Centre for Studies and Research in Cognitive Neuroscience, University of Bologna, Via Rasi e Spinelli 176, 47521, Cesena, Italy.
Department of Psychology, University of Bologna, Viale Berti Pichat 5, 40121, Bologna, Italy.
Brain Struct Funct. 2022 Mar;227(2):709-723. doi: 10.1007/s00429-021-02279-8. Epub 2021 Apr 24.
A variety of evidence supports the dominance of the right hemisphere in perceptual and visuo-spatial processing. Although growing evidence shows a strong link between alpha oscillations and the functionality of the visual system, asymmetries in alpha oscillatory patterns still need to be investigated. Converging findings indicate that the typical alpha desynchronization occurring in the transition from the eyes-closed to the eyes-open resting state might represent an index of reactivity of the visual system. Thus, investigating hemispheric asymmetries in EEG reactivity at the opening of the eyes in brain-lesioned patients may shed light on the contribution of specific cortical sites and each hemisphere in regulating the oscillatory patterns reflecting the functionality of the visual system. To this aim, EEG signal was recorded during eyes-closed and eyes-open resting state in hemianopic patients with posterior left or right lesions, patients without hemianopia with anterior lesions and healthy controls. Hemianopics with both left and right posterior lesions showed a reduced alpha reactivity at the opening of the eyes, suggesting that posterior cortices have a pivotal role in the functionality of alpha oscillations. However, right-lesioned hemianopics showed a greater dysfunction, demonstrated by a reactivity reduction more distributed over the scalp, compared to left-lesioned hemianopics. Moreover, they also revealed impaired reactivity in the theta range. This favors the hypothesis of a specialized role of the right hemisphere in orchestrating oscillatory patterns, both coordinating widespread alpha oscillatory activity and organizing focal processing in the theta range, to support visual processing at the opening of the eyes.
各种证据表明右半球在感知和视空间处理中占主导地位。尽管越来越多的证据表明α 振荡与视觉系统的功能之间存在很强的联系，但α 振荡模式的不对称性仍需要进一步研究。趋同的发现表明，从闭眼到睁眼静息状态过渡过程中典型的α去同步化可能代表视觉系统反应性的指标。因此，研究脑损伤患者睁眼时 EEG 反应的半球不对称性可能有助于阐明特定皮质部位和每个半球在调节反映视觉系统功能的振荡模式方面的贡献。为此，在左侧或右侧后部病变的偏盲患者、无偏盲的前部病变患者和健康对照组中，记录了闭眼和睁眼静息状态下的 EEG 信号。双侧后部病变的偏盲患者在睁眼时的α反应性降低，表明后部皮质在α 振荡功能中起着关键作用。然而，与左侧病变的偏盲患者相比，右侧病变的偏盲患者表现出更大的功能障碍，表现为头皮上更广泛的反应性降低。此外，他们还显示出θ 频段的反应性受损。这支持了右侧半球在协调振荡模式方面具有专门作用的假设，这种作用既协调广泛的α 振荡活动，又在θ 频段组织焦点处理，以支持睁眼时的视觉处理。
