Is access to the body structural description sensitive to a body part's significance for action and cognition? A study of the sidedness effect using feet

Does the body talk to the body? The relationship between different body representations while observing others' body parts

The way human bodies are represented is central in everyday activities. The cognitive system must combine internal, visceral, and somatosensory, signals to external, visually driven information generated from the spatial placement of others’ bodies and the own body in the space. However, how different body representations covertly interact among them when observing human body parts is still unclear. Therefore, we investigated the implicit processing of body parts by manipulating either the body part stimuli’ posture (conditions a and b) or the participants’ response body posture (conditions c, d, and e) in healthy participants (N = 70) using a spatial compatibility task called Sidedness task. The task requires participants to judge the colour of a circle superimposed on a task‐irrelevant body part picture. Responses are facilitated when the spatial side of the responding hand corresponds to the spatial code generated by the hand stimulus's position with respect to a body of reference. Results showed that the observation of the task‐irrelevant body parts oriented participants’ attention and facilitated responses that were spatial compatible with the spatial position such body parts have within a configural representation of the body structure (i.e., Body Structural Representation) in all the five experimental conditions. Notably, the body part stimuli were mentally attached to the body according to the most comfortable and less awkward postures, following the anatomo‐physiological constraints. Moreover, the pattern of the results was not influenced by manipulating the participants’ response postures, suggesting that the automatic and implicit coding of the body part stimuli does not rely on proprioceptive information about one's body (i.e., Body Schema). We propose that the human body's morphometry knowledge is enriched by biomechanical and anatomo‐physiological information about the real body movement possibilities. Moreover, we discuss the importance of the automatic orienting of attention based on the sidedness within the context of imitational learning.

Cognitive Training Improves Disconnected Limbs' Mental Representation and Peripersonal Space after Spinal Cord Injury

Paraplegia following spinal cord injury (SCI) affects the mental representation and peripersonal space of the paralysed body parts (i.e., lower limbs). Physical rehabilitation programs can improve these aspects, but the benefits are mostly partial and short-lasting. These limits could be due to the absence of trainings focused on SCI-induced cognitive deficits combined with traditional physical rehabilitation. To test this hypothesis, we assessed in 15 SCI-individuals the effects of adding cognitive recovery protocols (motor imagery–MI) to standard physical rehabilitation programs (Motor + MI training) on mental body representations and space representations, with respect to physical rehabilitation alone (control training). Each training comprised at least eight sessions administered over two weeks. The status of participants’ mental body representation and peripersonal space was assessed at three time points: before the training (T0), after the training (T1), and in a follow-up assessment one month later (T2). The Motor + MI training induced short-term recovery of peripersonal space that however did not persist at T2. Body representation showed a slower neuroplastic recovery at T2, without differences between Motor and the Motor + MI. These results show that body and space representations are plastic after lesions, and open new rehabilitation perspectives.

The Effect of Sport Practice on Enhanced Cognitive Processing of Bodily Indices: A Study on Volleyball Players and Their Ability to Predict Hand Gestures

To program proper reactions, athletes must anticipate opponents’ actions on the basis of previous visuomotor experience. In particular, such abilities seem to rely on processing others’ intentions to act. We adopted a new approach based on an attentional spatial compatibility paradigm to investigate how elite volleyball players elaborate both spatial and motor information at upper-limb posture presentation. Forty-two participants (18 volleyball players and 17 nonathlete controls assigned to Experiments 1 a and b, and eight basketball players assigned to Experiment 2) were tested to study their ability to process the intentions to act conveyed by hands and extract motor primitives (i.e., significant components of body movements). Analysis looked for a spatial compatibility effect between direction of the spike action (correspondence factor) and response side for both palm and back of the hand (view factor). We demonstrated that volleyball players encoded spatial sport-related indices from bodily information and showed preparatory motor activation according to the direction of the implied spike actions for the palm view (Experiment 1; hand simulating a cross-court spike, p = 0.013, and a down-the-line spike, p = 0.026) but both nonathlete controls (Experiment 1; both p < 0.05) and other sports athletes (basketball players, Experiment 2; p = 0.34, only cross-court spike) did not. Results confirm that elite players’ supremacy lies in the predictive abilities of coding elementary motor primitives for their sport discipline.

Body representation in people with apraxia post Stroke- an observational study

Objective: To investigate how two types of body representation (body schema and body image) were affected in people with and without apraxia following a supratentorial stroke.Design: Observational cross-sectional studySetting: Level 1 Specialist Neurological Rehabilitation UnitParticipants: 30 participants post-stroke diagnosed with (n = 10) and without apraxia (n = 20) according to a modified version of the short Ideomotor Apraxia Test.Interventions: Not applicableMain Outcome Measures: Body schema assessed using the hand laterality recognition test and body part knowledge test; Implicit body image assessed using the sidedness test.Results: Left-sided lesions were more common in the apraxic group. Compared to people without apraxia post-stroke, those with apraxia showed significantly reduced accuracy and longer reaction times on the hand laterality test and fewer correct responses on the body part knowledge test. There was no between-groups difference in the sidedness test.Conclusions: People with apraxia showed deficits in online body representations (body schema) that are used to plan and execute actions. Future research studies could target body schema deficits as an adjunct in the rehabilitation of apraxia.

A letter on a hand: Rotating together or separately?

The motor system plays a role in some object mental rotation tasks, and researchers have reported that people may use a strategy of motor simulation to mentally rotate objects. In this study, we used images of a hand with a letter printed on the palm to directly determine whether a hand image can be automatically rotated during the deliberate mental rotation of an object and whether the hand and object are rotated in the same trajectory. A total of 41 participants were shown the stimuli and asked to decide whether the letters, which were upright or tilted at specific degrees, were normal or mirrored. The hand images in the background showed either a left or a right hand in the palm view, with fingers pointing upwards, medial, downwards, or lateral. Reaction times and error rates were measured to determine the speed and accuracy of mental rotation. A complex interaction between the hand posture and letter orientation revealed that the hand image was mentally rotated automatically, together with the deliberate mental rotation of the letter. The biomechanical constraints of the hand also influenced reaction times, suggesting the involvement of the motor system in the concomitant mental rotation of the hand image. Consistent with the motor simulation theory, the participants seemed to imagine the hand carrying the object in its movement. These behavioural data support the motor simulation theory and elucidate specific processes of mental rotation that have not been addressed by neuroimaging studies.

Action and Non-Action Oriented Body Representations: Insight from Behavioural and Grey Matter Modifications in Individuals with Lower Limb Amputation

Objective

Following current model of body representations, we aimed to systematically investigate the association between brain modifications, in terms of grey matter loss, and body representation deficits, in terms of alterations of the body schema (BS) and of non-action oriented body representations (NA), in individuals with lower limb amputation (LLA).

Method

BS and NA (both semantic and visuospatial NA) were evaluated in 11 healthy controls and in 14 LLA, considering the impact of clinical variables such as prosthesis use. The association between BS and NA deficits and grey matter loss was also explored in LLA by using Voxel Based Morphometry analysis.

Results

LLA's performance was fine in terms of semantic NA, while it showed behavioural impairments both in BS and visuospatial NA as compared to healthy controls. Interestingly the visuospatial NA performance was related to the amount of prosthesis use. NA deficits in terms of visuospatial body map processing were associated with grey matter reduction in left (lobule VIII) and right (crus II) cerebellum, while BS deficits were associated with grey matter reduction in right anterior cingulate cortex and the bilateral cuneus. No significant association was detected for semantic NA.

Conclusion

The study of BS and NA representations after limb loss has informed our understanding of the different dynamics (i.e., adjustments to body change) of such representations, supporting current cognitive models of body representation. The clinical relevance of present findings is also discussed.

Finger posture modulates structural body representations

Patients with lesions of the left posterior parietal cortex commonly fail in identifying their fingers, a condition known as finger agnosia, yet are relatively unimpaired in sensation and skilled action. Such dissociations have traditionally been interpreted as evidence that structural body representations (BSR), such as the body structural description, are distinct from sensorimotor representations, such as the body schema. We investigated whether performance on tasks commonly used to assess finger agnosia is modulated by changes in hand posture. We used the 'in between' test in which participants estimate the number of unstimulated fingers between two touched fingers or a localization task in which participants judge which two fingers were stimulated. Across blocks, the fingers were placed in three levels of splay. Judged finger numerosity was analysed, in Exp. 1 by direct report and in Exp. 2 as the actual number of fingers between the fingers named. In both experiments, judgments were greater when non-adjacent stimulated fingers were positioned far apart compared to when they were close together or touching, whereas judgements were unaltered when adjacent fingers were stimulated. This demonstrates that BSRs are not fixed, but are modulated by the real-time physical distances between body parts.

Observed bodies generate object-based spatial codes

Contemporary studies of spatial and social cognition frequently use human figures as stimuli. The interpretation of such studies may be complicated by spatial compatibility effects that emerge when researchers employ spatial responses, and participants spontaneously code spatial relationships about an observed body. Yet, the nature of these spatial codes - whether they are location- or object-based, and coded from the perspective of the observer or the figure - has not been determined. Here, we investigated this issue by exploring spatial compatibility effects arising for objects held by a visually presented whole-bodied schematic human figure. In three experiments, participants responded to the colour of the object held in the figure's left or right hand, using left or right key presses. Left-right compatibility effects were found relative to the participant's egocentric perspective, rather than the figure's. These effects occurred even when the figure was rotated by 90° to the left or to the right, and the coloured objects were aligned with the participant's midline. These findings are consistent with spontaneous spatial coding from the participant's perspective and relative to the normal upright orientation of the body. This evidence for object-based spatial coding implies that the domain general cognitive mechanisms that result in spatial compatibility effects may contribute to certain spatial perspective-taking and social cognition phenomena.

To move or not to move, that is the question! Body schema and non-action oriented body representations: An fMRI meta-analytic study

Many studies have attempted to identify the different cognitive components of body representation (BR). Due to methodological issues, the data reported in these studies are often confusing. Here we summarize the fMRI data from previous studies and explore the possibility of a neural segregation between BR supporting actions (body-schema, BS) or not (non-oriented-to-action-body-representation, NA). We performed a general activation likelihood estimation meta-analysis of 59 fMRI experiments and two individual meta-analyses to identify the neural substrates of different BR. Body processing involves a wide network of areas in occipital, parietal, frontal and temporal lobes. NA selectively activates the somatosensory primary cortex and the supramarginal gyrus. BS involves the primary motor area and the right extrastriate body area. Our data suggest that motor information and recognition of body parts are fundamental to build BS. Instead, sensory information and processing of the egocentric perspective are more important for NA. In conclusion, our results strongly support the idea that different and segregated neural substrates are involved in body representations orient or not to actions.

Tool-use: An open window into body representation and its plasticity

Over the last decades, scientists have questioned the origin of the exquisite human mastery of tools. Seminal studies in monkeys, healthy participants and brain-damaged patients have primarily focused on the plastic changes that tool-use induces on spatial representations. More recently, we focused on the modifications tool-use must exert on the sensorimotor system and highlighted plastic changes at the level of the body representation used by the brain to control our movements, i.e., the Body Schema. Evidence is emerging for tool-use to affect also more visually and conceptually based representations of the body, such as the Body Image. Here we offer a critical review of the way different tool-use paradigms have been, and should be, used to try disentangling the critical features that are responsible for tool incorporation into different body representations. We will conclude that tool-use may offer a very valuable means to investigate high-order body representations and their plasticity.

Please don't! The automatic extrapolation of dangerous intentions

Facial emotions and emotional body postures can easily grab attention in social communication. In the context of faces, gaze has been shown as an important cue for orienting attention, but less is known for other important body parts such as hands. In the present study we investigated whether hands may orient attention due to the emotional features they convey. By implying motion in static photographs of hands, we aimed at furnishing observers with information about the intention to act and at testing if this interacted with the hand automatic coding. In this study, we compared neutral and frontal hands to emotionally threatening hands, rotated along their radial-ulnar axes in a Sidedness task (a Simon-like task based on automatic access to body representation). Results showed a Sidedness effect for both the palm and the back views with either neutral and emotional hands. More important, no difference was found between the two views for neutral hands, but it emerged in the case of the emotional hands: faster reaction times were found for the palm than the back view. The difference was ascribed to palm views' “offensive” pose: a source of threat that might have raised participants' arousal. This hypothesis was also supported by conscious evaluations of the dimensions of valence (pleasant-unpleasant) and arousal. Results are discussed in light of emotional feature coding.