Newton Allen T, Morgan Victoria L, Gore John C
Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37232-2310, USA.
Hum Brain Mapp. 2007 Jul;28(7):663-72. doi: 10.1002/hbm.20294.
Correlations in blood oxygen level-dependent (BOLD) MRI signals from separate areas within the human brain have been used as a measure of functional connectivity. Steady-state measures of interregional correlations are particularly useful because they do not depend on the specific design of a task nor on subtracting conditions in a blocked design task. However, the conditions under which such correlations are measured may influence these indices of functional connectivity. The aim of this study was to investigate the influence of task demand on interregional correlations within the motor system. Specifically, tapping rates in audibly paced finger-tapping tasks were controlled and varied between runs in order to observe their effects on interregional correlations to contralateral primary motor cortex (PM). Regions of interest included the supplementary motor area, ipsilateral cerebellum, ipsilateral auditory cortex, and a control region. It was found that tapping rate was a significant factor in determining the mean correlation of some regions to PM, and that correlations measured during tapping in general increased relative to resting state. Furthermore, analysis of the percent of voxels in each region significantly correlated to PM suggested that changes in the mean correlation of that region to PM could be accounted for by changes in the fraction of significantly correlated voxels within a region. This provides insight into the manner in which steady-state correlations are modified in response to different task demands and further evidence that low-frequency fluctuations in BOLD signals reflect functional connectivity.
来自人类大脑不同区域的血氧水平依赖（BOLD）磁共振成像信号之间的相关性已被用作功能连接性的一种度量。区域间相关性的稳态测量尤为有用，因为它们不依赖于任务的具体设计，也不依赖于在组块设计任务中减去不同条件。然而，测量这些相关性的条件可能会影响这些功能连接性指标。本研究的目的是调查任务需求对运动系统内区域间相关性的影响。具体而言，在可听见节奏的手指敲击任务中，敲击速率在不同轮次中受到控制并有所变化，以便观察其对与对侧初级运动皮层（PM）区域间相关性的影响。感兴趣的区域包括辅助运动区、同侧小脑、同侧听觉皮层以及一个对照区域。研究发现，敲击速率是决定某些区域与PM平均相关性的一个重要因素，并且在敲击过程中测量到的相关性相对于静息状态总体上有所增加。此外，对每个区域中与PM显著相关的体素百分比的分析表明，该区域与PM平均相关性的变化可以由该区域内显著相关体素比例的变化来解释。这为响应不同任务需求时稳态相关性的改变方式提供了见解，并进一步证明了BOLD信号中的低频波动反映了功能连接性。
