In addition to the above discussion which offers novel ideas for future research in light of findings with the present thesis, the broader scope for future directions towards the understanding and treatment of body image and its disturbances within EDs are briefly discussed below.
7.3.1 The Use of Virtual and Augmented Reality in the Treatment of Body Image
The use of three-dimensional, multisensory illusion paradigms to investigate body image has been a valuable method afforded to researchers in recent years. With the rapid progression and availability of modern technology, immersive virtual and augmented-reality techniques (e.g. Oculus Rift) are becoming an increasingly popular and cost-efficient tool to investigate body perception, providing a non-invasive approach to accurately manipulate sensory input and measure perceptual and emotional changes (Gardner & Brown, 2014). Using such experimental techniques, previous research has been able to modulate the size and appearance of the owned body (part), and establish a direct link between perceptual and emotional changes related to the body amongst healthy individuals (Ehrsson, Kito, Sadato, Passingham, & Naito, 2005; Hagman et al., 2015; Preston & Ehrsson, 2014, 2016, 2018).
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Indeed, Normand et al. (2011) provided evidence that participants temporarily perceived their own stomach to be larger following synchronous visuotactile stimulation of a virtual body with a larger stomach (see also, Piryankova et al., 2014, for similar methodology). This shows that despite a typically stable body representation amongst healthy individuals, multisensory techniques can, to some degree, temporarily change the perception of body size and thus body satisfaction.Additionally, such techniques have been used within research (Keizer et al., 2016; Serino et al., 2016) and in the treatment (Gutiérrez-Maldonado, Ferrer-García, Dakanalis, & Riva, 2017; Gutiérrez- Maldonado, Wiederhold, & Riva, 2015) of body image disturbances within the clinical ED population, which have provided short-term efficacy in improving such altered perception to date (Serino & Dakanalis, 2017). Nevertheless, the future scope of using such techniques provides a promising strategy to objectively determine the differences between one’s perceived current body image compared with their ideal body image, and address any perceptual inaccuracies that patients may be experiencing within a controlled, experimental setting (Riva & Dakanalis, 2018). Taken together, the use of multisensory body illusions via virtual and augmented reality offers new insights into treatment interventions which could target perceptual body image disturbances amongst ED patients. From the above evidence, links between body perception and body satisfaction amongst healthy individuals and ED groups highlight the importance of perceptual and cognitive-affective relations with regard to body image. This strengthens the argument for treatments to use more neuroscientific, perceptual methodologies that target inaccurate body-related experiences, which can subsequently improve upon cognitive-affective outcomes (e.g. body dissatisfaction) within therapeutic programmes, which currently remain poor (Castellini et al., 2011). Despite some progress being made in treating EDs, it is widely agreed that there remains considerable room for improvement (Fairburn et al., 2009). Therefore, beyond a greater understanding of multisensory perception towards body image, such an experimental technique could offer useful clinical implications in targeting the separate routes of body representation with the aim to improve prognosis of the disorder.
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7.3.2 Restoring Coherent Reference Frame Processing in Eating Disorders
Increasing research has proposed separate routes for updating the human body representation based on information from first-person and third-person perspectives (Riva, 2012). Indeed, evidence within Chapter 3 of the present thesis has shown how different visual perspectives of perceived bodies can modulate neural response within higher-order regions of visual cortex (EBA). Recent evidence has suggested that accurate updating of body perception can be achieved through viewing the body from a different visual angle, as an observer or using a mirror (Ehrsson, 2007; Jenkinson & Preston, 2015; Preston et al., 2015). For example, somatoparaphrenia patients, who deny ownership of their own limbs, show temporary restoration of limb ownership when viewing it in a mirror (Fotopoulou et al., 2011). This dissociation between visual perspectives has also been related to a neuroscientific model within ED research, regarding the allocentric lock hypothesis (Guardia et al., 2013; Riva, 2012). This hypothesis attempts to explain inaccuracies of body size perception observed in EDs, suggesting that patients’ representations of their own body are based on inaccurate memories locked in an allocentric, third-person perspective which are not updated by bottom-up perception-driven input from an egocentric, first-person perspective (Riva & Gaudio, 2012; Serino et al., 2015). Thus, the processing and integration of egocentric (first-person) and allocentric (third-person) visual perspectives of the body may be problematic in maintaining a stable body representation within this population. Moreover, it is reported that some ED patients can recognize their emaciation when inadvertently viewing their reflection, but not when viewing their body from a normal first-person perspective (Espeset et al., 2012).
Consequently, using the techniques discussed above, future research should aim to experimentally modulate the visual perspective of the body with a view to improving ED patients’ perceptual accuracy of their own body. One such method could provide individuals with an illusory experience of ownership over another human’s body and view their own body as an observer, using the body swap illusion (Petkova & Ehrsson, 2008). In this experiment, participants sit directly opposite the experimenter whilst wearing a virtual reality headset connected to a stereo camera strapped to the experimenter’s head. This enables participants to see a live video feed from the cameras which capture the experimenter’s