Browsing by Author "Nummenmaa, Lauri, Prof., University of Turku, Finland"
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- Brain basis of sharing and transmitting representations of social world
School of Science | Doctoral dissertation (article-based)(2018) Smirnov, DmitrySocial communication is a crucial element of human behavior. Every day we resolve conflicts, empathize with our peers, exchange opinions and observe other's behaviors. While the brain basis of these processes has been studied in single individuals, it remains unresolved how such complex patterns of social interaction are parsed in the brains of interacting humans. This thesis addresses the brain basis of social communication in three domains: motor actions, language and emotions. These represent the main channels of human communication, and are tightly linked between each other. We used functional magnetic resonance imaging to collect the data, naturalistic stimulation as an experimental design principle and pseudo-hyperscanning to address the interaction in the experiments. We developed a novel hypeclassification approach, which combined pattern classification with functional realignment of data to investigate the shared neural codes between interacting individuals.In the first study we compared the neural coupling across multiple observers during active simulation versus passive watching of naturalistic boxing match videos by computing the time-varying intersubject phase synchrony of multiple observers' brain activity. We have shown that shared perspective synchronized brain networks involved in action execution and observation. In the second study we adopted a novel hyperclassification approach to investigate shared neural codes between action execution and observation in two individuals. We successfully showed that observed actions can be classified using the model trained on actor's data. The results revealed that action observation and execution share neural information in the brains of two interacting individuals. In the third study we used pseudo-hyperscanning to investigate the neural "coupling" between individuals telling emotional stories, and listeners of these stories. We measured the synchronization of their brain activity time series and revealed that as the experienced emotions became stronger and more similar between speaker and listener, their neural synchronization in attentional, limbic, somatosensory and midline structures increased. The fourth and final study investigated contextual effects on naturalistic speech comprehension. By manipulating context for a narrative, we addressed functional connectivity in the brain of listeners. Results of this study showed increase in functional connectivity in linguistic, attentional and error monitoring brain networks when individuals successfully understood speech in presence of relevant context. These results provide evidence for significant role of intersubject neural synchronization and shared neural codes in social interaction. Such synchronization may provide a window into mind state of another individual and enhance one's ability to understand and predict behavior of others. - Decoding emotions from brain activity and connectivity patterns
School of Science | Doctoral dissertation (article-based)(2018) Saarimäki, HeiniEmotions guide both human and animal behavior providing the means for survival in a constantly changing environment. Different emotions seem to be distinct from each other in several aspects, including physiological changes, bodily sensations, facial expressions, and subjective experience. Whether and how such emotion categories exist at the neural level remains however under debate. The goal of this dissertation was to employ pattern classification methods to investigate the neural underpinnings of different emotion states. Specifically, it was hypothesized that if different emotions have distinct neural bases, we should be able to reliably classify them from brain activity and connectivity patterns. Further, it was hypothesized that the classifier confusions presumably reveal which emotions have similar neural substrates. Multiple emotional states were induced in four studies with altogether 109 participants using emotional movies, mental imagery, and narratives while participants' brain activity was measured with functional magnetic resonance imaging (fMRI). Several approaches to the fMRI data analyses were employed: multivariate pattern classification to distinguish voxel activity and functional connectivity patterns underlying different emotions, representational similarity analysis to compare experienced and neural similarity of different emotions, functional connectivity analysis to reveal emotional modulations in brain connectivity, univariate methods such as general linear model (GLM) to visualize the neural substrates of different emotions, and correlation analyses to compare the relationship of different emotions at different emotion-related components. Results from these studies show that specific emotions can be classified from both voxel activity and functional connectivity patterns. Successful pattern classification of voxel activity across the whole brain shows that different emotions have distinct brain activity patterns that generalize across participants and across emotion induction techniques. Further, emotions that subjectively feel more similar also have more similar neural underpinnings. Functional connectivity is modulated by emotional content and shows distinct patterns for different emotions especially within the default mode network (DMN). DMN regions especially in the cortical midline, together with somatomotor, sensory, and subcortical areas, support most emotions. Finally, distinctness of emotions is related at the level of different components, including facial expressions, bodily sensations, emotional evaluations, subjective experiences, and neural substrates. To conclude, emotions have distinct brain activity and connectivity patterns that encompass large extent of the brain. Emotions can thus be viewed as systemic states that, at a given moment, facilitate and constrain other mental functions. - Maintaining social bonds via touching: A cross-cultural study
School of Science | Doctoral dissertation (article-based)(2018) Suvilehto, Juulia T.Touching is the most intimate way of social interaction and also the first way of communicating between the mother and the infant. In non-human primates social touching is also the primary way of maintaining social relationships. The extant research suggests that social relationships also govern the use of social touch in humans, but the role of social touch in human bonding in different reproductive, affiliative, and kinship-based relationships remains unresolved. This Thesis investigates social touching across different kin-based and affiliative relationships in different cultures. This was done by using Internet-based surveys where participants from Finland, France, Italy, Japan, Russia, and the United Kingdom indicated where they would allow different members of their social network to touch them. Topographical organization of bodily regions triggering sexual arousal in romantic relationships was established in a separate study. Finally, functional Magnetic Resonance Imaging was used to reveal the neural correlates of experiencing and anticipating touch from different individuals. We found that touch is used in relationship-specific manner. The bodily area where touching was allowed was linearly dependent on the emotional bond with the toucher. Moreover, the results indicate that the use of social touch is culturally universal and culture-specific variation is minimal. In romantic relationships, genitals and chest area had the highest potency for eliciting sexual arousal, but partner's touch to practically any bodily area could elicit significant sexual arousal. Finally, neuroimaging data established that relationship-specific information regarding social touch is represented already in the early sensory cortices.These findings highlight the central role of social touch in human relationships. Together with earlier work these results suggest that humans do use social touch to establish and maintain social relationships, both in romantic pair bonds and in the wider social network. - Opioidergic regulation of human affiliative behavior - Evidence from positron emission tomography studies
School of Science | Doctoral dissertation (article-based)(2019) Karjalainen, TomiHumans display a remarkable pattern of affiliative behavior. We talk, laugh, play games, and celebrate various events, such as birthdays. Our social networks are also much larger than those of our evolutionary closest cousins, nonhuman primates. Social life is so important for humans that social problems, such as isolation and loneliness, are detrimental to our mental and somatic health. Sociality is indeed one of the basic human needs, similarly as food, water, and safety. Despite the fundamental role of sociality to humans, the neurobiological mechanisms influencing human affiliative behavior are still poorly understood. Animal models of social behavior suggest that endogenous opioid system–a neurotransmitter system modulating pain and pleasure in all mammals–regulates also affiliative behavior. Proposedly, motivation for social interaction partly arises from decreased opioidergic activity in the brain, and various forms of social behavior increase opioidergic processing. This increase results in pleasant affective states and facilitates inter-personal bonding between the interacting individuals. While the results from animal studies are mostly consistent with this model, it is still unknown whether and how the opioid system regulates affiliative behavior of humans. The aim of this Thesis was to characterize the role of the opioid system in human affiliative behavior using neuroimaging with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The Thesis focuses on individual differences in self-reports of approach–avoidance behavior and affective responses measured with fMRI. The Thesis also tested if laughing induces release of endogenous opioids. [11C]carfentanil, a selective µ-opioid receptor (MOR) agonist tracer, was used to quantify cerebral MOR availability in all four studies. The first study showed that cerebral MOR availability is positively associated with approach motivation. This finding is in line with data from animal studies, suggesting that baseline opioidergic activity influences how actively humans seek reward. The second study showed that laughing with friends induces endogenous opioid release, consistent with the hypothesis that laughing facilitates interpersonal bonding in humans via opioidergic mechanisms. The third and fourth studies showed that individuals with high MOR availability, particularly in rostral anterior cingulate cortex and insular cortex, have blunted hemodynamic responses to painful and otherwise arousing movie scenes. These findings are consistent with the opioid system's role in regulation of pain and anxiety, suggesting that inter-individual differences in MOR availability may explain why some humans often find themselves highly aroused, while others may be perfectly calm in the same situations. In sum, results of the Thesis support the involvement of opioids in transmitting not only signals related to pain and pleasure but also to sociality in humans.