Role of the thalamocortical networks in obsessive-compulsive disorder

décembre 2010

Directeur(s) de thèse : Pierre BURBAUD

Résumé de thèse

Obsessive-compulsive disorder (OCD) is a frequent and disabling anxiety disorder. Available treatments are effective for most patients but impairing residual symptoms and treatment resistance are common in OCD patients. Therefore, a better understanding of OCD pathophysiology is essential for further improvement of therapeutic strategies. The main goal of my thesis was to assess the anatomical and funtional thalamocortical alterations associated with OCD. Concerning the anatomical thalamocortical alterations associated with OCD, we conducted two meta-analyses of anatomical neuroimaging studies and an original volumetric neuroimaging study. We reported a smaller thalamic volume and a greater orbitofrontal volume, but also an inverse relationship between the volume changes in OCD patients compared with healthy subjects. Furthermore, we showed that gray matter density within the orbitofrontal cortex and the putamen were enhanced in OCD. Concerning the functional thalamocortical alterations associated with OCD, we reported data coming from a meta-analysis of functional neuroimaging studies, an experimental study in subhuman primates using local brain pharmacological manipulations and an event-related neuroimaging study in OCD patients. In our meta-analysis, we showed that the orbitofrontal cortex, the thalamus and the striatum were involved in the mediation of OCD symptoms. In subhuman primates, the pharmacologically induced overactivity within the ventralanterior thalamic nucleus leaded to the emergence of compulsive-like behaviors. Then, in our neuroimaging study, we found that doubt-related orbitofrontal dysfunctions were not modulated by neither error signals nor compulsive-like behaviors in OCD patients, compared with healthy subjects. Finally, we described by using meta-analytic data that anatomical and functional brain alterations overlap with the lateral orbitofrontal cortex in OCD. In conclusion, our results suggest that the thalamo-orbitofrontal network may play a primary role in the genesis and mediation of OCD symptoms.