A new perceptual paradigm to investigate the visual remapping of others’ tactile sensations onto one’s own body shows “mirror touch” for the hands

The last two decades have seen a multitude of publications showing the activation of an observer's somatosensory cortical system during the observation of touch on another person. Behavioral demonstrations of "mirror touch," however, have been slow in coming forward, and have so far primarily been shown as "visual remapping of touch" on the face. The present study uses a new paradigm to investigate the mirroring of others' tactile sensations: a 2-AFC task of intensity judgment for touch on the observer's left and right index finger pads. Observers viewed a left and right hand in an egocentric position, which were either touched passively (pencil moving to touch index finger pad) or actively sought touch (index finger moving to touch pencil). Touch and no-touch events for the two viewed hands were designed to eliminate confounding effects of spatial attention. Felt touches were either concurrent with viewed touch or no-touch events, or were delayed in time to assess potential response bias. The findings demonstrate visual remapping of touch for touch on the hands. If touch was shown on one of the hands only (e.g., left), observers were more likely to perceive touch on the same hand (i.e., their own left hand) as more intense than touch on the other hand even if tactile intensities did not differ, compared to touch shown on both or neither hand. These remapping effects occurred only when viewed and felt touches were concurrent, they were strongly modulated by the way in which viewed touch was incurred, and they were more reliable for touch on the left hand. A second, control experiment, in which touch observation was replaced by bright dots shown on or next to the finger pads, confirmed that these effects were largely due to genuine tactile mirroring rather than to somatotopic cueing. This 2-AFC tactile intensity judgment task may be a useful paradigm to investigate the remapping of others' tactile sensations onto an observer's own body. © 2014 Gillmeister

Evidence for ERP biomarkers of eating disorder symptoms in women.

Growing evidence suggests that the brain processes bodies distinctively from other stimuli, but little research has addressed whether visual body perception is modulated by the observer's thoughts and feelings about their own body. The present study thus investigated the relationship between body image and electrophysiological signatures of body perception, with the aim of identifying potential biomarkers of body image disturbances. Occipito-parietal (P1 and N1) and fronto-central (VPP) processing of body and non-body stimuli were assessed in 29 weight-restored eating disordered (ED) women and compared to 27 healthy controls. Rapid early visual processing was seen in the ED group, as the entire P1-N1 complex unfolded significantly earlier compared to controls. ED women also showed a gender-sensitive response to other women's bodies over N1 and VPP components. Such gender-sensitivity was not evident in controls. Moreover, ERP effects correlated with scores on the Eating Disorder Inventory-II (EDI-2), indicating a close link between the observers' ED symptomatology, including body image, and the visual analysis of human bodies during very early stages of cortical processing. The temporal dynamics of visual body perception may therefore serve as potential neural markers for the identification of ED symptomatology in 'at risk' populations

Bodily self‐relatedness in vicarious touch is reflected at early cortical processing stages

Studies have suggested that there is a strong link between the bodily self and the mechanisms underlying vicarious representations. Here, we used somatosensory ERPs to investigate the temporal dynamics of vicarious touch for stimuli that are more or less related to one's own body (human hands vs. rubber gloves). We found that vicarious touch effects were restricted to self‐relatable events (human hands) at early implicit stages of somatosensory processing (P45). At later more cognitive stages of processing (late positive complex, LPC), the vicarious touch effect was stronger for self‐relatable events (touch on human hands) than nonself‐relatable events (touch on rubber gloves) but present for both. Both effects, but especially the vicarious touch effect for human hands at P45, were stronger in individuals with higher levels of interoceptive awareness. Our results confirm that there is a tight link between vicarious touch and the bodily self and characterize P45 effects of vicarious touch as its likely neural basis. We propose that vicarious processes and the embodied self may be representationally indistinct (linked in a common neural representation) at early implicit somatosensory processing stages

Object-Guided Spatial Selection in Touch Without Concurrent Changes in the Perceived Location of the Hands

In an endogenous cueing paradigm with central visual cues, observers made speeded responses to tactile targets at the hands, which were either close together or far apart, and holding either two separate objects or one common object between them. When the hands were far apart, the response time costs associated with attending to the wrong hand were reduced when attention had to be shifted along one object jointly held by both hands compared to when it was shifted over the same distance but across separate objects. Similar reductions in attentional costs were observed when the hands were placed closer together, suggesting that processing at one hand is less prioritized over that at another when the hands can be “grouped” by virtue of arising from the same spatial location or from the same object. Probes of perceived hand locations throughout the task showed that holding a common object decreased attentional separability without decreasing the perceived separation between the hands. Our findings suggest that tactile events at the hands may be represented in a spatial framework that flexibly adapts to (object-guided) attentional demands, while their relative coordinates are simultaneously preserved. </jats:p

Object-guided Spatial Attention in Touch: Holding the Same Object with Both Hands Delays Attentional Selection

Abstract Previous research has shown that attention to a specific location on a uniform visual object spreads throughout the entire object. Here we demonstrate that, similar to the visual system, spatial attention in touch can be object guided. We measured event-related brain potentials to tactile stimuli arising from objects held by observers' hands, when the hands were placed either near each other or far apart, holding two separate objects, or when they were far apart but holding a common object. Observers covertly oriented their attention to the left, to the right, or to both hands, following bilaterally presented tactile cues indicating likely tactile target location(s). Attentional modulations for tactile stimuli at attended compared to unattended locations were present in the time range of early somatosensory components only when the hands were far apart, but not when they were near. This was found to reflect enhanced somatosensory processing at attended locations rather than suppressed processing at unattended locations. Crucially, holding a common object with both hands delayed attentional selection, similar to when the hands were near. This shows that the proprioceptive distance effect on tactile attentional selection arises when distant event locations can be treated as separate and unconnected sources of tactile stimulation, but not when they form part of the same object. These findings suggest that, similar to visual attention, both space- and object-based attentional mechanisms can operate when we select between tactile events on our body surface.</jats:p

Evidence for altered configural body processing in women at risk of disorders characterized by body image disturbance

Two studies were conducted to assess appearance‐related visual processing mechanisms in populations at risk of disorders characterized by body image disturbance. Using inverted stimuli, Experiment 1 assessed visual processing mechanisms associated with body, face, and house viewing in adolescents. Experiment 2 applied the same protocol to assess appearance‐related configural processing in high‐ and low‐risk adolescent women, and women recovering from disorders characterized by body image disturbance. Experiment 1 found evidence for typical configural face and body processing, although adolescent women reported higher levels of body image concern (BIC) and self‐objectified to a greater extent than adolescent men. In Experiment 2, typical body inversion effects were seen in the low‐risk group, whilst there was some evidence to suggest a disruption to the configural processing of body stimuli in high‐risk adolescents and in women recovering from body image disorders. Women in recovery were also quicker to respond to all stimuli, whilst high‐risk adolescents took longer to respond to bodies than to other stimuli. Configural face processing was intact in all groups, and effects did not directly relate to BIC or self‐objectification. These findings have implications for future research looking to inform early interventions and treatment, suggesting that there could be a tendency to visually process individual body parts at the expense of the whole‐body form in women at risk of developing body image disorders, as well as those in recovery

Interpersonal representations of touch in somatosensory cortex are modulated by perspective

Observing others being touched activates similar brain areas as those activated when one experiences a touch oneself. Event-related potential (ERP) studies have revealed that modulation of somatosensory components by observed touch occurs within 100 ms after stimulus onset, and such vicarious effects have been taken as evidence for empathy for others' tactile experiences. In previous studies body parts have been presented from a first person perspective. This raises the question of the extent to which somatosensory activation by observed touch to body parts depends on the perspective from which the body part is observed. In this study (N = 18), we examined the modulation of somatosensory ERPs by observed touch delivered to another person's hand when viewed as if from a first person versus a third person perspective. We found that vicarious touch effects primarily consist of two separable components in the early stages of somatosensory processing: an anatomical mapping for touch in first person perspective at P45, and a specular (mirror like) mapping for touch in third person perspective at P100. This is consistent with suggestions that vicarious representations exist to support predictions for one's own bodily events, but also to enable predictions of a social or interpersonal kind, at distinct temporal stages

Interpersonal Touch and the Importance of Romantic Partners for Older Adults’ Neuroendocrine Health

Interpersonal touch is an essential aspect of human interaction that has the ability to regulate physiological stress responses. Prolonged exposure to stress can have cumulative multiphysiological effects; for example, allostatic load. Despite the increased susceptibility of social isolation for older adults, there is a paucity of research on the efficacy of touch in regulating stress responses among this population. It is also unknown whether touch confers benefits regardless of the person with whom it is shared. This study investigates the difference in physiological stress based on the frequency of touch (hugs, holding, or other close physical contact) shared with romantic partners as compared to other close adults (family, friends, and neighbours) in an older adult population. Data were analysed from 1419 respondents (aged 57–85 years) of the National Social Life, Health, and Aging Project (NSHAP) in 2005–2006. Principal components analysis determined whether the eight markers of allostatic load measured in the NSHAP function as a singular system or as distinct components. Analyses revealed three components of allostatic load: metabolic, cardiovascular, and neuroendocrine health. The results of multiple regression revealed that a higher frequency of interpersonal touch shared with romantic partners was associated with better neuroendocrine health (β = 0.13, p = 0.004) following adjustment for a variety of covariates (but not with better metabolic or cardiovascular health), with no associations apparent for touch from other close adults. These findings highlight the importance of promoting interpersonal touch with romantic partners for older adults’ neuroendocrine health

Affective responses to body stimuli: comparing male and female bodies with cropped heads and masked faces

Three studies were conducted in order to determine whether headless bodies evoke affective responses that might confound neuroimaging and electrophysiological findings. In Experiment 1, 224 participants used an online questionnaire to rate pictures, including bodies with cropped heads and masked faces, for disgust, fear, naturalness, valence and arousal. In Experiment 2, 38 participants completed a free word association task whilst viewing images that included bodies with cropped heads and masked faces. In Experiment 3, 57 participants completed a similar rating task to that disseminated in Experiment 1, whilst galvanic skin responses were measured. Results from all studies found no differences in the affective response elicited by bodies without heads versus bodies with masked faces. Female bodies were thought of more positively than male bodies, however. These findings suggest that headless body stimuli are not abhorrent in any way and are thus the preferable stimuli for investigating body-selective perceptual processes as they do not evoke face-processing mechanisms. Our findings also suggest that differences between male and female body viewing should be considered when investigating visual body perception

Is that me in the mirror? Depersonalisation modulates tactile mirroring mechanisms

Our sense of self is thought to develop through sensory-motor contingencies provided, not only by observing one's own body, but also by mirroring interactions with others. This suggests that there is a strong link between mirroring mechanisms and the bodily self. The present study tested whether this link is expressed at early, implicit stages of the mirroring process or at later, more cognitive stages. We also provide, to the best of our knowledge, the first demonstration of how inter-individual differences in our sense of bodily self may affect mirroring mechanisms. We used somatosensory event-related potentials (SEPs) to investigate the temporal dynamics of mirroring highly self-related information (viewed touch on one's own face) compared to other-related information (viewed touch on a stranger's face), in individuals with low and high levels of depersonalisation, a mental condition characterised by feeling detached or estranged from one's self and body. For the low-depersonalisation group, mirroring for self-related events (P45) preceded mirroring for other-related events (N80). At later stages (P200), mirroring was stronger for other-related than self-related events. This shows that early, implicit and later, more cognitive processes play different relative roles in mirroring self- and other-related bodily events. Critically, mirroring differed in the high-depersonalisation group, specifically for self-related events. An absence of early, implicit mirroring for self-related events over P45 suggests that the associated processes may be the neural correlates of the disembodiment experienced in depersonalisation. A lack of differential mirroring for self- and other-related events over P200 may reflect compensatory mechanisms that redress deficiencies in mirroring at earlier stages, which may break down to give rise to symptoms of depersonalisation. Alternatively, or in addition, they may represent an attenuation of processes related to self-other distinction. Our study thus shows that mirroring, especially for events on one's own face, can be strongly affected by how connected the observer feels to their own bodily self