Neural correlates of uncertainty, psychophysiological and pathophysiological approachesdécembre 2014 Directeur(s) de thèse : Dominique GUEHL Résumé de thèse
Uncertainty is a cognitive process that frequently influences our decisions in everyday life. In obsessive-compulsive disorder (OCD), the high level of uncertainty usually alters the decision-making process. This work aimed to a better understanding of physiological and pathophysiological aspects of uncertainty, by exploring its relationships with working memory abilities and its neural correlates. An original task derived from a delayed matching-to-sample task was created with the possibility to express felt uncertainty during decision-making. With this « uncertainty task », we demonstrated that baseline working memory abilities predicted the occurrence of uncertainty in healthy individuals whereas uncertainty was followed by a decrease in working memory abilities in OCD patients. The role of working memory abilities in the occurrence of uncertainty was further confirmed in a clinical population of epileptic patients suffering from baseline working memory impairments. For the study of the neural correlates of uncertainty, we measured intracerebral local field potentials (LFPs) in regions involved in decision-making during the uncertainty task. Cortical and subcortical LFPs were obtained in epileptic and OCD patients, respectively. We showed that uncertainty was associated with: 1/ a decreased amplitude of evoked responses in cortical prefrontal and premotor regions, 2/ a reduced synchronization of alpha-beta frequency bands in time-frequency analyses, 3/ an increased amplitude of evoked responses in the subthalamic nucleus. Our findings suggested a diminished cortical activation in uncertain decision-making and confirmed the role of the subthalamic nucleus in OCD pathophysiology and in the mechanisms underlying the occurrence of pathological uncertainty.