Functional Connectivity Density Mapping

National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 05/2010; 107(21):9885-90. DOI: 10.1073/pnas.1001414107
Source: PubMed


Brain networks with energy-efficient hubs might support the high cognitive performance of humans and a better understanding of their organization is likely of relevance for studying not only brain development and plasticity but also neuropsychiatric disorders. However, the distribution of hubs in the human brain is largely unknown due to the high computational demands of comprehensive analytical methods. Here we propose a 10(3) times faster method to map the distribution of the local functional connectivity density (lFCD) in the human brain. The robustness of this method was tested in 979 subjects from a large repository of MRI time series collected in resting conditions. Consistently across research sites, a region located in the posterior cingulate/ventral precuneus (BA 23/31) was the area with the highest lFCD, which suggest that this is the most prominent functional hub in the brain. In addition, regions located in the inferior parietal cortex (BA 18) and cuneus (BA 18) had high lFCD. The variability of this pattern across subjects was <36% and within subjects was 12%. The power scaling of the lFCD was consistent across research centers, suggesting that that brain networks have a "scale-free" organization.


Available from: Dardo Tomasi, Sep 09, 2015
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    • "To avoid a priori selection of specific regions of interest (ROIs), we used a data-driven approach to map the wFCS at the voxel level and identified the regions that showed aberrant FCS in the TS patients. Similar approaches have been applied to study mental dysfunction (Gotts et al. 2012; Wang et al. 2014) and to search for connectivity hubs within the brain (Buckner et al. 2009; Tomasi and Volkow 2010). A set of regions including the bilateral IPS, ANG, cuneus, and cerebellum showed reduced wFCS in the TS patients compared with the HCs. "
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    ABSTRACT: Turner syndrome (TS), a disorder caused by the congenital absence of one of the 2 X chromosomes in female humans, provides a valuable human "knockout model" for studying the functions of the X chromosome. At present, it remains unknown whether and how the loss of the X chromosome influences intrinsic functional connectivity (FC), a fundamental phenotype of the human brain. To address this, we performed resting-state functional magnetic resonance imaging and specific cognitive assessments on 22 TS patients and 17 age-matched control girls. A novel data-driven approach was applied to identify the disrupted patterns of intrinsic FC in TS. The TS girls exhibited significantly reduced whole-brain FC strength within the bilateral postcentral gyrus/intraparietal sulcus, angular gyrus, and cuneus and the right cerebellum. Furthermore, a specific functional subnetwork was identified in which the intrinsic FC between nodes was mostly reduced in TS patients. Particularly, this subnetwork is composed of 3 functional modules, and the disruption of intrinsic FC within one of these modules was associated with the deficits of TS patients in math-related cognition. Taken together, these findings provide novel insight into how the X chromosome affects the human brain and cognition, and emphasize an important role of X-linked genes in intrinsic neural coupling.
    Cerebral Cortex 10/2015; DOI:10.1093/cercor/bhv240 · 8.67 Impact Factor
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    • "This idea is supported by a growing number of EEG/MEG/ECOG studies (He et al. 2008; Nir et al. 2008) that have identified different frequency-specific correlates of fMRI-RSNs, as well as mechanisms of their interaction (de Pasquale et al. 2010; Brookes, Woolrich, et al. 2011; de Pasquale et al. 2012; Hipp et al. 2012; Betti et al. 2013; Marzetti et al. 2013). Electrophysiological RSNs therefore provide a model to study functional segregation and integration in the brain (Bullmore and Sporns 2009; Tomasi and Volkow 2010). One MEG correlate of fMRI RSNs is the coupled fluctuation of BLP in alpha/beta frequency band between different RSN nodes (de Pasquale et al. 2010; Brookes, Woolrich, et al. 2011; de Pasquale et al. 2012; Hipp et al. 2012; Betti et al. 2013). "
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    ABSTRACT: Spontaneous brain activity is spatially and temporally organized in the absence of any stimulation or task in networks of cortical and subcortical regions that appear largely segregated when imaged at slow temporal resolution with functional magnetic resonance imaging (fMRI). When imaged at high temporal resolution with magneto-encephalography (MEG), these resting-state networks (RSNs) show correlated fluctuations of band-limited power in the beta frequency band (14–25 Hz) that alternate between epochs of strong and weak internal coupling. This study presents 2 novel findings on the fundamental issue of how different brain regions or networks interact in the resting state. First, we demonstrate the existence of multiple dynamic hubs that allow for across-network coupling. Second, dynamic network coupling and related variations in hub centrality correspond to increased global efficiency. These findings suggest that the dynamic organization of across-network interactions represents a property of the brain aimed at optimizing the efficiency of communication between distinct functional domains (memory, sensory-attention, motor). They also support the hypothesis of a dynamic core network model in which a set of network hubs alternating over time ensure efficient global communication in the whole brain.
    Cerebral Cortex 09/2015; DOI:10.1093/cercor/bhv185 · 8.67 Impact Factor
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    • "The predominance of lFCD in occipito - parietal cortices at the group level is consistent with findings from our previous studies at lower spatiotemporal resolution ( Tomasi and Volkow 2010 , 2011b ) . The strength of the lFCD hubs in cuneus and primary vis - ual cortex was 10 times or higher than the whole brain average . "
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    ABSTRACT: Brain regions with high connectivity have high metabolic cost and their disruption is associated with neuropsychiatric disorders. Prior neuroimaging studies have identified at the group-level local functional connectivity density ( L: FCD) hubs, network nodes with high degree of connectivity with neighboring regions, in occipito-parietal cortices. However, the individual patterns and the precision for the location of the hubs were limited by the restricted spatiotemporal resolution of the magnetic resonance imaging (MRI) measures collected at rest. In this work, we show that MRI datasets with higher spatiotemporal resolution (2-mm isotropic; 0.72 s), collected under the Human Connectome Project (HCP), provide a significantly higher precision for hub localization and for the first time reveal L: FCD patterns with gray matter (GM) specificity >96% and sensitivity >75%. High temporal resolution allowed effective 0.01-0.08 Hz band-pass filtering, significantly reducing spurious L: FCD effects in white matter. These high spatiotemporal resolution L: FCD measures had high reliability [intraclass correlation, ICC(3,1) > 0.6] but lower reproducibility (>67%) than the low spatiotemporal resolution equivalents. GM sensitivity and specificity benchmarks showed the robustness of L: FCD to changes in model parameter and preprocessing steps. Mapping individual's brain hubs with high sensitivity, specificity, and reproducibility supports the use of L: FCD as a biomarker for clinical applications in neuropsychiatric disorders. Published by Oxford University Press 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.
    Cerebral Cortex 07/2015; DOI:10.1093/cercor/bhv171 · 8.67 Impact Factor
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