Yamanaka Kaori, Tomioka Hiroi, Kawasaki Shingo, Noda Yumiko, Yamagata Bun, Iwanami Akira, Mimura Masaru
Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan.
Department of Neuropsychiatry, Showa University School of Medicine, Tokyo, Japan.
PLoS One. 2014 Jul 14;9(7):e102306. doi: 10.1371/journal.pone.0102306. eCollection 2014.
In a previous study, we succeeded in improving the spatial working memory (WM) performance in healthy young persons by applying transcranial magnetic stimulation (TMS) to the parietal cortex and simultaneously measuring the oxygenated hemoglobin (oxy-Hb) level using near-infrared spectroscopy (NIRS). Since an improvement in WM was observed when TMS was applied to the right parietal cortex, the oxy-Hb distribution seemed to support a model of hemispheric asymmetry (HA). In the present study, we used the same study design to evaluate healthy elderly persons and investigated the effect of TMS on WM performance in the elderly, comparing the results with those previously obtained from young persons. The application of TMS did not affect WM performance (both reaction time and accuracy) of 38 elderly participants (mean age = 72.5 years old). To investigate the reason for this result, we conducted a three-way ANOVA examining oxy-Hb in both young and elderly participants. For the right parietal TMS site in the elderly, TMS significantly decreased the oxy-Hb level during WM performance; this result was the opposite of that observed in young participants. An additional three-way ANOVA was conducted for each of the 52 channels, and a P value distribution map was created. The P value maps for the young participants showed a clearly localized TMS effect for both the WM and control task, whereas the P map for the elderly participants showed less significant channels and localization. Further analysis following the time course revealed that right-side parietal TMS had almost no effect on the frontal cortex in the elderly participants. This result can most likely be explained by age-related differences in HA arising from the over-recruitment of oxy-Hb, differentiation in the parietal cortex, and age-related alterations of the frontal-parietal networks.
在之前的一项研究中，我们通过对顶叶皮层施加经颅磁刺激（TMS），并同时使用近红外光谱（NIRS）测量氧合血红蛋白（oxy-Hb）水平，成功改善了健康年轻人的空间工作记忆（WM）表现。由于在对右侧顶叶皮层施加TMS时观察到WM有所改善，氧合血红蛋白的分布似乎支持半球不对称（HA）模型。在本研究中，我们采用相同的研究设计来评估健康老年人，并研究TMS对老年人WM表现的影响，同时将结果与之前从年轻人那里获得的结果进行比较。对38名老年参与者（平均年龄 = 72.5岁）施加TMS并未影响其WM表现（反应时间和准确性）。为了探究这一结果的原因，我们对年轻和老年参与者的氧合血红蛋白进行了三因素方差分析。对于老年参与者右侧顶叶的TMS部位，TMS在WM表现期间显著降低了氧合血红蛋白水平；这一结果与在年轻参与者中观察到的相反。针对52个通道中的每一个又进行了一次三因素方差分析，并创建了P值分布图。年轻参与者的P值图显示，对于WM任务和对照任务，TMS效应都有明显的局部定位，而老年参与者的P值图显示出显著性较低的通道和定位。随时间进程的进一步分析表明，右侧顶叶TMS对老年参与者的额叶皮层几乎没有影响。这一结果很可能可以用与年龄相关的半球不对称差异来解释，这种差异源于氧合血红蛋白的过度募集、顶叶皮层的分化以及额叶 - 顶叶网络的年龄相关变化。
