The functional body: Does body representation reflect functional properties?

There is a growing interest in the distortions of body representation in healthy population and most studies have focused their attention on specific parts of the body, such as the hands. Only three studies have considered the representation of the body as a whole. Findings, acquired by different means of assessment methods, are partially contrasting, leading to different interpretations. The present study aims to investigate which aspects of body representation can be preserved regardless of the method adopted and whether current and previous findings can be explained by a unique theoretical model. In Experiments 1a and 1b we adopted a modified version of the Body Image Task to investigate body representations in real scale and the relationship of its parts. Participants judged the location of body landmarks by pointing on their own silhouette imagined on a wall in front of them. In Experiment 2 we investigated i) whether the pattern of distortions observed in the first experiment are maintained across different methods by asking participants to estimate the veracity and proportionality of the length of their own body parts; and ii) whether similar distortions can be generalized to stereotypical representations. Overall, we observed a consistent pattern of distortions, whereby upper body limbs are underestimated and lower parts of the body are overestimated across all experiments and conditions. These findings are then interpreted as the result of a functional relationship between body parts and daily actions, which underlie a close modulation of body schema and body image. This interpretation offers a reconciliation of seemingly contradictory findings in the literature and supports to the co-construction model (Pitron et al., 2018)

The Fluff test: Improved scoring system to account for different degrees of contralesional and ipsilesional personal neglect in brain-damaged patients

The Fluff test is a simple test to assess evidence of personal neglect (PN) in brain damaged patients. While blindfolded, patients are asked to remove targets previously attached on their body and the number of targets detached provides information about possible spatial bias. This test has been widely used for clinical and research purposes. However, the current scoring system presents some limitations, which make difficult to interpret patients’ performance in terms of both contralalesional and ipsilesional PN when they omit targets on the ipsilesional side. Moreover, it does not consider possible confounding variables, such as non-spatial cognitive deficits or lack of compliance that may affect patients’ performance and lead to incorrect diagnosis. The present paper proposes a new scoring method overcoming the limitations mentioned above and it analyses data from a large sample of 243 brain damaged patients. Findings showed that contralesional PN was significantly more severe, but not more frequent, following right (31%) than left (21%) brain damage. We also found evidence of left ipsilesional PN and cases of potential mis-diagnosis that would have passed unnoticed with the original scoring system. The new scoring method allows to identify different degrees of contralesional and ipsilesional PN and potential confounding variable

Same action in different spatial locations induces selective modulation of body metric representation

© 2021 Springer Nature Switzerland AG. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1007/s00221-021-06135-3Recent studies have hypothesised that the stereotypical representation of the body may reflect some functional aspects of routine actions that are performed in specific peripersonal domains. For example, the lower and upper limbs tend to ‘act’ in different peripersonal spaces and perform different functions. The present study aims to directly investigate the relationship between body representation and the spatial context where actions are performed. By means of a modified version of the Body Image Task we investigated body representation before and after a sorting task training in two groups of participants who were asked to carry out the same task/actions in two different spaces: on a table or on the floor, while sitting on a chair. Findings showed that a significant recalibration of the perceived upper arms’ length occurred when participants were asked to perform a motor task on the floor. These results seem to suggest that the modulation of the body representation reflects an increase action capabilities driven by the contribution of motor training modulates and, importantly, the location in which the action occurs. Furthermore, the modulation was not limited to the body part actively involved in the action (the arms), it extended to other upper body parts (the torso) to maintain, we propose, a functionally coherent representation of the upper body.Peer reviewe

Selective effects of a brain tumor on the metric representation of the hand: a pre- versus post-surgery comparison

Body representation disorders are complex, varied, striking and very incapacitating in most cases. Deficits of body representation have been described after lesions to multimodal and sensorimotor cortical areas. A few studies have reported the effects of tumors on the representation of the body, but little is known about the changes after tumor resection. Moreover, impact of brain lesions on the hand size representation has been investigated in few clinical cases. Hands are of special importance as no other body part has the ability for movement and interaction with the environment that the hands have, and we use them for a multitude of daily activities Studies with clinical population can add further knowledge into the way hands are represented. Here, we report a single case study of a patient (AM) who was an expert bodybuilder and underwent a surgery to remove a glioblastoma in the left posterior prefrontal and precentral cortex at the level of the hand’s motor region. Pre- (20 days) and post- (4 months) surgery assessment did not show any motor or cognitive impairments. A hand localization task was used, before and after surgery (12 months), to measure possible changes of the metric representation of his right hand. Results showed a modulation on the hand representation with an overall improvement after the surgery in the accuracy of the hand representation, especially on width dimension. These findings support the direct involvement of sensorimotor areas in the implicit representation of the body size and its relevance on defining specific size representation dimensions

The signing body: Extensive sign language practice shapes the size of hands and face

The representation of the metrics of the hands is distorted but is susceptible to malleability due to expert dexterity (magicians) and long-term tool use (baseball players). However, it remains unclear whether modulation leads to a stable representation of the hand that is adopted in every circumstance, or whether the modulation is closely linked to the spatial context where the expertise occurs. To this aim, a group of 10 experienced Sign Language (SL) interpreters were recruited to study the selective influence of expertise and space localisation in the metric representation of hands. Experiment 1 explored differences in hands’ size representation between the SL interpreters and 10 age-matched controls in near-reaching (Condition 1) and far-reaching space (Condition 2), by using the localisation task. SL interpreters presented reduced hand size in near-reaching condition, with characteristic underestimation of finger lengths, and reduced overestimation of hands and wrists widths in comparison with controls. This difference was lost in far-reaching space, confirming the effect of expertise on hand representations is closely linked to the spatial context where an action is performed. As SL interpreters are also experts in the use of their face with communication purposes, the effects of expertise in the metrics of the face were also studied (Experiment 2). SL interpreters were more accurate than controls, with overall reduction of width overestimation. Overall, expertise modifies the representation of relevant body parts in a specific and context-dependent manner. Hence, different representations of the same body part can coexist simultaneously

The flubbed body: pathological body size representation in personal neglect

Personal Neglect (PN) is a disorder in which patients fail to attend or explore the contralateral side of their body. An increasing number of studies have considered PN as a form of body representation disorder frequently observed following damage to parietal areas. The extent and the direction of the body misrepresentation is still unclear with recent studies suggesting a general reduction of contralesional hand size. However, little is known about the specificity of this representation and whether the misrepresentation also generalises to other body parts. We explored the features of the representation of the hands and face in a group of 9 right brain damaged patients with (PN+) and without PN (PN-), when compared to a healthy control group. For this, we used a body size estimation task with pictures, in which patients were required to choose the one that most closely matched the perceived size of their body part. We found that PN+ patients showed a labile body representation for both hands and face, having a larger distorted representational range. Interestingly, in comparison with PN+ patients and healthy controls, PN- patients also showed misrepresentation of the left contralesional hand which could be related to impaired motor performance of their upper limb. Our findings are discussed within a theoretical framework suggesting a reliance on multisensory integration (body representation, ownership, and motor influences) for an ordered representation of the size of the body

The different impact of attention, movement and sensory information on body metric representation

© Experimental Psychology Society 2023. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1177/17470218231187385A growing body of research investigating the relationship between body representation and tool-use has shown that body representation is highly malleable. The nature of the body representation does not consist only of sensory attributes but also of motor action-oriented qualities, which may modulate the subjective experience of our own body. However, how these multisensory factors and integrations may specifically guide and constrain body reorientation’s plasticity has been under-investigated. In the present study, we used a forearm bisection task to selectively investigate the contribution of motor, sensory and attentional aspects in guiding body representation malleability. Results show that the perceived forearm midpoint deviates from the real one. This shift is further modulated by a motor task but not by a sensory task, whereas the attentional task generates more uncertain results. Our findings provide novel insight into the individual role of movement, somatosensation and attention in modulating body metric representation.Peer reviewe

My true face: Unmasking one's own face representation

Face recognition has been the focus of multiple studies, but little is still known on how we represent the structure of one's own face. Most of the studies have focused on the topic of visual and haptic face recognition, but the metric representation of different features of one's own face is relatively unknown. We investigated the metric representation of the face in young adults by developing a proprioceptive pointing task to locate face landmarks in the first-person perspective. Our data revealed a large overestimation of width for all face features which resembles, in part, the size in somatosensory cortical representation. In contrast, face length was compartmentalised in two different regions: upper (underestimated) and bottom (overestimated); indicating size differences possibly due to functionality. We also identified shifts of the location judgments, with all face areas perceived closer to the body than they really were, due to a potential influence of the self-frame of reference. More importantly, the representation of the face appeared asymmetrical, with an overrepresentation of right side of the face, due to the influence of lateralization biases for strong right-handers. We suggest that these effects may be due to functionality influences and experience that affect the construction of face structural representation, going beyond the parallel of the somatosensory homunculus