The Organization of Local and Distant Functional Connectivity in the Human Brain

Abstract

Information processing in the human brain arises from both interactions between adjacent areas and from distant projections that form distributed brain systems. Here we map interactions across different spatial scales by estimating the degree of intrinsic functional connectivity for the local (≤14 mm) neighborhood directly surrounding brain regions as contrasted with distant (>14 mm) interactions. The balance between local and distant functional interactions measured at rest forms a map that separates sensorimotor cortices from heteromodal association areas and further identifies regions that possess both high local and distant cortical-cortical interactions. Map estimates of network measures demonstrate that high local connectivity is most often associated with a high clustering coefficient, long path length, and low physical cost. Task performance changed the balance between local and distant functional coupling in a subset of regions, particularly, increasing local functional coupling in regions engaged by the task. The observed properties suggest that the brain has evolved a balance that optimizes information-processing efficiency across different classes of specialized areas as well as mechanisms to modulate coupling in support of dynamically changing processing demands. We discuss the implications of these observations and applications of the present method for exploring normal and atypical brain function.

Coupling of functional connectivity and regional cerebral blood flow reveals a physiological basis for network hubs of the human brain

“…Stronger FCS-rCBF correlation was found in long-range connectivity in the current study, suggesting that brain hubs with abundant long-range connections couple more closely with blood/energy supply to facilitate their greater participation in neural processes (16). High short-range connectivity was observed in mPFC, lPFC, and primary sensorimotor and visual cortices, which corresponds well with a previous study (18). However, the spatial distribution of short-range hubs showed a relative lower correlation with the rCBF map, probably due to the mismatch between short-range FCS and rCBF in the primary sensory and motor areas.…”

“…Disparate spatial patterns of the number of short-versus long-range functional connections have been reported previously (18), suggesting disproportionate metabolic demands of the two measures. In the present study, brain regions with high long-range FCS were mainly located in association cortical areas including mPFC/lPFC, paralimbic regions of PCC/PCu, and temporal and parietal cortices, showing a high spatial overlap with the rCBF map.…”

“…Therefore, the first goal of this study is to investigate whether intrinsic functional network connectivity is closely related to rCBF in resting human brains. If so, given that both functional network connectivity (7,18) and rCBF (19,20) undergo changes in response to varying cognitive tasks, the second goal is to examine whether this connectivity-rCBF relationship is preserved during a working-memory task and modulated by changes in cognitive task load.…”

Synchronization, non-linear dynamics and low-frequency fluctuations: Analogy between spontaneous brain activity and networked single-transistor chaotic oscillators

“…While in this work geodesic mapping was not performed, node degree of short-and long-range connectivity is significantly coupled across cortical regions; this incidentally also allays concerns over the impact of short-range correlation introduced by spatial Gaussian smoothing of the time-series. 87 Second, only one spatiotemporal window (the one accessible to functional MRI) was considered, and it is necessary to determine whether the observed relationship also holds at finer temporal resolution (1 ms vs. 1 s scale) and on the microscopic and mesoscopic levels. This will help clarify if the observed relationships are generalizable rather than "epiphenomena" of specific experimental settings.…”

A review of functional magnetic resonance imaging for Brainnetome

“…For example, some studies have reported consistent components with potential functional relevance, consisting of regions known to be involved in motor, visual, and auditory processing, memory, executive functioning, and the so-called default-mode network [49] . In addition, some studies have explored the spatially-distributed patterns of connectivity, such as regional homogeneity [50] and the degree/density of local and distant connectivity [51,52] . including scale scores [53,54] , illness duration [44,55] and genotypic variations [35,56] .…”