Self /other recognition and distinction in adolescents with Anorexia Nervosa: a double mirror paradigm

doi:10.21203/rs.3.rs-1943634/v2

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Self /other recognition and distinction in adolescents with Anorexia Nervosa: a double mirror paradigm

https://doi.org/10.21203/rs.3.rs-1943634/v2

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Background

The body plays a major role in defining, understanding and treating anorexia nervosa. Much research has focused on patients' physical body representation or their own perceived body, but without explicit reference to their relationship to others and the social processes involved. Yet, there are a several arguments supporting impairments in interpersonal relationships in these patients. Notably, some evidence suggests that self/other distinction (SOD), the ability to distinguish one's own body, actions and mental representations from those of others could be impaired in anorexia. But research remains scarce in this area.

Material and Methods

A single-centre, prospective pilot study was conducted to investigate, for the first time, self-recognition and SOD in seven adolescents with anorexia nervosa (AN) compared with matched healthy controls (HCs) using the "Alter Ego"TM double mirror paradigm. This innovative device allows the progressive morphing of one’s own face to that of another and vice versa between two subjects that interact on opposite sides of the device. Two judgement criteria were used: 1) M1: the threshold at which subjects start to recognize their own face during other-to-self morphing, and 2) M2: the threshold at which subjects start to recognize the other’s face during self-to-other morphing. In a second part, the same procedure was reproduced under 5 different sensorimotor conditions to examine their effects on self-recognition and SOD.

Results

The results showed that the participants with AN exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence. Furthermore, in contrast with that of HCs, the critical threshold for switching between self and other varied with the direction of morphing in AN participants. Finally, when AN subjects were seated in a chair with the backrest and footrest touching their body, the self-recognition threshold (M1) increased significantly, approaching that of controls.

Conclusions

Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in individuals with AN through an embodied, semiecological face-recognition paradigm. Relationships between body perception and alterations in interpersonal relationships are discussed as well as new research and therapeutic perspectives are presented.

Biological sciences/Neuroscience

Biological sciences/Psychology

Health sciences/Diseases

Health sciences/Signs and symptoms

Anorexia nervosa

self/other distinction

self recognition

mirror

bodily self

consciousness – embodiment

Anorexia nervosa (AN) is an increasingly common eating disorder mainly occuring in adolescent girls and young women. It is a psychiatric disorder with one of the the highest mortality rate (Treasure et al., 2010). Currently, the etiology is not fully understood; most theories on the pathogenesis and maintenance of AN are based on cognitive-behavioral models that do not provide a pathogenic explanation that includes the experiential, phenomenological, and interpersonal aspects of the disorder that are prominent in the clinical presentation (Amianto, 2016).

On the other hand, several authors proposed that at the root of AN was fundamentally a deficit of the self (Bruch, 1982) and that AN symptoms are a way of managing painful internal experiences related to this deficit (Tasca & Balfour, 2014, Williams et al., 2016). This has been particularly studied at the physical self level since the body is central to understanding and treating AN. In the last decade, a growing number of researchers have attempted to understand the disturbed experience of the body in AN from a neuropsychological point of view: they have shown alterations in body representation, not only in body image (Cash & Deagle III, 1997, Smeets et al., 1999, Farrell et al., 2005) but also in body schema (Guardia et al., 2013, Guardia, Conversy et al., 2012, Nico et al., 2010, Grunwald et al., 2001) possibly related to more profound alterations in bodily self-consciousness (Legrand, 2010).

Despite the great interest of this research, it has mainly focused on the representation of the physical body through evaluations of the body to the environment or even to objects, but without explicit reference to others or to the social processes involved in the relations between self and others. Yet, self-representations are essential not only for self-consciousness but also for the relationship between self and others (Harter, 1998). Thus, even recent studies do not elucidate the links between abnormalities of the physical self and other work from psychodynamic theories or cognitive science showing that AN is associated with alterations in social-cognitive and interpersonal functioning (Heath et al., 2021). Notably, theory of mind and emotional empathy may be impaired as well as emotional and social functioning (Davies et al., 2011, Oldershaw et al., 2011, Russell et al., 2009, Tchanturia et al., 2013).

In recent years, the concept of self/other distinction (SOD) has received increasing interest (Simantov et al., 2021, Brass & Wiersema, 2021, Cheng-hui et al., 2020, Lamm et al., 2016). Despite a variety of terminology, including "differentiation”, "distinction”, "switching," or "agency" of self or other, all of the postulated processes seem to share a common characteristic of "controlling" shared representations between self and other (Sowden & Shah, 2014, Decety & Sommerville, 2003). The ability to differentiate one's own body, actions, and mental states from those of others is crucial for establishing relationships with others while maintaining a stable sense of self (Bird & Viding, 2014, Lamm et al., 2016, Tsakiris et al., 2007). Such social experiences involve both an ability to identify with others and an ability to distinguish ourselves from others (Lombardo et al., 2010, Steinbeis & Singer, 2014). In the absence of this capacity for self/other distinction (SOD), confusion between self and other can occur: the experience of others can be confused as coming from the self (i.e., "altercentric" bias), or one can assume an understanding of the other’s mind based on one's own experience (i.e., "egocentric" bias) (Hoffmann et al, 2016; Silani et al., 2013).

Disruptions in SOD have been previously demonstrated in a number of diseases or conditions such as borderline personality disorder (De Meulemeester et al., 2021), schizophrenia (Keromnes et al., 2018), Autism Spectrum Disorders (ASD) (Lamm et al., 2016) and alexythmia (Saito et al., 2016). Interestingly, patients with AN show increased levels of alexithymia (Kinnaird et al., 2020), and there are numerous studies supporting the links between AN and ASD (Kerr-Gaffney, 2020).

There are several arguments supporting SOD impairment in individuals with AN. First, pychodynamic works on the pathogenesis of the disorder argues that AN is frequently associated with the notion of "false self" (Winnicott, 1960), which is a common condition in early childhood in which children perceive their caregivers' thoughts or desires as their own because they cannot distinguish them. Similarly, AN is frequently associated with a failure in the separation-individuation line of development (Chatoor, 1989, Blatt & Blass, 1990). In addition, findings from cognitive science have shown that AN is associated with an empathy deficit (Kerr Gaffney, 2019), which encompasses difficulty distinguishing between the respective perspectives of self and others and the ability to switch between them (Berthoz & Thirioux, 2010). Moreover, authors have highlighted impairments in spatial cognition in AN, including predominant egocentricity during spatial performance tasks (Guardia, Cottencin, et al., 2012), and many studies support the relationship between altered spatial references, perspective changes, and social cognition or empathy (Nico & Daprati, 2009 ; Frith & de Vignemont, 2005 ; Berthoz & Thirioux, 2010 ; Decety & Lamm, 2007).

Some neurobiological findings further support SOD disorders in AN. In an RMI study, Sachdev explored the neural basis of self-body recognition in AN patients compared to healthy controls. When the two groups were compared in terms of differential activation with self versus non-self images, patients with AN showed no significant region activation with self images relative to baseline (Sachdev et al., 2008). In addition, Vocks et al. exposed AN patients and control subjects to photographs of their own body and to the body of an unfamiliar other person (Vocks et al., 2010). In the AN group, visualization of their own body was associated with a significant decrease in a complex neural network. According to the authors, these results could reflect a body-related avoidance behavior. However, an alternative hypothesis could be a disruption of self-recognition processing since this neural network is also involved in visual self-recognition (Devue et al., 2007).

Overall, these results suggest the idea that AN may be associated with both difficulties in self-recognition, but also with abnormalities in the ability to distinguish the self from the other.

To date, studies that have explored SOD generally used prerecorded static images or movies that progressively morph from one’s own face to another’s face and vice versa, both in healthy individuals (Heinisch et al., 2011, Tajadura-Jiménez et al., 2012, Uddin et al., 2006) and in patients with psychiatric disorders (De Meulemeester et al., 2021).

Interestingly, Hirot et al. (2015) have assessed self-recognition abilities in patients with AN via such a randomized self/other face morphing task using static images. They showed a significative difference with healthy subjects, with ANs having more difficulty detecting facial changes and requiring images containing more ''self'' for self-recognition. The authors concluded that there was an impairment in recognition of one's own face in ANs, known to be a marker of self-awareness. Moreover, these results also indicate disturbances in the ability to distinguish one's own face from that of another.

However, it can be questioned whether static image recognition paradigms are sufficient for SOD assessment. Indeed, the sense of one’s own body, variously termed “embodiment” (Arzy et al., 2006) or bodily self-consciousness (Legrand, 2006), is considered, notably in the phenomenological tradition, the cornerstone of mental life and a starting point for theories of the self (Merleau-Ponty, 2012, Gallagher, 2000). In particular, several studies have supported the notion that embodiment is increasingly relevant for understanding clinical conditions such as AN (Cascino et al., 2019, Fuchs, 2022). Therefore, studies of AN from an embodied perspective are urgently needed, as well as paradigms involving participants who are physically present to improve our understanding of AN physiopathology (Guardia et al., 2010). These considerations have led to the search for new paradigms that do not rely on static images but explore SOD in a more ecologically relevant manner.

Here, for the first time, we examined self-recognition in a mirror and SOD abilities in individuals with AN using a self-versus-other face identification task through a novel paradigm using the Double Mirror "Alter Ego"TM invented by the artist Moritz Werhmann. This new paradigm developed by Alain Berthoz and Berangere Thirioux allows us to specifically explore SOD under greater ecologically relevant conditions than the use of static images by merging the faces of two subjects physically facing each other and interacting on two sides of the mirror. It has been successfully used in several studies on self/other interactions in healthy subjects (Thirioux et al., 2016) and patients with psychiatric disorders, especially schizophrenia (Keromnes et al., 2018) and Autism spectrum disorders (Lavenne-Collot et al.,in press ).

As shown in Fig. 1, participants watch a double mirror in which a picture of their own face gradually transforms into the face of an unfamiliar other (self-to-other sequence) or vice versa (other-to-self direction) and indicate at which point they judge the morph to look more like their own face than the other person’s face.

The objective of the present study was to examine self-recognition and SOD abilities in adolescents with AN compared to Healthy controls (HCs) by using the ability provided by this device to progressively change the identity of self and other in the mirror with changes in lighting on both sides of the device. This is a special kind of morphing using real actors, in contrast with the computerized methods usually used in such studies (Heinisch et al., 2011, 2012, Tajadura-Jiménez et al., 2012, Uddin et al., 2006, De Meulemeester et al., 2021)

Furthermore, in order to explore the relationships between bodily self-consciousness and impairments in social interaction and cognition, different sensorimotor conditions were applied to examine their effects on self-recognition and SOD.

Thus, by considering face recognition in a mirror as a key marker of self-consciousness (Keenan et al., 2003, Amsterdam, 1972) but also the crucial first interface between self and other, our study aims to explore an interpersonal dimension of self-disturbance in AN, which is still lacking in the literature.

2.1. Participants

The study was conducted with seven individuals with AN (mean age: 15.6 years; 1 males, 6 females) matched by age and sex with seven unfamiliar Healthy control (HC) individuals. For logistical reasons related to the availability of the device, we were not able to recruit more participants at this stage of the research. However, this limitation is compatible with the hypotheses of this pilot study; specifically, that independent of the statistical representativeness of the study, AN individuals would exhibit differences in SOD compared to HCs on semiecological Double Mirror paradigm. Nevertheless, we successfully matched our participants with respect to age and age at testing.

Individuals with AN were recruited from Brest University Psychiatric Hospital in a unit specialized in the treatment of AN. None of the patients suffered from acute symptom exacerbations at the inclusion and were all stabilized at recruitment and testing.The inclusion criteria were (a) a diagnosis of AN made by a psychiatrist according to the DSM-5 (American Psychiatric Association, 2013) and ICD-10 (Wordld Health Organization, 1992) criteria; (b) aged between 12 and 17 years old to ensure that a stable body schema had been acquired (Assaiante et al., 2014). We excluded individuals with (a) a history of epilepsy, (b) claustrophobia, (c) achluophobia, or (d) the presence of distinctive signs or visual deficits requiring vision correction (eyeglasses or contact lenses).

The HC individuals matched with the AN patients were recruited in the Brest area by oral communication with local schools via participants and staff working at the hospital. They were unfamiliar with individuals in the AN group to avoid confusion between self-identiﬁcation and familiarity. They were determined to (1) be free of any significant developmental, neurological or psychiatric disorders based on a medical examination and (2) attend typical schooling for which their chronological age corresponded to their developmental age. Similar to the AN group, the exclusion criteria for the HCs were (1) a history of epilepsy, (2) claustrophobia, (3) achluophobia, and (4) the presence of distinctive signs or visual deficits requiring vision correction (eyeglasses or contact lenses).

The study protocol was approved by an ethical standards committee and performed in accordance with the ethical standards laid down in the Declaration of Helsinki. Written informed consent was obtained from all participants and their parents prior to their inclusion in the study.

2.2. Paradigm

In this experiment, we used a new double mirror paradigm based on the Alter Ego System, which consists of a semitransparent double mirror (70 cm × 50 cm × 0.4 cm; height×width×depth) with a set of computer-controlled white light-emitting diodes (LEDs) fixed on the mirror frame on both sides (Fig 1a).

These sets of LEDs can emit continuous lighting at different intensities, either separately (i.e., LEDs turned on for only one side of the mirror) or simultaneously (i.e., LEDs turned on for both sides of the mirror). Both the sampling switch between the two LED sets and the flicker frequency range (1–20 Hz) were controlled by a PC using E-Prime software. This system enables the generation of different self-face and other-face perceptual conditions when two individuals, A and B, are facing either side of the mirror (Fig 1b):

-If the LEDs are turned on for subject A’s side, whereas the LEDs are turned off for subject B’s side, subject A can see his or her own face reflected in the mirror without seeing subject B's face through the mirror. This perceptual condition is referred to by Thirioux (2016) and Keromnes (2018) as the self condition.

-Using this same lighting mode, subject B can see subject A's face through the mirror (through a transparent window) without seeing his or her own reflection. This perceptual condition is referred to as the other condition (Thirioux et al., 2016, Keromnes et al., 2018).

-When both sets of LEDs are on, the reflections of subject A's and subject B's faces merge in the mirror, making it potentially difficult for an individual to recognize his or her own face. The higher the light intensity is, the more visible the image of an individual in the mirror.

The experimental setting is described in Fig 1.

2.3. Protocol and task

2.3.1. Procedure

The experimental procedure had a duration of approximately 90 minutes and was divided into 2 parts:

First, the neutral condition ;
Then, the sensorimotor stimulation condition

First part : Neutral condition

This experimental protocol was inspired by the one previously used by Foucaud Du Boisgueheneuc in Alzheimer’s disease patients , Gaelle Keromnes and Sylvie Tordjman in patients with schizophrenia (Keromnes et al., 2018) and Nathalie Lavenne-Collot in patients with ASD (Lavenne-Collot et al., in press) : the light intensity of the two LED sets were gradually and independently increased or decreased on the two sides of the mirror, such that the two individuals found themselves alternatively in the other condition or the self condition, as explained below.

At the beginning of the experiment, the patient was in the other condition, i.e., he starts by seeing the control subject’s face through the mirror without seeing his own face; then, the patient’s own image in the mirror becomes increasingly more apparent as a function of the light intensity.

Then, the patient is in the self condition, i.e., he begins to see his own face reflected in the mirror without seeing the control’s face; then, with changes in the light intensity, the control subject’s image in the mirror becomes increasingly more apparent.

At the same time, the control subject undergoes the same procedure, except that he starts in the self condition which transforms into the other condition.

Similar to Keromnes et al. (2018), we called a “passage back and forth” the series of conditions that permitted each subject to return to the starting conditions after the conditions with identical light intensities was presented twice.

The simultaneous alterations in light intensity on each side of the mirror experienced by the AN patient and his matched control are presented in Fig 2a. Importantly, since modifications in the light intensity on one side of the mirror modify its reflective properties on both sides, we should consider the relative light intensity that is actually perceived by participants on each side, as shown in Fig 2b.

After every change in light intensity, the participants were instructed to identify whether the presented image mostly corresponded to their own face or to the other’s face. Both subjects were asked a simple question: “who do you recognize most in the mirror?” The expected response was either “me” or “him/her” (to designate the other person), without any other alternative (i.e., there were no different answers and no answer was not permitted). The question was always addressed first to the individual with AN and then to the HC participant. Each stimulus was presented for 10 s each during a progressive sequence. The response time was unlimited. Once the answer was given by each participant, the next stimulus was presented. The type of response measured and recorded was a verbal response. The use of response button boxes was initially discussed as a way to control for bias in participants' verbal responses. However, in addition to the difficulty of using manual buttons in totally dark lighting conditions, visual control might have been required to press the button, and thus, attention to the mirror image could have been disrupted or the movement could have induced a misalignment of the 2 faces. In addition, as in Keromnes (2018), oral responses seemed to reassure these patients, as the task involved maintaining relationships with others and were more relevant in terms of identity reinforcement and assertive self-recognition (using language and designation pronouns), which are central issues of this work.

Second part: Sensorimotor stimulation condition

In this second part, the same procedure was applied i.e. each stimulus of identical light intensity was presented twice to the participants during one passage back and forth as previously described in the neutral condition, but the postural or sensory stimulation conditions for the AN individuals were changed while the configuration for the HC individuals remained unchanged throughout the whole procedure (see explanations in the limitations section).

These tasks investigated the effects of different postural and sensorimotor patterns on mirror self-recognition and SOD in individuals with AN. Importantly, these tasks were chosen with psychomotor therapists specifically involved in the care of patients with anorexia nervosa, and based on the sensorimotor and postural difficulties typically encountered in these patients. There were 5 different tasks, testing different sensorimotor conditions. These tasks included different sensory inputs and locations: tactile or somatosensory, vestibular, proprioceptive, which were applied either to the medial axis of the body of the individuals with AN, or laterally to their right or left half.

Participants were tested successively on each of these distinct tasks that were administered always in the same order:

Right hemi-body weighting (RHB) condition: Weights of 75 grams were placed around the AN patient's right wrist and right ankle
Left hemi-body weighting (LHB) condition: Weights of 75 grams were placed around the patient’s left wrist and left ankle
Back- and Foot- Rest (BFR) condition: Patients with AN were no longer seated on a stool but in a chair with a backrest and a step was placed under their feet to allow for pelvic flexion
Unstable Cushion (UC) condition: Patients with AN were sitting on an unstable cushion installed on the stool
Neoprene (NP) condition : Patients wore a neoprene jacket

The whole task consisted of one passage back and forth in neutral then a second one in sensorimotor stimulation condition. There was a 10-min pause between the first and second parts to allow attentional recovery.

Debriefing occurred at the end of the experiment during an informal and friendly period of time that did not include data collection. A snack with cakes and drinks was offered during this period. The participants were asked about their feelings regarding the task and their awareness about differences in stimulation, asked whether they found face recognition and discrimination difficult, and whether they were familiar with this type of morphing (as some teenagers regularly use morphing applications).

2.3.2. Data analysis

The main outcome was the light intensity levels at which critical changes in self/other identification occurred:

Level M1 was the critical perceptual threshold corresponding to the first time the individual recognized himself when his own image progressively appeared in the mirror during the other-to-self morphing sequence.
Conversely, level M2 was the critical perceptual threshold corresponding to the first time the individual recognized the other's image in the mirror when this image progressively appeared in the mirror during the self-to-other morphing sequence.

To summarize, the lower the M1 or M2 levels were, the larger the proportion of self was in the image (and the smaller the proportion of the other), which reflected a difficulty for the individual to uncouple from his own image.

Determination of M1 and M2 levels as well as a synthesis of the experimental procedure are shown in Fig 3.

2.3.3. Statistical analysis

After each step (change in light intensity), the participant's verbal responses were recorded. The analysis of the main outcome variable was conducted by comparing the M1/M2 levels (expressed as percentage of light intensity) between individuals with AN and HCs. As this variable was not normally distributed, the nonparametric one-tailed Mann–Whitney test was used to compare M1 and M2 levels between the two groups.

The effects of differents sensorimotor tasks on the M1 and M2 levels were assessed by using the non-parametric Wilcoxon test to compare for the AN patients the results obtained in the neutral condition and the results obtained in the 5 sensorimotor conditions (RHB, LHB, BFR, UC, NP).

The comparison of the results for the self/other distinction task in the different conditions between individuals with AN and HCs are presented in Table 1.

Table 1. Comparison of the results for the recognition task between individuals with AN (N = 7) and Healthy controls (N = 7) in Neutral (Neu), Right hemi-body weighting (RHB), Left hemi-body weighting (LHB) , Back- and Foot- Rest (BFR), Unstable Cushion (UC) and Neoprene (NP) conditions.

	Individuals with AN			Healthy controls (HCs)
	(N=7)			(N=7)
	Mean	Median value	SD	Mean	Median value	SD	P-value
	Mean	Median value	SD	Mean	Median value	SD	P-value

M1 Neu	77.1	70	18	132.9	130	17.0	0.001
M1 RHB	84.3	80	22.3	137.1	140	29.8	0.004
M1 LHB	87.1	80	26.9	128.6	140	21.9	0.004
M1 BFR	107.1	90	32	125.7	140	25.7	0.149
M1 UC	80	80	20.8	135.7	140	27	0.004
M1 NP	84.3	90	15.1	130	140	22.3	0.003
M2 Neu	135.7	130	11.3	150	150	10	0.021
M2 RHB	117.1	110	18.9	141.4	150	12.1	0.012
M2 RHL	118.6	120	15.7	141.4	140	9	0.004
M2 BFR	124.3	130	18.1	128.6	130	17.7	0.277
M2 UC	111.4	110	10.7	140	140	11.5	0.001
M2 NP	111.4	110	10.7	135.7	130	11.3389	0.003

3.1. Neutral condition

In neutral condition, M1 levels were significantly lower in the individuals with AN than in the HCs (p =0.001). This indicated that the AN individuals in the individuals with AN than in the HCs, showed an “earlier” self -recognition in the other condition (i.e., when one’s own image was gradually appearing in the mirror in the other-to-self direction of the morphing).

Similarly, M2 levels were significantly lower in the AN individuals than in the HCs (p=0.02). This indicated that the AN individuals showed a delay in recognizing the other in the self condition (i.e., when the image of the other was gradually appearing in the mirror in the self-to-other direction of the morphing).

The Wilcoxon paired-samples test comparing M1 and M2 showed that M2 levels were significantly higher than M1 levels in individuals with AN (p=0.02). Conversely, there was no significant difference between M1 and M2 levels in HCs (p=0.09). This indicated that, in the HCs, the critical perceptual threshold corresponding to the ability to recognize self and other was the same regardless of the direction of morphing. In other words, the critical threshold for switching between self and other appeared when viewing morphed faces that contained the same proportion of facial features of self and other, regardless of whether it was the other condition or self condition. In contrast, in the individuals with AN, this perceptual threshold varied depending on the direction of the morphing, and the shift from self to other or from other to self did not occur at the same threshold. Indeed, the AN group needed a smaller proportion of self (image of themselves) to recognize their own face in the other-to-self direction versus the self-to-other direction.

Comparison of M1 and M2 levels in ANs and HCs are presented in Fig 4 and a synthesis of M1 and M2 distribution levels in neutral condition is presented in Fig 5.

3. 2. Sensorimotor stimulation condition

When the AN individuals were installed in the LHB, RHB, UC and NP conditions, M1 levels were significantly lower in the AN individuals than in the HCs. This indicated that, in all those conditions, AN individuals showed an earlier self- recognition in the other condition (i.e., when one’s own image was gradually appearing in the mirror in the other-to-self direction of the morphing).

Conversely, there was no significative difference on M1 levels in ANs compared to HCs in the BFR condition. This indicated that, when AN individuals were seated in a chair with a backrest and a support under their feet, there was no significant difference in self-recognition levels compared to HCs. Distribution plots of M1 thresholds for ANs and HCs in the different conditions are presented in Fig 6.

When the AN individuals were installed in the LHB, RHB, UC and NP conditions, M2 levels were significantly lower in the AN individuals than in the HCs. This indicated that, in all those conditions, AN individuals showed a delay in recognizing the other in the self condition (i.e., when the image of the other was gradually appearing in the mirror in the self-to-other direction of the morphing).

Conversely, there was no significant difference in M2 levels between ANs and HCs in the BFR condition. This indicated that, when AN individuals were set up in the BFR condition, there was no significant difference in other- recognition level compared to HCs.

Distribution plots of M2 levels in different conditions for individuals with AN and HCs are presented in Fig 7.

To summarize, in the AN patients, M1 and M2 levels were significantly lower than in HCs in neutral, LHB, RHB, UC, and NP conditions, indicating that patients with AN recognized their own image earlier when it appeared in the mirror in the other condition and that they recognized the other person’s image later when the other was gradually appearing in the mirror in the self condition.

Conversely, there was no difference between ANs and HCs on the M1 and M2 levels when the AN individuals were installed in the BFR condition.

3.3. Comparison between neutral and sensorimotor conditions

In the AN group, M1 levels were significantly higher in the BFR than in the neutral condition. Conversely, there were no significative differences on M1 level between neutral and LHB, RHB, UC and NP conditions.

In the AN group, M2 levels were significantly lower in the LHB, RHB, UC, and NP conditions than in the neutral condition. Conversely, there was no significant difference on M2 levels in the BFR condition compared with the neutral condition

These results indicated that when the recognition task was associated with the BFR condition versus the neutral condition, AN participants showed a delay in self recognition but no significant difference in other recognition. Conversely, in ANs, there was a delay in recognition of the other when the visual recognition was associated with the LHB, RHB, UC, NP conditions compared to the neutral condition, but no significant difference in self recognition.

Our results are based on a very small sample; therefore, the preliminary nature of this study must be taken into account when analysing and discussing the results.

4.1. Self recognition in the mirror

4.1.1. Comparison with static images

Our results showed that the AN individuals required images that contained less proportion of self than controls to recognize themselves in the reflected image, regardless of the direction of the morphing (i.e., in the "self" or "other" conditions). These results contrast with those found by Hirot et al. (2015) during a self/other morphing task using static images that showed that patients required images containing more ''self'' to recognize themselves. Howewer, our experimental design diﬀers from that of Hirot’s study because they used an aleatory protocol thought we presented the morphs incrementally from 0% self/other to 100% self/other in two directions separately. Moreover, supporting this discrepancy are several arguments highlighting that static images and mirror self-processing can not be considered as equivalent measures: First, (i) contrary to photo, looking at ourselves in the mirror gives us access to our own image, besides the proprioceptive, tactile and motor sensory cues that are necessary for the representation of one’s own face (Tsakiris, 2008); (ii) studies have found that mirror self-recognition emerges prior to photo self-recognition (Courage et al., 2004); (iii) different neural responses have been found when comparing mirror and photo self-processing (Butler et al., 2012) and; (iv) preserved self-face recognition on photographs despite incapacity in mirrors has been described in some neurological patients showing a kind of agnosia for recognition of their own reflected image (Breen et al., 2001).

4.1.2. Bodily self -consciousness

The results of the present study support that AN individuals show a difference in mirror face recognition thresholds compared to HCs on the double mirror task. These results are consistent with previous research showing that self-recognition abilities may be impaired in AN (Hirot et al., 2015, Sachdev et al., 2008). However, while previous researches have mainly focused on the body due to its fundamental place in the psychopathology of AN, less is known about the fundamental aspect of the physical self that is face recognition, which plays a crucial role in identity and social interaction as well (Sproull et al., 1996).

Furthermore, in line with previous research showing the value of the double mirror device in studying bodily self-consciousness (Keromnes, 2018, 2019), our results support the notion that self-disorder is an important dimension of AN (Bruch, 1982; Amianto et al., 2016) and, in particular, that the embodied aspects of the self could be disturbed (Legrand, 2010).

4.2. Egocentricity in Self/other distinction

4.2.1. Implications for sensory processing

Our results showed that the AN individuals, compared to the HCs, judged the morphs to be more like the self in both directions of morphing. These findings can be interpreted as a greater level of assimilation of the other’s face in the representation of one’s own face among the AN individuals than the HCs. Such misattribution of others’ facial features to oneself has been reproduced in nonclinical populations through simple psychophysical manipulations in a procedure involving sensory processing called interpersonal multisensory stimulation (Tajadura-Jiménez et al., 2012). Indeed, studies using body ownership illusions have shown that, under certain conditions, the sense of self can be manipulated to include a fake or another person’s body part, for instance, the hand (Botvinick & Cohen, 1998), face (Tsakiris, 2008, Sforza et al., 2009, Apps et al., 2015) or whole body (Kilteni et al., 2015).

The double mirror task involves a simultaneous visual perceptual conflict between the visual input (“I see the other”) and the proprioceptive experience (“I expect to see myself in the mirror”). This conflict is reinforced by the everyday experience we may have developed that, when we look in the mirror, we see ourselves and not another person. As specified by Thirioux (2016), here we studied the eﬀect of a unisensory (visual) conﬂict, whereas previous studies have typically studied the eﬀect caused by multisensory (especially visual-tactile) illusions (Tajadura-Jiménez et al., 2012).

In AN, distortions in multisensory integration processing that is fundamental to the acquisition and updating of body awareness (Tsakiris et al., 2007) have been demonstrated in many sensory modalities (for a review see (Teaford et al., 2021)).

In particular, individuals with AN have been found to exhibit greater sensitivity to the rubber hand illusion (Botvinick & Cohen, 1998), indicative of a greater susceptibility to appropriating and embodying an object external to their own body, i.e., a more plastic bodily-self (Eshkevari et al., 2012). To our knowledge, this greater susceptibility to the embodiment illusion has never been explored at the level of the face in individuals with AN, as assessed through paradigms such as the “enfacement illusion” (Sforza et al., 2009, Porciello et al., 2018). However, both body plasticity and face representation have been shown relying on the same multisensory integration processes (Tsakiris, 2007, 2008). Thus, the results of the present study are consistent with the generalization to the face of a greater tendency to the embodiment illusion in AN individuals.

Moreover, our results indicated that people with AN continued to recognize themselves in the mirror despite the increase in the proportion of the other person's face in the image, regardless of the direction of the morphing. These results may indicate that, in the AN individuals, the proprioceptive system would be less vulnerable to bias originating from visual information (i.e., AN individuals depend more heavily on proprioceptive information than on visual information when incongruent). This finding is in line with previous studies that pointed out an overreliance on proprioception in the presence of competing signals from other modalities (Case et al., 2012). Moreover, they are also consistent with reduced integration of visual and proprioceptive information in AN, also supported by the ubiquitous clinical finding in these patients that their visual perception of the body, especially in a mirror, does not correct their distorted body image (Demartini et al., 2021).

4.2.2. Imbalance mechanisms of projection / simulation

Our results showed that the AN individuals, compared to the HCs, judged the morphs to be more like the self in both directions of morphing. Importantly, the comparison between self and other conditions shows that, unlike the HCs, the AN individuals switched from other to self and from self to other at different thresholds. This discrepancy indicated that the confusion between self and other may have been determined by a unidirectional overinclusion of the other’s attributes by the AN individuals. Conversely, the HCs may have exhibited compensatory mechanisms with bidirectional self- and other-facial feature attribution. i.e., they projected their facial features onto the other's face as much as they introjected their partner's facial features onto their own face. This understanding is supported by Thirioux's findings using a double mirror in healthy subjects (Thirioux, 2016) and human interpersonal understanding based on balanced mechanisms of self-projection and simulation (Bastiaansen et al., 2009, Seinbeis & Singer, 2014). Indeed, as noted by Freud “the boundaries of the self are not constant” (Freud, 1930). That is, both processes also transformed the margins between the self and the other, either by externalizing facial features of the self into the other (projection) or by alienating facial features that do not belong to the self but to the other (introjection) (Feinberg & Keenan, 2005). Thus, our findings are consistent with psychoanalysts who described anorexia as a failure of identification and a pathology of object relations (McIntosh et al, 2020) particularly marked by deficiencies in the balanced introjection/projection mechanisms that are necessary to establish a sense of identity, leading to characteristic forms of pathological projective identification often evident in these patients (Quagliata, 2004).

4.3. Implications regarding visuospatial abilities

4.3.1. Prevalent egocentricity

The results obtained in the present study showing earlier self-recognition and delayed other recognition in the AN individuals, compared to the HCs, could also be interpreted as a difficulty to inhibit their own perspective during the face recognition task and adopt the reference frame of the other, resulting in a privileged use of the egocentric reference frame.

Indeed, unlike when one is faced with a simple photograph, the mirror requires processes of perspective shifting and spatial transformations beyond pure self-recognition. In particular, self-recognition in the mirror requires matching one's sensorimotor experience (1st person perspective) with the object seen in the mirror (3rd person perspective), thereby identifying the "I" with the "me" and representing that self as an object to others and to oneself (Butler et al., 2012 ). Moreover, the face-to-face postural configuration of both subjects during the Alter Ego double mirror task requires a 180° mental rotation of one’s own body. In particular, Thirioux et al. (2016) emphasized the role of visuospatial abilities on self-recognition and SOD within this task.

Our results are consistent with previous studies showing alterations in spatial cognition in ANs and, in particular, a privileged use of the egocentric frame of reference during spatial performance tasks (Guardia et al., 2013). To date, these alterations have only been studied using paradigms that did not involve interpersonal interaction. However, there is considerable evidence supporting the implication of altered spatial references on social frames and implications for social cognition (Nico & Daprati, 2009; Frith & de Vignemont, 2005), including empathy (Berthoz & Thirioux, 2010).

4.3.2. Switching between the abstracts of self and other

Our experimental design requires switching from self to other and from other to self as the morphing gradually shifts from 0% to 100% between self and other and vice versa. Thus, the double mirror Alter Ego task is consistent with recent conceptualizations of SOD as being achieved through the ability to switch between representations of self and other and to inhibit the representation that is not relevant in a given situation (Steinbeis, 2016). In our study, differences in M1 and M2 thresholds between the AN individuals and HCs were consistent with AN being associated with an inadequate control of the self/other control or switch (Sowden & Shah, 2014). Interestingly, impairments in shifting from one frame of reference to another have previously been reported in AN through the allocentric lock-in theory (ALT) (Riva & Gaudio, 2012). This hypothesis suggests that individuals with AN may be locked to a negative allocentric (observer's view) memory of the body that is no longer updated by perceptually directed egocentric representations (Lander et al., 2020).

4.4. Impact of sensorimotor tasks on self recognition and SOD

4.4.1. Back and foot support condition

Our results showed a significant increase in the M1 threshold in the BFR condition compared to the neutral condition. This indicated that, when installed in the BFR condition, the AN participants showed a delayed self-recognition, i.e., they continued to perceive the other longer while their own image was gradually appearing. .

Back support is an essential early developmental modality for the construction of one's identity, and in particular one's body. Indeed, during fetal development, the uterine wall provides the primary back support that allows for the development of oral activities (swallowing, etc.). Even after birth, back support remains fundamental, especially in the sensorimotor model developed by Bullinger (2004) that argues that postural control and tonic-sensory balance allow infants to interact with their environment and develop social involvement (Kloeckner et al., 2009). Notably, in a pilot study, Rahme et al. showed a significant increase in social attention, in the back support condition compared to no back support in children with Austism Spectrum Disorders (Rahme & Oliveira, 2015). Similarly, the results of our study are consistent with the idea that the BFR condition may have helped the AN individuals to be more other-centered.

4.4.2. Weakened central axis

In contrast to the results obtained in the neutral condition, when the ANs were placed in the BFR condition, there was no difference in self-recognition and SOD thresholds between HC and AN groups. These results indicated that the BFR condition may have resulted in normalized performance in the double mirror task in ANs and support that the provision of back support may have compensated for bodily-consciousness deficits by strengthening a more fragile midbody axis in individuals with AN. This hypothesis is consistent with clinical observations showing, in AN patients, a misalignment of the whole body, especially with respect to the medial axis, as well as a restricted breathing pattern coupled with muscle rigidity having a major negative impact on body stability (Kolnes, 2012).

Furthermore, in our study, the BFR condition supported not only the back, but also the feet, thereby improving pelvic flexion as well as upper and lower body connections. Thus, the compensation effects observed under BFR conditions are quite consistent with clinical observations revealing postural disturbances in AN patients, including problems with stabilizing the back and pelvis in a neutral position, difficulties in performing pelvic movements (Winberg et al., 1997) as well as gait abnormalities with biomechanical differences mainly at the pelvis and hip (Cimolin et al., 2013).

4.4.3. Other sensorimotor conditions

As far as other sensorimotor conditions are concerned, both left and right hemibodies ballasting, unstable cushion and neorprene conditions had a greater effect on M2 threshold than on M1, including a decrease in M2 threshold. This indicates that these conditions had no significant effect on self-recognition, but were significantly associated with delayed other-recognition, suggesting that they may have helped the AN individuals to be more self-centered. These results are in line with previous research using double mirror in schizophrenia patients that showed that tactile and kinesthetic tasks helped to be more self-centered (Keromnes et al., 2018).

Regarding the Neoprene condition, previous research conducted in a single case study by Grunwald showed that intensive somatosensory stimulation with a neoprene diving suit led to improved body image in the AN participants (Grunwald & Weiss, 2005). However, the neoprene suit was worn for one hour, three times a day whereas in our study, this condition may have been applied for an insufficient duration to produce a change in self-recognition patterns.

Furthermore, our results did not show any significant difference regarding the right- or left-lateralized tasks, which did not support a preferential input lateralization effect on face recognition and SOD thresholds in the AN individuals. These results contrast with previous research supporting similarities found in AN patients with hemineglect patients (Nico et al., 2010) with divergent results in the same way that the existence of a hemispheric predominance still remains debated (Guardia, Cottencin, 2012). Rather than an hemispatial neglect in the neurological sense, our results support a functional cleavage or split between both hemibodies, possibly related to a weakener median body axis supposed to connect these two parts.

4.5. Implications for AN comprehension: what’s new?

4.5.1. Relationship between bodily self and socio cognitive functioning

In summary, our results highlight: (i) disturbances in mirror self-recognition suggesting bodily-consciousness impairments in AN; (ii) an egocentric bias in self/other disctinction found in AN participants compared to HCs and; (iii) changes in self-recognition and SOD thresholds were observed when sensorimotor or postural conditions were modified in individuals with AN.

Interestingly, previous work has already pointed to greater egocentricity and disturbances in bodily self-consciousness in AN. However, to date, the question of the nature of these links has not been resolved, as evidenced by the question raised in Guardia (Guardia et al., 2013): is it the weak ability to integrate egocentric and allocentric spatial frames of reference that can impair self-consciousness (top down effect)? Or, conversely, is it the weak bodily self-consciousness that would impair the ability to change frames of reference (bottom up effect)?

Interestingly, the results of the present study rather support the second hypothesis since changing some sensorimotor conditions that are supposed to reinforce the bodily-self seems to have improved frame-shifting abilities in the AN and helped subjects to become less egocentered. This hypothesis is consistent with Thirioux (2016) who showed that inducing self-fragility during self/other fusion through the double mirror alters self-referential processes including egocentric spatial abilities in healthy subjects. .

4.5.2. Further therapeutic and research implications

As they highlight the importance of the physical self in understanding alterations in social-cognitive and interpersonal functioning in AN, our results also support the value of physical treatments in this condition. In particular, our results support that exercises focused on strengthening and stabilizing the weakened body axis could improve self-consciousness, which could then have training effects on social-cognitive functioning.

In addition, our results may also support a developmental approach to AN. In particular, the significant effect of the BFR condition, also observed in neurodevelopmental disorders such as ASD (Bullinger, 2004; Rahme & Oliveira, 2015) raises the hypothesis of disruptions in the very early stages of body construction during the first years of life in AN patients. Therefore, it may be of interest to study the possible existence of early signs, particularly in the sensorimotor area, similar to retrospective studies using home movies conducted for other neurodevelopmental disorders (Saint Georges et al., 2010).

Finally, using the same protocol respectively in patients with schizophrenia and also ASD versus healthy controls, Keromnes and Tordjman (2018) and Lavenne-Collot (in press) found similar results to the presen study.(i.e., earlier self-recognition and later other-recognition). This raises the question of considering SOD disturbances as a transdiagnostic dimension shared with other psychiatric or neurodevelopmental disorders and support the interest of complementary research using the double mirror Alter Ego at the diagnostic but also therapeutic level.

Limitations

Some limitations of the study should be recognized. First, this is a preliminary study conducted with very small samples. Future studies are therefore needed to replicate the results in larger, samples.

Moreover, the self–other facial morphing task used in this study taps into perceptual SOD, that is, the capacity to identify one's own body (here, one's face) and to distinguish it from others. Therefore, it raises the question of whether the findings from the present study could be generalized to other domains of SOD. Although perceptual SOD and mental-state SOD should not be equated, evidence shows that they may be related (Steinbeis, 2016) and that SOD may operate in a domain-general rather than domain-specific manner (Quesque & Brass 2019).

Another limitation of this study is that the differences between AN individuals and HCs may have occurred at the attentional or information processing level, i.e., upstream of the SOD process. Notably, our results could have been influenced by the cognitive functioning typically described in AN, including a deficit in cognitive flexibility, although these alterations showed contrary results in the literature (for a review see (Miles et al., 2020)). However, if a deficit in cognitive flexibility could account for the delay observed in the ability to switch from self to other that was found in the self condition, a similar delay should have been observed in the other condition, which is contrary to our results.

In addition, patients with AN usually show a great intolerance to uncertainty and experience it as stressful. Typically, uncertain situations result in a strong desire for control that manifests itself in extreme organization and planning (Dahlenburg et al., 2019). Given their common perfectionism and fear of making mistakes, one might have expected a later self-recognition in individuals with AN, i.e., the presented images would have had to contain more of the participant's own face to be recognized (similar to Hirot's results (2015)) and be more certain before responding. Interestingly, again, our results are the opposite.

As far as experimental setting is concerned, there might be a bias of participants' oral responses influencing each other. To decrease this possible bias in the individuals with AN, these participants were consistently asked to respond first during the task. Aleatory variations in light intensity rather than progressive linear changes were initially discussed to control for possible habituation bias in participants. However, abrupt changes in light intensity and the reflected images could have been stressful for the participants. Moreover, in line with other studies (Heinisch et al., 2011, Tajadura-Jiménez et al., 2012, Uddin et al., 2006), we presented the morphs incrementally from 0% self/other to 100% self/other in the two directions separately. This allowed us to differentiate the morphing directions and disentangle the two types of self/other confusion (i.e., egocentric bias and altercentric bias) and the critical thresholds for switching between self and other.

Similarly, the order of the presentation of the task was not randomized, which could have led to carry-over effects. However, there was no significant time effect on the results of the recognition task in the individuals with AN or the HCs, which allowed us to reduce the possible carryover and learning effects of the task.

Furthermore, in the second part of the study, the postural and sensorimotor tasks were applied only to patients with AN. As a result, the effects of these tasks on self-recognition thresholds and SOD in healthy subjects remained unknown. However, here, the purpose of our study was primarily (i) to clarify the relationship between physical self and SOD abilities only in AN individuals (ii) to explore whether certain sensorimotor conditions supposed to reinforce the physical self could lead to normalized performance in anorexic subjects. Therefore, the tasks were used only for AN patients to examine this potential compensatory effect compared to healthy controls.

Finally, in our study, when AN individuals were in the BFR condition, there was no possible discrimination between the effects of threshold normalization due to body enhancement or due to improved visual perception. However, if the BFR condition had only contributed to an improvement in visual discrimination abilities, M1 and M2 thresholds should have been similarly influenced in the BFR condition.Conversely, the BFR condition showed a significant effect on the M1 threshold (self-recognition) but no significant effect on the M2 (other- recognition of others).

Although further research is needed to replicate these results, this study uncovered novel findings showing the first behavioural evidence of impaired SOD in individuals with AN through an embodied face-recognition paradigm generating a self–other face merging illusory effect in ecologically relevant conditions, i.e., when two individuals are physically facing each other and interacting

This study is a first step in exploring the links between, on the one hand, body representation and sense of ownership, and, on the other hand, alterations in social interactions and cognitions that have unduly always been explored separately in the literature on AN.

The double mirror Alter Ego may also offer new therapeutic perspectives for AN based on

a potential remediation pathway using double mirrors by practising control of representations of self and others and simultaneously improving the sense of body ownership, supporting self-differentiation, and correcting the poor self-perception that plays a causal role in the development, persistence, and relapse of AN..

Ethics approval and consent to participate

Our manuscript include a statement on ethics approval and consent. The study protocol was approved by an ethical standards committee CPP sud méditerranée Nice 2020-A03276-33 and performed in accordance with the ethical standards laid down in the Declaration of Helsinki. Written informed consent was obtained from all participants and their parents prior to their inclusion in the study.

Consent for publication

Not applicable.

Availability of data and materials

Most of the data analysed during this study are included in this published article. Others datasets analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

The authors have no funding to declare

Authors' contributions

M.W. designed the double mirror device. N.LC., E.M, S.D., M.B. and A.B. conceived and performed the study protocol. E.M. included the participants. N.LC., E.M. and S.D. analyzed the data. N.LC. wrote the main manuscript text. A.B., M.B. and G.B. were major contributors in writing and proffreading the manuscript. All authors read and approved the final manuscript.

Acknowledgements

The authors thank the youth who participated in the study as well as Pierre Ailliot for the statistical analysis.

Amsterdam, B. (1972). Mirror self-image reactions before age two. Developmental Psychobiology, 5(4), 297‑305. https://doi.org/10.1002/dev.420050403
American Psychiatric Association (APA). (2013). Diagnostic and statistical manual of mental disorders (DSM-5®). American Psychiatric Pub.
Amianto, F., Northoff, G., Abbate Daga, G., Fassino, S., & Tasca, G. A. (2016). Is anorexia nervosa a disorder of the self? A psychological approach. Frontiers in psychology, 7, 849.
Apps MAJ, Tajadura-Jiménez A, Sereno M, Blanke O, Tsakiris M. Plasticity in Unimodal and Multimodal Brain Areas Reflects Multisensory Changes in Self-Face Identification. Cereb Cortex. 2015 Jan 1;25(1):46–55.
Arzy S, Overney LS, Landis T, Blanke O. Neural Mechanisms of Embodiment: Asomatognosia Due to Premotor Cortex Damage. Arch Neurol. 2006;63(7):1022–1025. doi:10.1001/archneur.63.7.1022
Assaiante C, Barlaam F, Cignetti F, Vaugoyeau M. Body schema building during childhood and adolescence: a neurosensory approach. Neurophysiol Clin. 2014 Jan;44(1):3-12. doi: 10.1016/j.neucli.2013.10.125. Epub 2013 Oct 30. PMID: 24502900
Bastiaansen, J. a. C. J., Thioux, M., & Keysers, C. (2009). Evidence for mirror systems in emotions. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1528), 2391‑2404. https://doi.org/10.1098/rstb.2009.0058
Berthoz, A., & Thirioux, B. (2010). A Spatial and Perspective Change Theory of the Difference Between Sympathy and Empathy. https://doi.org/10.1524/para.2010.0003
Bird, G., & Viding, E. (2014). The self to other model of empathy : Providing a new framework for understanding empathy impairments in psychopathy, autism, and alexithymia. Neuroscience and Biobehavioral Reviews, 47, 520‑532. https://doi.org/10.1016/j.neubiorev.2014.09.021
Blatt, S. J., & Blass, R. B. (1990). Attachment and separateness. A dialectic model of the products and processes of development throughout the life cycle. The Psychoanalytic Study of the Child, 45, 107‑127.
Botvinick, M., & Cohen, J. (1998). Rubber hands « feel » touch that eyes see. Nature, 391(6669), 756. https://doi.org/10.1038/35784
Brass, M., & Wiersema, J. R. (2021). Self-Other Distinction and Social Cognition in ASD. In F. R. Volkmar (Éd.), Encyclopedia of Autism Spectrum Disorders (p. 4159‑4163). Springer International Publishing. https://doi.org/10.1007/978-3-319-91280-6_102194
Breen, N., Caine, D., & Coltheart, M. (2001). Mirrored-self Misidentification : Two Cases of Focal Onset Dementia. Neurocase, 7, 239‑254. https://doi.org/10.1093/neucas/7.3.239
Bruch, H. (1982). Anorexia Nervosa : Therapy and theory. The American Journal of Psychiatry, 139(12), 1531‑1538. https://doi.org/10.1176/ajp.139.12.1531
Bullinger, A. (2004). Le développement sensori—-Moteur de l’enfant et ses avatars, un parcours de recherche erès. Pierre Delion. Ramonville-St-Agne: Éditions Érès.
Butler, D. L., Mattingley, J. B., Cunnington, R., & Suddendorf, T. (2012). Mirror, Mirror on the Wall, How Does My Brain Recognize My Image at All? PLOS ONE, 7(2), e31452. https://doi.org/10.1371/journal.pone.0031452
Cascino, G., Castellini, G., Stanghellini, G., Ricca, V., Cassioli, E., Ruzzi, V., Monteleone, P., & Monteleone, A. M. (2019). The Role of the Embodiment Disturbance in the Anorexia Nervosa Psychopathology : A Network Analysis Study. Brain Sciences, 9(10), 276. https://doi.org/10.3390/brainsci9100276
Case, L. K., Wilson, R. C., & Ramachandran, V. S. (2012). Diminished size–weight illusion in anorexia nervosa : Evidence for visuo-proprioceptive integration deficit. Experimental brain research, 217(1), 79‑87.
Cash, T. F., & Deagle III, E. A. (1997). The nature and extent of body-image disturbances in anorexia nervosa and bulimia nervosa : A meta-analysis. International Journal of Eating Disorders, 22(2), 107‑126.
Chatoor, I. (1989). Infantile anorexia nervosa : A developmental disorder or separation and individuation. The Journal of the American Academy of Psychoanalysis, 17(1), 43‑64. https://doi.org/10.1521/jaap.1.1989.17.1.43
Cheng-hui T a. N, Shan-shan MA, Chuan-lin ZHU, Yuan Z, Xuan-yi W, De-ming SHU, et al. (2020).The self-other distinction in interpersonal interaction: A multi-level exploration. Adv Psychol Sci. 15;28(11):1890.
Cimolin, V., Galli, M., Vismara, L., Vimercati, S. L., Precilios, H., Cattani, L., De Souza, S. F., Petroni, M. L., & Capodaglio, P. (2013). Gait analysis in anorexia and bulimia nervosa. Journal of Applied Biomaterials & Functional Materials, 11(2), 122‑128.
Courage, M. L., Edison, S. C., Howe, M. L., & Howe, M. (2004). Variability in the early development of visual self-recognition. Infant Behavior and Development, 27(4), 509‑532.
Dahlenburg, S. C., Gleaves, D. H., & Hutchinson, A. D. (2019). Anorexia nervosa and perfectionism : A meta-analysis. The International Journal of Eating Disorders, 52(3), 219‑229. https://doi.org/10.1002/eat.23009
Davies, H., Schmidt, U., Stahl, D., & Tchanturia, K. (2011). Evoked facial emotional expression and emotional experience in people with anorexia nervosa. International Journal of Eating Disorders, 44(6), 531‑539.
De Meulemeester, C., Lowyck, B., Panagiotopoulou, E., Fotopoulou, A., & Luyten, P. (2021). Self-other distinction and borderline personality disorder features : Evidence for egocentric and altercentric bias in a self-other facial morphing task. Personality Disorders, 12(4), 377‑388. https://doi.org/10.1037/per0000415
Decety, J., & Lamm, C. (2007). The Role of the Right Temporoparietal Junction in Social Interaction : How Low-Level Computational Processes Contribute to Meta-Cognition. The Neuroscientist, 13(6), 580‑593. https://doi.org/10.1177/1073858407304654
Decety J, Sommerville J. (2003). Shared representations between self and other: a social cognitive neuroscience view. Trends Cogn Sci., 7(12):527-33. doi: 10.1016/j.tics.2003.10.004. PMID: 14643368.
Demartini, B., Nisticò, V., Tedesco, R., Marzorati, A., Ferrucci, R., Priori, A., Gambini, O., & Caputo, G. B. (2021). Visual perception and dissociation during Mirror Gazing Test in patients with anorexia nervosa : A preliminary study. Eating and Weight Disorders - Studies on Anorexia, Bulimia and Obesity, 26(5), 1541‑1551. https://doi.org/10.1007/s40519-020-00977-6
Devue, C., Collette, F., Balteau, E., Degueldre, C., Luxen, A., Maquet, P., & Brédart, S. (2007). Here I am : The cortical correlates of visual self-recognition. Brain Research, 1143, 169‑182. https://doi.org/10.1016/j.brainres.2007.01.055
Eshkevari, E., Rieger, E., Longo, M. R., Haggard, P., & Treasure, J. (2012). Increased plasticity of the bodily self in eating disorders. Psychological Medicine, 42(4), 819‑828. https://doi.org/10.1017/S0033291711002091
Farrell, C., Lee, M., & Shafran, R. (2005). Assessment of body size estimation : A review. European Eating Disorders Review: The Professional Journal of the Eating Disorders Association, 13(2), 75‑88.
Feinberg, T. E., & Keenan, J. P. (2005). Where in the brain is the self? Consciousness and Cognition, 14(4), 661‑678. https://doi.org/10.1016/j.concog.2005.01.002
Freud, S. (1930). Civilization and its discontents. Broadview Press.
Frith, U., & de Vignemont, F. (2005). Egocentrism, allocentrism, and Asperger syndrome. Consciousness and Cognition, 14(4), 719‑738. https://doi.org/10.1016/j.concog.2005.04.006
Fuchs, T. (2022). The disappearing body : Anorexia as a conflict of embodiment. Eating and Weight Disorders-Studies on Anorexia, Bulimia and Obesity, 27(1), 109‑117.
Gallagher, S. Philosophical conceptions of the self: implications for cognitive science. Trends in cognitive sciences, 2000, vol. 4, no 1, p. 14-21.
Grunwald, M., Ettrich, C., Krause, W., Assmann, B., Dhne, A., Weiss, T., & Gertz, H.-J. (2001). Haptic perception in anorexia nervosa before and after weight gain. Journal of Clinical and Experimental Neuropsychology, 23(4), 520‑529.
Grunwald, M., & Weiss, T. (2005). Inducing sensory stimulation in treatment of anorexia nervosa. QJM: An International Journal of Medicine, 98(5), 379‑380. https://doi.org/10.1093/qjmed/hci061
Guardia, D., Carey, A., Cottencin, O., Thomas, P., & Luyat, M. (2013). Disruption of Spatial Task Performance in Anorexia Nervosa. PLoS ONE, 8(1), e54928. https://doi.org/10.1371/journal.pone.0054928
Guardia, D., Conversy, L., Jardri, R., Lafargue, G., Thomas, P., Dodin, V., Cottencin, O., & Luyat, M. (2012). Imagining One’s Own and Someone Else’s Body Actions : Dissociation in Anorexia Nervosa. PLOS ONE, 7(8), e43241. https://doi.org/10.1371/journal.pone.0043241
Guardia, D., Cottencin, O., Thomas, P., Dodin, V., & Luyat, M. (2012). Spatial orientation constancy is impaired in anorexia nervosa. Psychiatry Research, 195(1), 56‑59. https://doi.org/10.1016/j.psychres.2011.08.003
Guardia, D., Lafargue, G., Thomas, P., Dodin, V., Cottencin, O., & Luyat, M. (2010). Anticipation of body-scaled action is modified in anorexia nervosa. Neuropsychologia, 48(13), 3961‑3966. https://doi.org/10.1016/j.neuropsychologia.2010.09.004
Harter, S. (1998). The development of self-representations. In Handbook of child psychology : Social, emotional, and personality development, Vol. 3, 5th ed (p. 553‑617). John Wiley & Sons, Inc.
Heath, D. S., Jhinjar, N., & Hayward, D. A. (2021). Altered social cognition in a community sample of women with disordered eating behaviours : A multi-method approach. Scientific Reports, 11(1), 1‑11.
Heinisch, C., Dinse, H. R., Tegenthoff, M., Juckel, G., & Brüne, M. (2011). An rTMS study into self-face recognition using video-morphing technique. Social Cognitive and Affective Neuroscience, 6(4), 442‑449. https://doi.org/10.1093/scan/nsq062
Hirot, F., Lesage, M., Pedron, L., Meyer, I., Thomas, P., Cottencin, O., & Guardia, D. (2015). Impaired processing of self-face recognition in anorexia nervosa. Eating and Weight Disorders - Studies on Anorexia, Bulimia and Obesity. https://doi.org/10.1007/s40519-015-0223-y
Hoffmann, F., Banzhaf, C., Kanske, P., Gärtner, M., Bermpohl, F., & Singer, T. (2016). Empathy in depression : Egocentric and altercentric biases and the role of alexithymia. Journal of Affective Disorders, 199, 23‑29. https://doi.org/10.1016/j.jad.2016.03.007
Keenan, J. P., Gallup, G. G., & Falk, D. (2003). The face in the mirror : The search for the origins of consciousness (p. xxiii, 278). HarperCollins Publishers.
Keromnes, G., Chokron, S., Celume, M.-P., Berthoz, A., Botbol, M., Canitano, R., Du Boisgueheneuc, F., Jaafari, N., Lavenne-Collot, N., Martin, B., Motillon, T., Thirioux, B., Scandurra, V., Wehrmann, M., Ghanizadeh, A., & Tordjman, S. (2019). Exploring Self-Consciousness From Self- and Other-Image Recognition in the Mirror : Concepts and Evaluation. Frontiers in Psychology, 10, 719. https://doi.org/10.3389/fpsyg.2019.00719
Keromnes, G., Motillon, T., Coulon, N., Berthoz, A., Du Boisgueheneuc, F., Wehrmann, M., Martin, B., Thirioux, B., Bonnot, O., Ridereau, R., Bellissant, E., Drapier, D., Levoyer, D., Jaafari, N., & Tordjman, S. (2018). Self-other recognition impairments in individuals with schizophrenia : A new experimental paradigm using a double mirror. NPJ Schizophrenia, 4(1), 24. https://doi.org/10.1038/s41537-018-0065-5
Kerr-Gaffney, J. (2020). Socio-emotional cognition and autism spectrum disorder symptoms in anorexia nervosa [Ph.D., King’s College London]. https://kclpure.kcl.ac.uk/portal/en/theses/socioemotional-cognition-and-autism-spectrum-disorder-symptoms-in-anorexia-nervosa(d08e63f9-2292-4c66-b511-ca21cd68e9af).html
Kerr-Gaffney, J., Harrison, A., & Tchanturia, K. (2019). Cognitive and Affective Empathy in Eating Disorders : A Systematic Review and Meta-Analysis. Frontiers in Psychiatry, 10, 102. https://doi.org/10.3389/fpsyt.2019.00102
Kilteni, K., Maselli, A., Kording, K. P., & Slater, M. (2015). Over my fake body : Body ownership illusions for studying the multisensory basis of own-body perception. Frontiers in Human Neuroscience, 9, 141. https://doi.org/10.3389/fnhum.2015.00141
Kinnaird, E., Stewart, C., & Tchanturia, K. (2020). Interoception in anorexia nervosa: Exploring associations with alexithymia and autistic traits. Frontiers in psychiatry, 11, 64.
Kloeckner, A., Jutard, C., Bullinger, A., Nicoulaud, L., Tordjman, S., & Cohen, D. (2009). Intérêt de l’abord sensorimoteur dans les pathologies autistiques sévères I : Introduction aux travaux d’André Bullinger. Neuropsychiatrie de l’Enfance et de l’Adolescence, 57(2), 154‑159. https://doi.org/10.1016/j.neurenf.2008.12.002
Kolnes, L.-J. (2012). Embodying the body in anorexia nervosa–a physiotherapeutic approach. Journal of bodywork and movement therapies, 16(3), 281‑288.
Lamm, C., Bukowski, H., & Silani, G. (2016). From shared to distinct self-other representations in empathy : Evidence from neurotypical function and socio-cognitive disorders. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 371(1686), 20150083. https://doi.org/10.1098/rstb.2015.0083
Lander, R., Heled, E., & Gur, E. (2020). Executive functioning and spatial processing in anorexia nervosa : An experimental study and its significance for the allocentric lock theory. Eating and Weight Disorders - Studies on Anorexia, Bulimia and Obesity, 25(4), 1039‑1047. https://doi.org/10.1007/s40519-019-00728-2
Lavenne-Collot N.; Tersiguel M., Dissaux N., Degrez C., Bronsard G., Botbol M. & Berthoz A. Self/other distinction in adolescents with autism spectrum disorder (ASD) assessed with a double mirror paradigm. PlosOne (In Press)
Lombardo MV, Chakrabarti B, Bullmore ET, Wheelwright SJ, Sadek SA, Suckling J, et al. Shared Neural Circuits for Mentalizing about the Self and Others. J Cogn Neurosci. 2010 Jul 1;22(7):1623–35.
Legrand, D. (2010). Subjective and physical dimensions of bodily self-consciousness, and their dis-integration in anorexia nervosa. Neuropsychologia, 48(3), 726‑737. https://doi.org/10.1016/j.neuropsychologia.2009.08.026
Legrand, D. (2006). The bodily self: The sensori-motor roots of pre-reflective self-consciousness. Phenomenology and the Cognitive Sciences, 2006, vol. 5, no 1.
McIntosh, V. V., Bulik, C. M., McKenzie, J. M., Luty, S. E., & Jordan, J. (2000). Interpersonal psychotherapy for anorexia nervosa. International Journal of Eating Disorders, 27(2), 125-139.
Merleau-Ponty, M. (2012). The Phenomenology of Perception. Transl. ed D. A. Landes. London; New York: Routledge.
Miles, S., Gnatt, I., Phillipou, A., & Nedeljkovic, M. (2020). Cognitive flexibility in acute anorexia nervosa and after recovery : A systematic review. Clinical Psychology Review, 81, 101905. https://doi.org/10.1016/j.cpr.2020.101905
Nico, D., & Daprati, E. (2009). The egocentric reference for visual exploration and orientation. Brain and Cognition, 69(2), 227‑235. https://doi.org/10.1016/j.bandc.2008.07.011
Nico, D., Daprati, E., Nighoghossian, N., Carrier, E., Duhamel, J.-R., & Sirigu, A. (2010). The role of the right parietal lobe in anorexia nervosa. Psychological Medicine, 40(9), 1531‑1539.
Oldershaw, A., Hambrook, D., Stahl, D., Tchanturia, K., Treasure, J., & Schmidt, U. (2011). The socio-emotional processing stream in anorexia nervosa. Neuroscience & Biobehavioral Reviews, 35(3), 970‑988.
Porciello, G., Bufalari, I., Minio-Paluello, I., Di Pace, E., & Aglioti, S. M. (2018). The ‘Enfacement’ illusion : A window on the plasticity of the self. Cortex, 104, 261‑275. https://doi.org/10.1016/j.cortex.2018.01.007
Quagliata, E. (2004). Some reflections on the processes of projection and introjection in eating disorders. In Exploring Eating Disorders in Adolescents. Routledge.
Rahme, I. P., & Oliveira, E. P. de. (2015). The effect of back support on attention in Autism Spectrum Disorder : A pilot study testing André Bullinger’s model. Enfance, 4(4), 515‑524.
Riva, G., & Gaudio, S. (2012). Allocentric lock in anorexia nervosa : New evidences from neuroimaging studies. Medical Hypotheses, 79(1), 113‑117. https://doi.org/10.1016/j.mehy.2012.03.036
Russell, T. A., Schmidt, U., Doherty, L., Young, V., & Tchanturia, K. (2009). Aspects of social cognition in anorexia nervosa : Affective and cognitive theory of mind. Psychiatry research, 168(3), 181‑185.
Sachdev, P., Mondraty, N., Wen, W., & Gulliford, K. (2008). Brains of anorexia nervosa patients process self-images differently from non-self-images : An fMRI study. Neuropsychologia, 46(8), 2161‑2168.
Saint-Georges, C., Cassel, R. S., Cohen, D., Chetouani, M., Laznik, M. C., Maestro, S., & Muratori, F. (2010). What studies of family home movies can teach us about autistic infants: A literature review. Research in Autism Spectrum Disorders, 4(3), 355-366.
Saito, N., Yokoyama, T., & Ohira, H. (2016). Self-Other Distinction Enhanced Empathic Responses in Individuals with Alexithymia. Scientific Reports, 6, 35059. https://doi.org/10.1038/srep35059
Sforza, A., Bufalari, I., Haggard, P., & Aglioti, S. (2009). My face in yours : Visuo-tactile facial stimulation influences sense of identity. Social neuroscience, 5, 148‑162. https://doi.org/10.1080/17470910903205503
Silani, G., Lamm, C., Ruff, C. C., & Singer, T. (2013). Right Supramarginal Gyrus Is Crucial to Overcome Emotional Egocentricity Bias in Social Judgments. The Journal of Neuroscience, 33(39), 15466‑15476. https://doi.org/10.1523/JNEUROSCI.1488-13.2013
Simantov, T., Lombardo, M., Baron-Cohen, S., & Uzefovsky, F. (2021). Self-Other Distinction. https://doi.org/10.1007/978-3-030-51890-5_5
Smeets, M. A., Ingleby, J. D., Hoek, H. W., & Panhuysen, G. E. (1999). Body size perception in anorexia nervosa : A signal detection approach. Journal of psychosomatic research, 46(5), 465‑477.
Sowden, S., & Shah, P. (2014). Self-other control : A candidate mechanism for social cognitive function. Frontiers in Human Neuroscience, 8. https://www.frontiersin.org/article/10.3389/fnhum.2014.00789
Sproull, L., Subramani, M., Kiesler, S., Walker, J. H., & Waters, K. (1996). When the Interface Is a Face. Human–Computer Interaction, 11(2), 97‑124. https://doi.org/10.1207/s15327051hci1102_1
Steinbeis, N., & Singer, T. (2014). Projecting my envy onto you : Neurocognitive mechanisms of an offline emotional egocentricity bias. NeuroImage, 102 Pt 2, 370‑380. https://doi.org/10.1016/j.neuroimage.2014.08.007
Steinbeis N.(2016). The role of self–other distinction in understanding others’ mental and emotional states: neurocognitive mechanisms in children and adults. Philos Trans R Soc B Biol Sci. 19;371(1686):20150074.
Tajadura-Jiménez, A., Grehl, S., & Tsakiris, M. (2012). The other in me : Interpersonal multisensory stimulation changes the mental representation of the self. PloS One, 7(7), e40682. https://doi.org/10.1371/journal.pone.0040682
Tasca, G. A., & Balfour, L. (2014). Attachment and eating disorders : A review of current research. The International Journal of Eating Disorders, 47(7), 710‑717. https://doi.org/10.1002/eat.22302
Tchanturia, K., Smith, E., Weineck, F., Fidanboylu, E., Kern, N., Treasure, J., & Baron Cohen, S. (2013). Exploring autistic traits in anorexia : A clinical study. Molecular Autism, 4(1), 1‑8.
Teaford, M., McMurray, M. S., Billock, V., Filipkowski, M., & Smart Jr, L. J. (2021). The somatosensory system in anorexia nervosa : A scoping review. Journal of Experimental Psychopathology, 12(1), 2043808720987346.
Thirioux, B., Wehrmann, M., Langbour, N., Jaafari, N., & Berthoz, A. (2016). Identifying Oneself with the Face of Someone Else Impairs the Egocentered Visuo-spatial Mechanisms : A New Double Mirror Paradigm to Study Self–other Distinction and Interaction. Frontiers in Psychology, 7. https://doi.org/10.3389/fpsyg.2016.01283
Treasure, J., Claudino, A. M., & Zucker, N. (2010). Eating disorders. Lancet (London, England), 375(9714), 583‑593. https://doi.org/10.1016/S0140-6736(09)61748-7
Tsakiris, M. (2008). Looking for myself : Current multisensory input alters self-face recognition. PloS One, 3(12), e4040. https://doi.org/10.1371/journal.pone.0004040
Tsakiris, M., Hesse, M., Boy, C., Haggard, P., & Fink, G. (2007). Neural signatures of body ownership : A sensory network for bodily self-consciousness. Cerebral cortex. https://doi.org/10.1093/CERCOR/BHL131
Uddin, L. Q., Molnar-Szakacs, I., Zaidel, E., & Iacoboni, M. (2006). RTMS to the right inferior parietal lobule disrupts self–other discrimination. Social Cognitive and Affective Neuroscience, 1(1), 65‑71. https://doi.org/10.1093/scan/nsl003
Vocks, S., Busch, M., Grönemeyer, D., Schulte, D., Herpertz, S., & Suchan, B. (2010). Neural correlates of viewing photographs of one’s own body and another woman’s body in anorexia and bulimia nervosa : An fMRI study. Journal of Psychiatry and Neuroscience, 35(3), 163‑176. https://doi.org/10.1503/jpn.090048
Wagner, A., Ruf, M., Braus, D. F., & Schmidt, M. H. (2003). Neuronal activity changes and body image distortion in anorexia nervosa. Neuroreport, 14(17), 2193‑2197.
Williams, K., King, J., & Fox, J. R. E. (2016). Sense of self and anorexia nervosa : A grounded theory. Psychology and Psychotherapy: Theory, Research and Practice, 89(2), 211‑228. https://doi.org/10.1111/papt.12068
Winberg, A., Persson, I., & Thorssell, M. (1997). Kroppsuppfattning hos patienter med anorexia och bulimia nervosa-en studie av några sjukgymnastiska undersøkningsmetoder (Body perception among patients with anorexia and bulimia nervosa-a study of some physiotherapeutic examination methods). Nordisk Fysioterapi, 1, 18‑28.
Winnicott, D.W. (1960) Ego Distortion in Terms of True and False Self. In: Winnicott, D.W., Ed., The Maturational Processes and the Facilitating Environment: Studies in the Theory of Emotional Development, Karnac Books, London, 140-152.
World Health Organization, (WHO). (1992). The ICD-10 classification of mental and behavioural disorders : Clinical descriptions and diagnostic guidelines.

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Self /other recognition and distinction in adolescents with Anorexia Nervosa: a double mirror paradigm

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