The Malleability of Body Representation in Anorexia Nervosa: the Sixth Finger Illusion

Anorexia Nervosa Clinical Trial

— SESTODITO_AN  

Official title:

The Malleability of Body Representation in Anorexia Nervosa: the Sixth Finger Illusion

Clinical Trial Details — Status: Recruiting

Administrative data

• NCT number: NCT06316674
• Other study ID #: 03C304
• Status: Recruiting
• Start date: May 1, 2023
• Est. completion date: April 30, 2024

Study information

• Verified date: March 2024
• Source: Istituto Auxologico Italiano
• Contact: Federico Brusa, Ph.D
• Phone: +393517797622
• Email: f.brusa[@]auxologico.it
• Is FDA regulated: No
• Study type: Observational

Clinical Trial Summary

Body representation can be explored using behavioural tasks such as motor imagery tasks as well as body illusions.

In both cases, evidence from studies on healthy individuals as well as patients with lesions to the central nervous system show that body representation is not set in stone: how we imagine our bodies is a dynamic and continuously updated process, to reflect changes in our own body as well as the environment.

In anorexia nervosa the representation of the body is very different from that of healthy individuals: the representation is more malleable, and easier to manipulate, while at the same time being more detached from physical constraints. These features of body representation in anorexia nervosa might contribute to the persistence of symptoms and to relapses too. Body representation has clear implications for treatment of anorexia nervosa too.

The study aims at evaluating the presence of differences in the malleability of the body representation, explored through the illusion of the sixth finger, between a group of people with AN and a group of normal weight people, taking into account the biomechanical constraints that characterize the physical and mentally represented body.

Description:

The ability to imagine our body in our mind is called body representation. This ability is grounded in sensory and perceptual process and it is crucial to plan action, to interact with the environment and so on. Body representation can be explored using behavioural tasks such as motor imagery tasks as well as body illusions.

Evidence from healthy individuals shows that we depend on physical constraints when we imagine actions we can do with our body: we are faster and more accurate in imagining an action that we can really perform. This phenomenon is called "biomechanical constraints effect" and it is an index that our brain is performing motor imagery. When a lesion occurs to the spinal cord, for example, this effect is not present anymore, supporting the idea that what occurs in our brain is strongly dependent on what we can do in the real word. This dependency from the real word, however, does not mean that the representation of the body in the mind is an exact copy of the physical body. For example, findings from experiments using body illusions show that we have a distorted representation of our body, even in absence of any lesion. Overall, evidence from body illusions in healthy individuals shows that we tend to overestimate features when we imagine our body, width in particular compared to length and height.

In both cases, evidence from studies on healthy individuals as well as patients with lesions to the central nervous system show that body representation is not set in stone: how we imagine our bodies is a dynamic and continuously updated process, to reflect changes in our own body as well as the environment.

Recent studies suggest that body representation is quite different in conditions that affect the body even in absence of central nervous system or brain impairments, such as anorexia nervosa. In patients affected by anorexia nervosa, motor imagery does not occur, and patients treat their body like it is an object. Similarly, when subjected to illusions of ownership, patients with anorexia nervosa experience the illusion more strongly than healthy individuals.

In anorexia nervosa the representation of the body is very different from that of healthy individuals: the representation is more malleable, and easier to manipulate, while at the same time being more detached from physical constraints. These features of body representation in anorexia nervosa might contribute to the persistence of symptoms and to relapses too. Body representation has clear implications for treatment of anorexia nervosa too.

The study aims at evaluating the presence of differences in the malleability of the body representation, explored through the illusion of the sixth finger, between a group of people with AN and a group of normal weight people, taking into account the biomechanical constraints that characterize the physical and mentally represented body.

Recruitment information / eligibility

• Status: Recruiting
• Enrollment: 60
• Est. completion date: April 30, 2024
• Est. primary completion date: April 30, 2024
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Female
• Age group: 18 Years to 55 Years

Eligibility

Inclusion Criteria:

• female

• 18-55 years

• bmi = 17.5 Kg/m2 for AN and BMI between 18.5 Kg/m2 e 25 Kg/m2 for healthy controls

Exclusion Criteria:

• psychopathologies related to psychosis or brain injury lesions

Related Conditions & MeSH terms

• Anorexia
• Anorexia Nervosa

Intervention

Behavioral:
• sixth finger illusion
Participants will undertake the sixth finger illusion that is a body illusion which elicits the presence of an extra numerary finger due to visuo-tactile stimulation.

Locations

Country	Name	City	State
Italy	Istituto Auxologico italiano IRCSS	Milan

Sponsors (4)

Lead Sponsor	Collaborator
Istituto Auxologico Italiano	Birkbeck, University of London, Catholic University of the Sacred Heart, Heriot-Watt University

Country where clinical trial is conducted

Italy, 

References & Publications (8)

Brusa F, Kretzschmar L, Magnani FG, Turner G, Garraffa M, Sedda A. Talking with hands: body representation in British Sign Language users. Exp Brain Res. 2021 Mar;239(3):731-744. doi: 10.1007/s00221-020-06013-4. Epub 2021 Jan 3. — View Citation

Brusa F, Suphi Erden M, Sedda A. Exploring the role of disgust in hands and feet laterality judgement tasks. Q J Exp Psychol (Hove). 2023 Nov 3:17470218231207336. doi: 10.1177/17470218231207336. Online ahead of print. — View Citation

de Vignemont F. Body schema and body image--pros and cons. Neuropsychologia. 2010 Feb;48(3):669-80. doi: 10.1016/j.neuropsychologia.2009.09.022. Epub 2009 Sep 26. — View Citation

Eshkevari E, Rieger E, Longo MR, Haggard P, Treasure J. Increased plasticity of the bodily self in eating disorders. Psychol Med. 2012 Apr;42(4):819-28. doi: 10.1017/S0033291711002091. Epub 2011 Oct 5. — View Citation

Eshkevari E, Rieger E, Longo MR, Haggard P, Treasure J. Persistent body image disturbance following recovery from eating disorders. Int J Eat Disord. 2014 May;47(4):400-9. doi: 10.1002/eat.22219. Epub 2013 Nov 18. — View Citation

Fiori F, Sedda A, Ferre ER, Toraldo A, Querzola M, Pasotti F, Ovadia D, Piroddi C, Dell'Aquila R, Redaelli T, Bottini G. Motor imagery in spinal cord injury patients: moving makes the difference. J Neuropsychol. 2014 Sep;8(2):199-215. doi: 10.1111/jnp.12020. Epub 2013 May 15. — View Citation

Holmes NP, Spence C. The body schema and the multisensory representation(s) of peripersonal space. Cogn Process. 2004 Jun;5(2):94-105. doi: 10.1007/s10339-004-0013-3. — View Citation

Scarpina F, Bastoni I, Villa V, Mendolicchio L, Castelnuovo G, Mauro L, Sedda A. Self-perception in anorexia nervosa: When the body becomes an object. Neuropsychologia. 2022 Feb 10;166:108158. doi: 10.1016/j.neuropsychologia.2022.108158. Epub 2022 Jan 14. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Sixth finger illusion questionnaire	Participants are asked to answer to a 6 questions questionnaire based on a likert scale	Through study completion, an average of 1 year