Functional connectivity in blood oxygenation level‐dependent and cerebral blood volume‐weighted resting state functional magnetic resonance imaging in the rat brain

Purpose:

To directly compare functional connectivity and spatiotemporal dynamics acquired with blood oxygenation level‐dependent (BOLD) and cerebral blood volume (CBV)‐weighted functional magnetic resonance imaging (fMRI) in anesthetized rats.

Materials and Methods:

A series of BOLD images were acquired in 10 rats followed by CBV‐weighted images created by injection of ultrasmall iron oxide particles. Functional connectivity, spectral information, and spatiotemporal dynamics were compared for the BOLD and CBV‐weighted resting state scans.

Results:

BOLD scans exhibited higher cross‐correlation values compared to CBV‐weighted scans, but the spatial patterns of correlation were similar. The BOLD spectrum contains power evenly distributed throughout the low‐frequency range while the CBV power spectrum exhibited a high power peak localized to ≈0.2 Hz. Both BOLD and CBV resting state scans showed similar propagating waves of activity along the cortex from the SII toward MI; however, these waves were detected more often in BOLD scans than in CBV scans.

Conclusion:

While the power spectrum of the CBV signal is different from that of the BOLD signal, both connectivity maps and spatiotemporal dynamics are similar for the two modalities. Further experiments should address the relationship between spontaneous neural activity, local changes in metabolism, and hemodynamic fluctuations to elucidate the origins of the BOLD and CBV signals. J. Magn. Reson. Imaging 2010;32:584–592. © 2010 Wiley‐Liss, Inc.