Centre for Studies and Research in Cognitive Neuroscience, University of Bologna, Cesena, Italy.
Department of Psychology, University of Bologna, Bologna, Italy.
Brain Struct Funct. 2022 Dec;227(9):2939-2956. doi: 10.1007/s00429-022-02502-0. Epub 2022 May 19.
Emerging evidence suggests a role of the posterior cortices in regulating alpha oscillatory activity and organizing low-level processing in non-alpha frequency bands. Therefore, posterior brain lesions, which damage the neural circuits of the visual system, might affect functional connectivity patterns of brain rhythms. To test this hypothesis, eyes-closed resting state EEG signal was acquired from patients with hemianopia with left and right posterior lesions, patients without hemianopia with more anterior lesions and healthy controls. Left-lesioned hemianopics showed reduced intrahemispheric connectivity in the range of upper alpha only in the lesioned hemisphere, whereas right-lesioned hemianopics exhibited reduced intrahemispheric alpha connectivity in both hemispheres. In terms of network topology, these impairments were characterized by reduced local functional segregation, with no associated change in global functional integration. This suggests a crucial role of posterior cortices in promoting functional connectivity in the range of alpha. Right-lesioned hemianopics revealed also additional impairments in the theta range, with increased connectivity in this frequency band, characterized by both increased local segregated activity and decreased global integration. This indicates that lesions to right posterior cortices lead to stronger impairments in alpha connectivity and induce additional alterations in local and global low-level processing, suggesting a specialization of the right hemisphere in generating alpha oscillations and in coordinating complex interplays with lower frequency bands. Importantly, hemianopic patient's visual performance in the blind field was linked to alpha functional connectivity, corroborating the notion that alpha oscillatory patterns represent a biomarker of the integrity and the functioning of the underlying visual system.
新出现的证据表明，后皮质在调节α 振荡活动和组织非α 频带的低水平处理方面发挥作用。因此，损伤视觉系统神经回路的后脑损伤可能会影响脑节律的功能连接模式。为了验证这一假设，从左侧和右侧后部病变的偏盲患者、没有偏盲但病变更靠前的患者和健康对照者中采集闭眼静息状态 EEG 信号。左侧病变的偏盲患者仅在病变半球的上α 频段表现出半球内连接性降低，而右侧病变的偏盲患者在两个半球的α 频段均表现出半球内连接性降低。就网络拓扑结构而言，这些损伤的特征是局部功能分离减少，而全局功能整合没有变化。这表明后皮质在促进α 频段的功能连接中起着至关重要的作用。右侧病变的偏盲患者在θ 频段也表现出额外的损伤，该频段的连接性增加，表现为局部隔离活动增加和全局整合减少。这表明右侧后皮质损伤导致 α 连接性更强的损伤，并诱导局部和全局低水平处理的额外改变，表明右半球在产生 α 振荡和协调与较低频段的复杂相互作用方面具有专业化。重要的是，偏盲患者在盲区内的视觉表现与α 功能连接有关，这证实了α 振荡模式是视觉系统完整性和功能的生物标志物的观点。
