Our body is generally perceived as a unique entity through which we can successfully interact with the external environment. Moreover, the body is particularly special as it can be considered both the object and subject of all experiences. Indeed, through our senses, we can act and interact in the environment but also perceive ourselves from the "inside." Since the perception and knowledge of our body come from different receptors and sensory modalities, numerous aspects are involved in representing our body. Body representation is intrinsically multimodal. Indeed, different sensory signals reach multimodal areas where the multisensory integration occurs to generate the sense of body ownership, i.e., the feeling that one's own body belongs to oneself. Furthermore, sensory information is combined to generate multiple body representations: different weights assigned to different sensory modalities originate distinct body representations. The exchange between senses and body representation seems to be bidirectional. Indeed, body representation would also play a role in influencing the information processing of different sensory modalities. Therefore, representations of different body features, such as shape, size, proportions, and posture, can result from integrating various sensory information. At the same time, the body representation can be the reference in processing sensory signals, thus influencing the perception of the external world. The present doctoral thesis aims to highlight this critical bidirectional relation between body representation and sensory processing: multisensory integration can modify body representation, and, simultaneously, body representation may influence perceptual phenomena. Accordingly, the first part of the thesis focuses on how the sensorimotor representation of one's own body in space and the representation of the space surrounding the body are constantly updated and modulated based on incoming sensory information (Study 1 and 2). Specifically, Study 1 reveals that a conflict between tactile and visual information can influence the perception of one's own body and of the potential space of action, emphasizing the reciprocity of the interaction between body and senses. Whereas Study 2 suggests how simply holding a tool in the hand, without performing any movement, can affect the morphological body representation (i.e., online incorporation of the tool). The second part of the thesis aims to test how body representation influences the processing of incoming sensory information (i.e., haptic and visual). More specifically, Study 3, using the established size-contrast aftereffect (i.e., Uznadze haptic Illusion), finds that the proprioceptive information about the arms position could modulate haptic size perception. Finally, Study 4 showed how visual size processing differs in the presence of bodily stimuli during the Uznadze visual Illusion, emphasizing the importance of the body in influencing sensory processing. In conclusion, the results of the experiments in this thesis highlight the critical reciprocal influence between the perception of the body and the external world, supporting the idea of a bidirectional relation between how the body is represented and how incoming sensory information is processed.
Il nostro corpo è percepito solitamente come un'entità unica attraverso la quale possiamo interagire con successo con l'ambiente esterno. Inoltre, il corpo è particolarmente speciale, poiché è sia l'oggetto che il soggetto di ogni esperienza. Infatti, attraverso i nostri sensi, possiamo agire e interagire nell'ambiente ma anche percepire noi stessi dall' "interno". Poiché la percezione e la conoscenza del nostro corpo provengono da diversi recettori e modalità sensoriali, numerosi aspetti sono coinvolti nella rappresentazione del corpo. Le rappresentazioni del corpo sono intrinsecamente multimodali. Ad esempio, il senso di ownership verso il proprio corpo, cioè la sensazione che il proprio corpo appartenga a se stessi, deriva dall’integrazione dei diversi segnali sensoriali che raggiungono le aree multimodali. Inoltre, le informazioni sensoriali vengono combinate per generare rappresentazioni corporee multiple: pesi diversi assegnati a diverse modalità sensoriali danno origine a rappresentazioni corporee distinte. Lo scambio tra sensi e rappresentazione corporea sembra essere bidirezionale. In effetti, la rappresentazione corporea avrebbe anche un ruolo nell'influenzare l'elaborazione delle informazioni provenienti da diverse modalità sensoriali. Pertanto, le rappresentazioni di diverse caratteristiche corporee, come la forma, le dimensioni, le proporzioni e la postura, possono derivare dall'integrazione di varie informazioni sensoriali. Allo stesso tempo, la rappresentazione corporea può essere il riferimento nell'elaborazione delle informazioni sensoriali, influenzando così la percezione del mondo esterno. La presente tesi di dottorato si propone di sottolineare questa relazione bidirezionale tra rappresentazione corporea ed elaborazione sensoriale: l'integrazione sensoriale può modificare la rappresentazione corporea e, allo stesso tempo, la rappresentazione corporea può influenzare l’elaborazione percettiva. In accordo, la prima parte della tesi si concentra su come la rappresentazione sensomotoria del proprio corpo nello spazio e la rappresentazione dello spazio circostante il corpo siano costantemente aggiornate e modulate in base alle informazioni sensoriali in arrivo (Studio 1 e 2). In particolare, lo Studio 1 mostra che un conflitto tra informazioni tattili e visive può influenzare la percezione del proprio corpo e dello spazio potenziale di azione, enfatizzando la reciprocità dell’interazione tra corpo e sensi. Mentre, lo Studio 2 suggerisce come il semplice mantenimento in mano di uno strumento, senza eseguire alcun movimento, possa influenzare la rappresentazione morfologica del corpo (cioè, incorporazione online dello strumento). La seconda parte della tesi (Studio 3 e 4) mira a verificare l'influenza della rappresentazione corporea sull'elaborazione delle informazioni sensoriali in entrata (cioè aptiche e visive). In particolare, lo Studio 3, utilizzando il noto aftereffect delle dimensioni (Illusione aptica di Uznadze) mostra che le informazioni propriocettive relative alla posizione delle braccia possono modulare la percezione aptica della dimensione degli stimoli. Infine, lo Studio 4 considera come l'elaborazione visiva delle dimensioni differisca in presenza di stimoli corporei durante l'Illusione visiva di Uznadze, sottolineando l'importanza del corpo come riferimento nell’elaborazione sensoriale. In conclusione, i risultati degli esperimenti di questa tesi evidenziano l’influenza reciproca tra la percezione del corpo e del mondo esterno, avvalorando l'idea di una relazione bidirezionale tra come il corpo è rappresentato e come le informazioni sensoriali in entrata sono elaborate.
From Senses to Body and Back: bidirectional relation between Body Representation and Sensory Processing
FRISCO, FRANCESCA
2023
Abstract
Our body is generally perceived as a unique entity through which we can successfully interact with the external environment. Moreover, the body is particularly special as it can be considered both the object and subject of all experiences. Indeed, through our senses, we can act and interact in the environment but also perceive ourselves from the "inside." Since the perception and knowledge of our body come from different receptors and sensory modalities, numerous aspects are involved in representing our body. Body representation is intrinsically multimodal. Indeed, different sensory signals reach multimodal areas where the multisensory integration occurs to generate the sense of body ownership, i.e., the feeling that one's own body belongs to oneself. Furthermore, sensory information is combined to generate multiple body representations: different weights assigned to different sensory modalities originate distinct body representations. The exchange between senses and body representation seems to be bidirectional. Indeed, body representation would also play a role in influencing the information processing of different sensory modalities. Therefore, representations of different body features, such as shape, size, proportions, and posture, can result from integrating various sensory information. At the same time, the body representation can be the reference in processing sensory signals, thus influencing the perception of the external world. The present doctoral thesis aims to highlight this critical bidirectional relation between body representation and sensory processing: multisensory integration can modify body representation, and, simultaneously, body representation may influence perceptual phenomena. Accordingly, the first part of the thesis focuses on how the sensorimotor representation of one's own body in space and the representation of the space surrounding the body are constantly updated and modulated based on incoming sensory information (Study 1 and 2). Specifically, Study 1 reveals that a conflict between tactile and visual information can influence the perception of one's own body and of the potential space of action, emphasizing the reciprocity of the interaction between body and senses. Whereas Study 2 suggests how simply holding a tool in the hand, without performing any movement, can affect the morphological body representation (i.e., online incorporation of the tool). The second part of the thesis aims to test how body representation influences the processing of incoming sensory information (i.e., haptic and visual). More specifically, Study 3, using the established size-contrast aftereffect (i.e., Uznadze haptic Illusion), finds that the proprioceptive information about the arms position could modulate haptic size perception. Finally, Study 4 showed how visual size processing differs in the presence of bodily stimuli during the Uznadze visual Illusion, emphasizing the importance of the body in influencing sensory processing. In conclusion, the results of the experiments in this thesis highlight the critical reciprocal influence between the perception of the body and the external world, supporting the idea of a bidirectional relation between how the body is represented and how incoming sensory information is processed.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/78347
URN:NBN:IT:UNIMIB-78347