Action Kinematics Research Articles

Review of domestic inventions on methods for diagnostics of postural disorders of the musculoskal system

The development of the musculoskeletal system depends on many components of anatomically determined changes in the body, the structure of movement patterns and the mechanisms of action involved in it. Postural disorders can arise as a result of various reasons and be a source of further changes in the body, influencing the development of compensatory changes and functional transformations of the motor sphere. Diagnosis of the state of the musculoskeletal system is an urgent task, through which many somatic changes can be corrected or compensated in a timely manner. This article reviews patent documents from databases such as FIPS, Orbit, Google patents over the past 30 years. It was revealed that the study of postural disorders is carried out in four areas of study: visual assessment in a standing position; diagnostic methods using stabilometric platforms; characteristics of disturbances in the assessment of muscle electrical potentials and analysis of the kinematics of motor actions during movement. In their content aspect, these diagnostic methods are focused on the quantitative and qualitative characteristics of the location of the boundaries of the regions of bone segments, the center of gravity of the body and the parameters of its movement during motor action; assessment of electromyographic indicators of coordination of muscle efforts in static and dynamic positions; analysis of the biomechanics of movement patterns with consideration of various components of the motor act.

The kinematics of false intent Conveyed by deceptive sidestep actions

Researchers have identified kinematic differences between deceptive and non-deceptive rugby reorientation actions. However, the honest and deceptive signals corresponded to ‘deception detection’ (accuracy increasing) rather than signals that caused deception (accuracy decreasing). In this study, statistical parametric mapping and multilevel modelling were applied to examine the kinematic differences between sidestep and non-deceptive actions during the time window of deception. The analysis compared three-dimensional motion capture data from 144 deceptive actions and 144 genuine actions performed by six high-skilled rugby players. Results indicated that the kinematics of deceptive actions were characterized by a combination of exaggerated head roll, outside foot and centre-of-mass displacement, and attenuated thorax roll and yaw relative to genuine actions. These are candidate sources for the cause of deception, either individually or in combination with other sources. Furthermore, the results indicate that previously identified ‘honest’ signals may not be reliable sources of information earlier in the action sequence.

Contextual Priors Shape Action Understanding before and beyond the Unfolding of Movement Kinematics.

Previous studies have shown that contextual information may aid in guessing the intention underlying others' actions in conditions of perceptual ambiguity. Here, we aimed to evaluate the temporal deployment of contextual influence on action prediction with increasing availability of kinematic information during the observation of ongoing actions. We used action videos depicting an actor grasping an object placed on a container to perform individual or interpersonal actions featuring different kinematic profiles. Crucially, the container could be of different colors. First, in a familiarization phase, the probability of co-occurrence between each action kinematics and color cues was implicitly manipulated to 80% and 20%, thus generating contextual priors. Then, in a testing phase, participants were asked to predict action outcome when the same action videos were occluded at five different timeframes of the entire movement, ranging from when the actor was still to when the grasp of the object was fully accomplished. In this phase, all possible action-contextual cues' associations were equally presented. The results showed that for all occlusion intervals, action prediction was more facilitated when action kinematics deployed in high- than low-probability contextual scenarios. Importantly, contextual priors shaped action prediction even in the latest occlusion intervals, where the kinematic cues clearly unveiled an action outcome that was previously associated with low-probability scenarios. These residual contextual effects were stronger in individuals with higher subclinical autistic traits. Our findings highlight the relative contribution of kinematic and contextual information to action understanding and provide evidence in favor of their continuous integration during action observation.

Forward effects from action observation: the role of attentional focus.

After viewing an image representing an action on an object, we recognize the forward states of the seen action faster than the backward states. The present study exploits a variant of a new experimental paradigm to investigate cognitive mechanisms underlying this effect. Participants viewed a series of still photos of unfolding actions on objects, each followed by a photo depicting either one of three (instead of two of the original paradigm) different and temporally distant moments after the image or one moment before the image, along with photos of different actions. Experiment 1 revealed the classical forward effects in this new context: when the task was to judge whether the action in the second photo was the same as in the first photo, evaluations were faster for all forward photos than for backward photos. In Experiment 2, we examined the role of participants' attention to the object alongside the role of attention to action kinematics in triggering these "forward effects" by manipulating participants' attentional focus. As the results showed, evaluations were faster for all forward photos when the focus was on the action kinematics, but when the focus was on the object, evaluations were faster only for the last forward photo showing the final action state. These results seem to suggest that focusing on the object triggers a representation of the action goal and thus modulates the mental simulation underlying action anticipation.

Functional role of the theory of mind network in integrating mentalistic prior information with action kinematics during action observation

Inferring intentions from verbal and nonverbal human behaviour is critical for everyday social life. Here, we combined Transcranial Magnetic Stimulation (TMS) with a behavioural priming paradigm to test whether key nodes of the Theory of Mind network (ToMn) contribute to understanding others' intentions by integrating prior knowledge about an agent with the observed action kinematics. We used a modified version of the Faked-Action Discrimination Task (FAD), a forced-choice paradigm in which participants watch videos of actors lifting a cube and judge whether the actors are trying to deceive them concerning the weight of the cube. Videos could be preceded or not by verbal description (prior) about the agent's truthful or deceitful intent. We applied single pulse TMS over three key nodes of the ToMn, namely dorsomedial prefrontal cortex (dmPFC), right posterior superior temporal sulcus (pSTS) and right temporo-parietal junction (rTPJ). Sham-TMS served as a control (baseline) condition. Following sham or rTPJ stimulation, we observed no consistent influence of priors on FAD performance. In contrast, following dmPFC stimulation, and to a lesser extent pSTS stimulation, truthful and deceitful actions were perceived as more deceptive only when the prior suggested a dishonest intention. These findings highlight a functional role of dmPFC and pSTS in coupling prior knowledge about deceptive intents with observed action kinematics in order to judge faked actions. Our study provides causal evidence that fronto-temporal nodes of the ToMn are functionally relevant to mental state inference during action observation.

Point-light display: a new tool to improve verb recovery in patients with aphasia? A pilot study

Some studies have demonstrated that Action Observation (AO) could help patients with aphasia to recover use of verbs. However, the role of kinematics in this effect has remained unknown. The main aim was to assess the effectiveness of a complementary intervention based on the observation of action kinematics in patients with aphasia. Seven aphasic patients (3 males, 4 females) aged between 55 and 88years participated in the studies. All patients received a classical intervention and an additional, specific intervention based on action observation. This consisted in visualizing a static image or a point-light sequence representing a human action and in trying to name the verb representing the action. In each session, 57 actions were visualized: 19 represented by a static drawing, 19 by a non-focalized point-light sequence, i.e., a point-light display with all dots in white, and 19 by a focalized point-light sequence, i.e., a point-light display (PLD) with the dots corresponding to the main limbs in yellow. Before (pre-test) and after (post-test) the intervention, each patient performed the same denomination task, in which all actions were presented in photographs. The results showed a significant improvement in performance between pre and post-test, but only when the actions were presented in focalized and non-focalized point-light sequences during the intervention. The presentation of action kinematics seems crucial in the recovery of verbs in patients with aphasia. This should be considered by speech therapists in their interventions.

A feature and conjunction visual search immersive virtual reality serious game for measuring spatial and distractor inhibition attention using response time and action kinematics

ABSTRACT Background Treisman (1980) proposed that visual-spatial attention to targets presented with distractors involves parallel and serial cognition. When the target is different from distractors by a single feature, the number of distractors does not influence search speed (parallel). However, when the target is different from the distractor by a conjunction of features, increased numbers of distractors increase task difficulty (serial). Here, we developed a serious game in immersive virtual reality (IVR) for evaluating spatial and distractor inhibition attention. Methods We tested 60 healthy participants. They performed the serious game in which they had to find a target mole wearing a red miner’s helmet. In the single feature parallel conditions, the distractor moles wore blue (miner’s or horned) helmets, and in the conjunction feature serial conditions, the distractor moles wore blue miner’s helmets or red horned helmets. There were 11–17–23 distractors. Responses were made with the dominant hand by hitting the target with a virtual hammer. We measured mean response time (RT), mean velocity (MV) and coefficient of variance of speed (CV). Results Participants were significantly slower (RT and MV) and showed greater CV when responding to targets in conjunction compared to single feature search tasks. Further, participants were slower (RT and MV) and showed greater CV when the number of distractors increased. A significant interaction between search tasks and distractors showed that RT and CV only increased with distractor number for the conjunction search tasks. MV decreased with distractor number for both single and conjunction tasks, with a stronger decrease for conjunction relative to single feature search. Conclusion The results replicated previous findings, providing support for the use of immersive virtual reality technology for the simultaneous evaluation of spatial and distractor inhibition attention using complex 3D objects.

Infants’ sensitivity to emotional expressions in actions: The contributions of parental expressivity and motor experience

Actions can convey information about the affective state of an actor. By the end of the first year, infants show sensitivity to such emotional information in actions. Here, we examined the mechanisms contributing to infants’ developing sensitivity to emotional action kinematics. We hypothesized that this sensitivity might rely on two factors: a stable motor representation of the observed action to be able to detect deviations from how it would typically be performed and experience with emotional expressions. The sensitivity of 12- to 13-month-old infants to happy and angry emotional cues in a manual transport action was examined using facial EMG. Infants’ own movements when performing an object transport task were assessed using optical motion capture. The infants’ caregivers’ emotional expressivity was measured using a questionnaire. Negative emotional expressivity of the primary caregiver was significantly related to infants’ sensitivity to observed angry actions. There was no evidence for such an association with infants’ own motor skill. Overall, our results show that infants’ experience with emotions, measured as caregivers’ emotional expressivity, may aid infants’ discrimination of others’ emotions expressed in action kinematics.

Coupling perception to action through incidental sensory consequences of motor behaviour

Researchers in the field of active perception study how sensory processes coalesce with motor actions to extract information from the world. Such actions intrinsically alter perceptual processing and have intended sensory outcomes, but also lead to incidental sensory consequences, which are side effects of moving the sensory surface to its intended goal. These incidental consequences of actions are generally considered a nuisance to perception that needs to be attenuated or suppressed during movement execution. In this Perspective, we propose instead that incidental sensory consequences of actions shape perceptual processes through action–perception couplings and we review evidence from the domain of active vision. We propose four hallmarks representing the degrees to which actions are an integral part of a perceptual processing architecture. Finally, we outline a research strategy for probing these hallmarks in active perceptual systems and conclude that researchers of perception should embrace the study of action kinematics in pursuit of their questions. Studying action is key for understanding perception because perceptual processes are shaped by movements of the sensory surface. In this Perspective, Rolfs and Schweitzer propose four hallmarks of action–perception coupling and outline a research strategy for the study of action kinematics in perception.

Action Intentions, Predictive Processing, and Mind Reading: Turning Goalkeepers Into Penalty Killers.

The key to action control is one’s ability to adequately predict the consequences of one’s actions. Predictive processing theories assume that forward models enable rapid “preplay” to assess the match between predicted and intended action effects. Here we propose the novel hypothesis that “reading” another’s action intentions requires a rich forward model of that agent’s action. Such a forward model can be obtained and enriched through learning by either practice or simulation. Based on this notion, we ran a series of studies on soccer goalkeepers and novices, who predicted the intended direction of penalties being kicked at them in a computerized penalty-reading task. In line with hypotheses, extensive practice in penalty kicking improved performance in penalty reading among goalkeepers who had extensive prior experience in penalty blocking but not in penalty kicking. A robust benefit in penalty reading did not result from practice in kinesthetic motor imagery of penalty kicking in novice participants. To test whether goalkeepers actually use such penalty-kicking imagery in penalty reading, we trained a machine-learning classifier on multivariate fMRI activity patterns to distinguish motor-imagery-related from attention-related strategies during a penalty-imagery training task. We then applied that classifier to fMRI data related to a separate penalty-reading task and showed that 2/3 of all correctly read penalty kicks were classified as engaging the motor-imagery circuit rather than merely the attention circuit. This study provides initial evidence that, in order to read our opponent’s action intention, it helps to observe their action kinematics, and use our own forward model to predict the sensory consequences of “our” penalty kick if we were to produce these action kinematics ourselves. In sum, it takes practice as a penalty kicker to become a penalty killer.

Threat Learning Shapes the Kinematics of Goal-Directed Actions

Threat Learning Shapes the Kinematics of Goal-Directed Actions

A dot that went for a walk: People prefer lines drawn with human-like kinematics.

A dominant theory of embodied aesthetic experience (Freedberg & Gallese, 2007, Trends in Cognitive Sciences, 11, 197) posits that the appreciation of visual art is linked to the artist’s movements when creating the artwork, yet a direct link between the kinematics of drawing actions and the aesthetics of drawing outcomes has not been experimentally demonstrated. Across four experiments, we measured aesthetic responses of students from arts and non‐arts backgrounds to drawing movements generated from computational models of human writing. Experiment 1 demonstrated that human‐like drawing movements with bell‐shaped velocity profiles (Sigma Lognormal [SL] and Minimum Jerk [MJ]) are perceived as more natural and pleasant than movements with a uniform profile, and in both Experiments 1 and 2 movements that were perceived as more natural were also preferred. Experiment 3 showed that this effect persists if lower‐level dynamic stimulus features are fully matched across experimental and control conditions. Furthermore, aesthetic preference for human‐like movements were associated with greater perceptual fluency in Experiment 3, evidenced by unbiased estimations of the duration of natural movements. In Experiment 4, line drawings with visual features consistent with the dynamics of natural, human‐like movements were preferred, but only by art students. Our findings directly link the aesthetics of human action to the visual aesthetics of drawings, but highlight the importance of incorporating artistic expertise into embodied accounts of aesthetic experience.

Contextual Priors Guide Perception and Motor Responses to Observed Actions.

In everyday-life scenarios, prior expectations provided by the context in which actions are embedded support action prediction. However, it is still unclear how newly learned action-context associations can drive our perception and motor responses. To fill this gap, we measured behavioral (Experiment 1) and motor responses (Experiment 2) during two tasks requiring the prediction of occluded actions or geometrical shapes. Each task consisted of an implicit probabilistic learning and a test phase. During learning, we exposed participants to videos showing specific associations between a contextual cue and a particular action or shape. During the test phase, videos were earlier occluded to reduce the amount of sensorial information and induce participants to use the implicitly learned action/shape-context associations for disambiguation. Results showed that reliable contextual cues made participants more accurate in identifying the unfolding action or shape. Importantly, motor responses were modulated by contextual probability during action, but not shape prediction. Particularly, in conditions of perceptual uncertainty the motor system coded for the most probable action based on contextual informativeness, regardless of action kinematics. These findings suggest that contextual priors can shape motor responses to action observation beyond mere kinematics mapping.

Adults Do Not Distinguish Action Intentions Based on Movement Kinematics Presented in Naturalistic Settings.

Predicting others’ actions is an essential part of acting in the social world. Action kinematics have been proposed to be a cue about others’ intentions. It is still an open question as to whether adults can use kinematic information in naturalistic settings when presented as a part of a richer visual scene than previously examined. We investigated adults’ intention perceptions from kinematics using naturalistic stimuli in two experiments. In experiment 1, thirty participants watched grasp-to-drink and grasp-to-place movements and identified the movement intention (to drink or to place), whilst their mouth-opening muscle activity was measured with electromyography (EMG) to examine participants’ motor simulation of the observed actions. We found anecdotal evidence that participants could correctly identify the intentions from the action kinematics, although we found no evidence for increased activation of their mylohyoid muscle during the observation of grasp-to-drink compared to grasp-to-place actions. In pre-registered experiment 2, fifty participants completed the same task online. With the increased statistical power, we found strong evidence that participants were not able to discriminate intentions based on movement kinematics. Together, our findings suggest that the role of action kinematics in intention perception is more complex than previously assumed. Although previous research indicates that under certain circumstances observers can perceive and act upon intention-specific kinematic information, perceptual differences in everyday scenes or the observers’ ability to use kinematic information in more naturalistic scenes seems limited.

Top-Down Attention Guidance Shapes Action Encoding in the pSTS.

The posterior superior temporal sulcus (pSTS) is a brain region characterized by perceptual representations of human body actions that promote the understanding of observed behavior. Increasingly, action observation is recognized as being strongly shaped by the expectations of the observer (Kilner 2011; Koster-Hale and Saxe 2013; Patel etal. 2019). Therefore, to characterize top-down influences on action observation, we evaluated the statistical structure of multivariate activation patterns from the action observation network (AON) while observers attended to the different dimensions of action vignettes (the action kinematics, goal, or identity of avatars jumping or crouching). Decoding accuracy varied as a function of attention instruction in the right pSTS and left inferior frontal cortex (IFC), with the right pSTS classifying actions most accurately when observers attended to the action kinematics and the left IFC classifying most accurately when observed attended to the actor's goal. Functional connectivity also increased between the right pSTS and right IFC when observers attended to the actions portrayed in the vignettes. Our findings are evidence that the attentive state of the viewer modulates sensory representations in the pSTS, consistent with proposals that the pSTS occupies an interstitial zone mediating top-down context and bottom-up perceptual cues during action observation.

Grasping Social Apathy: The Role of Reach-To-Grasp Action Kinematics for the Assessment of Social Apathy in Mild Neurocognitive Disorders.

Social apathy, a reduction in initiative in proposing or engaging in social activities or interactions, is common in mild neurocognitive disorders (MND). Current apathy assessment relies on self-reports or clinical scales, but growing attention is devoted to defining more objective, measurable and non-invasive apathy proxies. In the present study we investigated the interest of recording action kinematics in a social reach-to-grasp task for the assessment of social apathy. Thirty participants took part in the study: 11 healthy controls (HC; 6 females, mean age = 68.3±10.5 years) and 19 subjects with MND (13 females, mean age = 75.7±6.3 years). Based on the Diagnostic Criteria for Apathy, MND subjects were classified as socially apathetic (A-MND, N = 9) versus non-apathetic (NA-MND, N = 10). SensRing, a ring-shaped wearable sensor, was placed on their index finger, and subjects were asked to reach and grasp a can to place it into a cup (individual condition) and pass it to a partner (social condition). In the reach-to-grasp phase of the action, HC and NA-MND showed different acceleration and velocity profiles in the social versus individual condition. No differences were found for A-MND. Previous studies showed the interest of recording patients' level of weekly motor activity for apathy assessment. Here we showed that a 10-min reach-to-grasp task may provide information to differentiate socially apathetic and non-apathetic subjects with MND, thus providing a tool easily usable in the clinical practice. Future studies with a bigger sample are needed to better characterize these findings.

Developing non‐invasive, objective assessment tools for social apathy in neurocognitive disorders: The role of action kinematics

AbstractBackgroundApathy, a reduction in goal‐directed activities in the domains of behavior, cognition, emotion and social interaction, is one of the most common behavioral symptoms in Neurocognitive Disorders (NCD)[1]. Current apathy assessment strongly relies on self‐reports or clinical scales, which are subjective and dependent on the information provided by patients and caregivers. For this reason, growing attention is devoted to defining more objective, measurable and non‐invasive apathy proxies. In the present study we investigated the interest of recording action kinematics in a short reach and grasp protocol[2] for the assessment of apathy social component, characterized by a reduction of the willingness to interact with others.Methods19 subjects with Mild NCD (6M, age=75,7±6,3y, MMSE=26,0±3,0) were recruited at the Nice Memory Center. Based on the Apathy Motivation Index (social motivation subscale[3]), subjects were classified as socially apathetic (N=9) vs non‐apathetic (N=10). SensRing, a novel ring‐shaped wearable sensor[4], was placed on their dominant hand’s index finger. Subjects were asked to reach and grasp a can to place it into a cup (individual condition) and pass it to a partner (social condition). Several parameters were extracted, including movement velocity, acceleration, jerk (representing the smoothness of the movement) and execution time.ResultsNon‐apathetic participants showed a significantly lower peak velocity (p=0,009) and a lower jerk (p=0,038) in the social vs individual condition when moving the can to the final position, suggesting a more careful approach in placing the object in the partner’s hand vs a cup. Non‐apathetic participants showed no significant differences between conditions in any of the extracted parameters.ConclusionPrevious studies showed the interest of recording patients’ level of weekly motor activity for apathy assessment. Here, for the first time, we showed that a 5‐minutes reach and grasp protocol may be able to show differences between socially apathetic and non‐apathetic subjects with Mild NCD, thus providing a tool easily usable in the clinical practice. Future studies with a bigger sample are needed to better characterize these findings. [1] Manera et al., 2019, doi.org/10.1002/gps.5125. [2] Becchio et al., 2008, doi.org/10.1016/j.concog.2007.03.003. [3] Ang et al., 2017, doi:10.1371/journal.pone.0169938. [4] Rovini et al., 2020, EMBC‐2020.

Predictive sensorimotor control in autism.

Autism spectrum disorder has been characterized by atypicalities in how predictions and sensory information are processed in the brain. To shed light on this relationship in the context of sensorimotor control, we assessed prediction-related measures of cognition, perception, gaze and motor functioning in a large general population (n = 92; Experiment 1) and in clinically diagnosed autistic participants (n = 29; Experiment 2). In both experiments perception and action were strongly driven by prior expectations of object weight, with large items typically predicted to weigh more than equally-weighted smaller ones. Interestingly, these predictive action models were used comparably at a sensorimotor level in both autistic and neurotypical individuals with varying levels of autistic-like traits. Specifically, initial fingertip force profiles and resulting action kinematics were both scaled according to participants' pre-lift heaviness estimates, and generic visual sampling behaviours were notably consistent across groups. These results suggest that the weighting of prior information is not chronically underweighted in autism, as proposed by simple Bayesian accounts of the disorder. Instead, our results cautiously implicate context-sensitive processing mechanisms, such as precision modulation and hierarchical volatility inference. Together, these findings present novel implications for both future scientific investigations and the autism community.

The Dorsal Striatum Energizes Motor Routines

The dorsal striatum (dS) has been implicated in storing procedural memories and controlling movement kinematics. Since procedural memories are expressed through movements, the exact nature of the dS function has proven difficult to delineate. Here, we challenged rats in complementary locomotion-based tasks designed to alleviate this confound. Surprisingly, dS lesions did not impair the rats' ability to remember the procedure for the successful completion of motor routines. However, the speed and initiation of the reward-oriented phase of the routines were irreversibly altered by the dS lesion. Further behavioral analyses, combined with modeling in the optimal control framework, indicated that these kinematic alterations were well explained by an increased sensitivity to effort. Our work provides evidence supporting a primary role of the dS in modulating the kinematics of reward-oriented actions, a function that may be related to the optimization of the energetic costs of moving.

Fuzzy Integral-Based CNN Classifier Fusion for 3D Skeleton Action Recognition

Action recognition based on skeleton key joints has gained popularity due to its cost effectiveness and low complexity. Existing Convolutional Neural Network (CNN) based models mostly fail to capture various aspects of the skeleton sequence. To this end, four feature representations, which capture complementary characteristics of the sequence of key joints, are extracted with novel contribution of features estimated from angular information, and kinematics of the human actions. Single channel grayscale images are used to encode these features for classification using four CNNs, with the complementary nature verified through Kullback-Leibler (KL) and Jensen-Shannon (JS) divergences. As opposed to straightforward classifier combination generally used in existing literature, fuzzy fusion through the Choquet integral leverages the degree of uncertainty of decision scores obtained from four CNNs. Experimental results support the efficacy of fuzzy combination of CNNs to adaptively generate final decision score based upon confidence of each information source. Impressive results on the challenging UTD-MHAD, HDM05, G3D, and NTU RGB+D 60 and 120 datasets demonstrate the effectiveness of the proposed method. The source code for our method is available at https://github.com/theavicaster/fuzzy-integral-cnn-fusion-3d-har