Graph coarse-graining reveals differences in the module-level structure of functional brain networks

Rainer Kujala*, Enrico Glerean, Raj Kumar Pan, Iiro P. Jääskeläinen, Mikko Sams, Jari Saramäki

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)


Networks have become a standard tool for analyzing functional magnetic resonance imaging (fMRI) data. In this approach, brain areas and their functional connections are mapped to the nodes and links of a network. Even though this mapping reduces the complexity of the underlying data, it remains challenging to understand the structure of the resulting networks due to the large number of nodes and links. One solution is to partition networks into modules and then investigate the modules' composition and relationship with brain functioning. While this approach works well for single networks, understanding differences between two networks by comparing their partitions is difficult and alternative approaches are thus necessary. To this end, we present a coarse-graining framework that uses a single set of data-driven modules as a frame of reference, enabling one to zoom out from the node- and link-level details. As a result, differences in the module-level connectivity can be understood in a transparent, statistically verifiable manner. We demonstrate the feasibility of the method by applying it to networks constructed from fMRI data recorded from 13 healthy subjects during rest and movie viewing. While independently partitioning the rest and movie networks is shown to yield little insight, the coarse-graining framework enables one to pinpoint differences in the module-level structure, such as the increased number of intra-module links within the visual cortex during movie viewing. In addition to quantifying differences due to external stimuli, the approach could also be applied in clinical settings, such as comparing patients with healthy controls.

Original languageEnglish
Pages (from-to)2673-2684
Number of pages12
JournalEuropean Journal of Neuroscience
Issue number9
Publication statusPublished - 1 Nov 2016
MoE publication typeA1 Journal article-refereed


  • Community detection
  • Functional connectivity
  • Functional magnetic resonance imaging
  • Modularity


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