Structural Brain Connectivity Constrains within-a-Day Variability of Direct Functional Connectivity

한글 요약

백질의 구조적 연결이 기능적 연결의 평균 강도를 제약한다는 것은 잘 알려져 있지만, 기능적 연결의 변동성까지 제약하는지는 밝혀지지 않았습니다. 이 연구는 하루 동안 여러 차례 반복 촬영한 휴지기 fMRI에서 피어슨 상관 기반 기능적 연결성, 부분상관 기반 직접 기능적 연결성, 그리고 둘의 차이인 유사 기능적 연결성의 하루 내 변동을 확산텐서영상(DTI) 섬유추적으로 얻은 구조적 연결과 비교했습니다. 구조적 연결은 유사 연결보다 직접 기능적 연결의 변동성을 더 강하게 제약했고, 그 정도는 반구 내 연결과 비대응 반구 간 연결, 리치클럽 구조에서의 피더 및 국소 연결에서 더 컸습니다. 개별 연결은 크게 변동했지만 리치클럽 영역 사이 직접 연결의 다변량 패턴은 시간에 따라 안정적이었습니다. 구조적 연결이 기능적 연결의 세기뿐 아니라 그 시간적 변동과 패턴까지 규정한다는 점을 보여준 결과입니다.

The idea that structural white matter connectivity constrains functional connectivity (interactions among brain regions) has widely been explored in studies of brain networks; studies have mostly focused on the "average" strength of functional connectivity. The question of how structural connectivity constrains the "variability" of functional connectivity remains unresolved. In this study, we investigated the variability of resting state functional connectivity that was acquired every 3 h within a single day from 12 participants (eight time sessions within a 24-h period, 165 scans per session). Three different types of functional connectivity (functional connectivity based on Pearson correlation, direct functional connectivity based on partial correlation, and the pseudo functional connectivity produced by their difference) were estimated from resting state functional magnetic resonance imaging data along with structural connectivity defined using fiber tractography of diffusion tensor imaging. Those types of functional connectivity were evaluated with regard to properties of structural connectivity (fiber streamline counts and lengths) and types of structural connectivity such as intra-/inter-hemispheric edges and topological edge types in the rich club organization. We observed that the structural connectivity constrained the variability of direct functional connectivity more than pseudo-functional connectivity and that the constraints depended strongly on structural connectivity types. The structural constraints were greater for intra-hemispheric and heterologous inter-hemispheric edges than homologous inter-hemispheric edges, and feeder and local edges than rich club edges in the rich club architecture. While each edge was highly variable, the multivariate patterns of edge involvement, especially the direct functional connectivity patterns among the rich club brain regions, showed low variability over time. This study suggests that structural connectivity not only constrains the strength of functional connectivity, but also the within-a-day variability of functional connectivity and connectivity patterns, particularly the direct functional connectivity among brain regions.