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Sheth, Sneha

University of British Columbia

One of the most striking features of human consciousness is its ability to foster an ongoing and seemingly continuous stream of thought. How do mental states unfold over time as the mind moves from one thought to another? The Dynamic Framework of Thought (DFT) has suggested a taxonomy of thought based on the way it moves over time (i.e., degree and type of constraints applied on thought) rather than on features of its content (e.g., task-relatedness). This dissertation explored two kinds of dynamics proposed in the DFT framework – deliberately constrained (i.e., goal-directed) and relatively unconstrained (i.e., spontaneous) thought – using first-person reports through experience sampling and third-person data from fMRI. In the first part, I investigated whether people have introspective access to these two types of thought dynamics. Using experience sampling, across various contexts, I found that the two dynamics were experienced as being phenomenally distinct from each other and shared a moderately negative correlation. Subsequently, I characterized the brain regions and networks involved in these phenomenally distinct transitions between mental states. In this real-time experience sampling paradigm, participants were asked to let their thoughts unfold naturally as they were intermittently probed to rate their thoughts on the degree of free-movement and active-direction while in an fMRI scanner. Results showed that regions in the medio-temporal and core subcomponents of the default network were more engaged when thoughts were freely-moving. Regions in the frontoparietal control network, on the other hand, were more engaged when thoughts were not freely-moving and when deliberately-constrained. These findings suggest that executive regions are more associated with strong constraints on the stream of thought, whereas default network regions are more associated with weak constraints on the stream of thought. This work sheds new light on our current understanding of the relationship between the default network and frontoparietal control network during self-generated thought. Overall, this dissertation represents progress in broadening the use of first-person, introspective accounts in neuroscience to advance our understanding of the stream of thought in the broader context of neurophenomenology.

Text

2023-10-03

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86057

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/