Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy.
Dept. of Neurophysiology and Diagnostic Epileptology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy; Dept. of Medical and Surgical Sciences of Communication and Behaviour, Neurology Section, University of Ferrara, Italy.
Clin Neurophysiol. 2014 Jan;125(1):63-8. doi: 10.1016/j.clinph.2013.06.016. Epub 2013 Aug 6.
Recent evidence mainly based on hemodynamic measures suggests that the impairment of functional connections between different brain areas may help to clarify the neuronal dysfunction occurring in patients with disorders of consciousness (DOC). The aim of this study was to evaluate effective EEG connectivity in a cohort of 18 patients in a chronic vegetative state (VS) observed years after the occurrence of hypoxic (eight) and traumatic or hemorrhagic brain insult.
we analysed the EEG signals recorded under resting conditions using a frequency domain linear index of connectivity (partial directed coherence: PDC) estimated from a multivariate autoregressive model. The results were compared with those obtained in ten healthy controls.
Our findings indicated significant connectivity changes in EEG activities in delta and alpha bands. The VS patients showed a significant and widespread decrease in delta band connectivity, whereas the alpha activity was hyper-connected in the central and posterior cortical regions.
These changes suggest the occurrence of severe circuitry derangements probably due to the loose control of the subcortical connections. The alpha hyper-synchronisation may be due to simplified networks mainly involving the short-range connections between intrinsically oscillatory cortical neurons that generate aberrant EEG alpha sources. This increased connectivity may be interpreted as a reduction in information capacity, implying an increasing prevalence of stereotypic activity patterns.
Our observations suggest a remarkable rearrangement of connectivity in patients with long-standing VS. We hypothesize that in persistent VS, after a first period characterized by a breakdown of cortical connectivity, neurodegenerative processes, largely independent from the type of initial insult, lead to cortex de-afferentation and to a severe reduction of possible cortical activity patterns and states.
最近的证据主要基于血流动力学测量，表明不同脑区之间功能连接的损害可能有助于阐明意识障碍（DOC）患者发生的神经元功能障碍。本研究旨在评估 18 例慢性植物状态（VS）患者的有效 EEG 连接，这些患者在发生缺氧（8 例）和创伤性或出血性脑损伤后多年进行观察。
我们使用从多变量自回归模型估计的频率域线性连接指数（偏部分相干性：PDC）分析在静息状态下记录的 EEG 信号。将结果与十名健康对照者的结果进行比较。
我们的发现表明 EEG 活动在 delta 和 alpha 波段的连接发生了显著变化。VS 患者的 delta 波段连接明显且广泛降低，而 alpha 活动在中央和后皮质区域过度连接。
这些变化表明存在严重的电路紊乱，可能是由于皮质下连接的控制松弛所致。alpha 超同步可能是由于简化的网络主要涉及产生异常 EEG alpha 源的内在振荡皮质神经元之间的短程连接。这种增加的连接性可以解释为信息容量的减少，意味着刻板活动模式的流行度增加。
我们的观察表明，长期 VS 患者的连接性有明显的重新排列。我们假设在持续的 VS 中，在皮质连接破裂的第一阶段之后，神经退行性过程，在很大程度上独立于初始损伤的类型，导致皮质去传入和可能的皮质活动模式和状态的严重减少。
