Prédire le suicide ou prédire l’imprévisible dans un monde incertain. Modèle du suicide selon l’apprentissage par renforcement.

in Santé Mentale au Québec (2012)

Predicting suicide or predicting the unpredictable in an uncertain world: Reinforcement Learning Model-Based analysis In general, it appears that the suicidal act is highly unpredictable with the current ... [more ▼]

Predicting suicide or predicting the unpredictable in an uncertain world: Reinforcement Learning Model-Based analysis In general, it appears that the suicidal act is highly unpredictable with the current scientific means available. In this article, the author submits the hypothesis that predicting suicide is complex because it results in predicting a choice, in itself unpredictable. The article pro- poses a Reinforcement learning model-based analysis. In this model, we integrate on the one hand, four ascending modulatory neurotransmitter systems (acetylcholine, noradrenalin, serotonin, and dopamine) with their regions of respective projections and afferences, and on the other hand, various observations of brain imaging identified until now in the suicidal process. [less ▲]

Sleep stabilizes visuomotor adaptation memory : an fMRI study

in Journal of Sleep Research (2012), Epub ahead of print

Depression alters "top-down" visual attention: a dynamic causal modeling comparison between depressed and healthy subjects.

in NeuroImage (2011), 54(2), 1662-8

Using functional magnetic resonance imaging (fMRI), we recently demonstrated that nonmedicated patients with a first episode of unipolar major depression (MDD) compared to matched controls exhibited an ... [more ▼]

Using functional magnetic resonance imaging (fMRI), we recently demonstrated that nonmedicated patients with a first episode of unipolar major depression (MDD) compared to matched controls exhibited an abnormal neural filtering of irrelevant visual information (Desseilles et al., 2009). During scanning, subjects performed a visual attention task imposing two different levels of attentional load at fixation (low or high), while task-irrelevant colored stimuli were presented in the periphery. In the present study, we focused on the visuo-attentional system and used "Dynamic Causal Modeling" (DCM) on the same dataset to assess how attention influences a network of three dynamically-interconnected brain regions (visual areas V1 and V4, and intraparietal sulcus (P), differentially in MDD patients and healthy controls. Bayesian model selection (BMS) and model space partitioning (MSP) were used to determine the best model in each population. The best model for the controls revealed that the increase of parietal activity by high attention load was selectively associated with a negative modulation of P on V4, consistent with high attention reducing the processing of irrelevant colored peripheral stimuli. The best model accounting for the data from the MDD patients showed that both low and high attention levels exerted modulatory effects on P. The present results document abnormal effective connectivity across visuo-attentional networks in MDD, which likely contributes to deficient attentional filtering of information. [less ▲]

Neural precursors of delayed insight

in Journal of Cognitive Neuroscience (2011), 23(8), 1900-1910

The solution of a problem left unresolved in the evening can sometimes pop into mind as a sudden insight after a night of sleep in the following morning. Although favorable effects of sleep on insightful ... [more ▼]

The solution of a problem left unresolved in the evening can sometimes pop into mind as a sudden insight after a night of sleep in the following morning. Although favorable effects of sleep on insightful behavior have been experimentally confirmed, the neural mechanisms determining this delayed insight remain unknown. Here, using functional magnetic resonance imaging (fMRI), we characterize the neural precursors of delayed insight in the number reduction task (NRT), in which a hidden task structure can be learned implicitly, but can also be recognized explicitly in an insightful process, allowing immediate qualitative improvement in task performance. Normal volunteers practiced the NRT during two fMRI sessions (training and retest), taking place 12 hours apart after a night of sleep. After this delay, half of the subjects gained insight into the hidden task structure ("solvers," S), whereas the other half did not ("nonsolvers," NS). Already at training, solvers and nonsolvers differed in their cerebral responses associated with implicit learning. In future solvers, responses were observed in the superior frontal sulcus, posterior parietal cortex, and the insula, three areas mediating controlled processes and supporting early learning and novice performance. In contrast, implicit learning was related to significant responses in the hippocampus in nonsolvers. Moreover, the hippocampus was functionally coupled with the basal ganglia in nonsolvers and with the superior frontal sulcus in solvers, thus potentially biasing participants' strategy towards implicit or controlled processes of memory encoding, respectively. Furthermore, in solvers but not in nonsolvers, response patterns were further transformed overnight, with enhanced responses in ventral medial prefrontal cortex, an area previously implicated in the consolidation of declarative memory. During retest in solvers, before they gain insight into the hidden rule, significant responses were observed in the same medial prefrontal area. After insight, a distributed set of parietal and frontal areas is recruited among which information concerning the hidden rule can be shared in a so-called global workspace. [less ▲]

Neuroimaging Insights into the Dreaming Brain

in Dreams and Dreaming (2010)

Working memory load modulates time-of-day and chronotype effects on task-related BOLD activity

in NeuroImage (2010), 51(Suppl. 1),

Les modèles etiologiques de la dépression

in Acta Psychiatrica Belgica (2010), 110(4), 34-42

La dépression est une maladie psychique fréquente, récurrente et invalidante pour la personne qui en souffre et son entourage. En deux siècles de psychiatrie, l’étiologie exacte de la dépression reste ... [more ▼]

La dépression est une maladie psychique fréquente, récurrente et invalidante pour la personne qui en souffre et son entourage. En deux siècles de psychiatrie, l’étiologie exacte de la dépression reste inconnue. C’est pourquoi différentes hypothèses étiologiques ont été et sont toujours proposées. Cette revue a pour but de présenter différent modèles étiologiques de la dépression : le modèle psychanalytique, le modèle comportemental et les théories environnementales, le modèle cognitif, le modèle systémique, le modèle biologique et neuropsychologique, et le modèle éthologique. [less ▲]

Neurobiological bases of suicidality in major depression

in World Journal of Biological Psychiatry (2009), 9(Suppl. 1),

Increased filtering of irrelevant information in obsessive-compulsive disorder (OCD) patient

Poster (2009)

Sleep and Sleep States: PET activation patterns

in Squire, Larry (Ed.) Encyclopedia of Neuroscience (2009)