Self/other distinction in adolescents with autism spectrum disorder (ASD) assessed with a double mirror paradigm.

BACKGROUND: Self/other distinction (SOD), which refers to the ability to distinguish one's own body, actions, and mental representations from those of others, is an essential skill for effective social interaction. A large body of clinical evidence suggests that disruptions in SOD may be key to social communication deficits in individuals with autism spectrum disorders (ASD). In particular, egocentric biases have been found in cognitive, affective, behavioural, and motor domains. However, research in this area is scarce and consists of recognition paradigms that have used only static images; these methods may be insufficient for assessing SOD, given the increasing role of embodiment in our understanding of the pathophysiology of ASD. METHOD: A single-centre, prospective pilot study was carried out to investigate, for the first time, self-recognition and SOD in seven adolescents with ASD compared with matched, typically developing controls (TDCs) using the "Alter Ego"TM double mirror paradigm. The participants viewed a double mirror in which their own face was gradually morphed into the face of an unfamiliar other (self-to-other sequence) or vice versa (other-to-self sequence); participants were instructed to indicate at which point the morph looked more like their own face than the other's face. Two judgement criteria were used: 1) M1: the threshold at which subjects started to recognize their own face during the other-to-self morphing sequence; 2) M2: the threshold at which subjects started to recognize the other's face during the self-to-other morphing sequence. RESULTS: Consistent with the predictions, the results showed that the participants with ASD exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence, suggesting an egocentric bias. SOD impairments were also marginally correlated with ASD severity, indicating earlier face recognition in more severely affected individuals. Furthermore, in contrast with that of TDCs, the critical threshold for switching between self and other varied with the direction of morphing in ASD participants. Finally, these differences in face recognition and SOD using mirrors, unlike previous research using static images, support the central place of bodily self-consciousness in SOD impairments. CONCLUSIONS: Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in ASD individuals on an embodied, semiecological face-recognition paradigm. Implications for understanding ASD are discussed from a developmental perspective, and new research and therapeutic perspectives are presented.

Dissociation between dreams and wakefulness: Insights from body and action representations of rare individuals with massive somatosensory deafferentation.

The realism of body and actions in dreams is thought to be induced by simulations based on internal representations used during wakefulness. As somatosensory signals contribute to the updating of body and action representations, these are impaired when somatosensory signals are lacking. Here, we tested the hypothesis that individuals with somatosensory deafferentation have impaired body and actions in their dreams, as in wakefulness. We questioned three individuals with a severe, acquired sensory neuropathy on their dreams. While deafferented participants were impaired in daily life, they could dream of themselves as able-bodied, with some sensations (touch, proprioception) and actions (such as running or jumping) which had not been experienced in physical life since deafferentation. We speculate that simulation in dreams could be based on former, "healthy" body and action representations. Our findings are consistent with the idea that distinct body and action representations may be used during dreams and wakefulness.

Age and sex impact on visuospatial working memory (VSWM), mental rotation, and cognitive strategies during navigation.

This study assessed the impact of sex and typical aging on visuospatial working memory (VSWM), mental rotations, and navigational strategies using behavioral information. Fifty healthy participants regrouped in older (OA) and young adults (YA) performed the Walking Corsi test (WalCT) and the Redrawn Mental Rotation Test (MRT) to explore mental rotation abilities. We recorded kinematic data such as locomotion trajectories, and spatial orientations during navigation. We created a new method of data analysis for the WalCT performances and compared it with the classical approach. This original method allowed us to identify cognitive strategies based on errors analysis. Our data suggested that VSWM and mental rotation capacities in locomotion were modulated by age (YA scored higher than OA), and sex (Young Adult Males (YA-M) having higher performance than Young Adult Females (YA-F). We observed a preferential use of cognitive strategies related to sex; YA-F relied more on egocentric strategies whereas YA-M relied more on allocentric strategies. The preferential use of cognitive strategies in the YA group was not observed in the OA group producing more random errors per sequence. The results suggest the effects that age and sex have on VSWM, cognitive strategies, and mental rotation during navigation and highlight the importance of navigational strategies training.

Goal-oriented locomotion in children with spastic diplegia: Anticipatory orienting strategies and trajectory formation.

Goal-oriented locomotion (GOL) is a complex task integrating navigation and gait control. To our knowledge, this is the first study of GOL in subjects with Cerebral Palsy (CP). Thirteen subjects with spastic diplegia and 26 with typical development were enrolled in the study. Subjects performed a GOL task to reach luminous targets. Within-subject trajectory variability, maximal head deviation from trajectory and mean head anticipation over trajectory were analyzed. While all subjects showed gait impairment, only 8 of 13 subjects also showed navigation abnormalities as revealed by either: a) abnormal head orientation and trajectory formation, or b) abnormal head orientation with normal trajectory formation. Abnormal gait patterns do not account for and can be distinguished from navigation disorders in spastic diplegic CP. This distinction has important implications for novel rehabilitation methods that should specifically address navigation, not only gait.

A New Paradigm for the Study of Cognitive Flexibility in Children and Adolescents: The "Virtual House Locomotor Maze" (VHLM).

Classical neuropsychological assessments are designed to explore cognitive brain functions using paper-and-pencil or digital tests. The purpose of this study was to design and to test a new protocol named the "Virtual House Locomotor Maze" (VHLM) for studying inhibitory control as well as mental flexibility using a visuo-spatial locomotor memory test. The VHLM is a simple maze including six houses using the technology of the Virtual Carpet Paradigm™. Ten typical development children (TD) were enrolled in this study. The participants were instructed to reach a target house as quickly as possible and to bear in mind the experimental instructions. We examined their planning and replanning abilities to take the shortest path to reach a target house. In order to study the cognitive processes during navigation, we implemented a spatio-temporal index based on the measure of kinematics behaviors (i.e., trajectories, tangential velocity and head direction). Replanning was tested by first repeating a path chosen by the subject to reach a given house. After learning this path, it was blocked imposing that the subject inhibited the learned trajectory and designed a new trajectory to reach the same house. We measured the latency of the departure after the presentation of each house and the initial direction of the trajectory. The results suggest that several strategies are used by the subjects for replanning and our measures could be used as an index of impulsivity.

The Virtual City ParadigmTM for Testing Visuo-Spatial Memory, Executive Functions and Cognitive Strategies in Children With ADHD: A Feasibility Study.

Navigation is a complex process, requiring target localization, route planning or retrieval, and physical displacement. Executive functions (EFs) such as working memory, inhibition and planning are fundamental for succeeding in this complex activity and are often impaired in Attention Deficit and Hyperactivity Disorder (ADHD). Our aim was to analyze the feasibility of a new ecological navigation task, the Virtual City paradigm™ (VC™) to test visuo-spatial memory and EFs in children with ADHD. Visuo-spatial short and working memory, inhibition and planning skills were tested with standardized tasks. The VC™, a new paradigm developed by our group, used the Virtual CarpetTM technology, consisting of a virtual town with houses, streets and crossroads projected on the ground. It includes a motion capture system, tracking body movement in 3D in real time. In one condition, children were required to walk through the city and reach a sequence of houses. In the other, before walking, they had to plan the shortest path to reach the houses, inhibiting the prepotent response to start walking. The results show a good feasibility of the paradigm (feasibility checklist and ad hoc questionnaire), being ecological and motivating. VC™ measures of span positively correlated with visuo-spatial short and working memory measures, suggesting that VC™ heavily relies on efficient spatial memory. Individual subject analyses suggested that children with ADHD may approach this task differently from typically developing children. Larger samples of ADHD and healthy children may further explore the specific role of EFs and memory, potentially opening new avenues for intervention.

Age-related decline in visuo-spatial working memory is reflected by dorsolateral prefrontal activation and cognitive capabilities.

INTRODUCTION: Visuo-spatial working memory (VSWM) performances undergo a decline throughout aging and are affected by the space in which the task is performed (reaching or navigational). Cerebral oxygenation and cognitive capabilities could explain this decline. We assessed the effects of age on cerebral oxygenation of the dorsolateral prefrontal cortex (dlPFC) in VSWM tasks in reaching and navigational space. We also assessed cognitive correlates of VSWM performance in each space. METHOD: Thirty-one (31) young adults (YA) and 24 healthy older adults (OA) performed a battery of neuropsychological tests and the electronic Corsi Block-tapping Test in reaching space (e-CBT) and in navigational space on the "Virtual Carpet" (VWCT). Participants were asked to memorize and recall a sequential pathway, progressively increasing from 2 to 9 blocks. Their span score reflected VSWM performance. The dlPFC oxygenation (oxyhaemoglobin: ΔO2Hb and deoxyhaemoglobin: ΔHHb) was measured by using functional Near-Infrared Spectroscopy (fNIRS) during the encoding of the sequential pathway in both tasks. RESULTS: YA had higher span scores than OA in both spaces. We identified a significantly stronger decrease of ΔHHb in YA compared to OA during encoding in VWCT. OA also exhibited significantly lower cerebral oxygenation in VWCT compared to e-CBT. A decrease of ΔHHb was also associated with a better performance in VWCT. Finally, we identified the association of mental rotation and executive functions with VSWM performance in both tasks. CONCLUSION: VSWM performance and cerebral oxygenation during encoding are impacted by aging. Space in which the task was performed was found to be associated with different cognitive functions and revealed differences in cerebral oxygenation.

Decoding the neural dynamics of free choice in humans.

How do we choose a particular action among equally valid alternatives? Nonhuman primate findings have shown that decision-making implicates modulations in unit firing rates and local field potentials (LFPs) across frontal and parietal cortices. Yet the electrophysiological brain mechanisms that underlie free choice in humans remain ill defined. Here, we address this question using rare intracerebral electroencephalography (EEG) recordings in surgical epilepsy patients performing a delayed oculomotor decision task. We find that the temporal dynamics of high-gamma (HG, 60-140 Hz) neural activity in distinct frontal and parietal brain areas robustly discriminate free choice from instructed saccade planning at the level of single trials. Classification analysis was applied to the LFP signals to isolate decision-related activity from sensory and motor planning processes. Compared with instructed saccades, free-choice trials exhibited delayed and longer-lasting HG activity during the delay period. The temporal dynamics of the decision-specific sustained HG activity indexed the unfolding of a deliberation process, rather than memory maintenance. Taken together, these findings provide the first direct electrophysiological evidence in humans for the role of sustained high-frequency neural activation in frontoparietal cortex in mediating the intrinsically driven process of freely choosing among competing behavioral alternatives.

Correction to: Victor Semeonovich Gurfnkel (April 2, 1922-January 14, 2020).

In the original publication of the article.

Does the Cerebellum Implement or Select Geometries? A Speculative Note.

During evolution, living systems, actively interacting with their environment, developed the ability, through sensorimotor contingencies, to construct functional spaces shaping their perception and their movements. These geometries were modularly embedded in specific functional neuro-architectures. In particular, human movements were shown to obey several empirical laws, such as the 2/3 power law, isochrony, or jerk minimization principles, which constrain and adapt motor planning and execution. Outstandingly, such laws can be deduced from a combination of Euclidean, affine, and equi-affine geometries, whose neural correlates have been partly detected in several brain areas including the cerebellum and the basal ganglia. Reviving Pellionisz and Llinas general hypothesis regarding the cerebrum and the cerebellum as geometric machines, we speculate that the cerebellum should be involved in implementing and/or selecting task-specific geometries for motor and cognitive skills. More precisely, the cerebellum is assumed to compute forward internal models to help specific cortical and subcortical regions to select appropriate geometries among, at least, Euclidean and affine geometries. We emphasize that the geometrical role of the cerebellum deserves a renewal of interest, which may provide a better understanding of its specific contributions to motor and associative (cognitive) functions.

Hyperscanning EEG and Classification Based on Riemannian Geometry for Festive and Violent Mental State Discrimination.

Interactions between two brains constitute the essence of social communication. Daily movements are commonly executed during social interactions and are determined by different mental states that may express different positive or negative behavioral intent. In this context, the effective recognition of festive or violent intent before the action execution remains crucial for survival. Here, we hypothesize that the EEG signals contain the distinctive features characterizing movement intent already expressed before movement execution and that such distinctive information can be identified by state-of-the-art classification algorithms based on Riemannian geometry. We demonstrated for the first time that a classifier based on covariance matrices and Riemannian geometry can effectively discriminate between neutral, festive, and violent mental states only on the basis of non-invasive EEG signals in both the actor and observer participants. These results pave the way for new electrophysiological discrimination of mental states based on non-invasive EEG recordings and cutting-edge machine learning techniques.

Rat Retrosplenial Cortical Involvement in Wayfinding Using Visual and Locomotor Cues.

The retrosplenial cortex (RSC) has been implicated in wayfinding using different sensory cues. However, the neural mechanisms of how the RSC constructs spatial representations to code an appropriate route under different sensory cues are unknown. In this study, rat RSC neurons were recorded while rats ran on a treadmill affixed to a motion stage that was displaced along a figure-8-shaped track. The activity of some RSC neurons increased during specific directional displacements, while the activity of other neurons correlated with the running speed on the treadmill regardless of the displacement directions. Elimination of visual cues by turning off the room lights and/or locomotor cues by turning off the treadmill decreased the activity of both groups of neurons. The ensemble activity of the former group of neurons discriminated displacements along the common central path of different routes in the track, even when visual or locomotor cues were eliminated where different spatial representations must be created based on different sensory cues. The present results provide neurophysiological evidence of an RSC involvement in wayfinding under different spatial representations with different sensory cues.

Exploring Self-Consciousness From Self- and Other-Image Recognition in the Mirror: Concepts and Evaluation.

A historical review of the concepts of self-consciousness is presented, highlighting the important role of the body (particularly, body perception but also body action), and the social other in the construction of self-consciousness. More precisely, body perception, especially intermodal sensory perception including kinesthetic perception, is involved in the construction of a sense of self allowing self-other differentiation. Furthermore, the social other, through very early social and emotional interactions, provides meaning to the infant's perception and contributes to the development of his/her symbolization capacities. This is a necessary condition for body image representation and awareness of a permanent self in a time-space continuum (invariant over time and space). Self-image recognition impairments in the mirror are also discussed regarding a comprehensive developmental theory of self-consciousness. Then, a neuropsychological and neurophysiological approach to self-consciousness reviews the role of complex brain activation/integration pathways and the mirror neuron system in self-consciousness. Finally, this article offers new perspectives on self-consciousness evaluation using a double mirror paradigm to study self- and other- image and body recognition.

Gravito-inertial ambiguity resolved through head stabilization.

It has been frequently observed that humans and animals spontaneously stabilize their heads with respect to the gravitational vertical during body movements even in the absence of vision. The interpretations of this intriguing behaviour have so far not included the need, for survival, to robustly estimate verticality. Here we use a mechanistic model of the head/otolith organ to analyse the possibility for this system to render verticality 'observable', a fundamental prerequisite to the determination of the angular position and acceleration of the head from idiothetic, inertial measurements. The intrinsically nonlinear head-vestibular dynamics is shown to generally lack observability unless the head is stabilized in orientation by feedback. Thus, our study supports the hypothesis that a central function of the physiologically costly head stabilization strategy is to enable an organism to estimate the gravitational vertical and head acceleration during locomotion. Moreover, our result exhibits a rare peculiarity of certain nonlinear systems to fortuitously alter their observability properties when feedback is applied.

Self-other recognition impairments in individuals with schizophrenia: a new experimental paradigm using a double mirror.

Clinical observations suggest early self-consciousness disturbances in schizophrenia. A double mirror combining the images of two individuals sitting on each side of the mirror was used to study self-other differentiation in 12 individuals with early onset schizophrenia (EOS) and 15 individuals with adult onset schizophrenia (AOS) compared to 27 typically developing controls (TDC) matched on age and sex. The effects of intermodal sensory perception (visual-tactile and visual-kinesthetic) on self-other recognition were also studied. The results showed that EOS and AOS individuals, independently of age and schizophrenia severity, were centered on their own image compared to TDC, with both significant earlier self-recognition and delayed other-recognition during the visual recognition task. In addition, there was no significant effect of intermodal sensory stimulation on self-other recognition in EOS and AOS patients, whereas self-centered functioning was significantly increased by visual-tactile stimulation and decreased by visual-kinesthetic stimulation in TDC. The findings suggest that self-other recognition impairments might be a possible endophenotypic trait of schizophrenia.

Interpersonal Synchronization, Motor Coordination, and Control Are Impaired During a Dynamic Imitation Task in Children With Autism Spectrum Disorder.

Background: Impairments in imitation abilities have been commonly described in children with autism spectrum disorder (ASD). How motricity in interpersonal coordination impacts imitation, during long lasting semi-ecological conditions, has not been carefully investigated. Methods: Eighty-five children and adolescents (39 controls with typical development, TD; 29 patients with ASD; 17 patients with developmental coordination disorder, DCD), aged 6 to 20 years, participated to a behavioral paradigm in which participants, standing and moving, interacted with a virtual tightrope walker standing and moving as well. During the protocol, we measured automatically and continuously bodily postures and movements from RGB sensor recording to assess participants' behavioral imitation. Results: We show that (1) interpersonal synchronization (as evidenced by the synchrony between the participant's and the tightrope walker's bars) and (2) motor coordination (as evidenced by the synchrony between the participant's bar and its own head axis) increased with age and were more impaired in patients with ASD. Also, motor control as evidenced by the movement angle standard deviations of participants' bar and head were significantly impaired in ASD compared to TD or DCD. Conclusion: Interpersonal synchronization and motor coordination during ecological interaction show both subtle impairment in children with ASD as compared to children with TD or DCD. These results questioned how motricity mature in terms of motor control and proprioception in children with ASD.

Behavioral Own-Body-Transformations in Children and Adolescents With Typical Development, Autism Spectrum Disorder, and Developmental Coordination Disorder.

Background: In motor imitation, taking a partner's perspective often involves a mental body transformation from an embodied, ego-centered viewpoint to a disembodied, hetero-centered viewpoint. Impairments of both own-body-transformation (OBT) and abnormalities in visual-spatial processing have been reported in patients with neurodevelopmental disorders including autism spectrum disorder (ASD). In the context of a visual-motor interactive task, studying OBT impairments while disentangling the contribution of visual-spatial impairments associated with motor coordination problems has not been investigated. Methods: 85 children and adolescents (39 controls with typical development, TD; 29 patients with ASD; 17 patients with developmental coordination disorder, DCD), aged 6-19 years, participated in a behavioral paradigm in which participants interacted with a virtual tightrope walker (TW) standing and moving with him. The protocol enables to distinguish ego-centered and hetero-centered perspectives. Results: We show that (1) OBT was possible but difficult for children with neurodevelopmental disorders, as well as for TD children, when the task required the participant to perform a mental rotation in order to adopt a hetero-centered perspective. (2) Using multivariate models, hetero-centered perspective score was significantly associated with age, TW orientation, latency, and diagnosis. ASD and TD groups' performances were close and significantly correlated with age. However, it was not the case for DCD, since this group was specifically handicapped by visual-spatial impairments. (3) ASD and DCD did not perform similarly: motor performance as shown by movement amplitude was better in DCD than ASD. ASD motor response was more ambiguous and hardly readable. Conclusion: Changing perspective in a spatial environment is possible for patients with ASD although delayed compared with TD children. In patients with DCD, their visual-spatial impairments negatively modulated their performances in the experiment.

Adaptive Gaze Strategies for Locomotion with Constricted Visual Field.

In retinitis pigmentosa (RP), loss of peripheral visual field accounts for most difficulties encountered in visuo-motor coordination during locomotion. The purpose of this study was to accurately assess the impact of peripheral visual field loss on gaze strategies during locomotion, and identify compensatory mechanisms. Nine RP subjects presenting a central visual field limited to 10-25° in diameter, and nine healthy subjects were asked to walk in one of three directions-straight ahead to a visual target, leftward and rightward through a door frame, with or without obstacle on the way. Whole body kinematics were recorded by motion capture, and gaze direction in space was reconstructed using an eye-tracker. Changes in gaze strategies were identified in RP subjects, including extensive exploration prior to walking, frequent fixations of the ground (even knowing no obstacle was present), of door edges, essentially of the proximal one, of obstacle edge/corner, and alternating door edges fixations when approaching the door. This was associated with more frequent, sometimes larger rapid-eye-movements, larger movements, and forward tilting of the head. Despite the visual handicap, the trajectory geometry was identical between groups, with a small decrease in walking speed in RPs. These findings identify the adaptive changes in sensory-motor coordination, in order to ensure visual awareness of the surrounding, detect changes in spatial configuration, collect information for self-motion, update the postural reference frame, and update egocentric distances to environmental objects. They are of crucial importance for the design of optimized rehabilitation procedures.

Does the cerebellum contribute to human navigation by processing sequential information?

OBJECTIVE: Several authors have proposed that the cerebellum has an important role in functions of higher order as a general mode of sequence detection, independently from the nature of the information. The aim of this study was to verify whether the cerebellum mediates the processing of navigational sequential information and to determine whether it is influenced by the modality of the stimuli presentation. METHOD: We tested 12 cerebellar patients and 12 healthy age-matched participants in 2 comparable navigational tasks (Walking Corsi Test and the Magic Carpet) requiring to memorizing a sequence of spatial locations. The 2 tasks differ each other for the modality of stimuli presentation: in the Walking Corsi Test the sequence is shown by an examiner that walks on the carpet, whereas in the Magic Carpet it is shown by a computer that lights up the tiles in the sequence. We hypothesize that different mental processes are implicated between the Walking Corsi Test and the Magic Carpet. Indeed, whereas watching the examiner, who performs the sequence on the carpet, allows the patient to simulate the action mentally in the Walking Corsi Test, such simulation cannot be triggered in the Magic Carpet. RESULTS: Our results showed that cerebellar patients obtained scores significantly lower than control participants only in the Magic Carpet. CONCLUSIONS: We interpreted the patients' performance as a specific deficit in detecting and ordering single independent stimuli as a sequence, when the maintenance of stimulus-response associations is more demanding. (PsycINFO Database Record