The primary intent of this study was to gain insight into children's ability to use visual information in planning reaching movements. More specifically, the work presented here examined, from a developmental perspective, the use of visual information to use a) egocentric cues, b) allocentric cues, and c) the combination, in the form of visual background around a target. Children representing the age groups 5-, 7-, 9-, 11 years and adults participated in three experiments. All experiments were conducted using an immediate (visually-guided) and response-delay (memory-guided) paradigm. Experiment 1 examined the ability of participants to use an egocentric frame of reference to estimate reach via motor imagery. Results indicated that introducing a >̲ 2s delay affected responses in all age groups, especially the younger age groups (5- and 7-year-olds). As delay increased, children as a group tended to overestimate, while adults underestimated. Experiment 2 investigated how participants used allocentric cues to estimate the location of objects in a perceptual estimate paradigm. Results revealed that introducing a delay affected the estimation of distance among all age groups, with greater effect on the younger age groups. Experiment 3 examined how a visual background surrounding a target would affect estimation of reach. Results revealed that there were no differences when targets were surrounded with or without a background. Results also showed that the 5- and 7-year-olds were most affected on their perception of reach and estimates by longer delays. Considered together, these results hint that: (1) there is a significant temporal constraint on the representation of movement through the visoumotor stream, especially with children 7 years and younger, and (2) children as a whole tend to operate and rely more on an egocentric frame of reference; therefore, responses of reachability and distance estimates were susceptible to greater error when performed after a 2s delay.

We examined the effects of keeping hand actions in working memory on the speed of naming handled objects. The features of the hand action and objects’ handle matched or mismatched on two dimensions: alignment (left vs. right), orientation (horizontal vs. vertical). For objects presented in their canonical upright position, the speed of naming was only slower when the actions were partially incongruent with the target object. For rotated objects, the effect was reversed. The pattern of results suggests that the identification system is more sensitive to the functional goal (i.e. the end state) of the rotated object in evoking action representations than the actions evoked by the depicted view (i.e. the beginning state). The findings, overall, strongly support the notion that action representations play a functional role in object identification. / Graduate / 0633 / 0623 / tlin23@gmail.com

We examined the effects of keeping hand actions in working memory on the speed of naming handled objects. The features of the hand action and objects’ handle matched or mismatched on two dimensions: alignment (left vs. right), orientation (horizontal vs. vertical). For objects presented in their canonical upright position, the speed of naming was only slower when the actions were partially incongruent with the target object. For rotated objects, the effect was reversed. The pattern of results suggests that the identification system is more sensitive to the functional goal (i.e. the end state) of the rotated object in evoking action representations than the actions evoked by the depicted view (i.e. the beginning state). The findings, overall, strongly support the notion that action representations play a functional role in object identification. / Graduate / 0633 / 0623 / tlin23@gmail.com

Evidence suggests that action representations associated with the functional and volumetric properties of an object are part of its conceptual representation (Bub, Masson, & Cree, 2008; Jax & Buxbaum, 2010). To further examine the dynamic interplay between functional and volumetric action representations during object perception, a series of experiments was carried out in which participants made a reach and grasp response in the context of an object pictured either upright or rotated. When trained to identify a colour cue as a prompt to make a specific hand action, with the cue presented at different stimulus onset asynchronies (SOA), participants showed priming effects as early as 300 ms before the presentation of an upright object prime for both functional and volumetric actions. With pictures of hand posture cues, at similar SOAs, participants showed the same pattern of consistent priming effects for both actions types. Surprisingly, a dissociation between the action types occurred when the object primes were rotated, in that only the volumetric and not the functional action representation was evoked. Furthermore, at 0 ms SOA, the primed V-action was associated with the canonical rather than the depicted view of the object. The results clarify the dynamic pattern of F- and V-grasps evoked by visual objects. For upright objects, both F- and V-grasps are strongly evoked over time. Rotated objects show a tendency to evoke only volumetric action representation. The latter result suggests that the V-grasp associated with a rotated object is based on a skeletal form of the object that does not include its functional properties. / Graduate

This study examines the state of competing affordances when an action is prepared for immediate production. More specifically, we investigated the nature of motor representations evoked by distinct action intentions, with a special interest in functional (grasp to use) and volumetric (grasp to lift) actions. With just two objects available, participants were asked to prepare an action on a particular object (e.g., preparing to lift the cellphone), and when signaled, either to perform this original action plan or to switch to executing an alternative one, either on the same or different object. By manipulating cueing methods used for indicating the preparatory and the target action plans, we found distinct patterns in the effect of preserving either object (different action on the same object) or action (same grasp type on a different object) on action execution. Changing either component of the action-object pairing incurred a cost in response time. In Experiment 1, a cost was observed when a prepared action was switched to an alternate action on the same object. For example, preparing to lift a cellphone but switching instead to a use action on the same object, incurred a cost. A further cost was found when subjects prepared a functional action to one object (e.g., use the cellphone) but switched to the same class of action on the alternate object (e.g., use the spray can). Both these effects were found to operate at the motor level. No costs were observed when subjects switched from a planned action to naming the target object (Experiment 3). Crucially, it was found that the nature of the cueing method instructing subjects to switch from a planned to an alternate action impacted the effect of action congruency. The cost observed in Experiment 1 when subjects switched to an alternate action on the same object occurred when the switch from a planned to an alternate action was cued by a verb-noun combination (e.g., use cellphone). No such cost occurred when the action was cued by a verb (e.g., use) and the target object was spatially cued by an arrow pointing to its location (Experiment 2). The cost of switching from a planned action type (e.g., a use action) to the same action type carried on the alternate object also depended on whether the planned action was verbally or spatially cued. These results provide new evidence on the nature of action representations associated with different motor intentions, as well as of the nature of action-object pairings. / Graduate

Parkinson’s disease (PD) is a neurodegenerative condition which results in severe motor impairment. Deterioration in multiple domains of cognition is another hallmark of PD. Together, these motor and cognitive impairments impact substantially on language and communication. Co-speech gestures are a form of action and are also part of linguistic processes, yet have rarely been explored in PD. Gestures can provide imagistic depictions of concepts described by speech and contribute to communication in healthy individuals. They rely on visual, spatial, and motor simulations and imagery, which may be impaired in PD. It is therefore of clinical importance to evaluate how co-speech gestures might be impaired to understand the extent of communicative impairment in PD. PD can also provide a useful model to understanding the cognitive basis of co-speech gesture in healthy people. In Chapter 2, participants described isolated actions. Gesture rate did not differ between the two groups, however, the groups differed in terms of the visual perspective they adopted when depicting actions in gesture. Controls preferred a “character viewpoint” or first-person perspective where their hands represented the hands of the actor, whereas PD patients preferred an “observer viewpoint” or third-person perspective, where their hand represented a whole person. This finding was replicated and extended in Chapter 3 where low-motion and high-motion actions were described in a longer narrative task. PD patients produced fewer character viewpoint gestures when describing high-motion action events, suggesting a difficulty in simulating these events from a first-person perspective. In addition, PD patients had difficult depicting “manner” (how an action is performed) features in gesture during high but not low motion. Extending the findings of Chapter 2, whilst overall rate of gesture production was not affected, PD patients produced action gestures at a significantly lower rate than controls. Chapter 4 took a different focus by investigating gesture depictions of static spatial (rather than dynamic action) features via a house description task. Gesture rate did not differ, but the groups depicted different types of spatial properties to a different extent. Whilst both groups predominantly gestured about location and relative position information, PD patients gestured more about directions whereas controls gestures more about shape and size information. This suggests that different strategies were being employed by the two groups. Finally, testing young adults’ comprehension of these spatial gestures in Chapter 5 revealed that gestures did not significantly improve comprehension of either PD patients’ or controls’ spoken messages, though there may have been ceiling effects. However, both PD patients and controls were viewed as more competent when their messages were viewed with gestures. The findings suggest a selective action-gesture deficit in PD which complements work demonstrating action-verb impairments in these patients, and supports gesture production theories which hypothesise a role for motor simulations and imagery. Overall gesture rate appears to be largely unaffected. The effects of PD can be felt beyond changes to goal-directed action, in the realms of language and social behaviour, but gestures may be able to improve listeners’ social perceptions of PD patients.

La fonction d’anticipation programmant l'action et ses conséquences sur la posture s’appuie sur les représentations sensorimotrice. L’adolescence étant caractérisée par des modifications du corps et du cerveau, cette thése évalue les liens qui unissent anticipation, représentations sensorimotrices et maturation cérébrale. La tâche bimanuelle de délestage met en jeu l’utilisation d’un bras postural, supportant le poids, et d’un bras manipulateur, qui le déleste. Dans cette tâche, l'anticipation s'exprime par les ajustements posturaux anticipés (APA), annulant la déstabilisation posturale causée par l'action. Des enregistrements cinématiques, EMG et EEG ont été utilisés. Bien qu’une stabilisation posturale stable soit reportée, les APAs à l’adolescence se caractérisent par une amélioration de la latence de l’inhibition des fléchisseurs. Chez l’adulte, les APA s’expriment par une désynchronisation du rythme mu et une onde positive au dessus de M1 impliqué dans la posture. Les caractéristiques temporelles de ces signatures varient à l’adolescence. L’apprentissage d’un nouveau contrôle postural est caractérisé par une amélioration rapide puis plus lente de la stabilisation posturale. Plus tardive à l'adolescence, cette acquisition repose sur la maitrise du réglage temporel de l’inhibition des fléchisseurs. Une intégration des retours proprioceptifs issus de l’action permettrait la construction d’une représentation sensorimotrice. Exprimée par la maitrise des paramètres temporels, la réactualisation des représentations sensorimotrice à l’adolescence passerait par une meilleure intégration des retours proprioceptifs. La maturation des régions cérébrales serait aussi capitale. / Voluntary action requires an anticipation, which predicts the consequence of action on posture. Anticipation rests on action and body representations. Adolescence is characterized by body modifications and cerebral maturation. This thesis explored the link between the anticipatory function, action and body representations, and the cerebral maturation. The bimanual load-lifting task engages a postural arm, supporting the load, and a motor arm, lifting the load. In this task, the anticipation, expressed by anticipatory postural adjustments (APA) cancelled the destabilizing effect of movement on the posture. Kinematics, EMG and EEG were recorded. Although performances of postural stabilization were stable, APAs at the adolescence were characterized by an earlier latency of inhibition on the postural flexors. In adults, APA are expressed by a mu rhythm desynchronization and a positive wave over M1involved in posture, which presented different temporal characteristics in adolescents. Thus, the improvement of APA would be underlain by a maturation of these EEG activities. Learning a new postural control was characterized by a rapid followed by a slow improvement of the postural stabilisation. This acquisition rested on the mastering of the temporal parameters of the flexors inhibition, which took more time at the adolescence. Integration of proprioceptive feedback coming from action allowed an update of sensorimotor representation. Expressed by the mastering of the temporal parameters, the update of body and action representations at adolescence would imply an enhancement of the integration of proprioceptive information. Maturation of the cerebral areas would be a key element.

Le jeu vidéo proposerait une nouvelle forme de subjectivation autour de l’action en mouvement, dont le moteur apparait dans l’organisation fantasmatique. L’auto-empathie va s’y déployer : processus par lequel un sujet se met à la place de l’autrui-en-soi, produisant un regard intériorisé sur soi pour représenter son monde subjectif. La médiatisation de ce processus d’auto-empathie dans les mondes virtuels va permettre au sujet de se mettre à la place d’une figure qui le représente, de telle façon que son attention et son empathie pour cette figure sont tournées indirectement vers lui-même. Ce second temps d'empathie virtuelle pour une figure de soi, que nous appelons auto-empathie médiatisée par un avatar ou auto-empathie virtuelle, favoriserait dans un troisième temps le développement d’une empathie pour soi. Enfin dans un quatrième temps, dans les jeux de rôle en ligne multi-joueurs, serait favorisé le développement d’une nouvelle forme de travail du lien intersubjectif : différenciateur plutôt que sexuel, engageant l’action dans des proto-conversations plutôt que les émotions entre joueurs, et ressortant du domaine fantasmatique, l’autre joueur étant toujours représenté par le sujet avant d’être perçu, sollicitant entre les joueurs un désir d’intersubjectivité par lequel il faut entendre le désir d’une rencontre dans le monde réel d’un autre joueur par la mise en jeu d’un fantasme dans lequel les représentations imaginaires sont tournées vers la figuration, imaginaire également, d’un sujet réel derrière un autre avatar / Video games propose a new form of subjectivity concerning action in motion, which motor appears in fantasy organization. Auto-empathy will deploy: process by which a subject puts himself instead of the other-in-self, producing an internalized view of self in order to represent his subjective world. The mediation of self-empathy process in virtual worlds will allow the subject to identify with the figure that represents him in the virtual worlds, so that his attention and empathy for this figure are turned indirectly towards himself. This second stage of virtual empathy for a self-figure, which we call self-empathy mediated by an avatar or virtual self-empathy, favors in a third time the development of empathy for oneself. Finally, in a fourth step in the multi-player online role-playing games, the development of a new form of intersubjective relationship work is favored: differentiating rather than sexual, engaging the action in proto-conversations rather than emotions between players and emerging from fantasy domain, the other player being always represented by the subject before being seen creates between players a desire for intersubjectivity through which the desire for a meeting in the real world of another player by putting in a fantasy in which imaginary representations are turned into figuration, also imaginary, of a real subject behind another avatar.

L’action humaine dans une séquence vidéo peut être considérée comme un volume spatio- temporel induit par la concaténation de silhouettes dans le temps. Nous présentons une approche spatio-temporelle pour la reconnaissance d’actions humaines qui exploite des caractéristiques globales générées par la technique de réduction de dimensionnalité MDS et un découpage en sous-blocs afin de modéliser la dynamique des actions. L’objectif est de fournir une méthode à la fois simple, peu dispendieuse et robuste permettant la reconnaissance d’actions simples. Le procédé est rapide, ne nécessite aucun alignement de vidéo, et est applicable à de nombreux scénarios. En outre, nous démontrons la robustesse de notre méthode face aux occultations partielles, aux déformations de formes, aux changements d’échelle et d’angles de vue, aux irrégularités dans l’exécution d’une action, et à une faible résolution. / Human action in a video sequence can be seen as a space-time volume induced by the concatenation of silhouettes in time. We present a space-time approach for human action recognition, which exploits global characteristics generated by the technique of dimensionality reduction MDS and a cube division into sub-blocks to model the dynamics of the actions. The objective is to provide a method that is simple, inexpensive and robust allowing simple action recognition. The process is fast, does not require video alignment, and is applicable in many scenarios. Moreover, we demonstrate the robustness of our method to partial occlusion, deformation of shapes, significant changes in scale and viewpoint, irregularities in the performance of an action, and low-quality video.