Dalmis Mehmet Ufuk, Akin Ata
Radboud University Medical Center, Department of Radiology and Nuclear Medicine, Diagnostic Image Analysis Group, Postbus 9101, 6500 HB Nijmegen, The Netherlands.
Istanbul Bilgi University, Department of Genetics and Bioengineering, Eski Silahtaraga Elektrik Santrali Kazim Karabekir Cad. No: 2/13 34060 Eyüp Istanbul, Turkey.
J Biomed Opt. 2015 Aug;20(8):86012. doi: 10.1117/1.JBO.20.8.086012.
One of the remaining challenges in functional connectivity (FC) studies is investigation of the temporal variability of FC networks. Recent studies focusing on the dynamic FC mostly use functional magnetic resonance imaging as an imaging tool to investigate the temporal variability of FC. We attempted to quantify this variability via analyzing the functional near-infrared spectroscopy (fNIRS) signals, which were recorded from the prefrontal cortex (PFC) of 12 healthy subjects during a Stroop test. Mutual information was used as a metric to determine functional connectivity between PFC regions. Two-dimensional correlation based similarity measure was used as a method to analyze within-subject and intersubject consistency of FC maps and how they change in time. We found that within-subject consistency (0.61±0.09 ) is higher than intersubject consistency (0.28±0.13 ). Within-subject consistency was not found to be task-specific. Results also revealed that there is a gradual change in FC patterns during a Stroop session for congruent and neutral conditions, where there is no such trend in the presence of an interference effect. In conclusion, we have demonstrated the between-subject, within-subject, and temporal variability of FC and the feasibility of using fNIRS for studying dynamic FC.
功能连接（FC）研究中尚存的挑战之一是对FC网络时间变异性的研究。近期聚焦于动态FC的研究大多使用功能磁共振成像作为成像工具来探究FC的时间变异性。我们尝试通过分析功能近红外光谱（fNIRS）信号来量化这种变异性，这些信号是在一项Stroop测试期间从12名健康受试者的前额叶皮层（PFC）记录的。互信息被用作一种度量来确定PFC区域之间的功能连接。基于二维相关性的相似性度量被用作一种方法来分析FC图谱在个体内和个体间的一致性以及它们如何随时间变化。我们发现个体内一致性（0.61±0.09）高于个体间一致性（0.28±0.13）。未发现个体内一致性具有任务特异性。结果还显示，在Stroop测试过程中，对于一致和中性条件，FC模式存在逐渐变化，而在存在干扰效应时则没有这种趋势。总之，我们证明了FC在个体间、个体内和时间上的变异性以及使用fNIRS研究动态FC的可行性。
