Başar Erol, Femir Banu, Emek-Savaş Derya Durusu, Güntekin Bahar, Yener Görsev G
Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, Istanbul 34156, Turkey.
Department of Psychology, Faculty of Letters, Dokuz Eylül University, Izmir 35160, Turkey; Department of Neurosciences, Institute of Health Sciences, Dokuz Eylül University, Izmir 35340, Turkey.
Neuroimage Clin. 2017 Mar 1;14:580-590. doi: 10.1016/j.nicl.2017.02.021. eCollection 2017.
Brain oscillatory responses can be used for non-invasive analyses of cortico-cortical connectivity, local neuronal synchronization, and coherence of oscillations in many neuropsychiatric conditions including Alzheimer's disease (AD). In the present paper, we examine sensory-evoked and event-related gamma coherences elicited by visual stimuli in three sub-gamma bands in two sub-groups of patients with AD (i.e., acetylcholinesterase-inhibitor treated and untreated) and healthy controls.
We studied a total of 39 patients with probable mild AD (according to NINCDS-ADRDA criteria) who had been sub-divided into untreated (n = 21) and treated (n = 18) (patients either on cholinergic monotherapy or combined therapy with memantine) AD groups, and 21 age-, gender-, and education-matched healthy elderly controls. A simple flash visual paradigm was applied for the acquisition of sensory-evoked coherences. Event-related coherences were elicited using a classical visual oddball paradigm. Both sensory-evoked and event-related gamma coherences were calculated for long-distance intrahemispheric pairs for three frequency ranges: 25-30 Hz, 30-35 Hz, and 40-48 Hz in post-stimulus 0-800 ms duration. The long-distance intrahemispheric pairs from both sides were fronto-parietal, fronto-temporal, fronto-temporoparietal, fronto-occipital, centro-occipital and parieto-occipital.
The sensory-evoked or event-related gamma coherences revealed that both treated and untreated AD patients had significantly increased values compared to healthy controls in all three sub-gamma bands. Moreover, the treated AD patients demonstrated significantly higher fronto-parietal gamma coherences during both sensory stimulation and oddball paradigm and lower occipito-parietal coherences during oddball paradigm in comparison to untreated AD patients.
The present study demonstrated that an increase of gamma coherences was present in response to both visual sensory and cognitive stimulation in AD patients in all gamma sub-bands. Therefore, gamma oscillatory activity seems to be fundamental in brain functions at both the sensory and cognitive levels. The increase of gamma coherence values was not due to cholinergic treatment to any significant extent, as both treated and untreated AD patients had increased gamma coherence values compared to healthy controls. The use of coherence values reflecting brain connectivity holds potential for neuroimaging of AD and understanding brain dynamics related to the effects of medication.
脑振荡反应可用于对包括阿尔茨海默病（AD）在内的许多神经精神疾病中的皮质 - 皮质连接、局部神经元同步以及振荡相干性进行无创分析。在本文中，我们研究了视觉刺激在AD患者的两个亚组（即接受乙酰胆碱酯酶抑制剂治疗和未治疗的患者）以及健康对照者的三个亚伽马频段中引发的感觉诱发性和事件相关伽马相干性。
我们共研究了39例可能患有轻度AD的患者（根据NINCDS - ADRDA标准），这些患者被分为未治疗组（n = 21）和治疗组（n = 18）（接受胆碱能单药治疗或与美金刚联合治疗的患者）AD组，以及21名年龄、性别和教育程度相匹配的健康老年对照者。应用简单的闪光视觉范式来获取感觉诱发性相干性。使用经典的视觉oddball范式诱发事件相关相干性。在刺激后0 - 800毫秒持续时间内，针对三个频率范围：25 - 30赫兹、30 - 35赫兹和40 - 48赫兹，计算双侧远距离半球内对的感觉诱发性和事件相关伽马相干性。双侧远距离半球内对包括额顶叶、额颞叶、额颞顶叶、额枕叶、中央枕叶和顶枕叶。
感觉诱发性或事件相关伽马相干性显示，在所有三个亚伽马频段中，与健康对照者相比，接受治疗和未接受治疗的AD患者的值均显著增加。此外，与未治疗的AD患者相比，接受治疗的AD患者在感觉刺激和oddball范式期间均表现出显著更高的额顶叶伽马相干性，在oddball范式期间枕顶叶相干性更低。
本研究表明，在所有伽马子频段中，AD患者对视觉感觉和认知刺激的反应均存在伽马相干性增加。因此，伽马振荡活动似乎在感觉和认知水平的脑功能中都起着重要作用。伽马相干性值的增加在很大程度上并非由于胆碱能治疗，因为与健康对照者相比，接受治疗和未接受治疗的AD患者的伽马相干性值均增加。使用反映脑连接性的相干性值在AD的神经成像以及理解与药物作用相关的脑动力学方面具有潜力。
