Imitation Of Gestures Research Articles

Gesture Imitation Performance and Visual Exploration in Young Children with Autism Spectrum Disorder.

Most studies in children with autism spectrum disorder (ASD) support a decrement in imitation performance. Factors related to visual attention and motor execution have been proposed to explain this phenomenon in ASD. However, studies investigated imitation with various methods, leading to inconsistent findings. Here, we examine imitation performance related to visual attention and motor execution. We focused on the imitation of meaningful and meaningless gestures, consistently reported as more affected than imitation of actions with objects in ASD. The imitation eye-tracking task consisted of a video of an actor demonstrating gestures and prompting children to imitate them. The demonstrations comprised meaningful and meaningless hand gestures, and meaningless facial gestures. We measured the fixation duration to the actor' face during child-directed speech and gesture demonstrations. We video-recorded children to assess their performance. Our sample comprised 100 participants (3.55 ± 1.11years old), including 84 children with ASD. The ASD and typically developing groups displayed the same visual attention toward gesture demonstrations, although children with ASD spent less time looking at the face during facial stimuli. Visual exploration of actors' gestures did not influence imitation performance. Imitation of meaningful gestures was associated with less severe autistic symptoms, whereas imitation of meaningless gestures was correlated with higher non-verbal cognitive and fine-motor skills. These findings contribute to a better understanding of the complexity of imitation. We delineated the distinct nature of imitation of meaningful and meaningless gestures in children with ASD. We discuss clinical implications in relation to assessment and intervention programs.

Higher or lower? Interpersonal behavioral and neural synchronization of movement imitation in autistic children.

How well autistic children can imitate movements and how their brain activity synchronizes with the person they are imitating have been understudied. The current study adopted functional near-infrared spectroscopy (fNIRS) hyperscanning and employed a task involving real interactions involving meaningful and meaningless movement imitation to explore the fundamental nature of imitation as a dynamic and interactive process. Experiment 1 explored meaningful and meaningless gesture imitation. The results revealed that autistic children exhibited lower imitation accuracy and behavioral synchrony than non-autistic children when imitating both meaningful and meaningless gestures. Specifically, compared to non-autistic children, autistic children displayed significantly higher interpersonal neural synchronization (INS) in the right inferior parietal lobule (r-IPL) (channel 12) when imitating meaningful gestures but lower INS when imitating meaningless gestures. Experiment 2 further investigated the imitation of four types of meaningless movements (orofacial movements, transitive movements, limb movements, and gestures). The results revealed that across all four movement types, autistic children exhibited significantly lower imitation accuracy, behavioral synchrony, and INS in the r-IPL (channel 12) than non-autistic children. This study is the first to identify INS as a biomarker of movement imitation difficulties in autistic individuals. Furthermore, an intra- and interindividual imitation mechanism model was proposed to explain the underlying causes of movement imitation difficulties in autistic individuals.

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.

Visuo-spatial complexity potentiates the body-part effect in intransitive imitation of meaningless gestures.

Recent studies on the imitation of intransitive gestures suggest that the body part effect relies mainly upon the direct route of the dual-route model through a visuo-transformation mechanism. Here, we test the visuo-constructive hypothesis which posits that the visual complexity may directly potentiate the body part effect for meaningless gestures. We predicted that the difference between imitation of hand and finger gestures would increase with the visuo-spatial complexity of gestures. Second, we aimed to identify some of the visuo-spatial predictors of meaningless finger imitation skills. Thirty-eight participants underwent an imitation task containing three distinct set of gestures, that is, meaningful gestures, meaningless gestures with low visual complexity, and meaningless gestures with higher visual complexity than the first set of meaningless gestures. Our results were in general agreement with the visuo-constructive hypothesis, showing an increase in the difference between hand and finger gestures, but only for meaningless gestures with higher visuo-spatial complexity. Regression analyses confirm that imitation accuracy decreases with resource-demanding visuo-spatial factors. Taken together, our results suggest that the body part effect is highly dependent on the visuo-spatial characteristics of the gestures.

Localizing apraxia in corticobasal syndrome: a morphometric MRI study.

Apraxia localization has relied on voxel-based, lesion-symptom mapping studies in left hemisphere stroke patients. Studies on the neural substrates of different manifestations of apraxia in neurodegenerative disorders are scarce. The primary aim of this study was to look into the neural substrates of different manifestations of apraxia in a cohort of corticobasal syndrome patients (CBS) by use of cortical thickness. Twenty-six CBS patients were included in this cross-sectional study. The Goldenberg apraxia test (GAT) was applied. 3D-T1-weighted images were analyzed via the automated recon-all Freesurfer version 6.0 pipeline. Vertex-based multivariate General Linear Model analysis was applied to correlate GAT scores with cortical thickness. Deficits in imitation of meaningless gestures correlated with bilateral superior parietal atrophy, extending to the angular and supramarginal gyri, particularly on the left. Finger imitation relied predominantly on superior parietal lobes, whereas the left angular and supramarginal gyri, in addition to superior parietal lobes, were critical for hand imitation. The widespread bilateral clusters of atrophy in CBS related to apraxia indicate different pathophysiological mechanisms mediating praxis in neurodegenerative disorders compared to vascular lesions, with implications both for our understanding of praxis and for the rehabilitation approaches of patients with apraxia.

Gesture profiles distinguish primary progressive aphasia variants: a preliminary study

ABSTRACT Background Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. The main variants of PPA – semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) – can be challenging to distinguish. Limb apraxia often co-occurs with PPA, but it is unclear whether PPA variants are associated with different gesture deficits. Prior evidence from stroke indicates that temporal lobe lesions are associated with reduced benefit from meaning in gesture performance. Temporal lesions are also associated with greater deficits in hand postures compared to arm kinematics in gesture imitation. Aims We tested the hypothesis that svPPA, who primarily exhibit temporal lobe atrophy, would differentially show this pattern. In addition, we predicted that as a group, individuals with PPA would more accurately produce meaningful than meaningless gestures and kinematic components than hand postures, as found in neurotypical adults and individuals with stroke. Methods & Procedures Participants with PPA completed meaningful and meaningless gesture imitation tasks. Performance was scored for hand posture and arm kinematic components. Bayesian mixed-effect models examined trial-level gesture imitation accuracy, while controlling for dementia severity and random effects of subjects and items. Fixed effects included an interaction between PPA variant, task condition/meaning, and gesture component. Outcomes & Results We found a critical interaction between PPA variant, meaning, and gesture component. In particular, unlike lvPPA and nfvPPA, svPPA subjects’ hand postures failed to benefit from gesture meaning. This preliminary research extends prior findings on the role of the temporal lobe in action representations associated with manipulable objects, and is among the first to demonstrate distinct gesture imitation patterns between PPA variants. Conclusions Characterizing gesture deficits in PPA may help inform diagnostics, compensatory communication strategies, and models of praxis.

Psychomotor Therapy Using the Body Schema for the Intellectually Disabled at the A.D.A.R-Tubahoze Centre

This study is the preliminary research focused on psychomotor therapy and body schemas for the intellectually disabled, hence the motor dimension with a test of balance, coordination and jumping in the pre-test and post-test of a BPM measurement at 60, 90 and 120 (BPM) with the YO and YC. The cognitive dimension with, for example, the Berces and Lezine test of body control and latero-spatial organization, the Piaget and Head tests of gesture imitation and latero-spatial organization. The affective dimension revolving around self-esteem was measured with the self-perception profile for adults with intellectual disabilities (SPPD) on physical appearance, athletic competence and psychomotor competence. At the end of the verification of research question and using methodological approach adopted on the present study on the motor dimension, the cognitive dimension and the affective dimension; it was found that with the motor dimension on the balance test, a trend on the performance of our intellectually disabled patients from A.D.A.R-Tubahoze centre during the psychomotor therapy sessions was tested positive in the post-test compared to the pre-test (BYO and BYC).With regard to the coordination test (CYO and CYC) at post-test and pre-test, the statistical frequencies with overall averages show that our intellectually impaired patients tended to obtain better results at post-test than at pre-test; this shows a success in the applicability of motor therapy to coordination disorder in intellectually impaired patients. Similarly, a positive performance trend was shown in the results of the jumping test at post-test than at pre-test. The trend in the results of the jump test (JYO and JYC) in the post-test than in the pre-test would have shown a positive result after our therapeutic-motor sessions with the IDs of the A.D.A.R. centre. From the cognitive dimension, using the test of imitation of gestures and lateral-spatial on different movements, has a score of 10 points in the test of imitation of simple gestures of hand movements, it would have been observed in MID patients that the test proved positive; with the Piaget’s Head test of latero-spatial organization administered to MID which was evaluated at a score of 40 points, had as a positive performance to all patients who took this test. The results of our work on the affective dimension of the dominant modality “Rather true”, was observed on items 12, 16, 20 and 24 of self-esteem, with physical appearance vis-à-vis items (5,10,18 and 22) and items 5 and 9 and then items 17, 13 and 1 of athletic competence; from items with a “Rather positive” modality with items 11, 3 and 2 3, 7, 15 and 19 of our MID patients that a positive trend on positive appreciation was satisfactorily observable.

Gesture imitation performance in community-dwelling older people: assessment of a gesture imitation task in the screening and diagnosis of mild cognitive impairment and dementia.

Gesture imitation, a simple tool for assessing visuospatial/visuoconstructive functions, is reportedly useful for screening and diagnosing dementia. However, gesture imitation performance in healthy older adults is largely unknown, as are the factors associated with lower performance. To address these unknowns, we examined the gesture imitation performance of a large number of community-dwelling older adults aged ≥65 years in Arao City, Kumamoto Prefecture (southern Japan). The examiner presented the participants with eight gesture patterns and considered it a success if they could imitate them within 10 s. The success rate of each gesture imitation was calculated for three diagnostic groups: cognitively normal (CN) (n = 1184), mild cognitive impairment (MCI) (n = 237), and dementia (n = 47). Next, we reorganised the original gesture imitation battery by combining six selected gestures with the following scoring method: if the participants successfully imitated the gestures, immediately or within 5 s, two points were assigned. If they succeeded within 5-10 s, one point was assigned. The sensitivity and specificity of the battery were investigated to detect the dementia and MCI groups. Factors associated with gesture imitation battery scores were examined. Except one complex gesture, the success rate of imitation in the CN group was high, approximately 90%. The sensitivity and specificity of the gesture imitation battery for discriminating between the dementia and CN groups and between the MCI and CN groups were 70%/88%, and 45%/75%, respectively. Ageing, male sex, and a diagnosis of dementia or MCI were associated with lower scores on the gesture imitation battery. Gesture imitation tasks alone may not be sufficient to detect MCI. However, by combining gestures with set time limits, gesture imitation tasks can be a low-burden and effective method for detecting dementia, even in community medicine, such as during health check-ups.

The cultural and linguistic adaptation of the Oxford Cognitive Screen to Tamil.

The Oxford Cognitive Screen (OCS) is a screening tool to assess stroke patients for deficits in attention, executive functions, language, praxis, numeric cognition, and memory. In this study, the OCS was culturally and linguistically adapted to Tamil, for use in India (OCS TA), considering the differences between formal and spoken versions of Tamil and consideration of its phonetic complexity. We adopted two-parallel form versions of the OCS and generated normative data for them. We recruited 181 healthy controls (Mean = 39.27 years, SD 16.52) (141 completed version A, 40 completed version B, 33 completed version A and B) and compared the data with the original UK normative sample. In addition, 28 native Tamil-speaking patients who had a stroke in the past three years (Mean = 62.76 years, SD 9.14) were assessed. Convergent validity was assessed with subtasks from Addenbrooke's Cognitive Examination III (ACE-III). We found significant differences between the UK normative group and the OCS TA normative group in age and education. Tamil-specific norms were used to adapt the cutoffs for the memory, gesture imitation, and executive function tasks. When domain-specific scores on the ACE-III were compared, OCS TA exhibited strong convergent validity. The OCS TA has shown the potential to be a useful screening tool for stroke survivors among Tamil speakers with the two-parallel forms demonstrating good equivalence. Further empirical evidence from larger studies is required to establish their psychometric performance and clinical validity.

The parietal architecture binding cognition to sensorimotor integration: a multimodal causal study.

Despite human's praxis abilities are unique among primates, comparative observations suggest that these cognitive motor skills could have emerged from exploitation and adaptation of phylogenetically older building blocks, namely the parieto-frontal networks subserving prehension and manipulation. Within this framework, investigating to which extent praxis and prehension-manipulation overlap and diverge within parieto-frontal circuits could help in understanding how human cognition shapes hand actions. This issue has never been investigated by combining lesion mapping and direct electrophysiological approaches in neurosurgical patients. To this purpose, 79 right-handed left-brain tumour patient candidates for awake neurosurgery were selected based on inclusion criteria. First, a lesion mapping was performed in the early postoperative phase to localize the regions associated with an impairment in praxis (imitation of meaningless and meaningful intransitive gestures) and visuo-guided prehension (reaching-to-grasping) abilities. Then, lesion results were anatomically matched with intraoperatively identified cortical and white matter regions, whose direct electrical stimulation impaired the Hand Manipulation Task. The lesion mapping analysis showed that prehension and praxis impairments occurring in the early postoperative phase were associated with specific parietal sectors. Dorso-mesial parietal resections, including the superior parietal lobe and precuneus, affected prehension performance, while resections involving rostral intraparietal and inferior parietal areas affected praxis abilities (covariate clusters, 5000 permutations, cluster-level family-wise error correction P < 0.05). The dorsal bank of the rostral intraparietal sulcus was associated with both prehension and praxis (overlap of non-covariate clusters). Within praxis results, while resection involving inferior parietal areas affected mainly the imitation of meaningful gestures, resection involving intraparietal areas affected both meaningless and meaningful gesture imitation. In parallel, the intraoperative electrical stimulation of the rostral intraparietal and the adjacent inferior parietal lobe with their surrounding white matter during the hand manipulation task evoked different motor impairments, i.e. the arrest and clumsy patterns, respectively. When integrating lesion mapping and intraoperative stimulation results, it emerges that imitation of praxis gestures first depends on the integrity of parietal areas within the dorso-ventral stream. Among these areas, the rostral intraparietal and the inferior parietal area play distinct roles in praxis and sensorimotor process controlling manipulation. Due to its visuo-motor 'attitude', the rostral intraparietal sulcus, putative human homologue of monkey anterior intraparietal, might enable the visuo-motor conversion of the observed gesture (direct pathway). Moreover, its functional interaction with the adjacent, phylogenetic more recent, inferior parietal areas might contribute to integrate the semantic-conceptual knowledge (indirect pathway) within the sensorimotor workflow, contributing to the cognitive upgrade of hand actions.

Multimodal imitative learning and synchrony in cetaceans: A model for speech and singing evolution.

Multimodal imitation of actions, gestures and vocal production is a hallmark of the evolution of human communication, as both, vocal learning and visual-gestural imitation, were crucial factors that facilitated the evolution of speech and singing. Comparative evidence has revealed that humans are an odd case in this respect, as the case for multimodal imitation is barely documented in non-human animals. While there is evidence of vocal learning in birds and in mammals like bats, elephants and marine mammals, evidence in both domains, vocal and gestural, exists for two Psittacine birds (budgerigars and grey parrots) and cetaceans only. Moreover, it draws attention to the apparent absence of vocal imitation (with just a few cases reported for vocal fold control in an orangutan and a gorilla and a prolonged development of vocal plasticity in marmosets) and even for imitation of intransitive actions (not object related) in monkeys and apes in the wild. Even after training, the evidence for productive or "true imitation" (copy of a novel behavior, i.e., not pre-existent in the observer's behavioral repertoire) in both domains is scarce. Here we review the evidence of multimodal imitation in cetaceans, one of the few living mammalian species that have been reported to display multimodal imitative learning besides humans, and their role in sociality, communication and group cultures. We propose that cetacean multimodal imitation was acquired in parallel with the evolution and development of behavioral synchrony and multimodal organization of sensorimotor information, supporting volitional motor control of their vocal system and audio-echoic-visual voices, body posture and movement integration.

Grapho-motor imitation training in children with handwriting difficulties: A single-center pilot study

Imitation is a crucial process for learning and brain development. It is based on the mirror neuron mechanism and underlies our understanding of actions and the gestures of others. Some researchers hypothesized a possible correlation between a low functioning mirror neuron system (MNS) and developmental coordination disorder, including dysgraphic deficit. However, no studies have verified whether imitation of graphic gestures by exploiting the properties of the MNS could improve handwriting. This study evaluates the effects of imitation training of handwriting in five children with handwriting difficulties aged 8 to 10 years. The training lasted for five months, and was undertaken three times a week, for a total number of 60 sessions for each child. Before and after the training, we evaluated the degree of handwriting impairment using the Concise Evaluation Scale for Children’s Handwriting (BHK). Our results suggest that handwriting imitation training produced a significant qualitative change in the children’s writing, likely due to exercises that stimulated fine motor imitation. Furthermore, the imitation also involved ergonomic and biomechanical aspects relevant to improving imitative writing after observing the model. Each child has therefore reached an adequate level of writing, suggesting the effectiveness of the proposed intervention.

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.

Gesture meaning modulates the neural correlates of effector-specific imitation deficits in left hemisphere stroke

BackgroundPrevious studies on left hemisphere (LH) stroke patients reported effector-specific (hand, fingers, bucco-facial) differences in imitation performance. Furthermore, imitation performance differed between meaningless (ML) and meaningful (MF) gestures. Recent work suggests that a gesture’s meaning impacts the body-part specificity of gesture imitation. MethodsWe tested the hypothesis that the gesture’s meaning (ML vs MF) affects the lesion correlates of effector-specific imitation deficits (here: bucco-facial vs arm/hand gestures) using behavioural data and support vector regression-based lesion-symptom mapping (SVR-LSM) in a large sample of 194 sub-acute LH stroke patients. ResultsBehavioural data revealed a significant interaction between the effector used for imitation and the meaning of the imitated gesture. SVR-LSM analyses revealed shared lesion correlates for impaired imitation independent of effector or gesture meaning in the left supramarginal (SMG) and superior temporal gyri (STG). Besides, within the territory of the left middle cerebral artery, impaired imitation of bucco-facial gestures was associated with more anterior lesions, while arm/hand imitation deficits were associated with more posterior lesions. MF gestures were specifically associated with lesions in the left inferior frontal gyrus and the left insular region. Notably, an interaction of effector-specificity and gesture meaning was also present at the lesion level: A more pronounced difference in imitation performance between the effectors for ML (versus MF) gestures was associated with left-hemispheric lesions in the STG, SMG, putamen, precentral gyrus and white matter tracts. ConclusionThe current behavioural data show that ML gestures are particularly sensitive in assessing effector-specific imitation deficits in LH stroke patients. Moreover, a gesture’s meaning modulated the effector-specific lesion correlates of bucco-facial and arm/hand gesture imitation. Hence, it is crucial to consider gesture meaning in apraxia assessments.

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.

Follow control of upper limb rehabilitation training based on Kinect and NAO robot

Gesture imitation is a common rehabilitation strategy in limb rehabilitation training. In traditional rehabilitation training, patients need to complete training actions under the guidance of rehabilitation physicians. However, due to the limited resources of the hospital, it cannot meet the training and guidance needs of all patients. In this paper, we proposed a following control method based on Kinect and NAO robot for the gesture imitation task in rehabilitation training. The method realized the joint angles mapping from Kinect coordination to NAO robot coordination through inverse kinematics algorithm. Aiming at the deflection angle estimation problem of the elbow joint, a virtual space plane was constructed and realized the accurate estimation of deflection angle. Finally, a comparative experiment for deflection angle of the elbow joint angle was conducted. The experimental results showed that the root mean square error of the angle estimation value of this method in right elbow transverse deflection and vertical deflection directions was 2.734° and 2.159°, respectively. It demonstrates that the method can follow the human movement in real time and stably using the NAO robot to show the rehabilitation training program for patients.

Differences in Praxis Errors in Autism Spectrum Disorder Compared to Developmental Coordination Disorder.

This study aimed to better understand how autism spectrum disorder (ASD) and developmental coordination disorder (DCD) differ in types of praxis errors made on the Florida Apraxia Battery Modified (FAB-M) and the potential relationships between praxis errors and social deficits in ASD. The ASD group made significantly more timing sequencing errors in imitation of meaningful gestures, as well as more body-part-for-tool errors during gesture-to-command compared to the other two groups. In the ASD group, increased temporal errors in meaningful imitation were significantly correlated with poorer affect recognition and less repetitive behaviors. Thus, in ASD, aspects of imitation ability are related to socioemotional skills and repetitive behaviors.

Neuropsychological Evidence for a Motor Working Memory Subsystem Related to Apraxia.

Recent evidence in healthy participants suggests that a motor subcomponent of working memory (mWM) may exist. We investigated whether this mWM is impaired in patients with a motor-dominant left hemisphere (LH) stroke and apraxia. Furthermore, we hypothesized that a deficient mWM contributes to deficits in motor cognition, that is, apraxia, in LH stroke. The study included 52 patients with LH stroke and 25 age-matched controls. Patients were classified into LH stroke patients with and without apraxia based on deficits in gesture imitation and object use. All participants were examined using the block span test (visuospatial WM), the digit span test (verbal WM), and a novel mWM task. In the latter, participants were presented with static pictures depicting three different actions: actions with objects, meaningless actions, and meaningful actions. In the mWM task, LH stroke patients with apraxia performed worse than age-matched controls. Notably, LH stroke patients with apraxia showed more pronounced mWM deficits than those without apraxia. These results remained significant even after controlling for visuospatial and verbal WM deficits. Regression analyses revealed that LH stroke patients' mWM deficits predicted deficits in imitation. Data provide neuropsychological evidence for a motor subsystem of WM and suggest that deficits in mWM contribute to the severity of apraxia in LH stroke patients.

Imitation of meaningless gestures in the Alzheimer’s disease: influence of egocentric and allocentric spatial reference frames

Imitation of meaningless gestures is a frequently used task to assess praxis skills in Alzheimer’s disease (AD). The visuospatial analysis is considered to be one of the cognitive mechanisms most involved in perceiving the gestures of the other (i.e. model to imitate) in the imitation of meaningless gestures. However, in order to perform a classic gesture imitation task (i.e. face model), it is also necessary to transpose the representation of the other’s gestures to better represent one’s own gestures. This transposition can be superimposed on the dichotomy of egocentric spatial reference frames (i.e. self-gestures) and allocentric spatial reference frames (i.e. gestures of the other). Given previous researches on the relation between hippocampus and allocentric performance, we predicted that AD patients could have imitation difficulties specifically for the allocentric imitation. We thus propose a specific methodology to evaluate the imitation of meaningless gestures in both egocentric and allocentric conditions using unimanual ( i.e. one hand gestures) as well bimanual (i.e. two hand gestures) gest modalities for each condition. Our results show significant differences between the AD group and control group, except under the bimanualallocentric condition. Moreover, correlation analyses with visuospatial assessments do not validate the essential role of visuospatial abilities in our gestural imitation tasks. The comparison of the within-group results shows a significant difference between egocentric and allocentric conditions only for the elderly control group suggesting that the impact of spatial reference frames in gestural imitation would not be specific to AD. However, one should also be alert to within-pathological variability in AD, which would require a future study with several subgroups of AD patients.

The gesture imitation test in dementia with Lewy bodies and Alzheimer's disease dementia.

ObjectivesDementia with Lewy bodies (DLB) is the second most common type of neurodegenerative dementia following Alzheimer's disease dementia (ADD). This study investigated the diagnostic role of the gesture imitation test in detecting DLB and differentiating DLB from ADD.MethodsA total of 63 patients with DLB, 93 patients with ADD, and 88 healthy controls were included in this study. All participants were administered the gesture imitation test, the Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA), the clock drawing test (CDT), and other neuropsychological tests.ResultsThe patients with DLB performed worse than the healthy controls in the global scores and on every item of the gesture imitation test (p < 0.001). The area under the curve (AUC) for the global scores was 0.889 (p < 0.001) in differentiating the DLB and control groups. Item 4 was a better discriminator, with a sensitivity of 79.37% and a specificity of 79.55%. The AUC for the global scores decreased to 0.593 and the difference was marginal (p = 0.079) in differentiating the DLB and ADD groups. The patients with DLB performed worse on Items 1 and 4 compared with the patients with ADD (p = 0.040, 0.004). The gesture imitation test was positively correlated with the scores of the MMSE (r = 0.355, p = 0.017), the MoCA (r = 0.382, p = 0.010), and the CDT (r = 0.407, p = 0.005) in patients with DLB.ConclusionThe gesture imitation test is an easy, rapid tool for detecting DLB and has a role in differentiating DLB from ADD, especially in Items 1 and 4.