaviour mapping methods led to inconsistent anatomical results, reporting various lesion locations to induce this symptom. We hypothesised that the inconsistencies might arise from limitations of mass-univariate lesion-behaviour mapping approaches if our ability to pantomime the use of objects is organised in a brain network. Thus, we investigated apraxia of pantomime by using multivariate lesion behaviour mapping based both on support vector regression and sparse canonical correlations in a sample of 130 left-hemisphere stroke patients. Both multivariate methods identified multiple areas to underlie high-order motor control, including inferior parietal lobule, precentral gyrus, posterior parts of middle temporal cortex, and insula. Further, long association fibres were affected, such as the superior longitudinal fascicle, inferior occipito-frontal fascicle, uncinated fascicle, and superior occipito-frontal fascicle. The findings underline the benefits of multivariate lesion-behaviour mapping in brain networks and provide new insights into the brain networks underlying higher-order motor control.

Pantomime of tool use depends on integrity of left inferior frontal cortex.

Pantomime of tool use is a frequently used test for apraxia. For basic cognitive neuroscience, pantomime of tool use is of interest because it constitutes a link between instrumental and communicative manual actions. We used lesion subtraction analysis to determine the locations specifically associated with defective pantomime of tool use in patients with left-brain damage and aphasia. Subtraction of lesions of patients with normal pantomime from those with defective pantomime yielded a maximum difference in the inferior frontal gyrus and adjacent portions of the insula and precentral gyrus. This result remained essentially the same when possible confounding influences of impaired language comprehension and of lesion size were controlled by selecting patients equated on these measures and when only patients with preserved imitation of gestures were considered. By contrast, parietal lesions did not have a specific impact on pantomime. We speculate that the vulnerability of pantomime to lesions of left inferior frontal cortex is due to the high demands on selection of a very restrained range of features out of the many features that may come to mind when imagining the actual use of the tool.

It takes two to pantomime: Communication meets motor cognition.

For over a century, pantomime of tool use has been employed to diagnose limb apraxia, a disorder of motor cognition primarily induced by left brain damage. While research consistently implicates damage to a left fronto-temporo-parietal network in limb apraxia, findings are inconsistent regarding the impact of damage to anterior versus posterior nodes within this network on pantomime. Complicating matters is the fact that tool use pantomime can be affected and evaluated at multiple levels. For instance, the production of tool use gestures requires the consideration of semantic characteristics (e.g. how to communicate the action intention) as well as motor features (e.g. forming grip and movement). Together, these factors may contribute substantially to apparent discrepancies in previously reported findings regarding neural correlates of tool use pantomime. In the current study, 67 stroke patients with unilateral left-brain damage performed a classic pantomime task. In order to analyze different error characteristics, we evaluated the proper use of grip and movement for each pantomime. For certain objects, healthy subjects may use body parts as representative for the object, e.g. use of the fingers to indicate scissors blades. To specify the pathological use of body parts as the object (BPO) we only assessed pantomime items that were not prone to this response in healthy participants. We performed modern voxel-based lesion analyses on MRI or CT data to determine associations between brain injury and the frequency of the specific types of pantomime errors. Our results support a model in which anterior and posterior nodes of the left fronto-temporo-parietal network contribute differentially to pantomime of tool use. More precisely, damage in the inferior frontal cortex reaching to the temporal pole is associated with an increased frequency of BPO errors, whereas damage to the inferior parietal lobe is predominantly linked to an increased frequency of movement and/or grip errors. Our work suggests that the validity of attempts to specify the neural correlates of limb apraxia based on tool use pantomime depends on differentiating the specific types of errors committed. We conclude that successful tool use pantomime involves dissociable functions with communicative aspects represented in more anterior (rather ventral) regions and motor-cognitive aspects in more posterior (rather dorsal) nodes of a left fronto-temporo-parietal network.

The neural basis of imitation is body part specific.

Imitation is an important constituent of the behavioral repertoire of human beings. We use imitation for learning motor skills, for facilitating comprehension of other persons' actions and mental states, and as a communicative reference to actions or people. Although some non-human species display imitative behaviors, none of them equals the versatility and perfection of human imitation. The versatility and apparent ease of human imitation is, however, not at all self-evident when one considers the neural and cognitive transformations that must be accomplished for successful imitation. Imitation of meaningless gestures poses a particular challenge for our brain, because similarity between the body of the model and one's own body must bridge fundamental differences between the perspective and modalities of perceiving and controlling one's own and other bodies. We analyzed the locations of left-hemisphere lesions disturbing imitation of meaningless gestures and found a clear-cut body part specificity. Disturbed imitation of finger postures was associated with anterior lesions including the opercular portion of the inferior frontal gyrus, whereas disturbed imitation of hand postures was associated with posterior lesions affecting the inferior parietal lobule and temporo-parieto-occipital junction. These locations do not correspond with known somatotopic maps of motor representations. Rather, they argue for an intermediate step of processing interpolated between perception and execution of gestures as has been suggested by the mirror neuron and the body part coding hypotheses.

Grip forces isolated from knowledge about object properties following a left parietal lesion.

When lifting two objects with equal weight but different size, we judge the smaller object to be heavier. This size-weight illusion has been intensively tested by the recruitment of fingertip grip forces during precision lifting. Previous findings have suggested that perceptual (object size) prediction can influence sensorimotor prediction (anticipatory grip force scaling to the object size) but these predictions could be processed independently. This study investigates whether the anticipatory scaling of the grip forces according to object properties critically depends on the integrity of the posterior parietal cortex (PPC) and how a deficit may affect the perceptual size-weight illusion. Here, we report the case of a patient, F.S., with a large left temporal parietal lesion intruding into the temporal cortex and limb apraxia, who did not show anticipatory scaling of fingertip grip force to object size whereas matched controls did. However, the patient's perception of the size-weight illusion was only impaired during his ipsi-lesional hand lifting. Our findings suggest that left parietal cortex may be particularly responsible for the anticipatory grip force scaling of both hands and the perceptual process of size-weight illusion involving ipsi-lesional hand motion.

The impact of dysexecutive syndrome on use of tools and technical devices.

We present two studies aimed at elucidating why patients with dysexecutive syndrome encounter difficulties with the use of tools and technical devices. Two different groups of patients with dysexecutive syndrome took part in them. Their results were compared with those of two groups of normal controls and in the first study also with those of patients with posterior left or right brain lesions. The first study contrasted single step with multi-step actions and explored the role of novelty and consecutive demands on problem solving. Dysexecutive patients encountered problems only with the multi-step actions. The rank order of strength of impairment corresponded to the presumed rank order of demands on problem solving, but the analysis of individual results demonstrated high variability of this pattern which moreover could not be fully replicated when the same tests were applied in the second study. The second study pursued the hypothesis that maintenance of goals and constraints in working memory is the crucial factor for difficulties of dysexecutive patients. Support for this hypothesis was less ambiguous, but as this study did not include patients with posterior lesions it remains open whether this factor is specific for dysexecutive syndrome and prefrontal brain damage or applies to brain damage regardless of its location.

Relationship between object-related gestures and the fractionated object knowledge system.

The praxic semantic system comprises a conceptual knowledge system, which stores functional information about objects, and an action knowledge system, which stores information about the correct manipulation of objects. Moreover, mechanical problem solving abilities permit to take advantages from objects structure to use unfamiliar tools or discover alternative ways of using familiar tools. This study aims at investigating whether conceptual knowledge, action knowledge and mechanical problem solving abilities intervene in the production of gestures with objects (i.e. pantomimes and object use) by testing a group of brain damaged patients. Results showed that the mechanical problem solving abilities are not sufficient to produce pantomimes and that only severe deficits in the praxic semantic system would affect the production of these gestures. Furthermore, a double dissociation was observed between mechanical problem solving abilities and the capacity to use multiple objects. Overall, the results indicate that the praxic semantic system can be disrupted at different levels, suggesting that the semantic system for object has to be conceived as fractionated in different entities.

Comprehensibility and neural substrate of communicative gestures in severe aphasia.

Communicative gestures can compensate incomprehensibility of oral speech in severe aphasia, but the brain damage that causes aphasia may also have an impact on the production of gestures. We compared the comprehensibility of gestural communication of persons with severe aphasia and non-aphasic persons and used voxel based lesion symptom mapping (VLSM) to determine lesion sites that are responsible for poor gestural expression in aphasia. On group level, persons with aphasia conveyed more information via gestures than controls indicating a compensatory use of gestures in persons with severe aphasia. However, individual analysis showed a broad range of gestural comprehensibility. VLSM suggested that poor gestural expression was associated with lesions in anterior temporal and inferior frontal regions. We hypothesize that likely functional correlates of these localizations are selection of and flexible changes between communication channels as well as between different types of gestures and between features of actions and objects that are expressed by gestures.

Spatial and kinematic features of apraxic movement depend on the mode of execution.

Knowledge about the dependency of apraxic movements on the mode of execution may enhance the understanding of apraxia and of the cerebral representation of actions. We examined a common tool-use action in nine patients with left hemisphere damage and apraxia. Arm movements during the use of a handsaw were measured and tested in three different modes of execution: pantomime, pantomime with a bar shaped like the handle of the saw, and actual sawing. Analysis concentrated on spatial and kinematic features of the wrist trajectories during these repetitive movements. In healthy control subjects, both pantomime conditions differed from actual use mainly by larger amplitudes during miming. Apraxic patients executed large proportions of their pantomiming movements in an incorrect direction away from the appropriate anteroposterior direction, while other movement features were normal. The availability of the handle-like bar did not improve performance. During actual use, movement direction was constraint by mechanical demands. In this condition patients moved with moderately decreased velocity. However, this deficit was not related to the errors in movement direction characteristic of pantomiming. These data suggest that pantomiming and actual execution of an action are dictated by different external requirements and constraints, pantomiming serves to convey information, while actual use has to obey the mechanical demands of the task. Due to these differences, spatial and kinematic movement features in healthy subjects vary between the modes of execution, movements are differently vulnerable to apraxia, and deficits in patients may dissociate.