University of Illinois at Urbana-Champaign, USA.
Neuroimage. 2014 Jan 15;85 Pt 1(0 1):592-607. doi: 10.1016/j.neuroimage.2013.04.113. Epub 2013 May 9.
Brain aging is characterized by changes in both hemodynamic and neuronal responses, which may be influenced by the cardiorespiratory fitness of the individual. To investigate the relationship between neuronal and hemodynamic changes, we studied the brain activity elicited by visual stimulation (checkerboard reversals at different frequencies) in younger adults and in older adults varying in physical fitness. Four functional brain measures were used to compare neuronal and hemodynamic responses obtained from BA17: two reflecting neuronal activity (the event-related optical signal, EROS, and the C1 response of the ERP), and two reflecting functional hemodynamic changes (functional magnetic resonance imaging, fMRI, and near-infrared spectroscopy, NIRS). The results indicated that both younger and older adults exhibited a quadratic relationship between neuronal and hemodynamic effects, with reduced increases of the hemodynamic response at high levels of neuronal activity. Although older adults showed reduced activation, similar neurovascular coupling functions were observed in the two age groups when fMRI and deoxy-hemoglobin measures were used. However, the coupling between oxy- and deoxy-hemoglobin changes decreased with age and increased with increasing fitness. These data indicate that departures from linearity in neurovascular coupling may be present when using hemodynamic measures to study neuronal function.
大脑老化的特征是血液动力学和神经元反应的变化，这些变化可能受到个体心肺适应能力的影响。为了研究神经元和血液动力学变化之间的关系，我们研究了年轻成年人和不同身体状况的老年人在视觉刺激（不同频率的棋盘反转）下的大脑活动。使用了四个功能性脑测量来比较 BA17 中的神经元和血液动力学反应：两个反映神经元活动的反应（事件相关光学信号 EROS 和 ERP 的 C1 反应），两个反映功能性血液动力学变化的反应（功能磁共振成像 fMRI 和近红外光谱 NIRS）。结果表明，年轻成年人和老年人的神经元和血液动力学效应之间均存在二次关系，在高水平的神经元活动下，血液动力学反应的增加减少。尽管老年人的激活减少，但当使用 fMRI 和脱氧血红蛋白测量时，在两个年龄组中观察到了相似的神经血管耦合功能。然而，随着年龄的增长，氧合血红蛋白和脱氧血红蛋白变化之间的耦合减少，而随着适应能力的增加而增加。这些数据表明，当使用血液动力学测量来研究神经元功能时，神经血管耦合可能会出现非线性偏离。
