Mayhew J, Zheng Y, Hou Y, Vuksanovic B, Berwick J, Askew S, Coffey P
Artificial Intelligence Vision Research Unit and Department of Psychology, University of Sheffield, Sheffield, S10 2TP, United Kingdom.
Neuroimage. 1999 Sep;10(3 Pt 1):304-26. doi: 10.1006/nimg.1999.0460.
Imaging of neural activation has been used to produce maps of functional architecture and metabolic activity. There is some uncertainty associated with the sources underlying the intrinsic signals. It has been reported that following increased neural activity there was little increased oxygen consumption ( approximately 5%), although glucose consumption increased by approximately 50%. The research we describe uses a modification of the Beer-Lambert Law called path-length scaling analysis (PLSA) to analyze the spectra of the hemodynamic and metabolic responses to vibrissal stimulation in rat somatosensory cortex. The results of the PLSA algorithm were compared with those obtained using a linear spectrographic analysis method (we refer to this as LMCA). There are differences in the results of the analysis depending on which of the two algorithms (PLSA or LMCA) is used. Using the LMCA algorithm, we obtain results showing an increase in the volume of Hbr at approximately 2 s, following onset of stimulation but no complementary decrease in oxygenated haemoglobin (HbO(2)). These results are similar to a previous report. In contrast, after using the PLSA algorithm, the time series of the chromophore changes shows no evidence for an increase in the volume of deoxygenated haemoglobin (Hbr). However, after further analysis of the time series from the PLSA using general linear models (GLM) to remove contributions from low frequency baseline oscillations, both the HbO(2) and Hbr times series of the response to stimulation were found to be biphasic with an early decrease in saturation peaking approximately 1 s after onset of stimulation followed by a larger increase in saturation peaking at approximately 3 s. Finally, following the PLSA-then-GLM analysis procedure, we do not find convincing evidence for an increase in cytochrome oxidation following stimulation, though we demonstrate the PLSA algorithm to be capable of disassociating changes in cytochrome oxidation state from changes in hemoglobin oxygenation.
神经激活成像已被用于生成功能结构和代谢活动图谱。与内在信号的潜在来源相关存在一些不确定性。据报道，神经活动增加后，耗氧量几乎没有增加（约5%），尽管葡萄糖消耗量增加了约50%。我们所描述的研究使用了一种对比尔-朗伯定律的改进方法，称为路径长度缩放分析（PLSA），来分析大鼠体感皮层对触须刺激的血流动力学和代谢反应的光谱。将PLSA算法的结果与使用线性光谱分析方法（我们将其称为LMCA）获得的结果进行了比较。根据使用的两种算法（PLSA或LMCA）中的哪一种，分析结果存在差异。使用LMCA算法，我们获得的结果显示，刺激开始后约2秒，去氧血红蛋白（Hbr）体积增加，但氧合血红蛋白（HbO₂）没有相应减少。这些结果与之前的一份报告相似。相比之下，使用PLSA算法后，发色团变化的时间序列没有显示去氧血红蛋白（Hbr）体积增加的证据。然而，在使用通用线性模型（GLM）对PLSA的时间序列进行进一步分析以去除低频基线振荡的贡献后，发现对刺激反应的HbO₂和Hbr时间序列都是双相的，饱和度在刺激开始后约1秒达到早期下降峰值，随后在约3秒达到更大的上升峰值。最后，按照PLSA然后GLM的分析程序，我们没有找到令人信服的证据表明刺激后细胞色素氧化增加，尽管我们证明了PLSA算法能够将细胞色素氧化状态的变化与血红蛋白氧合的变化区分开来。
