Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
J Neurosci. 2011 Oct 19;31(42):15053-64. doi: 10.1523/JNEUROSCI.0101-11.2011.
The relationship between neuronal activity and hemodynamic changes plays a central role in functional neuroimaging. Under normal conditions and in neurological disorders such as epilepsy, it is commonly assumed that increased functional magnetic resonance imaging (fMRI) signals reflect increased neuronal activity and that fMRI decreases represent neuronal activity decreases. Recent work suggests that these assumptions usually hold true in the cerebral cortex. However, less is known about the basis of fMRI signals from subcortical structures such as the thalamus and basal ganglia. We used WAG/Rij rats (Wistar albino Glaxo rats of Rijswijk), an established animal model of human absence epilepsy, to perform fMRI studies with blood oxygen level-dependent and cerebral blood volume (CBV) contrasts at 9.4 tesla, as well as laser Doppler cerebral blood flow (CBF), local field potential (LFP), and multiunit activity (MUA) recordings. We found that, during spike-wave discharges, the somatosensory cortex and thalamus showed increased fMRI, CBV, CBF, LFP, and MUA signals. However, the caudate-putamen showed fMRI, CBV, and CBF decreases despite increases in LFP and MUA signals. Similarly, during normal whisker stimulation, the cortex and thalamus showed increases in CBF and MUA, whereas the caudate-putamen showed decreased CBF with increased MUA. These findings suggest that neuroimaging-related signals and electrophysiology tend to agree in the cortex and thalamus but disagree in the caudate-putamen. These opposite changes in vascular and electrical activity indicate that caution should be applied when interpreting fMRI signals in both health and disease from the caudate-putamen, as well as possibly from other subcortical structures.
神经元活动与血液动力学变化之间的关系在功能神经影像学中起着核心作用。在正常情况下和癫痫等神经疾病中,通常假设功能磁共振成像 (fMRI) 信号的增加反映了神经元活动的增加,而 fMRI 信号的减少则代表了神经元活动的减少。最近的研究表明,这些假设在大脑皮层中通常是正确的。然而,对于来自丘脑和基底神经节等皮质下结构的 fMRI 信号的基础,人们了解得较少。我们使用 WAG/Rij 大鼠(Rijswijk 的 Wistar 白化 Glaxo 大鼠),一种人类失神性癫痫的成熟动物模型,在 9.4 特斯拉下进行 fMRI 研究,使用血氧水平依赖对比和脑血容量(CBV)对比,以及激光多普勒脑血流(CBF)、局部场电位(LFP)和多单位活动(MUA)记录。我们发现,在棘波放电期间,体感皮层和丘脑显示出 fMRI、CBV、CBF、LFP 和 MUA 信号的增加。然而,尾状核-壳核显示出 fMRI、CBV 和 CBF 的减少,尽管 LFP 和 MUA 信号增加。类似地,在正常的胡须刺激期间,皮层和丘脑显示出 CBF 和 MUA 的增加,而尾状核-壳核显示出 CBF 的减少和 MUA 的增加。这些发现表明,神经影像学相关信号和电生理学在皮层和丘脑上趋于一致,但在尾状核-壳核上不一致。血管和电活动的这些相反变化表明,在健康和疾病状态下,从尾状核-壳核以及可能从其他皮质下结构解释 fMRI 信号时应谨慎,这一点很重要。
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