# Fusion of Multi-Task fMRI Data: Guided Solutions for IVA and Transposed IVA

## TL;DR

This paper introduces new methods for analyzing multi-task fMRI data using IVA and tIVA, showing how these approaches improve the understanding of brain networks and behavioral effects.

## Contribution

The novel contribution is the successful application of constrained IVA and tIVA to multi-task fMRI data, enhancing interpretability and analysis of brain networks.

## Key findings

- Constrained IVA identifies distinct brain networks linked to specific tasks.
- Using sMRI priors improves detection of group differences in task-related networks.
- Constrained tIVA allows targeted analysis of behavioral effects on brain networks.

## Abstract

Independent vector analysis (IVA) has emerged as a powerful tool for fusing and analyzing functional magnetic resonance imaging (fMRI) data. Applying IVA to multi-task fMRI data enhances analytical power by capturing the relationships across different tasks in order to discover their underlying multivariate relationship to one another. Incorporation of prior information into IVA enhances the separability and interpretability of estimated components. In this paper, we demonstrate successful fusion of multi-task fMRI feature data under two settings: constrained IVA and constrained transposed IVA (tIVA). We show that using these methods for fusing multi-task fMRI feature data offers novel ways to improve the quality and interpretability of the analysis. While constrained IVA extracts components linked to distinct brain networks, tIVA reverses the roles of spatial components and subject profiles, enabling flexible analysis of behavioral effects. We apply both methods to a multi-task fMRI dataset of 247 subjects. We demonstrate that for task-based fMRI, structural MRI (sMRI) references provide a better match for task data than resting-state fMRI (rs-fMRI) references, and using sMRI priors improves identification of group differences in task-related networks, such as the sensory-motor network during the Auditory Oddball (AOD) task. Additionally, constrained tIVA allows for targeted investigation of the effects of behavioral variables by applying them individually during the analysis. For instance, by using the letter number sequence subtest, a measure of working memory, as a behavioral constraint in tIVA, we observed significant group differences in the auditory and sensory-motor networks during the AOD task. Results show that the use of two constrained approaches, guided by well-aligned structural and behavioral references, enables a more comprehensive analysis of underlying brain function as modulated by task.