Effect of Fixed-Density Thresholding on Structural Brain Networks: A Demonstration in Cerebral Small Vessel Disease
Utrecht VCI Study Group
(2020) Brain Connectivity, volume 10, issue 3, pp. 121 - 133
(Article)
Abstract
A popular solution to control for edge density variability in structural brain network analysis is to threshold the networks to a fixed density across all subjects. However, it remains unclear how this type of thresholding affects the basic network architecture in terms of edge weights, hub location, and hub connectivity
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and, especially, how it affects the sensitivity to detect disease-related abnormalities. We investigated these two questions in a cohort of patients with cerebral small vessel disease and age-matched controls. Brain networks were reconstructed from diffusion magnetic resonance imaging data using deterministic fiber tractography. Networks were thresholded to a fixed density by removing edges with the lowest number of streamlines. We compared edge length (mm), fractional anisotropy (FA), proportion of hub connections, and hub location between the unthresholded and the thresholded networks of each subject. Moreover, we compared weighted graph measures of global and local connectivity obtained from the (un)thresholded networks between patients and controls. We performed these analyses over a range of densities (2-20%). Results indicate that fixed-density thresholding disproportionally removes edges composed of long streamlines, but is independent of FA. The edges removed were not preferentially connected to hub or nonhub nodes. Over half of the original hubs were reproducible when networks were thresholded to a density ≥10%. Furthermore, the between-group differences in graph measures observed in the unthresholded network remained present after thresholding, irrespective of the chosen density. We therefore conclude that moderate fixed-density thresholds can successfully be applied to control for the effects of density in structural brain network analysis.
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Keywords: brain connectivity, cerebral small vessel disease, diffusion tensor imaging, network density, network thresholding, General Neuroscience
ISSN: 2158-0014
Publisher: Mary Ann Liebert Inc.
Note: Funding Information: This work was supported by ZonMw, The Netherlands Organisation for Health Research and Development (Vidi Grant 91711384 and Vici Grant 91816616 to Geert Jan Biessels). Yael D. Reijmer receives funding from Alzheimer Nederland and ZonMw/Deltaplan Dementie (Grant #733050503) and a Young Talent Fellowship from the Brain Center Rudolf Magnus, University Medical Center Utrecht. Jil Meier is funded by a Weston Brain Institute Rapid Response grant and by the ALS Foundation Netherlands. The research of Alexander Leemans is supported by VIDI grant 639.072.411 from the Netherlands Organization for Scientific Research (NWO). Funding Information: This work was supported by ZonMw, The Netherlands Organisation for Health Research and Development (Vidi Grant 91711384 and Vici Grant 91816616 to Geert Jan Biessels). Yael D. Reijmer receives funding from Alzheimer Nederland and ZonMw/Deltaplan Dementie (Grant #733050503) and a Young Talent Fellowship from the Brain Center Rudolf Magnus, University Medical Center Utrecht. Jil Meier is funded by a Weston Brain Institute Rapid Response grant and by the ALS Foundation Netherlands. The research of Alexander Leemans is supported by VIDI grant 639.072.411 from the Netherlands Organization for Scientific Research (NWO). Members of the Utrecht Vascular Cognitive Impairment (VCI) study group involved in this study (in alphabetical order by department): University Medical Center Utrecht, The Netherlands, Department of Neurology: E. van den Berg, J.M. Biesbroek, G.J. Biessels, M. Brundel, W.H. Bouvy, L.G. Exalto, C.J.M. Frijns, O. Groeneveld, S.M. Heringa, N. Kalsbeek, L.J. Kappelle, Y.D. Reijmer, J. Verwer; Department of Radiology/Image Sciences Institute: J. de Bresser, H.J. Kuijf, A. Leemans, P.R. Luijten, M.A. Viergever, K.L. Vincken, J.J.M. Zwanenburg; Department of Geriatrics: H.L. Koek; Hospital Diakonessenhuis Zeist, The Netherlands: M. Hamaker, R. Faaij, M. Pleizier, E. Vriens. Publisher Copyright: © Copyright 2020, Mary Ann Liebert, Inc., publishers 2020.
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