Negative BOLD with large increases in neuronal activity.
Blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is widely used in neuroscience to study brain activity. However, BOLD fMRI does not measure neuronal activity directly but depends on cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of oxygen (CMRO(2)) consumption. Using fMRI, CBV, CBF, neuronal recordings, and CMRO(2) modeling, we investigated how the signals are related during seizures in rats. We found that increases in hemodynamic, neuronal, and metabolic activity were associated with positive BOLD signals in the cortex, but with negative BOLD signals in hippocampus. Our data show that negative BOLD signals do not necessarily imply decreased neuronal activity or CBF, but can result from increased neuronal activity, depending on the interplay between hemodynamics and metabolism. Caution should be used in interpreting fMRI signals because the relationship between neuronal activity and BOLD signals may depend on brain region and state and can be different during normal and pathological conditions.
Department of Neurology, Yale University, New Haven, CT 06510, USA.
Ulrich
U
Schridde
Manjula
M
Khubchandani
Joshua E
JE
Motelow
Basavaraju G
BG
Sanganahalli
Fahmeed
F
Hyder
Hal
H
Blumenfeld
D000818:Animals; D001921:Brain / Q000098:blood supply / Q000378:metabolism; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006624:Hippocampus / Q000098:blood supply / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009474:Neurons / Q000378:metabolism*; D010100:Oxygen / Q000097:blood* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D010100:Oxygen