Schridde Ulrich, Khubchandani Manjula, Motelow Joshua E, Sanganahalli Basavaraju G, Hyder Fahmeed, Blumenfeld Hal
Department of Neurology, Yale University, New Haven, CT 06510, USA.
Cereb Cortex. 2008 Aug;18(8):1814-27. doi: 10.1093/cercor/bhm208. Epub 2007 Dec 5.
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.
血氧水平依赖（BOLD）功能磁共振成像（fMRI）在神经科学领域被广泛用于研究大脑活动。然而，BOLD功能磁共振成像并非直接测量神经元活动，而是依赖于脑血流量（CBF）、脑血容量（CBV）以及脑氧代谢率（CMRO₂）消耗。利用功能磁共振成像、脑血容量、脑血流量、神经元记录以及脑氧代谢率建模，我们研究了大鼠癫痫发作期间这些信号之间的关系。我们发现，血流动力学、神经元及代谢活动的增加与皮质中的正向BOLD信号相关，但与海马体中的负向BOLD信号相关。我们的数据表明，负向BOLD信号不一定意味着神经元活动或脑血流量降低，而是可能由神经元活动增加导致，这取决于血流动力学与代谢之间的相互作用。在解释功能磁共振成像信号时应谨慎，因为神经元活动与BOLD信号之间的关系可能取决于脑区和状态，并且在正常和病理条件下可能有所不同。
