Spatial correlations of laminar BOLD and CBV responses to rat whisker stimulation with neuronal activity localized by Fos expression.
The spatial relationship between a measured fMRI signal and its underlying neuronal activity remains unclear. One obstacle is the localization of neuronal activity; another is the spatial resolution of fMRI. In the present study, high-resolution BOLD and CBV fMRI experiments (voxel size: 156 x 156 x 2000 microm3) were conducted in the rat whisker barrel cortex at 3 T; neuronal activity across cortical layers was mapped using the Fos expression technique. Results show that BOLD response is weighted by blood volume and that pixels with high BOLD response can be located at the cortical surface or in deep layers, depending on local vasculature. In contrast to BOLD response, the pixels with high CBV response were consistently clustered in the deep cortical layers. Percentage-CBV change in cortical layers IV-V was 7.3 +/- 1.5%, which was significantly higher than in layers I-III (4.1 +/- 0.9%) and VI (4.3 +/- 0.7%) (mean +/- SEM). The laminar distribution of CBV response correlates well with neuronal activity localized by Fos expression. We conclude that neuronal activity can be inferred from CBV fMRI data with high spatial accuracy. The data indicate that both intracolumn functional connectivity and neurovascular coupling can be studied using CBV fMRI.
Lu
Hanbing
H
Department of Biophysics, Medical College of Wisconsin, Milwaukee 53226, USA.
Patel
Sachin
S
Luo
Feng
F
Li
Shi-Jiang
SJ
Hillard
Cecilia J
CJ
Ward
B Douglas
BD
Hyde
James S
JS
D000818:Animals; D001931:Brain Mapping; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D017352:Echo-Planar Imaging / Q000379:methods*; D004558:Electric Stimulation; D016762:Genes, fos; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014738:Vibrissae / Q000294:innervation
D003287:Contrast Media; D016760:Proto-Oncogene Proteins c-fos