Changes in breathing during observation of effortful actions

Respiration and heart rates were recorded in normal subjects watching effortful actions produced by an actor in front of them. Subjects remained immobile throughout. Two experiments were performed. In experiment 1, subjects watched a weight-lifting performance, either static or dynamic, with increasing weights. In experiment 2, they watched a walking/running performance on a treadmill moving at increasing speed. In both experiments, no change was found in observers' heart rate. By contrast, consistent changes were found in respiration rate. These changes tended to follow the exercise rhythm of the actor, specially during accelerated running (from 2.5 to 10 km/h) where respiration rate increased linearly with speed of the treadmill. Average maximum increase ranged between 25 and 30% above resting rate. This finding demonstrates activation of central mechanisms related to action performance during observation of effortful actions. It could represent a basis for understanding and imitating actions performed by other people.     

Gesture imitation in autism: II. Symbolic gestures and pantomimed object use

We report an experimental study of imitation of two types of meaningful gestures: (a) social-communicative gestures, and (b) pantomimed actions with objects (including counterfunctional object use) by children and adolescents with autism. Controls were (a) children with nonautistic developmental delays, matched for chronological age and receptive language age, and (b) typically developing children matched for receptive language. Children in both comparison groups imitated actions more accurately than did children with autism, who nonetheless demonstrated understanding of the meaning of the gestures. However, the autistic group tended to have difficulty naming gestures and also was less able than controls to produce actions on verbal request. Children with lower levels of language ability, including those with autism, had difficulty imitating unconventional use of objects, instead using the object for their conventional functions. The discussion addresses the implications of these results and our own previous related findings for representational and executive accounts of praxic deficits in autistic spectrum disorders.     

The panoply of field-dependent behavior in 1436 stroke patients. The mirror neuron system uncoupled and the consequences of loss of personal autonomy

Evaluation of the multifaceted nature of frontal network syndromes is uniquely challenging and rarely tested in the acute/sub-acute stroke period. Field-dependent behavior such as imitation behavior, utilization behavior, and environmental dependency syndrome, as a component of altered environmental autonomy, may be a reliable bedside test. This research focused on the frequency of field-dependent behavior in stroke, the subtypes and relation to frontal lobe lesion location and stroke etiology. A validated frontal network score incorporating a 10-point imitation behavior scale was applied to alert patients without significant aphasia, encephalopathy, dementia, or substance abuse. Discriminative validity assessment with magnetic resonance imaging, diffusion weight imaging (MRI-DWI brain) was performed and correlational validity was established using standard neuropsychological tests. Of the stroke patients (n = 1436), those with frontal network symptoms (335/1203; 28%) were analyzed further. In the 73 patients with lesions restricted to the frontal lobes or the frontal subcortical circuits, 56 complied with the 10-point imitation behavior scale testing. Forty-five of 56 (80%) demonstrated imitation behavior (sensitivity 73% and specificity 94%). Correlational validity testing with four commonly used frontal lobe neuropsychological tests was good. The stroke etiology included 26 (59%) “other” causes, 9 (20%) intracerebral hemorrhages, 3 (7%) cardioembolic causes, 3 (7%) large vessel disease, 2 (4%) small vessel disease, and 2 (4%) unknown etiology. Field-dependent behaviour subtypes included imitation behavior (n = 45), utilization behavior (n = 9), environmental dependency syndrome (n = 4), and complex other forms of environmental dependence syndrome (n = 5). It was concluded that imitation behavior is a relatively common occurrence with lesions in the frontal lobes in the acute/sub-acute stroke period and is associated predominantly with non-mainstream (other) stroke causes and intracerebral hemorrhage.     

Left posterior parietal theta burst stimulation affects gestural imitation regardless of semantic content

ObjectiveNeuro-imaging studies have suggested that the ability to imitate meaningless and meaningful gestures may differentially depend on superior (SPL) and inferior (IPL) parietal lobule. Therefore, we hypothesized that imaging-guided neuro-navigated continuous theta burst stimulation (cTBS) over left SPL mainly affects meaningless and over left IPL predominantly meaningful gestures.MethodsTwelve healthy subjects participated in this study. High resolution structural MRI was used for imaging guided neuro-navigation cTBS. Participants were targeted with one train of cTBS in three experimental sessions: sham stimulation over vertex and real cTBS over left SPL and IPL, respectively. An imitation task, including 24 meaningless and 24 meaningful gestures, was performed ‘offline’.ResultscTBS over both left IPL and SPL significantly interfered with gestural imitation. There was no differential effect of SPL and IPL cTBS on gesture type (meaningless versus meaningful).ConclusionsOur findings confirm that left posterior parietal cortex plays a predominant role in gestural imitation. However, the hypothesis based on the dual route model suggesting a differential role of SPL and IPL in the processing of meaningless and meaningful gestures could not be confirmed.SignificanceLeft SPL and IPL play a common role within the posterior–parietal network in gestural imitation regardless of semantic content.     

Social learning,culture and the ‘socio-cultural brain’ of human and non-human primates

Noting important recent discoveries, we review primate social learning, traditions and culture, together with associated findings about primate brains. We survey our current knowledge of primate cultures in the wild, and complementary experimental diffusion studies testing species’ capacity to sustain traditions. We relate this work to theories that seek to explain the enlarged brain size of primates as specializations for social intelligence, that have most recently extended to learning from others and the cultural transmission this permits. We discuss alternative theories and review a variety of recent findings that support cultural intelligence hypotheses for primate encephalization. At a more fine-grained neuroscientific level we focus on the underlying processes of social learning, especially emulation and imitation. Here, our own and others’ recent research has established capacities for bodily imitation in both monkeys and apes, results that are consistent with a role for the mirror neuron system in social learning. We review important convergences between behavioural findings and recent non-invasive neuroscientific studies.     

Deficient internal models for planning hand-object interactions in apraxia

Motor imagery (MI) has been associated with planning stages of motor production, and in particular, with internal models that predict the sensory consequences of motor commands and specify the motor commands required to achieve a given outcome. In this study we investigated several predictions derived from the hypothesis that ideomotor apraxia (IM), a deficit in pantomime and imitation of skilled actions, may be attributable in part to deficits in internal models for planning object-related actions, in the face of relatively intact on-line, feedback-driven control of action. This hypothesis predicts that in IM, motor imagery should be (a) strongly correlated with other motor tasks not providing strong visual, tactile, and proprioceptive feedback from objects, i.e., object-related pantomime and imitation; (b) poorly correlated with performance tasks providing strong environmental feedback about the locations of effectors and targets, i.e., actual interaction with objects; and (c) particularly deficient in conditions that are computationally difficult for the motor planning system. Eight left fronto-parietal stroke patients with IM, five stroke patients without IM, and six healthy matched controls imagined grasping dowels and widgets presented at varying orientations, and actually grasped the same objects. The experimental predictions were confirmed. In addition, patients with IM and motor imagery deficits were significantly more likely than the non-apraxic group to have lesions in the intraparietal sulcus, a region previously implicated in imagery for hand-object interactions. The findings suggest a principled explanation for the deficits of IM patients in object-related gesture pantomime, imitation, and learning of new object-related gestures.     

The inhibition of imitative and overlearned responses: a functional double dissociation

Neuropsychological research has established that the inhibition of dominant response tendencies is a function of the prefrontal cortex. These inhibitory mechanisms are tested using tasks like the Stroop task, in which the prepotency of the dominant response is based on a learned relationship of stimulus and response. However, it has also been reported that patients with prefrontal lesions may have problems inhibiting imitative responses. The question arises of whether the inhibition of overlearned and imitative responses entails the same or different functional mechanisms and cortical networks. In a recent neuropsychological study with prefrontal patients we found first evidence for such a dissociation. The present fMRI study further investigated this question by directly comparing brain activity in the inhibition of overlearned and imitative response tendencies. It emerges that response inhibition in the two tasks involves different neural networks. While the inhibition of overlearned responses requires a fronto-parietal network involved in interference control and task management, the inhibition of imitative responses involves cortical areas that are required to distinguish between self-generated and externally triggered motor representations. The only frontal brain area that showed an overlap was located in the right inferior frontal gyrus and is probably related to the generation of the stop signal.     

A Systematic Review of Action Imitation in Autistic Spectrum Disorder

Imitative deficits have been associated with autistic spectrum disorder (ASD) for many years, most recently through more robust methodologies. A fresh, systematic review of the significance, characteristics, and underlying mechanism of the association is therefore warranted. From 121 candidates, we focused on 21 well-controlled studies involving 281 cases of ASD. Overall, children with ASD performed worse on imitative tasks (Combined Logit p value < .00005). The emerging picture is of delayed development in imitation, implicating a deficit in mapping neural codings for actions between sensory and motor modalities, rather than in motivation or executive function. We hypothesise that ASD is characterised by abnormal development of these mappings. such that they are biased towards object-oriented tasks at the expense of those required for action imitation per se.     

Discriminating which fork to use: Teaching selective imitation to people with autism

Little empirical research has focused on teaching of imitation to learners with autism in ordinary environments. Typically-developing individuals imitate the behavior of others in ordinary social environments. One possible reason that learners with autism do not imitate in ordinary environments is they are not observing relevant discriminative stimuli that should set the occasion for imitative responding. This paper will review the operant research on generalized imitation with the goal of identifying procedures to teach learners with autism to imitate in ordinary environments. A stimulus-control account of imitation in ordinary environments is included with the goal of the development of effective teaching procedures. Imitation in ordinary environments is discussed in relation to the discriminative stimuli that occasion imitative responding. The use of differential observing responses to increase discrimination of relevant stimuli in ordinary environments is suggested as a possible strategy to increase imitation among individuals with autism in ordinary environments.     

数字人体的虚拟与仿真技术

本文首先介绍了数字人体虚拟与仿真技术的基本概念;然后讨论了数字人体虚拟现实系统的基本类型、技术系统的结构、虚拟VR-(IS技术特点与应用、数字人体虚拟系统的关键理论、虚拟系统模型;最后阐述了虚拟现实技术的发展、虚拟现实系统的类型和构成.