Functionality appreciation is associated with improvements in positive and negative body image in patients with an eating disorder and following recovery.

BACKGROUND: Research on body image in eating disorders has predominantly focused on negative body image, only recently shifting to positive body image. Findings suggest that enhancing positive body image can, amongst other things, serve as a protective mechanism against (re)developing a negative body image. One suggested way of enhancing positive body image is to focus on enhancing body functionality appreciation. Although studies show promising effects, this research is mainly conducted in non-clinical samples. METHODS: The current study investigated the levels of positive and negative body image in an online community sample of patients with an eating disorder (PAT, n = 227), patients recovered from an eating disorder (REC, n = 102) and controls (HC, n = 175) (self-reported diagnosis, not confirmed). In addition, we tested whether body functionality appreciation was associated with appearance dissatisfaction (negative body image) and body appreciation (positive body image). RESULTS: REC showed similar results to controls to most of the body image measures except for how much importance one places on their appearance (no different between REC and PAT), and how satisfied one is with certain body parts. For this measure, REC scored in-between PAT and HC. We further found functionality appreciation to be significantly associated with of both positive and negative body image, except for appearance evaluation in patients with an eating disorder. CONCLUSIONS: This study showed a positive association between body functionality appreciation and positive body image and a negative association between body functionality appreciation and negative body image. Further research is required to investigate the effectiveness of interventions targeting body functionality appreciation in clinical settings.

People with an eating disorder often suffer from a negative body image. This negative body image has been found to be hard to treat. Recently researchers started to not only look at ways to decrease negative body image but also enhance positive body image. It has been found that it is beneficial for people with a negative body image to learn to focus on appreciating the functions of the body (body functionality appreciation), as this leads to a more positive body image. However, this research was done on people without an eating disorder. In this questionnaire study, we looked at whether there is a relationship between body functionality appreciation and body image in patients with a (self-reported) eating disorder diagnosis and those who are recovered from an eating disorder. We found that functionality appreciation is associated with increased positive body image and decreased negative body image in all groups. Further studies should investigate the effectiveness of clinical interventions that focus on body functionality appreciation to enhance body image.

Changes in perceived peripersonal space following the rubber hand illusion.

Peripersonal space (PPS), the region immediately surrounding the body is essential for bodily protection and goal directed action. Previous studies have suggested that the PPS is anchored to one's own body and in the current study we investigated whether the PPS could be modulated by changes in perceived body ownership. While theoretically important, this anchoring can also have implications for patients with altered body perception. The rubber hand illusion (RHI) is a way to manipulate body ownership. We hypothesized that after induction of a left hand RHI, the perceived space around the body shifts to the right. Sixty-five participants performed a landmark task before and after a left hand RHI. In the landmark task, participants had to determine whether a vertical landmark line was left or right from the center of a horizontal screen. One group of the participants was exposed to synchronous stroking, the other group experienced asynchronous stroking. Results showed a shift in space to the right (e.g. away from the own arm), but only for the 'synchronous stroking' group. These results suggest that the relevant action space becomes linked to the fake hand. Critically, subjective ownership experience did not correlate with this shift, but proprioceptive drift did. This suggests that multisensory integration of bodily information drives this shift in space around the body and not feelings of ownership.

Affective touch perception and longing for touch during the COVID-19 pandemic.

Interpersonal touch and affective touch play a crucial role in social interactions and have a positive influence on mental health. The social distancing regulations implemented during the COVID-19 pandemic have reduced the ability to engage in interpersonal touch. This could cause longing for touch, and it might subsequently alter the way in which affective touch is perceived. To investigate this, we conducted an online survey and included 1982 participants, which contained questions regarding the COVID-19 regulations, longing for touch, and the perceived pleasantness of affective and non-affective touch. Results showed that participants reported feelings of longing for touch. This significantly increased with the duration and severity of the COVID-19 regulations. In addition, participants who experienced more longing for touch rated videos of affective and non-affective touch as more pleasant. Current results provide insight in the impact of sudden and prolonged COVID-19 regulations and show that increasing the duration and severity of these regulations is associated with a higher desire for touch, which is associated with increased perceived pleasantness of observing touch.

Body ownership and the absence of touch: approaching the rubber hand inside and outside peri-hand space.

It is widely accepted that the integration of visual and tactile information is a necessity to induce ownership over a rubber hand. This idea has recently been challenged by Ferri et al. (Proc R Soc B 280:1-7, 2013), as they found that sense of ownership was evident by mere expectation of touch. In our study, we aimed to further investigate this finding, by studying whether the mere potential for touch yields a sense of ownership similar in magnitude to that resulting from actually being touched. We conducted two experiments. In the first experiment, our set-up was the classical horizontal set-up (similar to Botvinick and Cohen, Nature 391:756, 1998). Sixty-three individuals were included and performed the classical conditions (synchronous, asynchronous), an approached but not touched (potential for touch), and a 'visual only' condition. In the second experiment, we controlled for differences between the current set-up and the vertical set-up used by Ferri et al. (Proc R Soc B 280:1-7, 2013). Fifteen individuals were included and performed a synchronous and various approaching conditions [i.e., vertical approach, horizontal approach, and a control approach (no hands)]. In our first experiment, we found that approaching the rubber hand neither induced a larger proprioceptive drift nor a stronger subjective sense of ownership than asynchronous stimulation did. Generally, our participants gained most sense of ownership in the synchronous condition, followed by the visual only condition. When using a vertical set-up (second experiment), we confirmed previous suggestions that tactile expectation was able to induce embodiment over a foreign hand, similar in magnitude to actual touch, but only when the real and rubber hand were aligned on the vertical axis, thus along the trajectory of the approaching stimulus. These results indicate that our brain uses bottom-up sensory information, as well as top-down predictions for building a representation of our body.

Body representation does not lag behind in updating for the pubertal growth spurt.

Both making perceptual judgments about your own body and successfully moving your body through the world depend on a mental representation of the body. However, there are indications that moving might be challenging when your body is changing. For instance, the pubertal growth spurt has been reported to be negatively correlated to motor competence. A possible explanation for this clumsiness would be that when the body is growing fast, updating the body representation may lag behind, resulting in a mismatch between internal body representation and actual body size. The current study investigated this hypothesis by testing participants ranging from aged 6 to 50 years on both a tactile body image task and a motor body schema task. Separate groups of participants, including those in the age range when pubertal growth spurt occurs, were asked to estimate the distance between two simultaneously applied tactile stimuli on the arm and to move their hand through apertures of different widths. Tactile distance estimations were equal between participants before, during, and after the age range where the pubertal growth spurt is expected. Similarly, Bayesian evaluation of informative hypotheses showed that participants in the age range of the growth spurt did not move through the apertures as if their representation of the hand was smaller than its physical size. These results suggest that body representations do not lag behind in updating for the pubertal growth spurt.

Peripersonal space boundaries around the lower limbs.

Neurophysiological investigations in non-human primates have shown that bi- and tri-modal fronto-parietal neurons exist that respond to touch on the body and visual (and/or auditory) stimuli near the body. The receptive fields of these neurons extend into space around the body, producing a zone wherein multisensory information is readily integrated. This space around the body, known as peripersonal space (PPS), has also been investigated behaviourally in humans. Some studies have focused on how far into depth the spatial boundaries of PPS extend. Most of these investigations have focused on the upper body (e.g., hands, face, trunk), while little is known about the size of PPS for the lower body (i.e. legs and feet). Thus, the aim of the current study was to delineate a PPS boundary around the lower limbs in healthy participants using a multisensory interaction task. Participants made speeded responses to the presence of vibrations applied to the toes while a task-irrelevant visual stimulus approached towards (Experiment 1) or receded from (Experiment 2) the feet. Participants responded significantly faster to tactile stimuli when the visual stimulus was within approximately 73 cm from the feet, but only when it approached (and not receded from) the legs. This is the first study, to our knowledge, to outline the size of PPS for the lower limbs. These findings could provide insight into the mechanisms underlying multisensory integration in the lower limbs, and add to the current body of knowledge on PPS representations.

On the contribution of overt tactile expectations to visuo-tactile interactions within the peripersonal space.

Since the discovery of neural regions in the monkey brain that respond preferentially to multisensory stimuli presented in proximal space, researchers have been studying this specialised spatial representation in humans. It has been demonstrated that approaching auditory or visual stimuli modulate tactile processing, while they are within the peripersonal space (PPS). The aim of the current study is to investigate the additional effects of tactile expectation on the PPS-related multisensory interactions. Based on the output of a computational simulation, we expected that as tactile expectation increases rapidly during the course of the motion of the visual stimulus, the outcome RT curves would mask the multisensory contribution of PPS. When the tactile expectation remains constant during the motion, the PPS-related spatially selective multisensory processes become apparent. The behavioural results on human experiments followed the pattern predicted by the simulation. That is, rapidly changing levels of tactile expectation, caused by dynamic visual stimuli, masks the outcome of the multisensory processes within peripersonal space. This indicates that both PPS-related multisensory interactions and tactile expectations play an important role in anticipating and responding to interactions with the body.

Laterality and body ownership: Effect of handedness on experience of the rubber hand illusion.

Body ownership has mainly been linked to the right hemisphere and larger interhemispheric connectivity has been shown to be associated with greater right hemispheric activation. Mixed-handed participants tend to have more interhemispheric connectivity compared to extreme handed participants. The aim of this study was to examine whether feelings of ownership as assessed with the rubber hand illusion (RHI) are differentiated by handedness and differed between the left and right hand. Sinistrals-, dextrals-, and mixed-handed individuals (n = 63) were subjected to the RHI. Stroking was synchronously and asynchronously performed on both the participant's hand and a rubber hand. Outcome measures were an embodiment questionnaire and proprioceptive drift. In contrast to our hypotheses we show a similar experience of ownership for all groups, which may indicate no hemispheric specialization for the illusion. In addition, plasticity of ownership and body ownership are similar for the left hand and right hand in all participants, which suggests similar representations for both hands in the brain. This might be useful to maintain a coherent sense of the body in space.

The influence of object identity on obstacle avoidance reaching behaviour.

When reaching for target objects, we hardly ever collide with other objects located in our working environment. Behavioural studies have demonstrated that the introduction of non-target objects into the workspace alters both spatial and temporal parameters of reaching trajectories. Previous studies have shown the influence of spatial object features (e.g. size and position) on obstacle avoidance movements. However, obstacle identity may also play a role in the preparation of avoidance responses as this allows prediction of possible negative consequences of collision based on recognition of the obstacle. In this study we test this hypothesis by asking participants to reach towards a target as quickly as possible, in the presence of an empty or full glass of water placed about half way between the target and the starting position, at 8 cm either left or right of the virtual midline. While the spatial features of full and empty glasses of water are the same, the consequences of collision are clearly different. Indeed, when there was a high chance of collision, reaching trajectories veered away more from filled than from empty glasses. This shows that the identity of potential obstacles, which allows for estimating the predicted consequences of collision, is taken into account during obstacle avoidance.

Frequency specific spatial interactions in human electrocorticography: V1 alpha oscillations reflect surround suppression.

Electrical brain signals are often decomposed into frequency ranges that are implicated in different functions. Using subdural electrocorticography (ECoG, intracranial EEG) and functional magnetic resonance imaging (fMRI), we measured frequency spectra and BOLD responses in primary visual cortex (V1) and intraparietal sulcus (IPS). In V1 and IPS, 30-120 Hz (gamma, broadband) oscillations allowed population receptive field (pRF) reconstruction comparable to fMRI estimates. Lower frequencies, however, responded very differently in V1 and IPS. In V1, broadband activity extends down to 3 Hz. In the 4-7 Hz (theta) and 18-30 Hz (beta) ranges broadband activity increases power during stimulation within the pRF. However, V1 9-12 Hz (alpha) frequency oscillations showed a different time course. The broadband power here is exceeded by a frequency-specific power increase during stimulation of the area outside the pRF. As such, V1 alpha oscillations reflected surround suppression of the pRF, much like negative fMRI responses. They were consequently highly localized, depending on stimulus and pRF position, and independent between nearby electrodes. In IPS, all 3-25 Hz oscillations were strongest during baseline recording and correlated between nearby electrodes, consistent with large-scale disengagement. These findings demonstrate V1 alpha oscillations result from locally active functional processes and relate these alpha oscillations to negative fMRI signals. They highlight that similar oscillations in different areas reflect processes with different functional roles. However, both of these roles of alpha seem to reflect suppression of spiking activity.

The role of self-touch in somatosensory and body representation disorders after stroke.

Somatosensory impairments occur in about half of the cases of stroke. These impairments range from primary deficits in tactile detection and the perception of features, to higher order impairments in haptic object recognition and bodily experience. In this paper, we review the influence of active- and self-touch on somatosensory impairments after stroke. Studies have shown that self-touch improves tactile detection in patients with primary tactile deficits. A small number of studies concerned with the effect of self-touch on bodily experience in healthy individuals have demonstrated that self-touch influences the structural representation of one's own body. In order to better understand the effect of self-touch on body representations, we present an informal study of a stroke patient with somatoparaphrenia and misoplegia. The role of self-touch on body ownership was investigated by asking the patient to stroke the impaired left hand and foreign hands. The patient reported ownership and a change in affect over all presented hands through self-touch. The time it took to accomplish ownership varied, based on the resemblance of the foreign hand to the patient's own hand. Our findings suggest that self-touch can modulate impairments in body ownership and affect, perhaps by helping to reinstate the representation of the body.

Relative finger position influences whether you can localize tactile stimuli.

To investigate whether the relative positions of the fingers influence tactile localization, participants were asked to localize tactile stimuli applied to their fingertips. We measured the location and rate of errors for three finger configurations: fingers stretched out and together so that they are touching each other, fingers stretched out and spread apart maximally and fingers stretched out with the two hands on top of each other so that the fingers are interwoven. When the fingers contact each other, it is likely that the error rate to the adjacent fingers will be higher than when the fingers are spread apart. In particular, we reasoned that localization would probably improve when the fingers are spread. We aimed at assessing whether such adjacency was measured in external coordinates (taking proprioception into account) or on the body (in skin coordinates). The results confirmed that the error rate was lower when the fingers were spread. However, there was no decrease in error rate to neighbouring fingertips in the fingers spread condition in comparison with the fingers together condition. In an additional experiment, we showed that the lower error rate when the fingers were spread was not related to the continuous tactile input from the neighbouring fingers when the fingers were together. The current results suggest that information from proprioception is taken into account in perceiving the location of a stimulus on one of the fingertips.

Choosing between alternative wrist postures: action planning needs perception.

When normal subjects grasp with their right hand a rectangular object placed at different orientations in the horizontal plane, they change from a 'thumb left' (clockwise) to a 'thumb right' (anti-clockwise) grasp when the orientation exceeds about 110 degrees , with respect to the mid-sagittal plane. This suggests planning of the final grip orientation at, or before the start of the prehension movement. The current study assessed performance of two visual agnosic patients (SB and DF) on a grasping task requiring the planning of final grip posture. Five healthy subjects were also tested. Subjects were required to grasp a triangular-section block, which was presented at one of seven different orientations (80-140 degrees). The healthy subjects showed a consistent relation between object orientation and hand orientation just before contact. In addition, they consistently used a clockwise grasp when object orientation was less than 100 degrees , and an anti-clockwise grasp when it was more than 110 degrees, with a sharply defined switch-point being identifiable for each subject. For both visual agnosic patients, hand orientation was also reliably related to object orientation. However, the selection of grasp posture was markedly abnormal: they did not consistently switch between clockwise and anti-clockwise grasps within the normal orientation range, and the switch, when it did occur, was not at all sharply defined. These results suggest that the planning of hand orientation during a grasp depends on a perceptually based judgement of the awkwardness of alternative movements. This would presumably involve ventral stream processing, which is disrupted in the visual agnosic patients.

The rubber hand illusion in action.

In the well-known rubber hand illusion (RHI), watching a rubber hand being stroked while one's own unseen hand is synchronously stroked, induces a relocation of the sensed position of one's own hand towards the rubber hand [Botvinick, M., & Cohen, J. (1998). Rubber hands 'feel' touch that eyes see. Nature, 391(6669), 756]. As one has lost the veridical location of one's hand, one should not be able to correctly guide one's hand movements. An accurate representation of the location of body parts is indeed a necessary pre-requisite for any correct motor command [Graziano, M. S. A., & Botvinick, M. M. (1999). How the brain represents the body: Insights from neurophysiology and psychology. In D. Gopher, & A. Koriat (Eds.), Attention and performance XVII-Cognitive regulation of performance interaction of theory and application (pp. 136-157)]. However, it has not yet been investigated whether action is indeed affected by the proprioceptive drift towards the rubber hand, nor has the resistance of visual capture in the RHI to new proprioceptive information been assessed. In the present two kinematic experiments, we show for the first time that action resists the RHI and that the RHI resists action. In other words, we show a dissociation between illusion-insensitive ballistic motor responses and illusion-sensitive perceptual bodily judgments. Moreover, the stimulated hand was judged closer to the rubber hand for the perceptual responses, even after active movements. This challenges the view that any proprioceptive update through active movement of the stimulated hand erases the illusion. These results expand the knowledge about representations of the body in the healthy brain, and are in line with the currently most used dissociation between two types of body representations so far mainly based on neuropsychological patients [Paillard, J. (1991). Knowing where and knowing how to get there. In J. Paillard (Ed.), Brain and space (pp. 461-481); Paillard, J. (1999). Body schema and body image: A double dissociation in deafferented patients. In G. N. Gantchev, S. Mori, & J.Massion (Eds.), Motor control, today and tomorrow (pp. 197-214)].

Acute neglect rehabilitation using repetitive prism adaptation: a randomized placebo-controlled trial.

PURPOSE: At present, prism adaptation is probably the most promising rehabilitation procedure for hemi-neglect. However, randomised controlled trials are lacking and no data are available on the effectiveness of prism adaptation in the treatment of acute neglect. METHODS: We followed sixteen neglect patients using a randomised controlled design in which six patients received four-day-in-a-row placebo treatment (CG) and ten patients received four-day-in-a row experimental treatment with 10 degrees rightward deviating prisms (EG) during their stay on the stroke unit. We examined whether patients in the EG improved faster than the CG by administering three neglect tasks (Schenkenberg Line Bisection, Letter Cancellation, Gainotti Scene Copying) immediately before and after each treatment. Second, we examined whether patients in the EG demonstrated a better long-term outcome at one month post-treatment (Behavioural Inattention Test). RESULTS: Patients in the EG improved faster on spatial tasks (line bisection, cancellation) than the CG but not on visuo-construction. Patients in the EG showed no differences with the CG in neglect outcome at one month post-treatment. CONCLUSIONS: Four consecutive prism sessions produced beneficial effects in patients with acute neglect. However, prism effects were either short-term, or placebo treatment with repeated pointing and/or repeated neglect testing was more helpful than we anticipated. Our results emphasize the importance of a placebo condition and a follow-up in rehabilitation studies.

Ipsilesional and contralesional sensorimotor function after hemispherectomy: differences between distal and proximal function.

Previous studies have reported mainly on contralesional somatosensory and motor function after hemispherectomy. So far, ipsilesional impairments have received little attention even though these have been reported in patients with less extensive lesions. In the current study we assessed ipsilesional and contralesional sensorimotor function in a group of 12 patients with hemispherectomy. In addition, we focused on differences between distal and proximal function and investigated several factors that may have contributed to individual differences between patients. The tests included tapping, force production, tactile double simultaneous stimulation, pressure sensitivity, passive joint movement sense and sensitivity to hot and cold. Ipsilesional impairments were found on all tests, except passive joint movement sense. Unexpectedly, no significant ipsilateral distal-proximal gradient was found for any of the measures. Both the removal of the diseased cerebral hemisphere and possible changes to the remaining brain structures may have affected ipsilesional sensorimotor function. Contralesional performance was impaired on all tests except for passive joint movement in the shoulder. The contralesional impairments were characterized by a distal-proximal gradient measured on all tests, except that of sensitivity to hot and cold. Distal function was always most impaired. The difference between distal and proximal motor function is in agreement with the established concepts of the motor pathways, with the motoneurons innervating proximal muscles receiving bilateral cortical and subcortical input. Age at onset of original brain damage correlated significantly with passive joint movement sense. Patients with known abnormalities to the remaining brain structures performed inferior on the tapping test only. No effect was found of the hemispheric side of removal.

Interference of grasping observation during prehension, a behavioural study.

During the last 10 years a considerable number of neurophysiological and functional imaging studies have provided evidence that observation and execution of movements activate common representations. Furthermore, several behavioural studies suggest that action observation can influence the performance of movements. Recently it was shown that viewing incongruent movements interferes with the execution of non-object oriented sinusoidal arm movements (Kil-ner et al. in Curr Biol 13:522-525, 2003). In the current study, we investigated whether interference of action observation also occurs during goal-directed prehension movements. Participants were required to grasp cubes of different sizes while simultaneously observing an actor performing grasping or pointing movements. The actors' movement could be directed at objects that were identical, or different in size to the cube grasped by the participant. The results showed that maximum grip aperture was affected by observation of grasping towards larger objects. No effect of object size was found during observation of pointing movements. These results suggest that observation of grasping movements can interfere with the on-line control of prehension movements and provides further evidence for overlapping networks for grasping observation and execution.

Dissociating body representations in healthy individuals: differential effects of a kinaesthetic illusion on perception and action.

Evidence from neuropsychological patients suggests that multiple body representations exist. The most common dissociation is between body schema to guide limb movements, and body image used to make perceptual judgements. In the current study we employed a kinaesthetic illusion in two experiments to dissociate body representations in healthy individuals. Tendon vibration creates an illusory lengthening of the muscle and an illusive displacement of the limb. In Experiment 1 two conditions were used. In the 'direct' condition the biceps of the dominant right arm of blindfolded participants was vibrated, creating illusory elbow extension. In the 'indirect' condition the right knee was held with the vibrated right arm, creating illusive lowering of the leg and knee. In both conditions, subjects performed with the non-vibrated arm a reaching as well as a matching response, theorized to be based on the body schema and body image, respectively. Results showed that the illusion was significantly larger for the matching as compared to the reaching response, with the most pronounced difference observed in the direct condition. In Experiment 2 reaching and matching without vibration and a passive matching response were implemented in the direct condition. The same differential effect of the illusion was found. Results further showed that passive and active matching were statistically similar but significantly different from the reaching response. In conclusion, these findings suggest that the effect of the kinaesthetic illusion on reaching and matching differed, consistent with the idea of separate underlying body representations for both responses.

Reaching errors in optic ataxia are linked to eye position rather than head or body position.

When reaching towards a visual stimulus, spatial information about the target must be transformed into an appropriate motor command. Visual information is coded initially in retinotopic coordinates, while the reaching movement ultimately requires the specification of the target position in limb-centred coordinates. It is well established that the posterior parietal cortex (PPC) plays an important role in transforming visual target information into motor commands. Lesions in the PPC can result in optic ataxia, a condition in which the visual guidance of goal-directed movements is impaired. Here, we present evidence from two patients with unilateral optic ataxia following right PPC lesions, that the pattern of reaching errors is linked to an eye-centred frame of reference. Both patients made large errors when reaching to visual targets on the left side of space, while facing and fixating straight ahead. By varying the location of fixation and the orientation of the head and body, we were able to establish that these large errors were made specifically to targets to the left of eye-fixation, rather than to the left of head-, body-, or limb-relative space. These data support the idea that visual targets for reaching movements are coded in eye-centred coordinates within the posterior parietal cortex.