Parcellating cortical functional networks in individuals

Abstract

The capacity to identify the unique functional architecture of an individual’s brain is a critical step towards personalized medicine and understanding the neural basis of variations in human cognition and behavior. Here, we developed a novel cortical parcellation approach to accurately map functional organization at the individual level using resting-state fMRI. A population-based functional atlas and a map of inter-individual variability were employed to guide the iterative search for functional networks in individual subjects. Functional networks mapped by this approach were highly reproducible within subjects and effectively captured the variability across subjects, including individual differences in brain lateralization. The algorithm performed well across different subject populations and data types including task fMRI data. The approach was then validated by invasive cortical stimulation mapping in surgical patients, suggesting great potential for use in clinical applications.

Long-range projections coordinate distributed brain-wide neural activity with a specific spatiotemporal profile

“…At present, functional connectivity is defined as the temporal coherence of neural activity patterns among spatially segregated brain regions at low and ultra-low frequencies, which has been most widely measured by rsfMRI (5)(6)(7)(8)(9)(10)(11)(12). However, interpretation of functional connectivity studies remains challenging because functional coupling changes dynamically.…”

“…This integrative architecture dictates the underlying principles of how brain-wide neural connectivity supports and organizes sensory, behavioral, and cognitive processes (3). Recent advances in structural (2,4) and functional connectivity (5)(6)(7)(8)(9)(10)(11)(12) mapping, as well as neural circuit modulatory tools, such as optogenetics (13,14), permit detailed, high-resolution neural examinations at unprecedented scales. In particular, functional connectivity mapping using resting-state functional MRI (rsfMRI) produces noninvasive visualization of slow and spontaneous hemodynamic fluctuations in humans (5-9) and animals (10)(11)(12).…”

Inferring Individual-Level Variations in the Functional Parcellation of the Cerebral Cortex

“…In the Wang's method [9], spurious variations were reduced using a group averaged parcellation template. This template did not only include the initialization assignment, but also the pre-estimated inter-subject variability in functional connectivity and temporal signal-to-noise ratio (SNR) [9].…”

“…This cortical functional parcellation varies substantially across different individuals [7][8][9]. Nevertheless, approaches to defining these are still under development or in early validation stages; neuroimaging studies of brain networks typically still address parcellation at a group level [10], ignoring explicit representations of individual-level variations in parcellations.…”

“…Gordon et al developed a procedure to match each cortical vertex in each subject to a group averaged parcellation template using the similarity of connectivity profiles [8]. Wang et al designed another group template matching method based on the similarity of BOLD signals, in which the template is updated with each iteration [9]. Prior knowledge increases the robustness of the parcellation methods, but further research regarding methods for adapting the strength of the prior constraints is needed, especially in application intended to discover variations for which correspondences to a normative template are uncertain or themselves the focus of study.…”