Date of Award

Spring 6-10-2023

Document Type

Thesis (Master's)

Department or Program

Psychological and Brain Sciences

First Advisor

Meghan Meyer

Second Advisor

Thalia Wheatley

Third Advisor

Mark Thornton


BACKGROUND AND AIM: People are remarkably self-focused, choosing to think and talk about themselves at disproportionately high levels. When people are instructed to think about the self in a task, activation occurs in the core subsystem of the default network, in particular the medial prefrontal cortex (MPFC). We hypothesize this tendency to “default back” to the core subsystem and MPFC as soon as we have a mental break sets our self-focus in motion. PROCEDURE: Participants completed a three-phase scanning session. In phase 1, they completed a resting state scan in which they intermittently answered questions about their thoughts. In phase 2, they were told that they were selecting the trials they would think about in a separate task that followed. Here, each trial started with a pre-trial jittered rest, then the trial in which participants chose who (themselves, a designated friend, or Biden) they wanted to think about in a later task. In phase 3, participants completed a self-reflection task. RESULTS: Multi-voxel pattern analysis (MVPA) revealed that spatial patterns in the MPFC during pre-trial rest predict the subsequent choice to think about the self (vs. others) on the next trial with 70% accuracy. Given that the MPFC is a key node in the core default mode network (DMN) subsystem, we next focused on DMN subsystem parcellations and found that the DMN core can predict the subsequent choice to focus on the self (vs. others) more accurately (81% accuracy) than a) other DMN subsystems and b) the whole brain. We named the weighted neural pattern generated by the classification analysis the "pre-self" pattern. We investigated the ability of this pattern to predict self-focus using Instatement Analysis in three ways: predicting self-reports of self-focus during a long rest, predicting the presence of an active self-reflection neural pattern, and predicting Internalizing scores in the Human Connectome Project. CONCLUSIONS: We know from both previous research and this study that people are particularly self-focused. Yet, the basic brain mechanisms that bias us towards self-focus remain unclear. The current results suggest that “defaulting back” to the MPFC and DMN core subsystem nudges us toward this self-focus.

Available for download on Thursday, May 15, 2025