PRAGMA: Interactively Constructing Functional Brain Parcellations

TL;DR

PRAGMA is an interactive visualization tool that enables neuroimaging experts to create individualized brain parcellations by leveraging hierarchical clustering and linked views, enhancing understanding of functional brain networks.

Contribution

This work introduces PRAGMA, a novel interactive method for deriving scan-specific brain parcellations, addressing limitations of population-level atlases.

Findings

PRAGMA effectively supports expert-driven, individualized brain parcellations.

User study shows PRAGMA enhances exploration of functional brain networks.

Experts found PRAGMA useful for understanding state-specific brain organization.

Abstract

A prominent goal of neuroimaging studies is mapping the human brain, in order to identify and delineate functionally-meaningful regions and elucidate their roles in cognitive behaviors. These brain regions are typically represented by atlases that capture general trends over large populations. Despite being indispensable to neuroimaging experts, population-level atlases do not capture individual differences in functional organization. In this work, we present an interactive visualization method, PRAGMA, that allows domain experts to derive scan-specific parcellations from established atlases. PRAGMA features a user-driven, hierarchical clustering scheme for defining temporally correlated parcels in varying granularity. The visualization design supports the user in making decisions on how to perform clustering, namely when to expand, collapse, or merge parcels. This is accomplished through a set of linked and coordinated views for understanding the user's current hierarchy, assessing intra-cluster variation, and relating parcellations to an established atlas. We assess the effectiveness of PRAGMA through a user study with four neuroimaging domain experts, where our results show that PRAGMA shows the potential to enable exploration of individualized and state-specific brain parcellations and to offer interesting insights into functional brain networks.