Dimitriadis Stavros I, Laskaris Nikolaos A, Simos Panagiotis G, Fletcher Jack M, Papanicolaou Andrew C
Artificial Intelligence and Information Analysis Laboratory, Department of Informatics, Aristotle UniversityThessaloniki, Greece; Neuroinformatics Group, Department of Informatics, Aristotle UniversityThessaloniki, Greece.
School of Medicine, University of Crete Crete, Greece.
Front Hum Neurosci. 2016 Apr 26;10:163. doi: 10.3389/fnhum.2016.00163. eCollection 2016.
Cross-frequency, phase-to-amplitude coupling (PAC) between neuronal oscillations at rest may serve as the substrate that supports information exchange between functionally specialized neuronal populations both within and between cortical regions. The study utilizes novel algorithms to identify prominent instantaneous modes of cross-frequency coupling and their temporal stability in resting state magnetoencephalography (MEG) data from 25 students experiencing severe reading difficulties (RD) and 27 age-matched non-impaired readers (NI). Phase coherence estimates were computed in order to identify the prominent mode of PAC interaction for each sensor, sensor pair, and pair of frequency bands (from δ to γ) at successive time windows of the continuous MEG record. The degree of variability in the characteristic frequency-pair PAC(f1-f2) modes over time was also estimated. Results revealed a wider repertoire of prominent PAC interactions in RD as compared to NI students, suggesting an altered functional substrate for information exchange between neuronal assemblies in the former group. Moreover, RD students showed significant variability in PAC modes over time. This temporal instability of PAC values was particularly prominent: (a) within and between right hemisphere temporo-parietal and occipito-temporal sensors and, (b) between left hemisphere frontal, temporal, and occipito-temporal sensors and corresponding right hemisphere sites. Altered modes of neuronal population coupling may help account for extant data revealing reduced, task-related neurophysiological and hemodynamic activation in left hemisphere regions involved in the reading network in RD. Moreover, the spatial distribution of pronounced instability of cross-frequency coupling modes in this group may provide an explanation for previous reports suggesting the presence of inefficient compensatory mechanisms to support reading.
静息状态下神经元振荡之间的跨频率、相位到幅度耦合（PAC）可能作为一种基础，支持皮质区域内和区域间功能特化的神经元群体之间的信息交换。该研究利用新算法来识别跨频率耦合的显著瞬时模式及其在静息态脑磁图（MEG）数据中的时间稳定性，这些数据来自25名有严重阅读困难（RD）的学生和27名年龄匹配的无阅读障碍读者（NI）。计算相位相干估计值，以便在连续MEG记录的连续时间窗口中，为每个传感器、传感器对以及每对频段（从δ到γ）识别PAC相互作用的显著模式。还估计了特征频率对PAC（f1-f2）模式随时间的变化程度。结果显示，与NI学生相比，RD学生中显著的PAC相互作用模式更多，这表明前一组中神经元组件之间信息交换的功能基础发生了改变。此外，RD学生的PAC模式随时间表现出显著变化。PAC值的这种时间不稳定性在以下情况中尤为突出：（a）右半球颞顶叶和枕颞叶传感器内部及之间；（b）左半球额叶、颞叶和枕颞叶传感器与相应右半球部位之间。神经元群体耦合模式的改变可能有助于解释现有数据，这些数据显示RD患者阅读网络中涉及的左半球区域与任务相关的神经生理和血流动力学激活减少。此外，该组中跨频率耦合模式明显不稳定的空间分布，可能为先前关于存在低效补偿机制以支持阅读的报道提供解释。
