Fuzzy approximate entropy analysis of resting state fMRI signal complexity across the adult life span

Moses O Sokunbi* (Corresponding Author), George G Cameron, Trevor S Ahearn, Alison D Murray, Roger T Staff

*Corresponding author for this work

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In this study, we present a method for measuring functional magnetic resonance imaging (fMRI) signal complexity using fuzzy approximate entropy (fApEn) and compare it with the established sample entropy (SampEn). Here we use resting state fMRI dataset of 86 healthy adults (41 males) with age ranging from 19 to 85 years. We expect the complexity of the resting state fMRI signals measured to be consistent with the Goldberger/Lipsitz model for robustness where healthier (younger) and more robust systems exhibit more complexity in their physiological output and system complexity decrease with age. The mean whole brain fApEn demonstrated significant negative correlation (r = −0.472, p<0.001) with age. In comparison, SampEn produced a non-significant negative correlation (r = −0.099, p = 0.367). fApEn also demonstrated a significant (p < 0.05) negative correlation with age regionally (frontal, parietal, limbic, temporal and cerebellum parietal lobes). There was no significant correlation regionally between the SampEn maps and age. These results support the Goldberger/Lipsitz model for robustness and have shown that fApEn is potentially a sensitive new method for the complexity analysis of fMRI data.
Original languageEnglish
Pages (from-to)1082-1090
Number of pages9
JournalMedical Engineering & Physics
Issue number11
Early online date21 Oct 2015
Publication statusPublished - Nov 2015

Bibliographical note

The authors would like to acknowledge the work of the International Consortium for Brain Mapping (ICBM) fMRI community in creating the resting state database and making it publicly available within the framework of the 1000 Functional Connectomes project (https://www.nitrc.org/projects/fcon_1000/). M.O. Sokunbi was supported by an MRC grant G1100629.


  • ageing
  • blood oxygen level dependent (BOLD)
  • complexity
  • fuzzy approximate entropy (fApEn)
  • resting state-functional magnetic resonance imaging (rs-fMRI)
  • sample entropy (SampEn)


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