Dissertations / Theses on the topic 'Peripersonal space'

Developing behaviours for interaction with objects close to the body is a primary goal for any organism to survive in the world. Being able to develop such behaviours will be an essential feature in autonomous humanoid robots in order to improve their integration into human environments. Adaptable spatial abilities will make robots safer and improve their social skills, human-robot and robot-robot collaboration abilities. This work investigated how a humanoid robot can explore and create action-based representations of its peripersonal space, the region immediately surrounding the body where reaching is possible without location displacement. It presents three empirical studies based on peripersonal space findings from psychology, neuroscience and robotics. The experiments used a visual perception system based on active-vision and biologically inspired neural networks. The first study investigated the contribution of binocular vision in a reaching task. Results indicated the signal from vergence is a useful embodied depth estimation cue in the peripersonal space in humanoid robots. The second study explored the influence of morphology and postural experience on confidence levels in reaching assessment. Results showed that a decrease of confidence when assessing targets located farther from the body, possibly in accordance to errors in depth estimation from vergence for longer distances. Additionally, it was found that a proprioceptive arm-length signal extends the robot’s peripersonal space. The last experiment modelled development of the reaching skill by implementing motor synergies that progressively unlock degrees of freedom in the arm. The model was advantageous when compared to one that included no developmental stages. The contribution to knowledge of this work is extending the research on biologically-inspired methods for building robots, presenting new ways to further investigate the robotic properties involved in the dynamical adaptation to body and sensing characteristics, vision-based action, morphology and confidence levels in reaching assessment.

The spatial location of environmental events with respect to one’s body largely dictates their behavioural relevance. Given that stimuli occurring near the body have a greater potential to cause harm, even the phylogenetically-old defensive hand-blink reflex (HBR) increases in magnitude with stimulus proximity. The HBR has allowed for a preliminary characterisation of a defensive peripersonal space (DPPS). The work described here provides a full spatial characterization of DPPS using formal geometrical modelling of HBR data, and highlights the functional significance of DPPS through its dependence on various contextual factors. Modelling and empirical results indicate that (1) the shape of the body area defended by this DPPS can be approximated as a half-ellipsoid centred on the face. (2) The DPPS extending from this to-be-defended area has the shape of a bubble elongated along the vertical axis. (3) This DPPS is malleable: its shape is continuously updated based on gravitational cues. The DPPS also changes in disease: while blind individuals do also display a HBR, (4) the nervous system only develops the ability to modulate HBR magnitude if vision is present during early childhood. (6) In trigeminal neuralgia (TN), a condition in which innocuous trigeminal stimulation triggers paroxysmal unilateral facial pain, DPPS is larger on the side of space ipsilateral to TN. This reflects an increased estimated potential of sensory events to cause harm on that side of space. Finally, (7) DPPS expands when the HBR-eliciting stimulus is moving towards the face. These findings show that the brain purposefully modulates the defensive HBR with proximity in a context-dependent manner, in order to ensure optimal behavior and protection from estimated threats. At a more theoretical level this work also critically discusses ambiguities in the terminology used to report empirical results about peripersonal space, which have generated much confusion in the field.

A successful interaction with objects in the environment requires integrating information concerning object-location with the shape, dimension and position of body parts in space. The former information is coded in a multisensory representation of the space around the body, i.e. peripersonal space (PPS), whereas the latter is enabled by an online, constantly updated, action-orientated multisensory representation of the body (BR) that is critical for action. One of the critical features of these representations is that both PPS and BR are not fixed, but they dynamically change depending on different types of experience. In a series of experiment, I studied plastic properties of PPS and BR in humans. I have developed a series of methods to measure the boundaries of PPS representation (Chapter 4), to study its neural correlates (Chapter 3) and to assess BRs. These tasks have been used to study changes in PPS and BR following tool-use (Chapter 5), multisensory stimulation (Chapter 6), amputation and prosthesis implantation (Chapter 7) or social interaction (Chapter 8). I found that changes in the function (tool-use) and the structure (amputation and prosthesis implantation) of the physical body elongate or shrink both PPS and BR. Social context and social interaction also shape PPS representation. Such high degree of plasticity suggests that our sense of body in space is not given at once, but it is constantly constructed and adapted through experience.
Allo scopo di interagire con oggetti presenti nell’ambiente esterno è necessario integrare le informazioni sulla posizione degli oggetti nello spazio con informazioni riguardanti la forma, dimensione e posizione delle singole parti del corpo rispetto all’oggetto stesso. Due diverse rappresentazioni supportano la codifica di tali informazioni: da una parte, la rappresentazione dello Spazio Peripersonale, una rappresentazione multisensoriale dello spazio intorno al corpo, e dall’altra una rappresentazione multisensoriale del corpo, costantemente aggiornata e orientata all’azione. Una caratteristica critica di queste rappresentazioni è rappresentata dalle loro proprietà plastiche, cioè dalla possibilità di modificarsi in seguito a diversi tipi di esperienza. In questa tesi mi sono focalizzata sullo studio delle proprietà plastiche delle rappresentazioni del corpo e dello spazio peripersonale. Ho sviluppato una serie di metodi per valutare il confine dello spazio peripersonale (Capitolo 4), per studiare i suoi correlati neurali (Capitolo 3) e per valutare le rappresentazioni multisensoriali del corpo. Questi compiti sono stati usati per studiare modificazioni plastiche del corpo e dello spazio peripersonale in seguito all’utilizzo di uno strumento (Capitolo 5), in seguito a una stimolazione multisensoriale (Capitolo 6), amputazione e impianto di protesi (Capitolo 7) e nell’ambito delle interazioni sociali. I risultati ottenuti hanno mostrato come la modificazione nella funzione (in seguito all’utilizzo di uno strumento) o della struttura fisica (in seguito ad amputazione ed impianto di protesi) del corpo determinano una estensione o una contrazione sia della rappresentazione dello spazio peripersonale che della rappresentazione del corpo. Inoltre, i risultati ottenuti hanno dimostrato che la rappresentazione dello spazio peripersonale viene plasmata anche dalle interazioni sociali. Tale livello di plasticità suggerisce che l’esperienza del nostro corpo viene continuata costruita e aggiornata tramite le diverse esperienze.

A successful interaction with objects in the environment requires integrating information concerning object-location with the shape, dimension and position of body parts in space. The former information is coded in a multisensory representation of the space around the body, i.e. peripersonal space (PPS), whereas the latter is enabled by an online, constantly updated, action-orientated multisensory representation of the body (BR) that is critical for action. One of the critical features of these representations is that both PPS and BR are not fixed, but they dynamically change depending on different types of experience. In a series of experiment, I studied plastic properties of PPS and BR in humans. I have developed a series of methods to measure the boundaries of PPS representation (Chapter 4), to study its neural correlates (Chapter 3) and to assess BRs. These tasks have been used to study changes in PPS and BR following tool-use (Chapter 5), multisensory stimulation (Chapter 6), amputation and prosthesis implantation (Chapter 7) or social interaction (Chapter 8). I found that changes in the function (tool-use) and the structure (amputation and prosthesis implantation) of the physical body elongate or shrink both PPS and BR. Social context and social interaction also shape PPS representation. Such high degree of plasticity suggests that our sense of body in space is not given at once, but it is constantly constructed and adapted through experience.
Allo scopo di interagire con oggetti presenti nell’ambiente esterno è necessario integrare le informazioni sulla posizione degli oggetti nello spazio con informazioni riguardanti la forma, dimensione e posizione delle singole parti del corpo rispetto all’oggetto stesso. Due diverse rappresentazioni supportano la codifica di tali informazioni: da una parte, la rappresentazione dello Spazio Peripersonale, una rappresentazione multisensoriale dello spazio intorno al corpo, e dall’altra una rappresentazione multisensoriale del corpo, costantemente aggiornata e orientata all’azione. Una caratteristica critica di queste rappresentazioni è rappresentata dalle loro proprietà plastiche, cioè dalla possibilità di modificarsi in seguito a diversi tipi di esperienza. In questa tesi mi sono focalizzata sullo studio delle proprietà plastiche delle rappresentazioni del corpo e dello spazio peripersonale. Ho sviluppato una serie di metodi per valutare il confine dello spazio peripersonale (Capitolo 4), per studiare i suoi correlati neurali (Capitolo 3) e per valutare le rappresentazioni multisensoriali del corpo. Questi compiti sono stati usati per studiare modificazioni plastiche del corpo e dello spazio peripersonale in seguito all’utilizzo di uno strumento (Capitolo 5), in seguito a una stimolazione multisensoriale (Capitolo 6), amputazione e impianto di protesi (Capitolo 7) e nell’ambito delle interazioni sociali. I risultati ottenuti hanno mostrato come la modificazione nella funzione (in seguito all’utilizzo di uno strumento) o della struttura fisica (in seguito ad amputazione ed impianto di protesi) del corpo determinano una estensione o una contrazione sia della rappresentazione dello spazio peripersonale che della rappresentazione del corpo. Inoltre, i risultati ottenuti hanno dimostrato che la rappresentazione dello spazio peripersonale viene plasmata anche dalle interazioni sociali. Tale livello di plasticità suggerisce che l’esperienza del nostro corpo viene continuata costruita e aggiornata tramite le diverse esperienze.

Our ability to interact with the environment requires the integration of multisensory information for the construction of spatial representations. The peripersonal space (i.e., the sector of space closely surrounding one's body) and the integrative processes between visual and tactile inputs originating from this sector of space have been at the center of recent years investigations. Neurophysiological studies provided evidence for the presence in the monkey brain of bimodal neurons, which are activated by tactile as well as visual information delivered near to a specific body part (e.g., the hand). Neuropsychological studies on right brain-damaged patients who present extinction and functional neuroimaging findings suggest the presence of similar bimodal systems in the human brain. Studies on the effects of tool-use on visual-tactile interaction revealed similar dynamic properties of the peripersonal space in monkeys and humans. The functional role of the multisensory coding of peripersonal space is, in our hypothesis, that of providing the brain with a sensori-motor interface for body-objects interactions. Thus, not only it could be involved in driving involuntary defensive movements in response to objects approaching the body, but could be also dynamically maintained and updated as a function of manual voluntary actions performed towards objects in the reaching space. We tested the hypothesis of an involvement of peripersonal space in executing both voluntary and defensive actions. To these aims, we joined a well known cross-modal congruency effect between visual and tactile information to a kinematic approach to demonstrate that voluntary grasping actions induce an on-line re-weighting of multisensory interactions in the peripersonal space. We additionally show that this modulation is handcentred. We also used a motor evoked potentials approach to investigate which coordinates system is used to code the peripersonal space during motor preparation if real objects rapidly approach the body. Our findings provide direct evidence for automatic hand-centred coding of visual space and suggest that peripersonal space may also serve to represent rapidly 3 approaching and potentially noxious objects, thus enabling the rapid selection of appropriate motor responses. These results clearly show that peripersonal space is a multisensori-motor interface that might have been selected through evolution for optimising the interactions between the body and the objects in the external world.

The abilities to adapt and act autonomously in an unstructured and human-oriented environment are necessarily vital for the next generation of robots, which aim to safely cooperate with humans. While this adaptability is natural and feasible for humans, it is still very complex and challenging for robots. Observations and findings from psychology and neuroscience in respect to the development of the human sensorimotor system can inform the development of novel approaches to adaptive robotics. Among these is the formation of the representation of space closely surrounding the body, the Peripersonal Space (PPS) , from multisensory sources like vision, hearing, touch and proprioception, which helps to facilitate human activities within their surroundings. Taking inspiration from the virtual safety margin formed by the PPS representation in humans, this thesis first constructs an equivalent model of the safety zone for each body part of the iCub humanoid robot. This PPS layer serves as a distributed collision predictor, which translates visually detected objects approaching a robot’s body parts (e.g., arm, hand) into the probabilities of a collision between those objects and body parts. This leads to adaptive avoidance behaviors in the robot via an optimization-based reactive controller. Notably, this visual reactive control pipeline can also seamlessly incorporate tactile input to guarantee safety in both pre- and post-collision phases in physical Human-Robot Interaction (pHRI). Concurrently, the controller is also able to take into account multiple targets (of manipulation reaching tasks) generated by a multiple Cartesian point planner. All components, namely the PPS, the multi-target motion planner (for manipulation reaching tasks), the reaching-with-avoidance controller and the humancentred visual perception, are combined harmoniously to form a hybrid control framework designed to provide safety for robots’ interactions in a cluttered environment shared with human partners. Later, motivated by the development of manipulation skills in infants, in which the multisensory integration is thought to play an important role, a learning framework is proposed to allow a robot to learn the processes of forming sensory representations, namely visuomotor and visuotactile, from their own motor activities in the environment. Both multisensory integration models are constructed with Deep Neural Networks (DNNs) in such a way that their outputs are represented in motor space to facilitate the robot’s subsequent actions.

This study will look into to the concepts of Peripersonal Space, The Body Schema and The Body Image. It examines how the terms are typically used and describes the various views about the concepts found in the literature, as well as the contradictions between these views. In the section “The Difficulty to Differentiate the Concepts” the reader gets a deeper understanding of which criteria researchers use to differentiate the concepts from one another. The fact that there are changes in kineamethic model and sensation in humans when they are using a rake is proposed as support for the idea that also the body schema is involved in tool use. In differentiating the Body schema – Body Image from each other (and other types of body representation) we come to the conclusion that positive definitions about different representations is needed and that researchers should unite their views what the definitions should be. We also mention a problem based on the possibility on infinite body representations and a solution by a Bayesian model is proposed that looks at the input as well as the output in experiments.

Spatial neglect is a neurological disorder where patients typically fail to orient or respond to events on their left side. Moreover, recent studies suggest that the severity of neglect may depend specifically on whether stimuli are presented within or beyond arm's reach. However, the evidence for such a general functional dissociation between near and far space processing in the brain remains conflicting: The majority of research has been focussed on line bisection errors which reflect only one small aspect of neglect behaviour. In addition, some behavioural findings suggest a functional dissociation only if a motor response is required. Finally, to date, the critical areas involved in distance related space processing have not been identified. Thus, it remains not only unclear whether neglect in near and far space is a task- and response independent phenomenon but also which damaged brain areas impair distance related space processing. In order to answer these questions the present study compared line bisection and visual search performance and its anatomical correlates in near and far space by using a combined single case- and group study approach. The results showed that neglect restricted to near or far space can vary not only depending on the type of task but also on the type of response required. Visual search tasks were particularly sensitive in detecting the dissociation between those two space sectors. Anatomically, neglect for near space was mainly associated with occipito-parietal lesions and medio-temporal structures, including the posterior cingulate. Neglect for far space was found to result from focal damage of medial, ventro-temporal structures and the prefrontal cortex. In conclusion, neglect for near and far space does not seem to result from a general impairment in distance related processing but from a combination of factors related to specific task demands as well as the location and extent of the brain damage.

The human interest on understanding how the surrounding space is perceived and processed has stimulated the scientific and experimental research in this field for several decades. Moreover, from the earliest human interaction with computer-generated virtual environments, interest in this subject has received increasing attention, in order to verify whether the observed behavior in virtual environments is similar to that seen in real environments. Virtual reality technologies are currently used in different fields, from the implementation in medicine to the rehabilitation of neuropsychological and psychological disorders, from the use in the military to the exploitation in industry. The positive results obtained through the use of virtual reality continue to support this new technology and its evolution. Research on the human brain mechanisms involved during interactions with these synthetic environments plays an important role from a neuropsychological point of view, and in terms of reliability and credibility of the instrument. Of particular importance in the study of spatial perception is the question of its representation that distinguishes the surrounding environment in peripersonal space, or near space, the space within arm reach, and extrapersonal space, or far space, defined the space beyond the arm reach. Neuropsychological evidences confirm the existence of different neural mechanisms involved in peripersonal and extrapersonal space representation. Moreover, it is known that the use of standard tools results in a modulation of the perceptual space, expanding the representation of peripersonal space to include the part of extrapersonal space occupied by the end of the tools manipulated. The aim of the present study is to analyze and understand some unclear aspects of this area of research, and to add information to the basic theory. To this end, several experiments were conducted to investigate the following aspects: • peripersonal and extrapersonal space limits during tool-use; • neural circuits involved in representation of peripersonal and extrapersonal space; • body and arm position influence in the perception of peripersonal and extrapersonal space; • the mechanism involved in extrapersonal space perception. The first chapter is an overview of peripersonal and extrapersonal space theories, and of the brain areas involved in their representation, through the analysis of researches and experiments with animal subjects; next, further studies are examined with human participants, in different situations and methods, in order to define the characteristics of this perceptual phenomenon. The second chapter presents the literature concerning the applications in the virtual reality field in the study of artificial environments spatial perception. The first part of the chapter introduces the basic concepts of the technology. Then, empirical evidences that support the utility and potential of this new technology are exposed Finally, an analysis of the researches concerning the phenomenon of peripersonal space perception in virtual environments is provided. The third chapter presents the research, and particularly explains the, methodology, experimental procedures and materials used for the experiments. The experimental paradigm used in the present work was the line bisection task. It is a widely used experimental paradigm since relatively easy for participants to perform, but provides valid results in terms of perception and visuospatial attention. The first study aimed to understand how far up tool-use can expand peripersonal space. The results showed an expansion of perceived peripersonal space when handling a tool up to a distance of 240 cm. The second study explored which brain areas are involved in a visuospatial attention task performed in a virtual environment, by using the neuroimaging technique functional Near Infrared Spectroscopy (i.e., fNIRS). The experiment represents one of the first attempts to investigate the neural correlates by using the fNIRS during an immersive virtual reality experience. Body position can influence the perception of the surrounding space and the space beyond arm reaching distance. Based on previous results, the third experiment investigated if the feeling of having the body blocked or free to move during a visuospatial attention task has implications in the attentional shift that modulates peripersonal and extrapersonal space perception. The results showed that both for the first and the second case, an abrupt attentional shift, not gradual, during the transition from peripersonal to extrapersonal space was observed. Arm position can influence the perception of the surrounding space and the space beyond arm reaching distance. Based on previous results, the fourth experiment investigated whether having the arm stretched or bent during a visuospatial attention task, has implications in the modulation of peripersonal and extrapersonal space perception. The results confirmed that the position of the arm affects visuospatial attention. The last experiment has specifically investigated the underlying causes of peripersonal space expansion when using a tool. It is believed that is the ability to actively manipulate the space the essential feature to induce the peripersonal space expansion. But, as noted in previous studies, it is possible that the visual continuity from the hand toward the manipulated region of space represents the key feature in modulating peripersonal space expansion. The results confirm the hypothesis that the essential feature in order to induce peripersonal space expansion is represented by the active manipulation of the observed region of space. The studies reported in the present study explored several issues relating to the understanding of the perception of the surrounding space and its implications on the attentional processes related. In the fourth chapter the results are discussed and evaluated.
L’interesse da parte dell’uomo di comprendere come lo spazio che lo circonda sia percepito ed elaborato stimola la ricerca scientifica e sperimentale ormai da diversi decenni. Inoltre, fin dalle prime interazioni umane con ambienti virtuali generati al computer, l'interesse per questo argomento ha ottenuto sempre maggiore attenzione, anche allo scopo di verificare se il comportamento osservato negli ambienti virtuali è simile a quello osservato negli ambienti reali. Le tecnologie di realtà virtuale sono attualmente impiegate in diversi settori, dall’implementazione in campo medico alla riabilitazione di disturbi psicologici e neuropsicologici, dall’utilizzo in campo militare allo sfruttamento in ambito industriale. I risultati positivi ottenuti attraverso l’utilizzo della realtà virtuale continuano a supportare questa nuova tecnologia e la sua evoluzione. La ricerca sulle reazioni del cervello umano durante le interazioni con tali ambienti sintetici svolge un ruolo importante da un punto di vista neuropsicologico, nonché in termini di affidabilità e credibilità dello strumento. Di particolare importanza nell’ambito dello studio della percezione spaziale è la questione riguardante la sua diversa rappresentazione che distingue l’ambiente circostante in spazio peripersonale, o spazio vicino, definito lo spazio di raggiungimento dei nostri arti, e spazio extrapersonale, o spazio lontano, definito lo spazio oltre il raggiungimento dei nostri arti. Evidenze neuropsicologiche confermano l'esistenza di differenti meccanismi neurali coinvolti nella rappresentazione dello spazio peripersonale ed extrapersonale. Inoltre, è noto che l’utilizzo di normali strumenti provochi una rielaborazione percettiva dello spazio, espandendo la rappresentazione dello spazio peripersonale ad includere la parte di spazio extrapersonale occupata dalle estremità degli strumenti manipolati. Lo scopo del presente elaborato è di analizzare e comprendere alcuni degli aspetti ancora inesplorati in questo ambito di ricerca, nonché di aggiungere informazioni alla teoria di base. A tal fine, sono stati condotti diversi esperimenti al fine di indagare i seguanti aspetti: • il limite di espansione dello spazio peripersonale attraverso l’utilizzo di uno strumento; • le aree cerebrali coinvolte nella percezione dello spazio peripersonale ed extrapersonale; • l’influenza della posizione del corpo e delle braccia nella percezione dello spazio peripersonale ed extrapersonale; • infine, il meccanismo coinvolto nella modulazione della percezione dello spazio extrapersonale. Nel primo capitolo è esposta una rassegna teorica sullo spazio peripersonale ed extrapersonale, sulle aree cerebrali coinvolte nella loro rappresentazione, attraverso l’analisi di ricerche ed esperimenti condotti con soggetti animali; in seguito, sono esaminati ulteriori studi realizzati con partecipanti umani, in diverse situazioni e modalità, al fine di delineare il funzionamento di questo particolare fenomeno percettivo. Nel secondo capitolo è presentata la letteratura riguardante le applicazioni in ambito virtuale inerenti allo studio della percezione spaziale all’interno di ambienti artificiali. Nella prima parte del capitolo sono introdotti i concetti di base sul funzionamento di questa particolare tecnologia; in seguito sono esposte evidenze empiriche a sostegno dell’utilità e delle potenzialità che questa nuova tecnologia fornisce. Infine viene analizzata una serie di ricerche inerenti al fenomeno di percezione dello spazio peripersonale all’interno di ambienti virtuali. Nel terzo capitolo è presentata la ricerca, ed in particolare sono illustrati gli scopi, la metodologia, le procedure sperimentali e gli strumenti utilizzati per gli esperimenti condotti. Il paradigma sperimentale utilizzato all’interno del presente lavoro è stato il compito di bisezione di linea. Si tratta di un paradigma sperimentale ampiamente utilizzato poiché relativamente semplice per i partecipanti da svolgere, tuttavia valido in termini di risultati riguardo attenzione visuospaziale e percezione. Il primo studio ha avuto come obiettivo principale quello di capire fino a che distanza l’utilizzo di uno strumento possa espandere lo spazio peripersonale. I risultati hanno mostrato un ampliamento dello spazio percepito peripersonale, durante la manipolazione dello strumento fino alla distanza di 240 cm. L'obiettivo del secondo studio è stato di identificare le aree cerebrali coinvolte durante un compito di attenzione visuospaziale in ambiente virtuale, tramite l’utilizzo della tecnica di neuroimmagine Spettroscopia Funzionale del Vicino Infrarosso (i.e., functional Near Infrared Spectroscopy; fNIRS). L’esperimento rappresenta uno dei primi tentativi di indagare i correlati neurali tramite l’utilizzo della fNIRS durante un’esperienza di realtà virtuale immersiva. La posizione del corpo può modificare il modo di percepire lo spazio circostante e lo spazio oltre la distanza di raggiungimento delle braccia. Sulla base di risultati ottenuti in studi precedenti, il terzo esperimento è volto a verificare se la sensazione di avere il corpo bloccato o libero di muoversi durante un compito di attenzione visuospaziale, abbia implicazioni sulla modulazione percettiva nello spostamento attentivo dallo spazio peripersonale a quello extrapersonale. I risultati hanno mostrato che sia nel primo sia nel secondo caso, si assiste ad uno spostamento attentivo netto, è non graduale, durante la transizione dallo spazio peripersonale a quello extrapersonale. La posizione del braccio può influenzare il modo di percepire lo spazio circostante e lo spazio oltre la distanza di raggiungimento del braccio. Sulla base di risultati ottenuti in studi precedenti, il quarto esperimento è volto a verificare se la distensione del braccio davanti al corpo o il suo posizionamento lungo un fianco durante un compito di attenzione visuospaziale, abbia implicazioni sulla modulazione percettiva dello spazio peripersonale ed extrapersonale. I risultati hanno confermato che la posizione del braccio influenza l’attenzione visuospaziale. Infine, l’ultimo esperimento ha indagato nello specifico le cause alla base dell’espansione dello spazio peripersonale durante l’utilizzo di uno strumento. Si ritiene che sia la capacità di manipolare attivamente lo spazio l'elemento essenziale per indurre l'espansione dello spazio peripersonale. Tuttavia, come osservato in studi precedenti, è possibile che anche la continuità visiva dalla mano verso la regione di spazio manipolato sia una caratteristica fondamentale per modulare l'espansione dello spazio peripersonale. I risultati confermano l’ipotesi che la caratteristica essenziale per indurre l'espansione dello spazio peripersonale è rappresentata dalla manipolazione attiva della regione di spazio osservata. Gli studi riportati nel presente elaborato hanno esplorato diverse questioni riguardanti la comprensione della percezione dello spazio circostante e le sue implicazioni sui processi di attenzione ad essa collegati. Nel quarto capitolo sono discussi e valutati i risultati alla luce della letteratura di riferimento.

The zone surrounding our body is of vital importance. In neuroscience this space is captured by the concept of peripersonal space (PPS), a plastic representation integrating tactile and visual stimuli presented on/close to the body. PPS is thought to contribute to the efficient guidance of actions, yet, a clear demonstration of this function is critically lacking. In the first study we provided strong support to this hypothesis by revealing that visual and tactile stimuli interact already during action planning. Such a PPS remapping that precedes motor execution is ideally suited to guiding actions. Recently, it has been suggested a possible PPS involvement in social interactions. In social psychology, interpersonal space (IPS) is the area individuals maintain around themselves into which others cannot intrude without arousing discomfort. Because of some similarities, some authors raised the question of whether PPS and IPS share some functional features. In the second and third study we tested this hypothesis by taking advantage of PPS remapping induced by tool-use. First, we showed that “standard” tool-use ‘extends’ PPS, as measured by reaching-distance toward a peer, but does not affect IPS, as measured by the comfort-distance toward the same peer. Then, we demonstrated that a novel “social” tool-use ‘extends’ PPS and ‘reduces’ IPS. These findings clearly disconfirm the hypothesis of functional overlap between the two spaces. The last study examines the sensitivity of PPS to a fundamental social dimension: ownership. The results indicate that ownership of an object is critical for the PPS remapping to emerge. Visual stimuli strongly affected touch perception during action only when the object belonged to the participant. A similar remapping emerged when simply observing a peer acting on her own object. Taken together, these findings critically inform current models about space perception and about its function in our sensorimotor and social inter-actions.

The peripersonal space (PPS) is the space immediately surrounding the body. It is coded in the brain in a multisensory, body part-centered (e.g. hand-centered, trunk-centered), modular fashion. This is supported by the existence of multisensory neurons (in fronto-parietal areas) with tactile receptive field on a specific body part (hand, arm, trunk, etc.) and visual/auditory receptive field surrounding the same body part. Recent behavioural results (Serino et al. Sci Rep 2015), obtained by using an audio-tactile paradigm, have further supported the existence of distinct PPS representations, each specific of a single body part (hand, trunk, face) and characterized by specific properties. That study has also evidenced that the PPS representations– although distinct – are not independent. In particular, the hand-PPS loses its properties and assumes those of the trunk-PPS when the hand is close to the trunk, as the hand-PPS was encapsulated within the trunk-PPS. Similarly, the face-PPS appears to be englobed into the trunk-PPS. It remains unclear how this interaction, which manifests behaviourally, can be implemented at a neural level by the modular organization of PPS representations. The aim of this Thesis is to propose a neural network model to help the comprehension of the underlying neurocomputational mechanisms. The model includes three subnetworks devoted to the single PPS representations around the hand, face and the trunk. Furthermore, interaction mechanisms– controlled by proprioceptive neurons – have been postulated among the subnetworks. The network is able to reproduce the behavioural data, explaining them in terms of neural properties and response. Moreover, the network provides some novel predictions, that can be tested in vivo. One of this prediction has been tested in this work, by performing an ad-hoc behavioural experiment at the Laboratory of Cognitive Neuroscience (Campus Biotech, Geneva) under the supervision of the neuropsychologist Dr Serino.

Lo spazio peripersonale (SPP) rappresenta una regione privilegiata di spazio immediatamente circostante il nostro corpo in cui stimoli visivi e tattili vengono integrati nelle aree cerebrali fronto-parietali (Hunley & Lourenco, 2018). L’ampiezza di SPP non è fissa ma può essere regolata da diversi fattori (Fogassi et al., 1996). Il presente lavoro di tesi si propone di indagare come l’integrazione visuo-tattile possa essere modulata dalla valenza intrinseca e acquisita degli stimoli visivi e da stati emotivi legati all’ansia. Negli Studi 1 e 3 è stato utilizzato il paradigma di interazione visuo-tattile (Canzoneri et al., 2012) in cui stimoli tattili venivano somministrati mentre stimoli visivi in avvicinamento a valenza intrinseca (Studio 1) e acquisita (Studio 3) si trovavano a specifiche distanze dal corpo dei partecipanti. I risultati dei due studi sono analoghi: a brevi distanze, tutti gli stimoli visivi comportano una facilitazione dell’elaborazione del tattile, a lunghe distanze dal corpo, invece, solo gli stimoli connotati da valenza modulano le interazioni visuo-tattili. Lo studio 2 è stato condotto per escludere che possibili effetti di aspettativa tattile potessero spiegare i risultati ottenuti nei due precedenti studi. Utilizzando lo stesso paradigma di interazione visuo-tattile, ora gli stimoli visivi si allontanano dal corpo anziché avvicinarsi ad esso. Contrariamente ai due studi summenzionati, si è qui riscontrato che la valenza degli stimoli non esercita nessun effetto sulla percezione spaziale, confermando dunque la validità degli Studi 1 e 3. Lo Studio 4 si propone di indagare le oscillazioni neurali sottostanti le interazioni visuo-tattili. Nello specifico, si vorrebbe replicare il risultato ottenuto da Wamain et al. (2016) il quale ha riportato un gradiente di attivazione della corteccia sensorimotoria dallo spazio peripersonale a quello extrapersonale, soltanto quando il compito richiedeva al soggetto una chiara intenzione motoria. Utilizzando un compito di discriminazione tattile, i partecipanti venivano invitati a rispondere ad una vibrazione consegnata sulla mano destra mentre osservavano stimoli visivi a valenza positiva e negativa, posizionati a varie distanze dal corpo. I risultati mostrano una chiara attivazione motoria quando tutti gli stimoli sono posizionati nello spazio peripersonale ma non in quello extrapersonale, portando prove a sostegno dell’esistenza di un sistema di codifica di SPP sottostante l’integrazione visuo-tattile (Maravita et al., 2003, Làdavas & Farnè, 2004). Nessun effetto legato alla valenza è stato registrato, avvalorando dunque i dati ottenuti nei precedenti esperimenti. Lo studio 5 è volto ad indagare come la congruenza tra stimoli visivi e tattili nello spazio sia modellata da stati emotivi legati ad ansia di stato e di tratto (Spielberger, 1983). Adottando una versione rivisitata del paradigma di Ordine di Giudizio Temporale (Filbrich et al., 2017), i partecipanti venivano invitati a riportare l’ordine di presentazione di stimoli visivi posizionati vicino o lontano dal proprio corpo, ignorando degli stimoli tattili consegnati 200 ms prima degli stimoli bersaglio. Tale procedura è stata somministrata prima e dopo il compito di induzione dell’ansia. Nonostante non sia stato replicato il generale effetto di facilitazione di congruenza visuo-tattile nello spazio vicino, è stato riscontrato che i soggetti con alta ansia di stato e di tratto mostrano rispettivamente un effetto inibitorio e facilitatorio dello stimolo tattile sull’elaborazione del visivo. Questo risultato è compatibile con studi già presenti in letteratura indicanti un ridotto controllo top-down per stimoli minacciosi nei soggetti ad alta ansia di stato (Bishop et al., 2004) e un compromesso controllo esecutivo nei soggetti ad alta ansia di tratto (Pacheco-Unguetti et al., 2010).
Peripersonal Space (PPS) is a privileged region of space, immediately surrounding our body, in which visual and bodily signals are promptly integrated in fronto-parietal areas of the brain (Hunley & Lourenco, 2018). PPS amplitude is not fixed, but it can be dynamically shaped by specific experimental manipulations (Fogassi et al., 1996). In Study 1 and 3, we tried to disentangle how visuo-tactile integration in space can be shaped by intrinsic and learned valence of objects. By using a visuo-tactile interaction paradigm, participants were asked to respond to a tactile stimulus while an approaching visual one (with intrinsic and learned valence in Study 1 and 3, respectively) was located at specific distances from their body (Canzoneri et al., 2012). The results of Study 1 and 3 seem aligned to each other: positive and negative stimuli entail larger visuo-tactile interactions in space than neutral ones. Indeed, at longer distances from the body, visuo-tactile interactions are dynamically modulated by valence-connoted looming visual stimuli. At shorter distances, instead, all stimuli acquire saliency regardless of their intrinsic or acquired valence, due to their proximity to the body. Study 3 aims to exclude that the above-mentioned results might be due to tactile expectancy (Kandula et al., 2017). Indeed, the more the visual stimulus approaches the body without tactile input, the more the bodily stimulus expectancy increases (Umbach et al. 2012). By using the same visual stimuli – that now recede away from participants’ body - and spatial distances as in Study 1, it was shown that the different valence of the stimuli is not able to produce any kind of effect in space, thus stressing the validity of the findings reported in Studies 1 and 3. Study 4 investigates the neuronal oscillations related to visuo-tactile coupling in near and far space for both positive and negative visual stimuli. In particular, we would like to replicate Wamain et al. (2016) results, which state that objects in near space are coded in motor terms, but only when the goal of the perceiver is to interact with them. By using a tactile discrimination task while valence-connoted visual stimuli were presented in near or far space, we found beta power desynchronization in near space over sensorimotor cortex, thus revealing a motor activation for valence-connoted visual stimuli close to the body but not when they were located far from it. This result corroborates the presence of such a multisensory system in the human brain (Maravita et al., 2003, Làdavas & Farnè, 2004). However, no effect of valence was found in the present EEG task, thus confirming Study 1 and 3 results. Study 5 explores how state and trait anxiety (Spielberger, 1983) can alter the prioritizing effect of congruent visuo-tactile stimulation in space. By adopting a revised version of the Temporal Order Judgment task as in Filbrich et al. (2017), participants were asked to report the order of near or far visual stimulus presentation before and after doing an anxiety provoking task, trying to ignore a tactile cue. Despite we were unable to report an overall prioritizing effect of congruent visuo-tactile interaction in near space, it has been found that participants who experienced a higher temporary state of anxiety showed an inhibitory effect of the congruent tactile cue on the near visual stimulus processing. On the other side, high trait anxiety participants’ response to the congruent multisensory stimulation seems to be more facilitated in near than in far space. This finding seems to be compatible with the reduced top-down control over threat-related distractors showed by high state anxiety individuals (Bishop et al., 2004) and with a reduced executive control in trait anxious subjects (Pacheco-Unguetti et al., 2010). Taken together, these five studies stress the privileged integration of visual and tactile stimuli inside PPS and its permeability to emotional related states.

Esperienze anomale del sé sono state associate ai disturbi dello spettro schizofrenico. Si ritiene che un debole senso del sé (sé minimale), un disturbato funzionamento corporeo implicito e della sintonizzazione intercorporea con gli altri siano manifestazioni di un sé corporeo disturbato nella schizofrenia (Sz). L’alterazione del sé minimale, correlata ai disturbi del riconoscimento di sé e della discriminazione sé-altro, dipende da deficit nell’ integrazione multisensoriale. Una delle esperienze di base del sé riguarda il senso di appartenenza del corpo (BO) che è legato sia alle parti corporee che al volto, un segno cruciale per la propria identità che consente di distinguerci dagli altri e di differenziarci dagli altri. La Sz è caratterizzata da deficit nel riconoscimento del proprio volto e di quello altrui, nonché da un BO alterato. Pertanto, lo scopo del primo studio è stato quello di integrare queste linee di ricerca indagando la propensione all'Enfacement Illusion (EI) nella Sz. I risultati hanno mostrato come l'EI abbia indotto la malleabilità del confine Sé-Altro sia nei controlli che nei pazienti; l’EI ha influenzato inoltre il confine Altro-Altro, suggerendo come l'EI non sia solo confinato alla sfera del sé, ma influenzi anche il modo in cui discriminiamo gli altri. Il secondo studio aggiunge nuove importanti evidenze nel contesto del sé corporeo nella Sz, focalizzandosi sul processamento implicito del sé corporeo, operazionalizzato nel cosiddetto effetto del vantaggio del sé (SAeff, rotazione mentale motoria più veloce con proprie parti corporee rispetto a quelle altrui in un giudizio di lateralità). I risultati hanno mostrato l'assenza del SAeff nella Sz rivelando un'alterazione nei processi sensorimotori delle proprie parti corporee, suggerendo una potenziale natura motoria distorta del sé minimale. Un altro aspetto cruciale che influenza tale senso del sé è la consapevolezza corporea, la sensazione di essere un sé corporeo nello spazio (sé spaziale), che dipende dall'integrazione di segnali multisensoriali che si verificano all'interno di una porzione di spazio circostante il corpo, lo Spazio Peripersonale (PPS). Il PPS non è fisso, ma si modella dinamicamente attraverso le esperienze motorie, come dopo l'uso di strumenti. Inoltre, l’estensione del PPS varia tra le persone al variare di diverse caratteristiche individuali, come la schizotipia (St). Tuttavia, ancora poco si conosce sulla relazione tra la plasticità del PPS e i tratti di personalità. A questo scopo, abbiamo studiato la plasticità del PPS dopo due diversi allenamenti motori (dopo l’utilizzo di uno strumento e dopo l’osservazione dell’utilizzo di quello strumento), lungo il continuum St. I risultati hanno mostrato l'espansione del PPS dopo l'uso dello strumento, mentre in seguito all’osservazione non è emersa alcuna espansione. Abbiamo riscontrato inoltre una maggiore espansione nel gruppo St relativamente basso rispetto a quello relativamente alto, indipendentemente dal tipo di allenamento motorio eseguito. Questi risultati sottolineano una potenziale alterazione funzionale del PPS all’aumentare del livello St. Tenendo conto dell'idea di un continuum che va dalla St alla psicosi conclamata, è ragionevole ipotizzare una minore malleabilità del PPS nella Sz. Nessuno studio ha fino ad ora indagato tale aspetto nella Sz; pertanto, questo rappresenta il focus dell'ultimo studio, che illustra i risultati preliminari sui pazienti Sz, rappresentando un altro importante contributo alla conoscenza del sé spaziale nella psicopatologia. Tutte queste evidenze arricchiscono l'attuale stato dell'arte dei disordini del sé minimale nella Sz, supportando l'idea di un sé fragile che si rompe in piccoli pezzi che includono molteplici aspetti corporei interrelati.
Anomalies of self-experiences have been associated with schizophrenia spectrum disorders. It has been proposed that the weak basic sense of self (‘minimal self’), the disturbed implicit bodily functioning and the disruption of intercorporeal attunement with others are manifestations of a disturbed bodily self in schizophrenia (Sz). This altered basic sense of self, strictly related to self-recognition and self-other discrimination impairments, have been linked to deficits in multisensory integration mechanisms. One of the basic experiences of self concerns the sense of body-ownership (BO) which is not only associated with body parts but also with the face, a crucial cue for self-identity allowing to distinguish the self from the others and in differentiating others. Sz is characterized by deficits in one’s own and others’ face recognition, as well as by a disturbed BO. Thus, the aim of the first study here presented was to integrate these lines of research investigating the Enfacement Illusion (EI) proneness in Sz. Results showed how EI induced the expected malleability of Self-Other boundary among both controls and patients; interestingly, it also demonstrated how Other-Other boundary is influenced by EI, suggesting how EI is not only confined to self-sphere but it also affects the way we discriminate others. The second study adds important new evidence in the context of the bodily self in Sz, focusing on the implicit bodily self processing, operationalized in the so-called self advantage effect (SAeff, a faster sensory motor mental rotation with self than others’ body-parts in a laterality judgment task). Results showed the absence of the SAeff in Sz revealing a specific alteration in the sensorimotor processes of self body parts, suggesting a potential distorted motor nature of the minimal self. Another crucial aspect shaping our sense of self is bodily self-awareness, the feeling of being a bodily self in space (spatial self). This experience depends on multisensory integration occurring within the portion of space surrounding our body, Peripersonal Space (PPS). PPS is not fixed, rather it dynamically shapes through motor experiences (e.g. after a tool-use). Moreover, the size of PPS largely varies across people depending on several individual characteristics, including schizotypy (St). However, little is still known about the relationship between PPS plasticity and personality traits. To this aim, we investigated PPS plasticity after two different motor trainings (i.e. after using a tool and after observing someone else using the tool), in participants along the St continuum. Results showed PPS expansion after tool-use, whereas absence of PPS expansion emerged after the observation task. Moreover, we found greater PPS expansion in the relatively-low St group than in the relatively-high one, regardless of the type of motor training performed. These results underline a potential general functional alteration of PPS with the increase of St level. Taking into account the idea of a dynamic continuum ranging from St to full-blown psychosis, it is reasonable to hypothesize a lesser malleability of PPS boundaries in Sz. No studies until now have investigated this functional aspect of PPS in Sz. Hence, this represents the focus of the last study that illustrates the preliminary results on Sz patients, constituting another relevant contribution to our understanding of the spatial self in psychopathology. Taken together, all this evidence enriches the current state of the art of the minimal self disorder in Sz, empirically supporting the idea of a fragile self, which shatters into a variety of small pieces that enclose multiple interrelated bodily aspects.

Dans le cadre de ce travail de thèse, nous nous sommes intéressés aux relations étroites qu'entretiennent processus moteurs et sensoriels pour déterminer les régions de l'espace où une action directe est possible. Dans ce but, nous nous sommes centrés sur la perception de l' "atteignabilité" d'un objet, c'est-à-dire sur les processus cérébraux qui vont permettre de décider si cet objet pourrait être atteignable ou pas par un mouvement du bras. Pour cela, nous faisons l'hypothèse que ces jugements requièrent la prise en compte de connaissances motrices et corporelles fonctionnelles en plus des informations visuelles extraites de l'environnement. Plus particulièrement, nous proposons qu'ils reposent sur une prédiction des conséquences des actes moteurs potentiels suggérés par cet objet et donc de leur faisabilité à un instant donné. Les études réalisées au cours de cette thèse ont ainsi permis d'écarter l'hypothèse de l'influence de l'effort associé à des actions sur la perception de l'espace atteignable. En revanche, le rôle critique de la prédiction des conséquences sensorimotrices des actions a été mis en évidence, grâce à la démonstration d'une relation forte entre d'une part les correspondances entre la distance visuelle et l'amplitude des mouvements, et d'autre part la distance à laquelle la limite d'atteignabilité est perçue. Les processus d'anticipation sensorimotrice ont également été mis en évidence lors de jugements de perception spatiale en présence de cibles dynamiques, rendant compte du caractère spatio-temporel des mécanismes impliqués. Enfin, une dernière étude a montré l'influence des représentations corporelles et de leur plasticité dans la perception de l'espace péripersonnel, mettant ainsi en lumière l'implication du corps en action dans les jugements perceptifs

In my PhD research project, I wanted to investigate infants’ representation of the peripersonal space, which is the portion of environment between the self and the others. In the last three decades research provided evidence on newborns’ and infants’ perception of their own bodies and of other individuals, whereas not many studies investigated infants’ perception of the portion of space where they can interact with both others and objects, namely the peripersonal space. Considering the importance of the peripersonal space, especially in light of its defensive and interactive functions, I decided to investigate the development of its representation focusing on two aspects. On one side, I wanted to study how newborns and infants processed the space around them, if they differentiated between near and far space, possibly perceiving and integrating depth cues across sensory modalities and when and how they started to respond to different movements occurring in the space surrounding their bodies. On the other side, I was interested in understanding whether already at birth the peripersonal space could be considered as a delimited portion of space with special characteristics and, relatedly, if its boundaries could be determined. In order to respond to my first question, I investigated newborns’ and infants’ looking behaviour in response to visual and audio-visual stimuli depicting different trajectories taking place in the space immediately surrounding their body. Taken together, the results of these studies demonstrated that humans show, since the earliest stages of their development, a rudimentary processing of the space surrounding them. Newborns seemed, in fact, to already differentiate the space around them, through an efficient discrimination of different moving trajectories and a visual preference for those directed towards their own body, possibly due to their higher adaptive relevance. They also seemed to integrate multimodal, audio-visual information about stimuli moving in the near space, showing a facilitated processing of congruent audio-visual approaching stimuli. Furthermore, the results of these studies could help understand the development of the integration of multimodal stimuli with an adaptive valence during infancy. When newborns’ and infants were presented with unimodal, visual stimuli, they all directed their visual preferences to the stimuli moving towards their bodies. Conversely, their pattern of looking times was more complex when they were presented with congruent and incongruent audiovisual stimuli. Right after birth infants showed a spontaneous visual preference for congruent audio-visual stimuli, which was challenged by a similarly strong visual preference for adaptively important visual stimuli moving towards their bodies. The looking behaviours of 5-month-old infants, instead, seemed to be driven only by a spontaneous preference for multimodal congruent stimuli, i.e. depicting motion along the same trajectory, irrespective of the adaptive value of the information conveyed by either of the two sensory components of the stimulus. Nine-month-old infants, finally, seemed to flexibly integrate multisensory integration principles with the necessity of directing their attention to ethologically salient stimuli, as shown by the fact that their visual preference for unexpected, incongruent audio-visual stimuli was challenged by the simultaneous presence of adaptively relevant stimuli. Similarly to what happened with newborns, presenting 9-month-old infants with the two categories of preferred stimuli simultaneously led to the absence of a visual preference. Within my project I also investigated the electroencephalographic correlates of the processing of unimodal, visual and auditory, stimuli depicting different trajectories in a sample of 5-month-old infants. The results seemed to provide evidence in support of the role of the primary sensory cortices in the processing of crossmodal stimuli. Furthermore, they seemed to support the possibility that infants’ brain could allocate, already during the earliest stages of processing, different amounts of attention to stimuli with different adaptive valence. Two further studies addressed my second question, namely whether already at birth the peripersonal space could be considered as a delimited portion of space with special characteristics and if its boundaries could be determined. In these studies I measured newborns’ saccadic reaction times (RTs) to tactile stimuli presented simultaneously to a sound perceived at different distances from their body. The results showed that newborns’ RTs were modulated by the perceived position of the sound and that their modulation was very similar to that shown by adults, suggesting that the boundary of newborns’ peripersonal space could be identified in the perceived sound position in whose correspondence the drop of RTs happened. This suggested that at birth the space immediately surrounding the body seems to be already invested of a special salience and characterised by a more efficient integration of multimodal stimuli. As a consequence, it might be considered as a rudimentary representation of the peripersonal space, possibly serving, as a working space representation, early interactions between newly born humans and their environment. Overall, these findings provide a first understanding of how humans start to process the space surrounding them, which, importantly, is the space linking them with others and the space where their first interactions will take place.
Il mio progetto di Dottorato è nato con l’obiettivo di investigare la rappresentazione dello spazio peripersonale, cioè la porzione di spazio tra noi stessi e gli altri, durante l’infanzia. Nel corso degli ultimi trent’anni diversi studi hanno dimostrato la capacità di neonati ed infanti di percepire il proprio corpo, così come gli altri individui. Al contrario, non molti studi si sono interessati alla loro percezione della porzione di spazio dove essi possono interagire con gli oggetti e con gli altri, definita “spazio peripersonale”. Vista l’importanza dello spazio peripersonale, specialmente alla luce delle sue funzioni difensiva da un lato ed interattiva dall’altro, ho deciso di investigarne la rappresentazione concentrandomi su due aspetti. Da un lato, ho studiato come i neonati e gli infanti elaborino lo spazio intorno a loro, se differenzino tra spazio vicino e lontano, se percepiscano ed integrino gli indicatori di profondità provenienti da diverse modalità sensoriali, nonché come e quando inizino a rispondere ai diversi movimenti che hanno luogo nello spazio che circonda il loro corpo. Dall’altro lato, ero interessata a capire se già alla nascita lo spazio peripersonale potesse essere considerato come una porzione delimitata di spazio, contraddistinta da caratteristiche specifiche, e se i suoi confini potessero già essere stimati. Per rispondere alla mia prima domanda, ho analizzato il comportamento visivo di neonati ed infanti in risposta a stimoli visivi e audio-visivi raffiguranti diverse traiettorie che avevano luogo nello spazio immediatamente circostante il corpo. I risultati di questi studi, complessivamente, dimostrano che gli esseri umani mostrano, fin dai primi stadi dello sviluppo, una rudimentale capacità di elaborare lo spazio che circonda il loro corpo. I neonati sembrano, infatti, poter già differenziare lo spazio che li circonda, attraverso un’efficiente discriminazione di diverse traiettorie di movimento ed una preferenza visiva per quelle dirette verso il loro corpo, forse a causa della loro maggiore importanza adattiva. Inoltre, essi sembrano capaci di integrare informazioni multimodali rispetto al movimento di stimoli nello spazio circostante, mostrando un’elaborazione facilitata di stimoli in avvicinamento segnalati, al tempo stesso, da componenti visive ed uditive congruenti. Inoltre, i risultati di questi studi hanno permesso di aumentare la comprensione dello sviluppo della capacità di integrare stimoli multimodali caratterizzati da un’alta valenza adattiva durante l’infanzia. Quando ai neonati ed agli infanti sono stati presentati stimoli visivi (unimodali), essi hanno sempre rivolto la loro preferenza visiva agli stimoli che mostravano un movimento diretto verso il loro corpo. Diversamente, il loro comportamento visivo si è dimostrato più complesso quando sono stati presentati loro stimoli audiovisivi congruenti o incongruenti. Subito dopo la nascita, i neonati hanno mostrato una spontanea preferenza visiva per gli stimoli multimodali caratterizzati da una direzione di movimento congruente, a sua volta contrastata da un’altrettanta forte preferenza visiva per quegli stimoli che, muovendosi verso il loro corpo, erano caratterizzati da una grande salienza adattiva. Il comportamento visivo degli infanti di cinque mesi di età, invece, è sembrato essere guidato solamente da una spontanea preferenza per gli stimoli multimodali congruenti, cioè quelli che rappresentavano movimenti lungo la stessa traiettoria, indipendentemente dal valore adattivo delle informazioni trasmesse da ognuna delle due componenti sensoriali degli stimoli. Gli infanti di nove mesi di età, infine, sono sembrati capaci di integrare con flessibilità i principi dell’integrazione multisensoriale con la necessità di dirigere la loro attenzione verso gli stimoli etologicamente rilevanti, come dimostrato dal fatto che la loro preferenza visiva per gli stimoli audiovisivi incongruenti ed inaspettati è stata contrastata dalla simultanea presenza di stimoli importanti a livello adattivo. Come successo per i neonati, quando agli infanti di questa età venivano presentati contemporaneamente stimoli facenti parte delle due categorie preferite, essi non hanno mostrato alcuna preferenza visiva. All’interno del mio progetto ho anche investigato i correlati elettroencefalografici dell’elaborazione di stimoli unimodali, visivi ed uditivi, raffiguranti diverse traiettorie in un campione di infanti di cinque mesi di età. I risultati sembrano supportare il ruolo delle cortecce sensoriali primarie nell’elaborazione di stimoli provenienti da diverse modalità sensoriali, così come la possibilità che il cervello degli infanti possa assegnare diversi quantitativi di attenzione a stimoli di diversa importanza adattiva, già durante i primissimi stadi dell’elaborazione. Due ulteriori studi hanno indirizzato la mia seconda domanda, ovvero se già alla nascita lo spazio peripersonale possa essere considerato quale una porzione delimitata di spazio contraddistinta da particolari caratteristiche e se i suoi confini possano essere determinati. In questi studi ho misurato i tempi di reazione saccadici ad una stimolazione tattile accompagnata da un suono percepito a diverse distanze dal corpo. I risultati hanno mostrato che i tempi di reazione dei neonati sono stati modulati dalla distanza percepita del suono dal corpo. Inoltre, la modulazione dei tempi di reazione nei neonati è risultata molto simile a quella mostrata dagli adulti, suggerendo che i confini dello spazio peripersonale dei neonati possono essere identificati nella posizione in corrispondenza della quale i tempi di reazione sono drasticamente diminuiti. Questo dato suggerisce che alla nascita lo spazio immediatamente circostante il corpo sembra possedere già un’importanza particolare e sembra essere caratterizzato da una più efficace integrazione di stimoli multimodali. Di conseguenza, potrebbe essere considerato come una rudimentale rappresentazione dello spazio peripersonale, che può essere considerata al servizio delle interazioni precoci tra i neonati ed il loro ambiente. Complessivamente, questi risultati forniscono una prima comprensione di come gli esseri umani inizino a processare lo spazio che li circonda, cioè è lo spazio che li unisce agli altri, nonché lo spazio nel quale le loro prime interazioni avranno luogo.

L'homme ne perçoit pas l'espace de manière homogène : le cerveau code l'espace proche du corps différemment de l'espace lointain. Cette distinction joue un rôle primordial notre comportement social : l'espace proche du corps, appelé espace péripersonnel (EPP), serait une zone de protection du corps, où la présence d'un individu est perçue comme une menace. L'EPP a été initialement décrit par la psychologie sociale et l'anthropologie, comme un facteur de la communication humaine. L'EPP a été plus tard décrit chez le singe par des études de neurophysiologie comme un espace codé par des neurones multisensoriels. Ces neurones déchargent uniquement en réponse à des évènements sensoriels situés à une distance limitée du corps du singe (qu'ils soient tactiles, visuels ou auditifs). L'ensemble de ces neurones multisensoriels code ainsi l'EPP tout autour du corps. Ce codage exclusif de l'EPP est crucial pour interagir avec le monde extérieur, car c'est dans cet espace que sont réalisées les actions visant à protéger le corps ou visant à atteindre des objets autour de soi. Le codage mutlisensoriel de l'EPP pendant des interactions sociales est à ce jour peu étudié. Dans ce travail de recherche, nous avons réalisé plusieurs études en vu d'identifier des facteurs contribuant à la perméabilité de l'EPP et ses aspects adaptatifs. Une première étude a examiné les frontières latérales de l'EPP chez des individus seuls, en mesurant l'interaction d'une source sonore dynamique s'approchant du corps avec le temps de détection de stimulations tactiles. Cette étude a montré des différences dans la taille de l'EPP entre les deux hémi-espaces, qui seraient liées à la latéralité manuelle. Une seconde étude a exploré les modulations de l'EPP dans des contextes sociaux. Elle a montré que l'EPP est modifié lorsque des individus réalisent une tâche en collaboration. La troisième étude est une recherche méthodologique qui vise à dépasser les limitations des paradigmes comportementaux utilisés actuellement pour mesurer l'EPP. Elle propose de nouvelles pistes pour évaluer comment les stimuli approchant le corps sont intégrés en fonction de leur distance et du contexte multisensoriel dans lequel ils sont traités. L'ensemble de ces travaux montre l'intérêt d'étudier l'intégration multisensorielle autour du corps dans l'espace 3D pour comprendre pleinement l'EPP, et les impacts potentiels de facteurs sociaux sur les processus multisensoriels de bas-niveaux. De plus, ces études soulignent l'importance pour les neurosciences sociales de développer des protocoles expérimentaux réellement sociaux, à plusieurs participants
The space near the body, called peripersonal space (PPS), was originally studied in social psychology and anthropology as an important factor in interpersonal communication. It was later described by neurophysiological studies in monkeys as a space mapped with multisensory neurons. Those neurons discharge only when events are occurring near the body (be it tactile, visual or audio information), delineating the space that people consider as belonging to them. The human brain also codes events that are near the body differently from those that are farther away. This dedicated brain function is critical to interact satisfactorily with the external world, be it for defending oneself or to reach objects of interest. However, little is known about how this function is impacted by real social interactions. In this work, we have conducted several studies aiming at understanding the factors that contribute to the permeability and adaptive aspects of PPS. A first study examined lateral PPS for individuals in isolation, by measuring reaction time to tactile stimuli when an irrelevant sound is looming towards the body of the individual. It revealed an anisotropy of reaction time across hemispaces, that we could link to handedness. A second study explored the modulations of PPS in social contexts. It was found that minimal social instructions could influence the shape of peripersonal space, with a complex modification of behaviors in collaborative tasks that outreaches the handedness effect. The third study is a methodological investigation attempting to go beyond the limitations of the behavioral methods measuring PPS, and proposing a new direction to assess how stimuli coming towards the body are integrated according to their distance and the multisensory context in which they are processed. Taken together, our work emphasizes the importance of investigating multisensory integration in 3D space around the body to fully capture PPS mechanisms, and the potential impacts of social factors on low-level multisensory processes. Moreover, this research provides evidence that neurocognitive social investigations, in particular on space perception, benefit from going beyond the traditional isolated individual protocols towards actual live social interactive paradigms

La construction de la représentation de soi est basée sur l'intégration des informations que l'on reçoit des différentes modalités sensorielles telles que les informations visuelles, auditives, tactiles ou proprioceptives. L'interaction entre les actions et les mouvements, et plus récemment les interactions sociales et l'espace ont été étudiées essentiellement au niveau comportemental, moins au niveau fonctionnel et beaucoup reste encore à élucider. En particulier, il est important et essentiel de comprendre exactement quels processus sont impliqués dans la construction d'une représentation spatiale et comment ces processus sont mis en oeuvre, non seulement au niveau local par l'activité de neurones spécifiques, dans une zone corticale spécifique, mais aussi à l'échelle du réseau dans son ensemble ainsi qu'à l'échelle du cerveau entier. Le premier axe de ma thèse s'intéresse à l'espace peripersonnel, qui est l'espace le plus proche de nous et qui représente l'un des sous-espaces fonctionnels de la représentation spatiale. Nous faisons l'hypothèse que ce sont les mêmes régions qui contribuent à la convergence multisensorielle, à la prédiction des conséquences sur le traitement tactile d'une stimulation visuelle approchant le corps et à la construction de l'espace peripersonnel. Pour tester cette hypothèse, nous avons étudié l'effet des aspects prédictifs temporels et spatiaux d'un stimulus visuel dynamique sur la détection du stimulus tactile chez l'Homme (étude comportementale) et le primate non humain (étude en IRM fonctionnelle) ainsi que les bases neuronales de la représentation de l'espace proche et de la représentation de l'espace lointain, chez le primate non humain (étude en IRM fonctionnelle). Nous mettons en évidence l'implication d'un réseau parieto-frontal, essentiellement composé par l'aire intrapariétale ventrale VIP et l'aire prémotrice F4 qui sont activées par ces trois mécanismes différents. Nous proposons que ce réseau traite non seulement la trajectoire de l'objet approchant vis-à-vis du corps, mais qu'il anticipe également ses conséquences sur le corps et prépare des actions de protection en réponse à ce stimulus approchant. Le deuxième axe de ma thèse porte sur la caractérisation de l'étendue de la plasticité dans la représentation visuelle dans le cerveau adulte (par opposition aux premiers stades de plasticité observées autour des périodes critiques du développement) et en particulier, sur des développements méthodologiques permettant de mesurer les changements fins dans le cortex visuel induits par une telle plasticité. Plus précisément, nous avons développé un ensemble de méthodes d'IRM à haute résolution : imagerie fonctionnelle (cartographie visuelle à haute résolution, IRM au repos), pharmacologique (imagerie spectroscopique du GABA) et structurelle (IRM anatomique, DTI basée sur la diffusion des molécules d'eau), afin de définir des mesures de référence pour évaluer les changements induits par la plasticité à différents moments après son induction, à travers une étude longitudinale réalisée chez les mêmes animaux. Certaines de ces méthodes nécessitent encore quelques raffinements et ajustements mais, dans l'ensemble, elles montrent leur potentiel prometteur pour étudier la plasticité chez les primates non humains. Dans l'ensemble, ce travail de thèse a permis de créer un lien fonctionnel entre les études d'IRMf effectuées chez l'Homme et les études d'enregistrement d'électrophysiologies chez le primate non humain. De plus, il entraine de nouvelles stratégies et pistes d'explorations à étudier dans le domaine de la représentation spatiale, à la fois chez l'Homme et le primate non humain
The construction of the representation of self is based on the integration of information received by our different sensory modalities such as visual, auditory, tactile or proprioceptive information. The interaction between actions and movements and more recently social interactions and space are being explored at the behavioral level, but less so at the functional level and much more remains to be elucidated. In particular, it is important and fundamental to understand exactly which processes are involved in space representation and how, not only from a partial view focusing on specific cortical areas and single neuron processes but at the scale of the whole brain and the functional networks. The first axis of my thesis focuses on peripersonal space, that is the space that is closest to us, and represents one of the functional subspaces of spatial representation. We assume that it is the same regions that contribute to multisensory convergence, to the prediction of the consequences of a looming visual stimulus onto tactile processing and to the construction of peripersonal space. To test this hypothesis, we investigated the effect of the temporal and spatial predictive aspects of a dynamical looming visual stimulus onto tactile stimulus detection in humans (behavioral study) and non-human primates (fMRI study); the neural bases of near space and far space representations, in non-human primate (fMRI study). We highlight the involvement of a parieto-frontal network, essentially composed by the ventral intraparietal area VIP, the premotor area F4 as well as striate and extra-striate cortical regions, which are activated by these three different mechanisms. We propose that this network not only processes the trajectory of the looming object with respect to the body, but also anticipates its consequences onto the body and prepares protective actions in response to the looming stimulus. The second axis of my thesis focuses on characterizing the extent of plasticity in the visual representation of the adult brain (as opposed to the early stages around the critical developmental periods) and in particular, how the associated fine-grained changes in the visual cortex can be precisely quantified along multiple dimensions (anatomical, functional, pharmacological). Specifically, we have developed a set of high-resolution MRI methods to assess functional (high-resolution visual mapping fMRI, rs-MRI), pharmacological (GABA spectroscopy imaging) and structural (anatomical MRI, DTI) imaging to define reference measures against which to evaluate the changes induced by plasticity at different times after its induction, through a longitudinal study performed in the same animals. Some of these methods need to be more refined but they show that they are really promising to study plasticity in nonhuman primate. On the whole, this present doctoral research allows to make a functional link between human fMRI studies and monkey single cell recording studies and provides new strategies and explorations to perform on the spatial representation field both in humans and non-human primates

In this work I present several studies, which might appear rather heterogeneous for both experimental questions and methodological approaches, and yet are linked by a common leitmotiv: spatial attention. I will address issues related to the assessment of attentional asymmetries, in the healthy individual as in patients with neurological disorders, their role in various aspects of human cognition, and their neural underpinning, driven by the deep belief that spatial attention plays an important role in various mental processes that are not necessarily confined to perception. What follows is organized into two distinct sections. In the first I will focus on the evaluation of visuospatial asymmetries, starting from the description of a new paradigm particularly suitable for this purpose. In the first chapter I will describe the effects of multitasking in a spatial monitoring test; the main result shows a striking decreasing in detection performance as a function of the introduced memory load. In the second chapter I will apply the same paradigm to a clinical population characterized by a brain lesion affecting the left hemisphere. Despite a standard neuropsychological battery failed to highlight any lateralized attentional deficit, I will show that exploiting concurrent demands might lead to enhanced sensitivity of diagnostic tests and consequently positive effects on patients’ diagnostic and therapeutic management. Finally, in the third chapter I will suggest, in light of preliminary data, that attentional asymmetries also occur along the sagittal axis; I will argue, in particular, that more attentional resources appear to be allocated around peripersonal space, the resulting benefits extending to various tasks (i.e., discrimination tasks). Then, in the second section, I will follow a complementary approach: I will seek to induce attentional shifts in order to evaluate their role in different cognitive tasks. In the fourth and fifth chapters this will be pursued exploiting sensory stimulations: visual optokinetic stimulation and galvanic vestibular stimulation, respectively. In the fourth chapter I will show that spatial attention is highly involved in numerical cognition, this relationship being bidirectional. Specifically, I will show that optokinetic stimulation modulates the occurrence of procedural errors during mental arithmetics, and that calculation itself affects oculomotor behaviour in turn. In the fifth chapter I will examine the effects of galvanic vestibular stimulation, a particularly promising technique for the rehabilitation of lateralized attention disorders, on spatial representations. I will discuss critically a recent account for unilateral spatial neglect, suggesting that vestibular stimulations or disorders might indeed affect the metric representation of space, but not necessarily resulting in spatial unawareness. Finally, in the sixth chapter I will describe an attentional capture phenomenon by intrinsically rewarding distracters. I will seek, in particular, to predict the degree of attentional capture from resting-state functional magnetic resonance imaging data and the related brain connectivity pattern; I will report preliminary data focused on the importance of the cingulate-opercular network, and discuss the results through a parallel with clinical populations characterized by behavioural addictions.
In questo lavoro presenterò una serie di ricerche che possono sembrare piuttosto eterogenee per quesiti sperimentali e approcci metodologici, ma sono tuttavia legate da un filo conduttore comune: i costrutti di ragionamento e attenzione spaziale. Affronterò in particolare aspetti legati alla valutazione delle asimmetrie attenzionali, nell'individuo sano come nel paziente con disturbi neurologici, il loro ruolo in vari aspetti della cognizione umana, e i loro substrati neurali, guidato dalla convinzione che l’attenzione spaziale giochi un ruolo importante in svariati processi mentali non necessariamente limitati alla percezione. Quanto segue è stato dunque organizzato in due sezioni distinte. Nella prima mi soffermerò sulla valutazione delle asimmetrie visuospaziali, iniziando dalla descrizione di un nuovo paradigma particolarmente adatto a questo scopo. Nel primo capitolo descriverò gli effetti del doppio compito e del carico attenzionale su un test di monitoraggio spaziale; il risultato principale mostra un netto peggioramento nella prestazione al compito di detezione spaziale in funzione del carico di memoria introdotto. Nel secondo capitolo applicherò lo stesso paradigma ad una popolazione clinica contraddistinta da lesione cerebrale dell’emisfero sinistro. Nonostante una valutazione neuropsicologica standard non evidenziasse alcun deficit lateralizzato dell’attenzione, mostrerò che sfruttare un compito accessorio può portare ad una spiccata maggiore sensibilità dei test diagnostici, con evidenti ricadute benefiche sull'iter clinico e terapeutico dei pazienti. Infine, nel terzo capitolo suggerirò, tramite dati preliminari, che asimmetrie attenzionali possono essere individuate, nell'individuo sano, anche lungo l’asse sagittale; argomenterò, in particolare, che attorno allo spazio peripersonale sembrano essere generalmente concentrate più risorse attentive, e che i benefici conseguenti si estendono a compiti di varia natura (ad esempio compiti di discriminazione). Passerò dunque alla seconda sezione, in cui, seguendo una logica inversa, indurrò degli spostamenti nel focus attentivo in modo da valutarne il ruolo in compiti di varia natura. Nei capitoli quarto e quinto sfrutterò delle stimolazioni sensoriali: la stimolazione visiva optocinetica e la stimolazione galvanico vestibolare, rispettivamente. Nel quarto capitolo mostrerò che l’attenzione spaziale è coinvolta nella cognizione numerica, con cui intrattiene rapporti bidirezionali. Nello specifico mostrerò da un lato che la stimolazione optocinetica può modulare l’occorrenza di errori procedurali nel calcolo mentale, dall'altro che il calcolo stesso ha degli effetti sull'attenzione spaziale e in particolare sul comportamento oculomotorio. Nel quinto capitolo esaminerò gli effetti della stimolazione galvanica vestibolare, una tecnica particolarmente promettente per la riabilitazione dei disturbi attentivi lateralizzati, sulle rappresentazioni mentali dello spazio. Discuterò in modo critico un recente modello della negligenza spaziale unilaterale, suggerendo che stimolazioni e disturbi vestibolari possano sì avere ripercussioni sulle rappresentazioni metriche dello spazio, ma senza comportare necessariamente inattenzione per lo spazio stesso. Infine, nel sesto capitolo descriverò gli effetti di cattura dell’attenzione visuospaziale che stimoli distrattori intrinsecamente motivanti possono esercitare nell'adulto sano. Cercherò, in particolare, di predire l’entità di questa cattura attenzionale partendo da immagini di risonanza magnetica funzionale a riposo: riporterò dati preliminari focalizzati sull'importanza del circuito cingolo-opercolare, effettuando un parallelismo con popolazioni cliniche caratterizzate da comportamenti di dipendenza.

La douleur est une expérience complexe avec un fort impact sur la vie des patients surtout quand elle devient chronique et invalidante. Actuellement de nouvelles approches thérapeutiques émergent fondées sur une nouvelle compréhension de la douleur.Les patients blessés médullaires (BM) représentent une population chez qui la prise en charge de la douleur est difficile et cela en partie par une faible représentation dans la recherche scientifique. La douleur neuropathique sous-lésionnelle (DNSL) des BM est un modèle intéressant car s’apparente à une douleur de membre fantôme, est encore difficilement comprise, prise en charge et elle, représente un modèle intéressant pour l’étude du lien entre représentation du corps et douleur.Nous avons entrepris deux recherches pour comprendre comment les modifications du système nerveux central peuvent participer à la douleur de ces patients et quel lien peut-il avoir entre douleur et représentation du corps chez eux.Nos résultats ont permis de mettre en avant que les patients présentant des DNSL montrent des signes de plasticité maladaptative au niveau du thalamus, du cortex moteur et du cortex cingulaire ce qui est cohérent avec des altérations de la dite “neuromatrice de la douleur” et une dysrythmie thalamo-corticale déjà décrit dans d’autres pathologies. Les données indiquent aussi une possible neuroplasticité protectrice au niveau du cortex somatosensoriel. Ces changements sont autant de cibles potentielles de pris en charge en rééducation.De même nous avons pu démontrer que les patients BM ont une altération de leur représentation corporelle et que celle-ci est corrélée à l’aspect neuropathique de la douleur.Les données apportées confirment nos hypothèses et ouvrent vers la possibilité d’explorer ces phénomènes plus en avant et de déterminer quels moyens de rééducation peuvent être utiles pour aider les patients avec des DNSL
Pain is a complex experience with a strong impact on patients' lives, especially when it becomes chronic and disabling. New therapeutic approaches are currently emerging based on a new understanding of pain.Spinal cord injury (SCI) patients represent a population in which pain management is difficult and this is due to low representation in scientific research. Sublesional neuropathic pain (SNP) in SCI is an interesting model because it is similar to phantom limb pain, is still difficult to understand, manage and represents an interesting model for studying the link between body representation and pain.We have undertaken two studies to understand how changes in the central nervous system can contribute to the pain of these patients and how pain can be related to body representation in these patients. Our results have shown that patients with SNP show signs of maladaptive plasticity in the thalamus, motor cortex and cingulate cortex, which is consistent with alterations in the so-called "pain neuromatrix" and a thalamocortical disrythmia already described in other pathologies. More surprising and the evidence indicating a possible protective neuroplasticity at the somatosensory cortex level. These changes are all potential targets for rehabilitation treatment.Similarly, we were able to demonstrate that BM patients have an alteration in their body representation and that this is correlated with the neuropathic aspect of pain.The data provided confirm our hypotheses and open up the possibility of exploring these phenomena further in order to determine which rehabilitation methods are appropriate to help patients with SNP

Peripersonal (reachable) and extrapersonal (beyond reach) space is linked to hand perception. Using a tool to reach farther than normal recalibrates previously unreachable space as peripersonal, evidenced by Intraparietal Sulcus (IPS) activity related to hand perception and lateral biases during line bisection. The current study looked at the role of a visual connection between the hand and body in the ability to manipulate objects within the extended area of reach. In an immersive virtual environment, participants bisected lines using a connected hand (via arm), a disconnected hand, or a floating dot. A rightward shift in bisection was seen only for the dot condition for far lines, indicating that it was the only "tool" incapable of extending peripersonal space.

The primary intent of this study was to gain insight into the developmental nature of spatial perception and representation. More specifically, the work presented here examined 1) the age-related ability to modulate peri- and extrapersonal space via hand and tool use, 2) the adjustment period associated with extending and retracting spaces, and 3) the effect of tool length on modulation of space. Seventy children representing age groups 7-, 9-, 11 years and adults were presented with two experiments using an estimation of reach paradigm involving hand and tool conditions and a switch-block of the opposite condition. Experiment 1 tested Hand and Tool (20cm length) estimation and found a significant effect for Age, Space, and an Age x Space interaction (ps <.05). Both children and adults were less accurate in extrapersonal space, indicating an overestimation bias. Interestingly, the adjustment period during the switch-block condition was immediate and similar across age. Experiment 2 was similar to Experiment 1 with the exception of using a 40cm length tool. Results of 55 participants also revealed a difference in estimation responses between Age groups (p <.05); 7- and 9-year-olds were similar and less accurate than adults, and 11-year-olds were not different from any other age group. There was also a difference in Space (p <.05), revealing that participants underestimated their reaching abilities with higher accuracy in extrapersonal space. Interestingly, whereas participants overall overestimated with the 20cm tool, they tended to underestimate while using the 40cm tool. This finding suggests that participants were less confident when presented with a longer tool, even though the adjustment period with both tool lengths was similar. Considered together, these results hint that: (1) children as young as 6 years of age are capable of re-scaling peripersonal space via tool use in the context of estimation reach, (2) the adjustment period associated with extending and retracting spaces is immediate rather than gradual, and (3) tool length may influence confidence of participants, shifting the general direction of error from overestimation with a 20cm tool to underestimation with a 40cm tool.

碩士
國立臺灣大學
心理學研究所
102
In the space within arms’ length that surrounds each individual, being able to estimate distance of objects relative to the body is important for interaction with the environment. Given that distance is an interval of magnitude one describing space, it is likely that distance and the commonly used estimations of magnitude, i.e., numbers, share a common representation system (the ATOM theory, Walsh, 2003). We test this hypothesis in the peripersonal space, on both the sagittal and transverse axes, to systematically explore the distance representations on the transverse plane. Participants in Experiment 1 were required to judge the parity of digits as quickly and correctly as possible by pressing one of two buttons (both were in front of participants): one set near the body and the other far away from it. We found that near responses were faster when paired with smaller numbers and far responses with larger numbers. When one button was set in front and the other in back in Experiment 2, no mapping was found. In Experiment 3, when both buttons were on the right side, one being near the body and the other being far aligned with the transverse axis, smaller numbers were also faster with near responses and larger numbers with far responses. However, no such effect was found on the left side, suggesting that this distance-number mapping and the left-to-right SNARC effect are counteracted. These results suggest that beyond the SNARC effect, numbers are also mapped onto the whole transverse plane of the peripersonal space, not only a left-to-right oriented number line.

碩士
國立陽明大學
神經科學研究所
99
Previous studies reported that tool-use can induce extension of peripersonal space (EPS), as evidenced by a dynamic, effector-centered congruency effect between visual and tactile perception whose pattern alternated depending on the way the tools were held. We suspect that the effector-centered EPS induced by tool-use may be a special case of temporal synchronization between one’s actions and consequential environmental events. EPS may still occur without physical contact between the effector and its acting site. We verified the viability of a visual-tactile congruency task in Experiment 1, which required location discrimination of brief tactile vibrations accompanied by visual flashes on a virtual object which participants could move synchronously and remotely. We found that the EPS could be induced when the physical connection was removed in Experiment 2 and 3. The results of Experiment 2 also implied that the familiarity of tool may influence the strength of EPS. In Experiment 3 and 4, we compared the EPS on the right hand and left hand, which have different familiarities with computer mouse-use, while the mouse was used actively, held passively, or not held at all. We found the EPS occurred only when the tool was used actively, but was not different between the two hands. To examine the sufficiency of temporal synchronization in EPS, in Experiment 5 we interfered with the spatial alignment and tried to make the temporal synchronization the only salient correspondence between tool and hand. The results showed that the temporal synchronization by itself may not be sufficient to induce the EPS. The spatial alignment may also play a crucial role. Taken together, these experiments suggest that the peripersonal space can extend to a remote tool only when the tool was used actively, and the familiarity and spatial alignment may affect the extension of peripersonal space.

Dissertação de mestrado integrado em Psicologia
The peripersonal space is a dynamic and abstract representation around the body where most man-environment interactions take place. Previous studies have explored the effect of the body’s properties, the action possibilities and the value given to stimuli in the peripersonal space representation. However, no previous study specifically explored the effect that the stimuli’s value may have on the peripersonal space in a socio-cooperative context. In the present study, the main goal is to analyze whether getting more (or less) points in an active versus passive cooperative interaction affects the strategy of selecting the targets and extension of the peripersonal space. In Experiment 1 (Active Cooperation), 10 dyads performed a cooperative task with the aim of maximizing the number of points added to a joint account, where the reward targets were equally distributed on the workspace. In Experiment 2 (Passive Cooperation), 20 dyads performed the same cooperative task but only one of the partners had an active participation in the task’s execution and, consequently, on the points accumulation in the joint account. The results showed that, in Experiment 1, participants executed movements with short amplitude accompanied by an increase of the peripersonal space. However, in Experiment 2, participants executed movements with mid amplitude but without changes on the peripersonal space. These findings seem to indicate that, in a social context during an active cooperation task, the changes in the peripersonal space come from the association between the result of the actions performed by the individual and those he observes in his/her confederate.
O espaço peripessoal é uma representação dinâmica e abstrata junto ao corpo, onde têm lugar a maioria das interações Homem-ambiente. Estudos anteriores exploraram o efeito das propriedades do corpo, as possibilidades de ação e o valor atribuído aos estímulos na representação do espaço peripessoal. No entanto, nenhum estudo prévio explorou, especificamente, o efeito que o valor atribuído aos estímulos em contexto sociocolaborativo poderá ter no espaço peripessoal. Assim, o presente estudo tem como principal objetivo analisar de que forma conseguir mais (ou menos) pontos em cooperação ativa ou passiva afeta a estratégia de seleção dos alvos e a extensão do espaço peripessoal. Na Experiência 1 (Cooperação Ativa), 10 díades realizaram uma tarefa de cooperação com o objetivo de maximizarem o número de pontos ganhos depositados numa conta conjunta, sendo que os alvos recompensadores estavam distribuídos de forma homogénea. Na Experiência 2 (Cooperação Passiva), 20 díades realizaram a mesma tarefa de cooperação, mas apenas um dos elementos da díade tinha uma participação ativa na execução da tarefa, e consequentemente na acumulação dos pontos na conta em comum. Os resultados mostraram que, na Experiência 1, os participantes executaram movimentos de curta amplitude acompanhados com um aumento do espaço peripessoal. Contudo, na Experiência 2, os participantes executaram movimentos de amplitude média mas sem diferenças no espaço peripessoal. Estas descobertas revelaram que, em contexto social durante cooperação ativa, as alterações do espaço pessoal resultam da integração das ações recompensadas que os participantes obtiveram com aquelas que observaram o seu parceiro a obter.