López María Eugenia, Garcés Pilar, Cuesta Pablo, Castellanos Nazareth P, Aurtenetxe Sara, Bajo Ricardo, Marcos Alberto, Montenegro Mercedes, Yubero Raquel, del Pozo Francisco, Sancho Miguel, Maestú Fernando
Age (Dordr). 2014 Jun;36(3):9643. doi: 10.1007/s11357-014-9643-2.
Mild cognitive impairment (MCI) is a stage between healthy aging and dementia. It is known that in this condition the connectivity patterns are altered in the resting state and during cognitive tasks, where an extra effort seems to be necessary to overcome cognitive decline. We aimed to determine the functional connectivity pattern required to deal with an internally directed cognitive state (IDICS) in healthy aging and MCI. This task differs from the most commonly employed ones in neurophysiology, since inhibition from external stimuli is needed, allowing the study of this control mechanism. To this end, magnetoencephalographic (MEG) signals were acquired from 32 healthy individuals and 38 MCI patients, both in resting state and while performing a subtraction task of two levels of difficulty. Functional connectivity was assessed with phase locking value (PLV) in five frequency bands. Compared to controls, MCIs showed higher PLV values in delta, theta, and gamma bands and an opposite pattern in alpha, beta, and gamma bands in resting state. These changes were associated with poorer neuropsychological performance. During the task, this group exhibited a hypersynchronization in delta, theta, beta, and gamma bands, which was also related to a lower cognitive performance, suggesting an abnormal functioning in this group. Contrary to controls, MCIs presented a lack of synchronization in the alpha band which may denote an inhibition deficit. Additionally, the magnitude of connectivity changes rose with the task difficulty in controls but not in MCIs, in line with the compensation-related utilization of neural circuits hypothesis (CRUNCH) model.
轻度认知障碍（MCI）是健康衰老与痴呆之间的一个阶段。众所周知，在此状态下，静息状态和认知任务期间的连接模式会发生改变，似乎需要额外努力来克服认知衰退。我们旨在确定健康衰老和MCI中应对内源性认知状态（IDICS）所需的功能连接模式。该任务不同于神经生理学中最常用的任务，因为需要抑制外部刺激，从而能够研究这种控制机制。为此，从32名健康个体和38名MCI患者身上采集了脑磁图（MEG）信号，包括静息状态和执行两个难度级别的减法任务时的信号。在五个频段中用锁相值（PLV）评估功能连接。与对照组相比，MCI患者在静息状态下，δ、θ和γ频段的PLV值较高，而α、β和γ频段则呈现相反模式。这些变化与较差的神经心理学表现相关。在任务期间，该组在δ、θ、β和γ频段表现出超同步，这也与较低的认知表现相关，表明该组存在功能异常。与对照组相反，MCI患者在α频段缺乏同步，这可能表示抑制缺陷。此外，连接性变化的幅度在对照组中随任务难度增加而上升，但在MCI患者中并非如此，这与神经回路补偿相关利用假说（CRUNCH）模型一致。
