Plasticity in body and peripersonal space representations

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.

Visual-somatosensory interactions in mental representations of the body and the face

The body is represented in the brain at levels that incorporate multisensory information. This thesis focused on interactions between vision and cutaneous sensations (i.e., touch and pain). Experiment 1 revealed that there are partially dissociable pathways for visual enhancement of touch (VET) depending upon whether one sees one’s own body or the body of another person. This indicates that VET, a seeming low-level effect on spatial tactile acuity, is actually sensitive to body identity. Experiments 2-4 explored the effect of viewing one’s own body on pain perception. They demonstrated that viewing the body biases pain intensity judgments irrespective of actual stimulus intensity, and, more importantly, reduces the discriminative capacities of the nociceptive pathway encoding noxious stimulus intensity. The latter effect only occurs if the pain-inducing event itself is not visible, suggesting that viewing the body alone and viewing a stimulus event on the body have distinct effects on cutaneous sensations. Experiment 5 replicated an enhancement of visual remapping of touch (VRT) when viewing fearful human faces being touched, and further demonstrated that VRT does not occur for observed touch on non-human faces, even fearful ones. This suggests that the facial expressions of non-human animals may not be simulated within the somatosensory system of the human observer in the same way that the facial expressions of other humans are. Finally, Experiment 6 examined the enfacement illusion, in which synchronous visuo-tactile inputs cause another’s face to be assimilated into the mental self-face representation. The strength of enfacement was not affected by the other’s facial expression, supporting an asymmetric relationship between processing of facial identity and facial expressions. Together, these studies indicate that multisensory representations of the body in the brain link low-level perceptual processes with the perception of emotional cues and body/face identity, and interact in complex ways depending upon contextual factors.

Pedagogy of healthcare interactions. A study on pediatric well-child visits as culture-oriented and culture-making sites

This study investigates interactions between parents and pediatricians during pediatric well-child visits. Despite constituting a pivotal moment for monitoring and evaluating children’s development during the critical ‘first thousand days of life’ and for family support, no study has so far empirically investigated the in vivo realization of pediatrician-parent interactions in the Italian context, especially not from a pedagogical perspective. Filling this gap, the present study draws on a corpus of 23 videorecorded well-child visits involving two pediatricians and twenty-two families with children aged between 0 and 18 months. Combining an ethnographic perspective and conversation analysis theoretical-analytical constructs, the micro-analysis of interactions reveals how well-child visits unfold as culture-oriented and culture-making sites. By zooming into what actually happens during these visits, the analysis shows that there is much more than the “mere” accomplishment of institutionally relevant activities like assessing children’s health or giving parents advice on baby care. Rather, through the interactional ways these institutional tasks are carried out, parents and pediatricians presuppose, ratify, and transmit culturally-informed models of “normal” growth, “healthy” development, “good” caring practices, and “competent” parenting, thereby enacting a pervasive yet unnoticed educational and moral work. Inaugurating a new promising line of inquiry within Italian pedagogical research, this study illuminates how a) pediatricians work as a “social antenna”, bridging families’ private “small cultures” and broader socio-cultural models of children’s well-being and caregiving practices, and b) parents act as agentive, knowledgeable, (communicatively) competent, and caring parents, while also sensitive to the pediatrician’s ultimate epistemic and deontic authority. I argue that a video-based, micro-analysis of interactions represents a heuristically powerful instrument for raising pediatricians’ and parents’ awareness of the educational and moral density of well-child visits. Insights from this study can constitute a valuable empirical resource for underpinning medical and parental training programs aimed at fostering pediatricians’ and parents’ reflexivity.

Seeing and feeling the body

Recognizing one’s body as separate from the external world plays a crucial role in detecting external events, and thus in planning adequate reactions to them. In addition, recognizing one’s body as distinct from others’ bodies allows remapping the experiences of others onto one’s sensory system, providing improved social understanding. In line with these assumptions, two well-known multisensory mechanisms demonstrated modulations of somatosensation when viewing both one’s own and someone else’s body: the Visual Enhancement of Touch (VET) and the Visual Remapping of Touch (VRT) effects. Vision of the body, in the former, and vision of the body being touched, in the latter, enhance tactile processing. The present dissertation investigated the multisensory nature of these mechanisms and their neural bases. Further experiments compared these effects for viewing one’s own body or viewing another person’s body. These experiments showed important differences in multisensory processing for one’s own body, and for other bodies, and also highlighted interactions between VET and VRT effects. The present experimental evidence demonstrated that a multisensory representation of one’s body – underlie by a high order fronto-parietal network - sends rapid modulatory feedback to primary somatosensory cortex, thus functionally enhancing tactile processing. These effects were highly spatially-specific, and depended on current body position. In contrast, vision of another person’s body can drive mental representations able to modulate tactile perception without any spatial constraint. Finally, these modulatory effects seem sometimes to interact with high order information, such as emotional content of a face. This allows one’s somatosensory system to adequately modulate perception of external events on the body surface, as a function of its interaction with the emotional state expressed by another individual.