Processus émotionnels au sein des ganglions de la base (études en électrophysiologie chez l'homme)

Les ganglions de la base (GB) sont un ensemble de noyaux sous-corticaux dont le noyau subthalamique (STN) et le globus pallidus interne (GPi). Ces structures sont étroitement connectées avec les aires corticales motrices et ont été impliquées dans la sélection de l action. Elles reçoivent également des projections des aires corticales et sous-corticales associatives et limbiques, suggérant leur implication dans les processus émotionnels. En accord, des modifications fonctionnelles au sein des GB sont à l origine de troubles du mouvement tels que la maladie de parkinson (MP), mais également de troubles neuropsychiatriques tels que le syndrome de Gilles de la Tourette (SGT) et le trouble obsessionnel compulsif (TOC). La stimulation cérébrale profonde (DBS), outil thérapeutique majeur dans la MP, a été récemment appliquée aux troubles neuropsychiatriques dont le TOC et le SGT. Cet élargissement des indications impose l étude de l intégration des informations émotionnelles au sein des GB. Dans ce but, des enregistrements électrophysiologiques en LFP ont été réalisés chez des patients implantés dans le cadre de la DBS, lors de la passation d une tâche de catégorisation émotionnelle. Ces enregistrements ont été réalisés dans le NST chez les patients MP et dans le GPi chez les patients SGT. Les résultats obtenus ont permis de mettre en évidence une implication de ces deux structures dans l évaluation des stimuli de l environnement et l encodage de la valence émotionnelle, indépendamment du contexte moteur. Ils soulignent l implication des GB dans les processus non moteurs et procurent des données susceptibles d expliquer certains effets comportementaux de la DBSPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Neural responses to heartbeats distinguish self from other during imagination

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Responses to heartbeats in ventromedial prefrontal cortex contribute to subjective preference-based decisions

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Does stroke volume influence heartbeat evoked responses?

International audienceWe know surprisingly little on how heartbeat-evoked responses (HERs) vary with cardiac parameters. Here, we measured both stroke volume, or volume of blood ejected at each heartbeat, with impedance cardiography, and HER amplitude with magnetoencephalography, in 21 male and female participants at rest with eyes open. We observed that HER co-fluctuates with stroke volume on a beat-to-beat basis, but only when no correction for cardiac artifact was performed. This highlights the importance of an ICA correction tailored to the cardiac artifact. We also observed that easy-to-measure cardiac parameters (interbeat intervals, ECG amplitude) are sensitive to stroke volume fluctuations and can be used as proxies when stroke volume measurements are not available. Finally, interindividual differences in stroke volume were reflected in MEG data, but whether this effect is locked to heartbeats is unclear. Altogether, our results question assumptions on the link between stroke volume and HERs. Highlights (3-5 bullet points, 85char max) • Beat-to-beat fluctuations in stroke volume mostly affect the cardiac/pulse artifact • A specific ICA correction strongly attenuates the influence of stroke volume on HER • Interbeat intervals and ECG amplitude are sensitive to stroke volume fluctuations • Inter-individual differences in stroke volume affect MEG dat

A causal role for the pedunculopontine nucleus in human instrumental learning

International audienceA critical mechanism for maximizing reward is instrumental learning. In standard instrumental learning models, action values are updated on the basis of reward prediction errors (RPEs), defined as the discrepancy between expectations and outcomes. A wealth of evidence across species and experimental techniques has established that RPEs are signaled by midbrain dopamine neurons. However, the way dopamine neurons receive information about reward outcomes remains poorly understood. Recent animal studies suggest that the pedunculopontine nucleus (PPN), a small brainstem structure considered as a locomotor center, is sensitive to reward and sends excitatory projection to dopaminergic nuclei. Here, we examined the hypothesis that the PPN could contribute to reward learning in humans. To this aim, we leveraged a clinical protocol that assessed the therapeutic impact of PPN deep-brain stimulation (DBS) in three patients with Parkinson disease. PPN local field potentials (LFPs), recorded while patients performed an instrumental learning task, showed a specific response to reward outcomes in a low-frequency (alpha-beta) band. Moreover, PPN DBS selectively improved learning from rewards but not from punishments, a pattern that is typically observed following dopaminergic treatment. Computational analyses indicated that the effect of PPN DBS on instrumental learning was best captured by an increase in subjective reward sensitivity. Taken together, these results support a causal role for PPN-mediated reward signals in human instrumental learning

Emotions Modulate Subthalamic Nucleus Activity: New Evidence in Obsessive-Compulsive Disorder and Parkinson’s Disease Patients

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