Anorexia nervosa (AN) is a mental disorder characterized by a relentless pursuit of thinness, severe food restriction, body image disturbances, and an extremely low body weight. The etiology of the disorder is not known. There has been considerable interest in the neurobiology associated with AN, and a wealth of neuroimaging studies have shed light on the neural correlates of this disorder.
Research have consistently shown that patients with AN are characterized by brain tissue reductions. To a large extent, these reductions are reversible with weight-gain and recovery, but it is unclear whether they fully normalize. Some studies have reported local gray matter reductions in recovered patients, which could reflect irreversible damage due to emaciation, or alternatively trait characteristics related to AN vulnerability. In contrast, other studies report normal brain tissue volumes in recovered patients.
AN is also associated with functional brain alterations in widespread circuits, including parietal, limbic, and prefrontal cortices. Available evidence suggests that AN is characterized by an imbalance within or between brain circuits related to cognitive control and emotion. Such alterations may be associated with the emotional dysregulation that characterizes AN. Still, the nature of these functional brain alterations is not understood.
The overall aim of this doctoral thesis was to advance our understanding of the structural and functional brain alterations associated with AN. Specifically, we wanted to a) determine the presence of brain tissue reductions in women recovered from AN, and b) investigate the neural responses in prefrontal and limbic brain circuits during emotional tasks in women recovered from AN.
To this end, we used magnetic resonance imaging to measure brain structure and function. We measured neural responses to emotional tasks which required emotional stimuli to be suppressed or ignored, thus hoping to shed light on neural responses involved in both bottom-up emotional arousal and top-down control over emotion. Women recovered from AN were compared to age-matched comparison women.
In Paper 1, we showed that brain tissue volumes in women recovered from AN were similar to comparison women. This contributes to the inconsistent research literature, and is in accordance with several previous studies. In Paper 2, we showed that women recovered from AN were characterized by altered amygdala responses during an emotional conflict task. This indicates that AN is associated with functional alterations in the emotion-circuitry. In Paper 3, we showed that women recovered from AN were characterized by alterations in the extrastriate cortex and medial prefrontal cortex during an attentional bias to threat task. These alterations may reflect altered saliency and cognitive control processes. Together, these results suggest that women recovered from AN are characterized by functional brain alterations in brain circuits involved in emotion generation and regulation, despite normal brain tissue volumes.
This thesis contributes to the existing research literature by advancing our understanding of the neurobiological underpinnings of AN.