Abstract
Functional MRI (fMRI) studies have traditionally relied on intersubject normalization based on global brain morphology, which cannot establish proper functional correspondence between subjects due to substantial intersubject variability in functional organization. Here, we reliably identified a set of discrete, homologous functional regions in individuals to improve intersubject alignment of fMRI data. These functional regions demonstrated marked intersubject variability in size, position, and connectivity. We found that previously reported intersubject variability in functional connectivity maps could be partially explained by variability in size and position of the functional regions. Importantly, individual differences in network topography are associated with individual differences in task-evoked activations, suggesting that these individually specified regions may serve as the “localizer” to improve the alignment of task-fMRI data. We demonstrated that aligning task-fMRI data using the regions derived from resting state fMRI may lead to increased statistical power of task-fMRI analyses. In addition, resting state functional connectivity among these homologous regions is able to capture the idiosyncrasies of subjects and better predict fluid intelligence (gF) than connectivity measures derived from group-level brain atlases. Critically, we showed that not only the connectivity but also the size and position of functional regions are related to human behavior. Collectively, these findings suggest that identifying homologous functional regions across individuals can benefit a wide range of studies in the investigation of connectivity, task activation, and brain-behavior associations.
Highlights
In functional MRI studies, comparing functional characteristics between subjects or groups requires aligning the individual’s data to an “average brain” based on global brain morphology [1]
We developed an approach to reliably identify homologous functional regions in each individual and demonstrated that aligning data based on these homologous functional regions can significantly improve the study of resting state functional connectivity, task-functional MRI (fMRI) activations, and brain-behavior associations
We showed that individual differences in size, position, and connectivity of brain functional regions are dissociable, and each can provide nonredundant information in explaining human behavior
Summary
In functional MRI (fMRI) studies, comparing functional characteristics between subjects or groups requires aligning the individual’s data to an “average brain” based on global brain morphology [1]. Focusing on subject-level analyses, Gordon and colleagues [19] and Braga and colleagues [23] carefully examined a few subjects who were densely sampled and discovered important features of brain networks that were missed in group-based templates but are evident within the individuals. These technical advances in subject-level functional mapping will facilitate the investigation of within-subject functional dynamics [24] that are necessary for personalized medicine [25,26,27] but will benefit traditional group-level functional studies by providing more meaningful landmarks for between-subject comparison. Aligning subjects based on homologous functional regions is expected to improve the specificity of functional signals in the networks being
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