TE-dependent spatial and spectral specificity of functional connectivity

Changwei W Wu, Hong Gu, Qihong Zou, Hanbing Lu, Elliot A Stein, Yihong Yang

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Previous studies suggest that spontaneous fluctuations in the resting-state fMRI (RS-fMRI) signal may reflect fluctuations in transverse relaxation time (T(2)(*)) rather than spin density (S(0)). However, such S(0) and T(2)(*) features have not been well characterized. In this study, spatial and spectral characteristics of functional connectivity on sensorimotor, default-mode, dorsal attention, and primary visual systems were examined using a multiple gradient-echo sequence at 3T. In the spatial domain, we found broad, local correlations at short echo times (TE ≤ 14 ms) due to dominant S(0) contribution, whereas long-range connections mediated by T(2)(*) became explicit at TEs longer than 22 ms. In the frequency domain, compared with the flat spectrum of S(0), spectral power of the T(2)(*)-weighted signal elevated significantly with increasing TE, particularly in the frequency ranges of 0.008-0.023 Hz and 0.037-0.043 Hz. Using the S(0) spectrum as a reference, we propose two indices to measure spectral signal change (SSC) and spectral contrast-to-noise ratio (SCNR), respectively, for quantifying the RS-fMRI signal. These indices demonstrated TE dependency of connectivity-related fluctuation strength, resembling functional contrasts in activation-based fMRI. These findings further confirm that large-scale functional circuit connectivity based on BOLD contrast may be constrained within specific frequency ranges in every brain network, and the spectral features of S(0) and T(2)(*) could be valuable for interpreting and quantifying RS-fMRI data.

Original languageEnglish
Pages (from-to)3075-84
Number of pages10
Issue number4
Publication statusPublished - Feb 15 2012
Externally publishedYes


  • Brain
  • Female
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Physiological Phenomena
  • Sensitivity and Specificity
  • Young Adult
  • Journal Article
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't


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