Automatic processing of food in patients with restrictive Anorexia Nervosa: from attention to behaviour

Anorexia Nervosa (AN) is a severe psychiatric disorder, characterized by a relapsing and protracted course, with high mortality rates. One of the main symptoms of AN is an extreme restriction of calorie intake, which leads to a significantly low body weight. Over the years, with the aim of developing new and more effective treatments, several neurobiological models have been proposed to explain calorie restriction in AN. According to some of these models, alterations in the automatic responses elicited by food stimuli may play a role in the maintenance of the disorder as they could facilitate patients in resisting high-calorie food consumption and pursuing a low-calorie diet. To test this hypothesis, the present project investigated the automatic responses elicited by both high and low-calorie foods in patients with restrictive AN, by looking at the process that goes from attention orientation to action preparation and execution. In Chapter 3 is presented a study assessing the temporal course of attentional deployment toward food stimuli using an eye-tracking system. The results revealed that while healthy participants continued to look at food stimuli over the course of the trial, patients with AN avoided maintaining their attention on food stimuli. However, the fact that this difference was observed only in advanced stages of attentional processing suggests the involvement of more controlled rather than automatic mechanisms. In Chapter 4, the interference effect elicited by different types of distractors (high-calorie foods, low-calorie foods and neutral objects) on participants goal-directed movements was assessed through an analysis of mouse trajectories. The results showed that healthy controls presented a similar deviation toward the three categories of stimuli. Patients with AN, instead, presented a greater deviation toward low-calorie foods and a reduced deviation toward high-calorie foods, compared to neutral objects. Lastly, in Chapter 5, automatic approach-avoidance tendencies toward foods were assessed by means of a novel mobile approach-avoidance task. As a first step (paragraph 5.1), we developed and tested the mobile application in a sample recruited from the general population. The results of this study indicated the presence of a general approach bias towards food stimuli. Moreover, it was observed that this bias was influenced by other factor such as participants' BMI and hunger level. As a second step (paragraph 5.2), approach-avoidance tendencies toward foods were assessed in a sample of patients with restrictive AN. The analyses conducted on both reaction times and movements’ force revealed that the natural tendency to approach food stimuli was reduced in patients with AN. Overall, these results suggest that even if patients and controls do not differ in their initial attentional orientation toward foods, the motor programs that are automatically elicited by these stimuli are different. In particular, evidence is consistent in showing a reduced tendency to approach high calorie foods in patients with AN, a mechanism that may contribute to the maintenance of the disorder. The findings presented in this project can serve a starting point for a better understanding of the neurobiological correlates of AN and contribute to the development of new and more informed therapeutic strategies.