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Functional MRI impulse response for BOLD and CBV contrast in rat somatosensory cortex
Author(s) -
Silva Afonso C.,
Koretsky Alan P.,
Duyn Jeff H.
Publication year - 2007
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21246
Subject(s) - full width at half maximum , somatosensory system , nuclear magnetic resonance , cerebral blood volume , nuclear medicine , functional magnetic resonance imaging , haemodynamic response , contrast (vision) , chemistry , temporal resolution , neuroscience , magnetic resonance imaging , physics , medicine , optics , radiology , psychology , heart rate , blood pressure
The contrast mechanism in functional MRI (fMRI) results from several vascular processes with different time scales, thus establishing a finite temporal resolution to fMRI experiments. In this work we measured the blood oxygen level‐dependent (BOLD) and iron‐oxide‐derived cerebral blood volume (CBV) impulse response (IR) in a rat model of somatosensory brain activation at 11.7T. A binary m‐sequence probe method was used to obtain high‐sensitivity single‐pixel estimates of the IR, from which two parameters—the full width at half maximum (FWHM) and the time to peak (TTP)—were determined as indices of the temporal resolution of the hemodynamic response (HDR). The results ( N = 11) show that the CBV IR ( N = 5, subset) is significantly narrower (FWHM = 1.37 ± 0.11 s), and peaks earlier (TTP = 1.65 ± 0.15 s) than the BOLD IR ( N = 11, FWHM = 1.92 ± 0.22 s and TTP = 2.18 ± 0.14 s, respectively). These findings indicate that neurovascular control mechanisms have a temporal resolution better than 1.5 s FWHM, and point to a substantial contribution to BOLD of the dispersive transit of oxygenated hemoglobin across the rat vasculature, bringing important implications for the ultimately attainable temporal resolution of fMRI. Magn Reson Med 57:1110–1118, 2007. © 2007 Wiley‐Liss, Inc.