Obsessive-compulsive disorderneuroimaging findings

Resumo

A variety of neuroanatomical models were advanced to explain the pathogenesis of Obsessive Compulsive Disorder with a common agreement on the existence of dysfunctional cortico-striatal–thalamus-cortical (CSTC) circuits. Despite this consensus on the role of frontal–subcortical loops in OCD, recent studies have shown that brain regions other than the CSTC loops may be needed to understand the complexity and diversity of cognitive and affective deficits in OCD. The objective of the present dissertation was to build on morphological, connectivity and functional neuroimaging methods to look for brain alterations that may contribute to elucidate cognitive and affective impairments. Four neuroimaging studies were carried out exploring morphological, connectivity, and functional alterations in OCD, brought evidence for the following findings. First we found evidences for the existence of widespread volumetric alterations in both gray and white matter regions in OCD (frontal, subcortical, and temporal-parietal regions) who may explain difficulties with inhibitory control, executive functioning, compulsive checkings, and visual-spatial deficits. Second, we observed the existence of alterations of white matter connectivity in white matter adjacent to a core brain region implicated in inhibitory control. Third, a functional neuroimaging study showed that OCD patients react to basic threat with a strong activation of a widespread brain network systems. In an opposite way, activation of the appetitive system was blocked when facing positive emotional triggers from the initial stages of visual processing. Finally, we found that OCD patients have difficulties in switching from a resting state network associated with self-referential processes (i.e., Default Mode Network - DMN) to an external focus characterized by the presentation of emotional provoking stimuli, particularly images with pleasant content.