ECE MS Thesis Defense: Ashutosh Singh

MS Thesis Defense: Variation is the Norm: Brain State Dynamics Evoked By Emotional Video Clips

Ashutosh Singh

Location: Zoom Link

Abstract: Past affective neuroscience studies have attempted to identify a “biomarker” or consistent pattern of brain activity (as measured externally using, for instance, fMRI) to indicate the presence of a single pre-defined category of emotion (e.g., fear) that remains consistent throughout all instances of that category for an individual across contexts and even across individuals. In this thesis, we investigated variation rather than consistency during emotional experiences. Using fMRI data acquired while individuals watched affect-invoking video clips that have been normed for their evoked emotion categories in prior population studies. Towards this end, we developed a probabilistic model of the temporal dynamics associated with the hypothetical affect-related brain states, fitted to the measured brain activity of the participants. We characterized brain states traversed while individuals watched these clips as distinct state occupancy periods between state transitions, inferred by blood oxygen level-dependent (BOLD) signal patterns captured in fMRI measurements. We found substantial variability in the state occupancy probability distributions across individuals watching the same video, hence supporting the hypothesis that when it comes to the brain correlates of emotional experience, variation may indeed be the norm. Studying the mean activation pattern associated with each state, as well as covariance (in the Gaussian conditional measurement model we assumed), we further improve our understanding of the variability between instances of these brain states. Additionally, we analyzed the presence of potential clusters of brain state trajectories among participants who showed less divergence in their response to each of these videos and checked for their consistency throughout all the video clips.