Bednařík Petr, Tkáč Ivan, Giove Federico, DiNuzzo Mauro, Deelchand Dinesh K, Emir Uzay E, Eberly Lynn E, Mangia Silvia
1] Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA [2] Division of Endocrinology, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA [3] Multimodal and Functional Neuroimaging Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
J Cereb Blood Flow Metab. 2015 Mar 31;35(4):601-10. doi: 10.1038/jcbfm.2014.233.
Several laboratories have consistently reported small concentration changes in lactate, glutamate, aspartate, and glucose in the human cortex during prolonged stimuli. However, whether such changes correlate with blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) signals have not been determined. The present study aimed at characterizing the relationship between metabolite concentrations and BOLD-fMRI signals during a block-designed paradigm of visual stimulation. Functional magnetic resonance spectroscopy (fMRS) and fMRI data were acquired from 12 volunteers. A short echo-time semi-LASER localization sequence optimized for 7 Tesla was used to achieve full signal-intensity MRS data. The group analysis confirmed that during stimulation lactate and glutamate increased by 0.26 ± 0.06 μmol/g (30%) and 0.28 ± 0.03 μmol/g (3%), respectively, while aspartate and glucose decreased by 0.20 ± 0.04 μmol/g (5%) and 0.19 ± 0.03 μmol/g (16%), respectively. The single-subject analysis revealed that BOLD-fMRI signals were positively correlated with glutamate and lactate concentration changes. The results show a linear relationship between metabolic and BOLD responses in the presence of strong excitatory sensory inputs, and support the notion that increased functional energy demands are sustained by oxidative metabolism. In addition, BOLD signals were inversely correlated with baseline γ-aminobutyric acid concentration. Finally, we discussed the critical importance of taking into account linewidth effects on metabolite quantification in fMRS paradigms.
几个实验室一直报告称，在长时间刺激过程中，人类大脑皮层中的乳酸、谷氨酸、天冬氨酸和葡萄糖浓度会发生微小变化。然而，这些变化是否与血氧水平依赖性功能磁共振成像（BOLD-fMRI）信号相关尚未确定。本研究旨在描述视觉刺激的组块设计范式中代谢物浓度与BOLD-fMRI信号之间的关系。从12名志愿者身上采集了功能磁共振波谱（fMRS）和fMRI数据。使用为7特斯拉优化的短回波时间半激光定位序列来获取全信号强度的MRS数据。组分析证实，在刺激过程中，乳酸和谷氨酸分别增加了0.26±0.06μmol/g（约30%）和0.28±0.03μmol/g（约3%），而天冬氨酸和葡萄糖分别减少了0.20±0.04μmol/g（约5%）和0.19±0.03μmol/g（约16%）。单受试者分析显示，BOLD-fMRI信号与谷氨酸和乳酸浓度变化呈正相关。结果表明，在存在强烈兴奋性感觉输入的情况下，代谢反应与BOLD反应之间存在线性关系，并支持这样一种观点，即增加的功能能量需求由氧化代谢维持。此外，BOLD信号与基线γ-氨基丁酸浓度呈负相关。最后，我们讨论了在fMRS范式中考虑线宽效应对代谢物定量的至关重要性。
