Brain Mechanisms Underlying Perception of Naturalistic Social Events

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto. fi Author Juha Lahnakoski Name of the doctoral dissertation Brain Mechanisms Underlying Perception of Naturalistic Social Events Publisher School of Science Unit Department of Biomedical Engineering and Computational Science Series Aalto University publication series DOCTORAL DISSERTATIONS 183/2014 Field of research Cognitive neuroscience Manuscript submitted 13 August 2014 Date of the defence 16 January 2015 Permission to publish granted (date) 30 September 2014 Language English Monograph Article dissertation (summary + original articles) Abstract Understanding the brain basis of the wide variety of skills needed to seamlessly interact with other people in the social world is one of the most important goals of social cognitive neuroscience. However, it has remained unclear how the elementary processes of social interaction that have been studied so far generalize to complex naturalistic settings where multiple social cues have to be dynamically tracked at the same time. The studies presented here employ movies to depict real-life-like social interactions and map the brain systems that participate in the perception of different aspects of the stimuli, particularly focusing on their social signals. Brain activity during viewing of the movies was recorded with functional magnetic resonance imaging. Additionally, the eye gaze of the subjects was recorded and behavioral measures were acquired in a subset of the experiments. Subjects' viewing patterns and interpretation of the movie were manipulated in one of the studies by asking the subjects to adopt two different perspectives. The brain activity was analyzed by multiple methods: parametric models of stimulus contents, inter-subject correlations of brain activity, independent component analysis, and network analysis. First study compared methods for analyzing both stimulus-related activity and covariation of networks of brain regions during naturalistic conditions to find networks responding to speech, sound, motion categories and low-level visual information. Second study elucidated the organization of the brain regions participating in processing several types of social contents. The results highlight the role of the posterior superior temporal sulcus as a key structure potentially integrating multiple types of social information. Finally, the third study provides first direct experimental evidence for the hypothesis that shared brain activity across individuals reflects shared understanding of the external world. Consistency of the findings demonstrate the feasibility of studying brain responses to simple stimulus features, social movie content as well as high-level perspective taking tasks during very rich naturalistic audiovisual stimulus conditions.Understanding the brain basis of the wide variety of skills needed to seamlessly interact with other people in the social world is one of the most important goals of social cognitive neuroscience. However, it has remained unclear how the elementary processes of social interaction that have been studied so far generalize to complex naturalistic settings where multiple social cues have to be dynamically tracked at the same time. The studies presented here employ movies to depict real-life-like social interactions and map the brain systems that participate in the perception of different aspects of the stimuli, particularly focusing on their social signals. Brain activity during viewing of the movies was recorded with functional magnetic resonance imaging. Additionally, the eye gaze of the subjects was recorded and behavioral measures were acquired in a subset of the experiments. Subjects' viewing patterns and interpretation of the movie were manipulated in one of the studies by asking the subjects to adopt two different perspectives. The brain activity was analyzed by multiple methods: parametric models of stimulus contents, inter-subject correlations of brain activity, independent component analysis, and network analysis. First study compared methods for analyzing both stimulus-related activity and covariation of networks of brain regions during naturalistic conditions to find networks responding to speech, sound, motion categories and low-level visual information. Second study elucidated the organization of the brain regions participating in processing several types of social contents. The results highlight the role of the posterior superior temporal sulcus as a key structure potentially integrating multiple types of social information. Finally, the third study provides first direct experimental evidence for the hypothesis that shared brain activity across individuals reflects shared understanding of the external world. Consistency of the findings demonstrate the feasibility of studying brain responses to simple stimulus features, social movie content as well as high-level perspective taking tasks during very rich naturalistic audiovisual stimulus conditions.