Aspects cognitifs, comportementaux et émotionnels de l’activité physique problématique dans l’anorexie mentale

Anorexia nervosa (AN) is a psychiatric illness characterised by weight and shape controlling behaviours, including food restriction and problematic physical activity. Despite its detrimental impact on prognosis and remission, the understanding of the mechanisms of development and maintenance of problematic physical activity in AN remains incomplete. The objective of this thesis is to examine the cognitive, behavioural and emotional factors involved in the problematic physical activity observed in AN through a translational approach. In the first section, the relationship between problematic physical activity and cognitive, emotional and neuropsychological alterations of AN is analyzed by clinical studies. The results underscore a worsening impact of physical activity on specific symptoms of the disorder, including body image distortion, and a reinforcing effect of physical exercise in patients with AN, manifested as elevated craving, and primarily linked to an improvement of positive emotions, displaying the characteristics of an endophenotype. Additionally, a new set of validated dynamic stimuli, comprising both sedentary activities and physical exercise, is presented. Cognitive alterations associated with AN contribute significantly to the chronicisation of problematic physical activity. A Bayesian approach to the analysis of decision-making capacity reveals a reduction in feedback sensitivity associated with the disease as a trait. However, this impact on decision-making is observed only in situations of undernutrition. The interaction between metabolic and emotional factors, such as anxiety, is crucial to the imbalance between food choice and physical activity observed in AN. Cognitive rigidity, an endophenotype of AN, paves the way to the inflexibility of this decision-making process. For the first time, a positive, AN-specific correlation is identified between cognitive rigidity and the amount of physical activity objectively measured by heart rate monitoring. Collectively, these clinical studies provide a foundation for a theoretical model of the development and maintenance of problematic physical activity specific to AN, incorporating AN-associated cognitive, emotional, and behavioural factors, and partly grounded in an intrinsic vulnerability that explains the strong reinforcing power of this practice in these patients. The second part of this thesis presents a novel animal model for the study of the motivational aspects of problematic physical activity in AN. This model is based on the principles of neuro-economics, operant conditioning and the 'Closed economy' paradigm. Initial experiments led to the identification of a genetic strain of mice that showed increased motivation and desire to run on a wheel. However, in a closed-economy setting with a competitive choice between food and the wheel, the BALB/c strain showed the greatest susceptibility to the development of a motivational imbalance between food and exercise. This phenotype is further exacerbated when, as in AN, the motivational effort associated with food is increased, while that associated with exercise is maintained at a low level. This animal research component builds upon and extends the findings of the clinical studies conducted as part of this thesis. In addition to its high ecological, face and construct validity, this model will facilitate the understanding of gene-environment interactions and the mechanisms underlying problematic physical activity in AN.