Resting-state functional connectivity in animal models: Modulations by exsanguination

Bharat B. Biswal, Sridhar S. Kannurpatti

Research output: Chapter in Book/Report/Conference proceedingChapter

25 Scopus citations


We studied the spatiotemporal characteristics of the resting state low frequency fluctuations in functional MRI (fMRI), blood oxygenation level dependent (BOLD) signal in isoflurane-anesthetized rats. fMRI-BOLD measurements at 9.4 Tesla were made during normal and exsanguinated condition previously known to alter cerebral blood flow (CBF) fluctuations in anesthetized rats. fMRI signal time series were low-pass filtered and studied by spectral analysis. During normal conditions, baseline mean arterial pressure (MAP) was 110 ± 10 mmHg and low-frequency fluctuations in BOLD signal were observed in the frequency range of 0.01-0.125 Hz. Following blood withdrawal (exsanguination), MAP decreased to 68 ± 7 mmHg, resulting in an increase in the amplitude of the low-frequency fluctuations in BOLD signal time series and an increase in power at several frequencies between 0.01 and 0.125 Hz. Spatially, the BOLD fluctuations were confined to the cortex and thalamus spanning both hemispheres with sparse presence in the caudate putamen and hippocampus during both normal and exsanguinated states. Spatial distribution of the low frequency fluctuations in BOLD signal, from cross correlation analysis, indicate substantial inter-hemispheric synchrony similar to that observed in the conscious human brain. The behavior of the resting state BOLD signal fluctuations similar to CBF fluctuations during exsanguination indicates a myogenic dependence. Also, a high inter-hemispheric synchrony combined with different phase characteristics of the low frequency BOLD fluctuations particularly in the hippocampus relative to the cortex emphasizes distinct functional networks.

Original languageEnglish (US)
Title of host publicationDynamic Brain Imaging
Subtitle of host publicationMulti-Modal Methods and In Vivo Applications
PublisherHumana Press
Number of pages20
ISBN (Print)9781934115749
StatePublished - 2009
Externally publishedYes

Publication series

NameMethods in Molecular Biology
ISSN (Print)1064-3745

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Genetics


  • BOLD fluctuation
  • Brain
  • CBF
  • Isoflurane
  • Rat
  • Resting state connectivity
  • fMRI


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