Halliday Drew W R, Mulligan Bryce P, Garrett Douglas D, Schmidt Stefan, Hundza Sandra R, Garcia-Barrera Mauricio A, Stawski Robert S, MacDonald Stuart W S
University of Victoria, Department of Psychology, Victoria, British Columbia, Canada.
University of Victoria, Institute on Aging and Lifelong Health, Victoria, British Columbia, Canada.
Neurophotonics. 2018 Jan;5(1):011013. doi: 10.1117/1.NPh.5.1.011013. Epub 2017 Sep 26.
although the preponderance of research on functional brain activity investigates mean group differences, mounting evidence suggests that variability in neural activity is beneficial for optimal central nervous system (CNS) function. Independent of mean signal estimates, recent findings have shown that neural variability diminishes with age and is positively associated with cognitive performance, underscoring its adaptive nature. The present investigation sought to employ functional near infrared spectroscopy (fNIRS) to derive two operationalizations of cerebral oxygenation, representing mean and variability [using standard deviation (SD)] in neural activity, and to specifically contrast these mean- and SD-oxyhemoglobin (HbO) estimates as predictors of cognitive function.
a total of 25 older adults (71 to 81 years of age) completed a test of cognitive interference (Multisource Interference Task) while undergoing fNIRS recording using a multichannel continuous-wave optical imaging system (TechEn CW6) over bilateral prefrontal cortex (PFC). Time-varying covariation models were employed to simultaneously estimate the within- and between-person effects of cerebral oxygenation on behavioral performance fluctuations.
mean effects were predominantly observed at the between-person level and suggest that greater concentrations of HbO are associated with slower and less accurate performance. Greater HbO variability at the between-person level was associated with slower performance, but was associated with faster performance at the within-person level.
these findings are in keeping with assertions that mean and variability confer complementary (as opposed to redundant) sources of information regarding the effective functioning of a neural system and suggest that fNIRS is a viable methodology for capturing meaningful variance in the hemodynamic response that is characteristic of adaptive CNS function.
尽管对大脑功能活动的大多数研究都在调查平均组间差异，但越来越多的证据表明，神经活动的变异性对中枢神经系统（CNS）的最佳功能有益。独立于平均信号估计，最近的研究结果表明，神经变异性会随着年龄的增长而降低，并且与认知表现呈正相关，这突出了其适应性本质。本研究旨在采用功能性近红外光谱（fNIRS）来得出脑氧合的两种运算方式，分别代表神经活动的平均值和变异性[使用标准差（SD）]，并特别对比这些平均和SD氧合血红蛋白（HbO）估计值作为认知功能的预测指标。
共有25名老年人（71至81岁）在使用多通道连续波光学成像系统（TechEn CW6）对双侧前额叶皮层（PFC）进行fNIRS记录时，完成了一项认知干扰测试（多源干扰任务）。采用时变协变模型来同时估计脑氧合对行为表现波动的个体内和个体间效应。
平均效应主要在个体间水平观察到，表明较高浓度的HbO与较慢且不准确的表现相关。个体间水平上较大的HbO变异性与较慢的表现相关，但在个体内水平上与较快的表现相关。
这些发现与以下观点一致，即平均值和变异性为神经系统有效功能提供了互补（而非冗余）的信息来源，并表明fNIRS是一种可行的方法，用于捕捉适应性CNS功能特征的血流动力学反应中有意义的差异。
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