Neurophysiological correlates of interpersonal discrepancy and social adjustment in an interactive decision-making task in dyads

Introduction: The pursuit of convergence and the social behavioral adjustment of conformity are fundamental cooperative behaviors that help people adjust their mental frameworks to reach a common goal. However, while social psychology has extensively studied conformity by its influence context, there is still plenty to investigate about the neural cognitive mechanisms involved in this behavior. Methods: We proposed a paradigm with two phases, a pre-activation phase to enhance cooperative tendencies and, later, a social decision-making phase in which dyads had to make a perceptual estimation in three consecutive trials and could converge in their decisions without an explicit request or reward to do so. In Study 1, 80 participants were divided in two conditions. In one condition participants did the pre-activation phase alone, while in the other condition the two participants did it with their partners and could interact freely. In Study 2, we registered the electroencephalographical (EEG) activity of 36 participants in the social decision-making phase. Results: Study 1 showed behavioral evidence of higher spontaneous convergence in participants who interacted in the pre-activation phase. Event related Potentials (ERP) recorded in Study 2 revealed signal differences in response divergence in different time intervals. Time-frequency analysis showed theta, alpha, and beta evidence related to cognitive control, attention, and reward processing associated with social convergence. Discussion: Current results support the spontaneous convergence of behavior in dyads, with increased behavioral adjustment in those participants who have previously cooperated. In addition, neurophysiological components were associated with discrepancy levels between participants, and supported the validity of the experimental paradigm to study spontaneous social behavioral adaptation in experimental settings

Theta oscillations integrate functionally segregated sub-regions of the medial prefrontal cortex

Reinforcement learning requires the dynamic interplay of several specialized networks distributed across the brain. A potential mechanism to establish accurate temporal coordination among these paths is through the synchronization of neuronal activity to a common rhythm of neuronal firing. Previous EEG studies have suggested that theta oscillatory activity might be crucial in the integration of information from motivational and attentional paths that converge into the medial Prefrontal Cortex (mPFC) during reward-guided learning. However, due to the low spatial resolution of EEG, this hypothesis has not been directly tested. Here, by combining EEG and fMRI, we show that theta oscillations serve as common substrate for the engagement of separated sub-regions within the mPFC (the pre-Supplementary Motor Area and the dorsomedial Prefrontal Cortex), underlying different cognitive operations (encoding of outcome valence and unsigned prediction errors) through separate functional paths (the Salience and the Central Executive Networks)

Neurophysiological correlates of interpersonal discrepancy and social adjustment in an interactive decision-making task in dyads

IntroductionThe pursuit of convergence and the social behavioral adjustment of conformity are fundamental cooperative behaviors that help people adjust their mental frameworks to reach a common goal. However, while social psychology has extensively studied conformity by its influence context, there is still plenty to investigate about the neural cognitive mechanisms involved in this behavior.MethodsWe proposed a paradigm with two phases, a pre-activation phase to enhance cooperative tendencies and, later, a social decision-making phase in which dyads had to make a perceptual estimation in three consecutive trials and could converge in their decisions without an explicit request or reward to do so. In Study 1, 80 participants were divided in two conditions. In one condition participants did the pre-activation phase alone, while in the other condition the two participants did it with their partners and could interact freely. In Study 2, we registered the electroencephalographical (EEG) activity of 36 participants in the social decision-making phase.ResultsStudy 1 showed behavioral evidence of higher spontaneous convergence in participants who interacted in the pre-activation phase. Event related Potentials (ERP) recorded in Study 2 revealed signal differences in response divergence in different time intervals. Time-frequency analysis showed theta, alpha, and beta evidence related to cognitive control, attention, and reward processing associated with social convergence.DiscussionCurrent results support the spontaneous convergence of behavior in dyads, with increased behavioral adjustment in those participants who have previously cooperated. In addition, neurophysiological components were associated with discrepancy levels between participants, and supported the validity of the experimental paradigm to study spontaneous social behavioral adaptation in experimental settings

Assessing Neuronal Synchrony and Brain Function Through Local Field Potential and Spike Analysis

Studies of neuronal network oscillations and rhythmic neuronal synchronization have led to a number of important insights in recent years, giving us a better understanding of the temporal organization of neuronal activity related to essential brain functions like sensory processing and cognition. Important principles and theories have emerged from these findings, including the communication through coherence hypothesis, which proposes that synchronous oscillations render neuronal communication effective, selective, and precise. The implications of such a theory may be universal for brain function, as the determinants of neuronal communication inextricably shape the neuronal representation of information in the brain. However, the study of communication through coherence is still relatively young. Since its articulation in 2005, the theory has predominantly been applied to assess cortical function and its communication with downstream targets in different sensory and behavioral conditions. The results herein are intended to bolster this hypothesis and explore new ways in which oscillations coordinate neuronal communication in distributed regions. This includes the development of new analytic tools for interpreting electrophysiological patterns, inspired by phase synchronization and spike train analysis. These tools aim to offer fast results with clear statistical and physiological interpretation

L’étude de la contribution des mécanismes dépendants de la répétition aux processus de consolidation des mémoires motrices dans le cortex moteur primaire et de la manifestation électrophysiologique du traitement des récompenses monétaires au-dessus des aires cérébrales motrices

Abstract : The present thesis seeks to provide insights into the contribution of the two major learning mechanisms driving motor memory consolidation in the primary motor cortex (M1): repetition-dependent and reward-based learning mechanisms. However, because evidence remains scarce on this last learning mechanism, the study of the neural manifestation of reward processing in motor areas was investigated. More specifically, the first scientific contribution presented in this thesis sought to address the contribution of repetition-dependent mechanisms to motor memory consolidation in M1. As such, the first project used single-pulse transcranial magnetic stimulation (TMS) to interfere with M1 activity as participants executed newly learned motor behaviors during a performance asymptote. Results revealed that motor memory formation in M1 was initiated when behaviors were repeating, suggesting that repetition-dependent mechanisms contributed to retention in M1. The second scientific contribution sought to use scalp electroencephalography (EEG) recordings to investigate the electrophysiological manifestations of reward processing over cortical motor areas. Overall, results revealed that increases in beta-band power (20-30 Hz) over contralateral motor electrodes are modulated by reward processing. Although these results did not allow specifically addressing the contribution of reward-based learning mechanisms to consolidation in M1, they nonetheless provide the plausible neural substrates involved in this learning mechanism. The discussion first sought to integrate these two projects and second to provide an overview of the future perspectives that the two projects have led to. Overall, the proposed research projects mainly revolve around the demonstration of the associations– even maybe causality – between motor memory consolidation in M1, reward processing, beta-band power and dopaminergic activity. Throughout the discussion, working hypotheses as well as the methodological means to test them – ranging from non-invasive brain stimulation to electroencephalography recordings and even to the study of interindividual variations in the expression of dopamine-related genes – are outlined.Le présent mémoire cherche à fournir un aperçu des mécanismes neurophysiologiques qui sous-tendent les deux mécanismes principaux d’apprentissage impliqués dans la consolidation des mémoires motrices dans le cortex moteur primaire (M1). Bien que le modèle cellulaire le plus accepté pour la formation des mémoires motrices soit la potentialisation à long-terme (long-term potentiation, en anglais), la littérature suggère que les mécanismes d’apprentissage qui initient le stockage synaptique des mémoires motrices dépendent de la plasticité Hebienne (i.e., répétitions dans les mouvements) et des récompenses vécues pendant l’acquisition d’une nouvelle habileté motrice. La première contribution scientifique du présent mémoire aborde la contribution des mécanismes Hebbiens d’apprentissage à la consolidation des mémoires motrices dans le M1. Dans ce premier projet, la stimulation magnétique transcrânienne (SMT) a été utilisée pour interférer avec l’activité neuronale du M1 lorsque les participants acquéraient et exécutaient de nouveaux comportements moteurs pendant l’atteinte d’un plateau de performance (i.e., répétitions dans les mouvements). Les résultats démontrent que la formation des mémoires motrices dans le M1 est initiée lorsque les comportements moteurs sont de plus en plus répétés, ce qui suggère que le stockage synaptique des mémoires motrices dans M1 est dépendant de la répétition des comportements pendant l’acquisition. Le deuxième projet scientifique a cherché à mettre en lumière la contribution des régions motrices au traitement des récompenses dans un contexte moteur en utilisant l’enregistrement d’activités électroencéphalographiques. Entre autres, suite à l’octroi d’une récompense, les résultats démontrent une augmentation de la puissance spectrale dans la bande de fréquences bêta (20-30 Hz) des électrodes motrices contralatérales à la main utilisée pendant la tâche motrice. Dans l’ensemble, bien que ce deuxième projet ne puisse statuer sur la contribution spécifique du M1 dans la consolidation des mémoires motrices sur la base des récompenses vécues pendant l’acquisition, les résultats qui en émergent pourraient être un reflet des substrats neuronaux impliqués dans ce mécanisme d’apprentissage. Dans un premier temps, la discussion intègre ces deux contributions et, dans un deuxième temps, donne un aperçu des perspectives futures de recherche qui émanent de ces deux contributions scientifiques. Globalement, les hypothèses de recherche suggérées se concentrent principalement autour de la démonstration d’une association ou d’un lien causal entre la formation des mémoires motrices dans le M1, le traitement de récompenses, les réponses spectrales en bêta ainsi que l’activité dopaminergique. Au travers de la discussion, les hypothèses spécifiques ainsi que les moyens méthodologiques pour les tester – qui vont des techniques de stimulation cérébrale non invasives à l’enregistrement d’activité électroencéphalographique et même jusqu’à l’étude des variations génétiques interindividuelles dans l’expression des gènes régulant l’activité dopaminergique – sont décrits

Neurophysiological correlates underlying social behavioural adjustment of conformity

[eng] Conformity is the act of changing one’s behaviour to adjust to other human beings. It is a crucial social adaptation that happens when people cooperate, where one sacrifices their own perception, expectations, or beliefs to reach convergence with another person. The aim of the present study was to increase the understanding of the neurophysiological underpinnings regarding the social behavioural adjustment of conformity. We start by introducing cooperation and how it is ingrained in human behaviour. Then we explore the different processes that the brain requires for the social behavioural adjustment of conformity. To engage in this social adaptation, a person needs a self-referenced learning mechanism based on a predictive model that helps them track the prediction errors from unexpected events. Also, the brain uses its monitoring and control systems to encode different value functions used in action selection. The use of different learning models in neuroscience, such as reinforcement learning (RL) algorithms, has been a success story identifying learning systems by means of the mapped activity of different regions in the brain. Importantly, experimental paradigms which has been used to study conformity have not been based in a social interaction setting and, hence, the results, cannot be used to explain an inherently social phenomenon. The main goal of the present thesis is to study the neurophysiological mechanisms underlying the social behavioural adjustment of conformity and its modulation with repeated interaction. To reach this goal, we have first designed a new experimental task where conformity appears spontaneously between two persons and in a reiterative way. This design exposes learning acquisition processes, which require iterative loops, as well as other cognitive control mechanisms such as feedback processing, value-based decision making and attention. The first study shows that people who previously cooperate increase their level of convergence and report a significantly more satisfying overall experience. In addition, participants learning on their counterparts’ behaviour can be explained using a RL algorithm as opposed to when they do not have previously cooperated. In the second study, we have studied the event-related potentials (ERP) and oscillatory power underlying conformity. ERP results show different levels of cognitive engagement that are associated to distinct levels of conformity. Also, time-frequency analysis shows evidence in theta, alpha and beta related to different functions such as cognitive control, attention and, also, reward processing, supporting the idea that convergence between dyads acts as a social reward. Finally, in the third study, we explored the intra- and inter- oscillatory connectivity between electrodes related to behavioural convergence. In intra-brain oscillatory connectivity coherence, we have found two different dynamics related to attention and executive functions in alpha. Also, we have found that the learning about peer’s behaviour as computed using a RL is mediated by theta oscillatory connectivity. Consequently, combined evidence from Study 2 and Study 3 suggests that both cognitive control and learning computations happening in the social behavioural adaptation of conformity are signalled in theta frequency band. The present work is one of the first studies describing, with credible evidence, that conformity, when this occurs willingly and spontaneously rather than induced, engages different brain activity underlying reward-guided learning, cognitive control, and attention.[spa] La conformidad es el acto de cambiar el comportamiento de uno a favor de ajustarnos a otros seres humanos. Se trata de una adaptación crucial que ocurre cuando la gente coopera, donde uno sacrifica su propia percepción, expectativas o creencias en aras de conseguir una convergencia con la otra persona. El objetivo del presente estudio ha sido tratar de aportar a la comprensión de las estructuras neurofisiológicas que soportan un ajuste social como el de la conformidad. En la primera parte de esta tesis comenzamos hablando de la cooperación y lo profundamente arraigada que está en nuestro comportamiento. Más tarde exploramos diferentes procesos que el cerebro requiere en el ajuste social de la conformidad. Así pues, para involucrarse en esta adaptación social, una persona requiere de un mecanismo de aprendizaje auto-referenciado basado en un modelo predictivo que le ayude a seguir el rastro de los errores de predicción que acompañan a los eventos inesperados. Además, el cerebro usa sus sistemas de control y predicción para codificar diferentes funciones de valor usadas en la selección de acción. El uso de diferentes modelos de aprendizaje en neurociencia, como los algoritmos de aprendizaje por refuerzo (RL), han sido una historia de éxito a la hora de identificar los sistemas de aprendizaje a través del mapeo de la actividad de diferentes regiones del cerebro. Es importante destacar que los paradigmas experimentales que se han usado para estudiar la conformidad no se han basado en entornos de interacción social y que, por lo tanto, sus resultados no pueden usarse para explicar un fenómeno inherentemente social. El objetivo principal de la presente tesis es el estudio de los mecanismos neurofisiológicos que fundamentan el comportamiento de ajuste social de la conformidad y su modulación con la interacción repetida. Para alcanzar este objetivo, primero hemos diseñado una nueva tarea experimental en la que la conformidad aparece de forma espontánea entre dos personas y, además, de forma reiterativa. Este diseño permite exponer tanto los procesos de adquisición del aprendizaje, que requieren de ciclos iterativos, así como otros mecanismos de control cognitivo tales como el procesamiento de la retroalimentación, las tomas de decisiones basadas en procesos valorativos y la atención. El primer estudio nos muestra que la gente que coopera previamente incrementa sus niveles de convergencia y reportan significativamente una experiencia generalmente más satisfactoria en el experimento. Adicionalmente, un modelo de RL nos explica que los participantes tratan de aprender del comportamiento de sus parejas en mayor medida si estos han cooperado previamente. En el segundo estudio, hemos estudiado los potenciales relacionados con eventos (ERP) y el poder de las oscilaciones que sustentan la conformidad. Los estudios de ERP muestran diferentes niveles de implicación cognitiva asociados con diferentes niveles de conformidad. Además, los análisis de tiempo-frecuencia muestran evidencia en theta, alfa y beta relacionados con diferentes funciones como el control cognitivo, la atención, y, también, el procesamiento de la recompensa, apoyando la idea de que la convergencia entre díadas actúa como una recompensa social. Finalmente, en el tercer estudio, exploramos la conectividad oscilatoria intra e inter entre electrodos que se pudieran relacionar con la conducta de convergencia. A propósito de la conectividad oscilatoria coherente intra, hemos hallado dos dinámicas relacionadas con la atención y las funciones ejecutivas en alfa. Asimismo, hemos encontrado que el aprendizaje de la conducta de la pareja computada a través de RL está mediada a través de la conectividad oscilatoria de theta. Consecuentemente, la evidencia combinada entre el estudio 2 y el estudio 3 sugiere que conjuntamente el control cognitivo y las computaciones de aprendizaje que ocurren en la conducta de adaptación social de la conformidad están relacionadas con la actividad de la banda de frecuencia theta. Este trabajo constituye uno de los primeros estudios que describen, con evidencia creíble, que la conformidad, cuando ocurre voluntaria y espontáneamente a diferencia cuando esta es inducida, involucra actividad del cerebro que se fundamenta en el aprendizaje guiado por reforzamiento, el control cognitivo y la atención