La dopamine et la sérotonine stimulent le traitement émotionnel du texte

Ils ont découvert des modèles distincts d’activité des neurotransmetteurs dans des régions du cerveau comme le thalamus et le cortex cingulaire antérieur, remettant en question les hypothèses sur leurs rôles dans le traitement émotionnel et linguistique.

Ces résultats suggèrent que les systèmes cérébraux développés pour la survie soutiennent également des fonctions humaines complexes comme l’interprétation du langage. La validation sur des modèles animaux a confirmé ces modèles, ouvrant la voie à de futures études sur la prise de décision et la santé mentale.

Faits essentiels

• Activité des neurotransmetteurs : la dopamine, la sérotonine et la noradrénaline réagissent de manière unique aux mots émotionnels, avec des modèles distincts liés au tonus émotionnel et aux régions du cerveau.
• Rôle inattendu du thalamus : le thalamus, traditionnellement non lié au langage ou à l’émotion, a montré des changements au niveau des neurotransmetteurs, suggérant une implication plus large dans le traitement émotionnel.
• Validation du modèle animal : des expériences optogénétiques sur des rongeurs ont confirmé les résultats, renforçant leur importance pour la compréhension des fonctions cérébrales humaines.

Source : Virginia Tech

Dans une nouvelle étude sans précédent publiée dans la revue  Cell Reports,  des chercheurs ont montré que des neurotransmetteurs dans le cerveau humain sont libérés lors du traitement du contenu émotionnel du langage, offrant de nouvelles perspectives sur la façon dont les gens interprètent la signification des mots.

The work, conducted by an international team led by Virginia Tech scientists, offers deeper understanding into how language influences human choices and mental health.

Spearheaded by computational neuroscientist Read Montague, a professor of the Fralin Biomedical Research Institute at VTC and director of the institute’s Center for Human Neuroscience Research, the study represents a first-of-its-kind exploration of how neurotransmitters process the emotional content of language — a uniquely human function.

Video Credit: Neuroscience News

The discovery, now online and slated for the Jan. 28 issue of Cell Reports, bridges the biological and the symbolic, linking neural processes that likely have evolved for survival in a vast array of species over the eons to the richness of human communication and emotion.

“The common belief about brain chemicals, like dopamine and serotonin, is that they send out signals related to the positive or negative value of experiences,” said Montague, co-corresponding and co-senior author of the study.

“Our findings suggest that these chemicals are released in specific areas of the brain when we process the emotional meaning of words.

“More broadly, our research supports the idea that the brain systems that evolved to help us react to good or bad things in our environment might also play a role in how we process words, which are just as important for our survival.”

The researchers are the first to simultaneously measure dopamine, serotonin, and norepinephrine release in humans in the context of the complex brain dynamics behind how people interpret and respond to language.

“The emotional content of words is shared across multiple transmitter systems, but each system fluctuates differently,” Montague said.

“There’s no single brain region handling this activity, and it’s not as simple as one chemical representing one emotion.”

Neurochemical measurements were taken in patients undergoing deep brain stimulation surgery for treatment of essential tremor, or for the surgical implantation of leads to monitor seizures in epilepsy patients.

The procedures target distinctly different brain regions – the thalamus and the anterior cingulate cortex, respectively.

While emotionally charged words were displayed on a screen, measurements were taken using carbon fiber electrodes in the thalamus, alongside traditional platinum-iridium electrodes in the anterior cingulate cortex.

The researchers discovered the words — positive, negative, or neutral — modulate neurotransmitter release.

By measuring the sub-second dynamics of the releases, they identified distinct patterns tied to emotional tone, anatomical regions, and which hemisphere of the brain was involved.

“The surprising result came from the thalamus,” said William “Matt” Howe, an assistant professor with the School of Neuroscience of the Virginia Tech College of Science.

“This region hasn’t been thought to have a role in processing language or emotional content, yet we saw neurotransmitter changes in response to emotional words. This suggests that even brain regions not typically associated with emotional or linguistic processing might still be privy to that information.

“For instance, parts of the brain responsible for mobilizing movement might benefit from having access to emotionally significant information to guide behavior.”

While the primary discovery was made in humans, validation in animal models provided additional confidence in the results.

Alec Hartle, a co-first author of the study and a School of Neuroscience doctoral student in Howe’s lab, conducted experiments in rodent models using a technique called optogenetics to confirm the patterns seen in humans.

By using light to control genetically modified cells, it allowed scientists to study the functions of specific neurons and neural circuits.

“What we observed in the human brain was extraordinary,” said Howe, co-corresponding and co-senior author of the study.

“The validation in animals supports and solidifies the broader implications of these neurotransmitters in decision-making systems.”

The new findings build on a recent study released in Nature Human Behavior, in which the research group highlighted dopamine and serotonin’s roles in social behavior.

“While previous studies focused on neurotransmission during decision-making, this research explores something uniquely human: the emotional content of written words,” said Seth Batten, first author of the study and a senior research associate with the Montague laboratory.

“Unlike animals, humans can understand words, their context, and meaning. The study examines how neurotransmitter systems process words with different emotional weight, reflecting the hypothesis that these systems, which evolved to keep us alive, now also help interpret language.”

While still in early stages, the study’s significance lies in its foundational nature and the questions it inspires for future research.

The words used in the study were drawn from the Affective Norms for English Words (ANEW) database, which rates words by positive, negative, or neutral emotional valence.

Abstract

Emotional words evoke region and valence-specific patterns of concurrent neuromodulator release in human thalamus and cortex

Words represent a uniquely human information channel—humans use words to express thoughts and feelings and to assign emotional valence to experience.

Work from model organisms suggests that valence assignments are carried out in part by the neuromodulators dopamine, serotonin, and norepinephrine.

Ici, nous nous demandons si la signalisation de valence par ces neuromodulateurs s’étend à la sémantique des mots chez l’homme en mesurant la dynamique des neuromodulateurs sous-seconde dans le thalamus ( N  = 13) et le cortex cingulaire antérieur ( N  = 6) des individus évaluant les mots à valence positive, négative et neutre.

Nos résultats combinés suggèrent que les mots valenced modulent la libération de neuromodulateurs à la fois dans le thalamus et le cortex, mais avec des modèles de réponse spécifiques à la région et à la valence, ainsi qu’une dépendance hémisphérique pour la libération de dopamine dans le cingulaire antérieur.

Dans l’ensemble, ces expériences démontrent que la signalisation de valence dépendante du neuromodulateur s’étend à la sémantique des mots chez l’homme, mais pas de manière simple, avec une valence par transmetteur.