基于神经影像的大脑老化对视觉空间注意及相关脑网络的影响研究

Brain degenerates in both function and structure during ageing, appearing as the reduction of cognitive function (e.g., attention) and behavioral abilities. Recently, our studies showed that the old subjects had diminished lateralized alpha (8–13 Hz) power of the electroencephalogram (EEG) at occipital cortex in selective visual-spatial attention, and the neural activities in the ipsilateral occipital cortex of attended location increased compared with pre-attention baseline. Note that the lateralization of alpha rhythm of the EEG at occipital cortex is one robust electrophysiological marker for preparatory spatial attention in young adults. These results imply that the neural mechanism of attention control in old subjects changes compared with young adults. As the brain activities of cortices in spatial attention cannot be reliably detected with high spatial resolution by EEG due to its limitations, studies based on magnetic resonance imaging are needed to further explore the visual-spatial attention mechanism of old subjects and the effects of ageing on neural activities and neural fibers in attention-related brain regions. To this aim, we would specially adopt a spatial-cueing attention paradigm with partial trial rapid event-related functional magnetic resonance imaging (fMRI) design, and record fMRI data from participants of both healthy young and old adults, and further investigate the effects of ageing on spatial attention control from the perspective of functional integration based on Beta series correlation analysis. Furthermore, we would also collect diffusion tensor imaging data to examine the effects of voluntary attention control (characterized by neural activities and functional connectivity in attention task state) and the controllability of attention-related brain regions (including fronto-parietal attention network, default mode network, and occipital visual network). Based on the structural balance theory of social network, we further explore the effects of ageing on the functional connectivity and structural connectivity between attention-related brain regions. For insightful connectivity analysis of the effects of ageing on attention, we would take the advantages of both functional and structural neuroimaging to develop methods of dynamic functional connectivity analysis and multimodal connectivity fusion analysis based on the theory of network controllability and the structural balance theory of social network. We believe that the outputs of this project would offer new insights on visual-spatial attention in ageing and thus provide useful information for cognitive interventions to old adults, which is of significant importance for both neuroscience and our society, especially as China already entered an ageing society.

大脑老化带来脑结构和注意等认知功能的衰退。申请人和合作者的研究发现，老年人在视觉空间选择性注意状态下的枕叶脑电alpha波能量偏侧性消失，注意视野同侧枕叶的神经活动相对于基线阶段出现增强，这提示老年人的注意机制相对于青年人发生了变化。限于脑电的局限性，老化对大脑注意机制及其对应脑网络的影响有赖基于磁共振成像的研究予以进一步揭示。本项目拟采用部分试次空间线索化范式，采集功能磁共振数据并基于Beta序列相关分析从功能性整合的角度研究老年人的视觉空间选择性注意机制，采集弥散张量成像数据并基于网络可控性理论考察老年人的主动注意调控效应和注意相关脑区可控性的关系，借鉴社交平衡理论探索老化对注意相关脑区间的功能性连接和结构性连接的影响，并针对性地发展多模态脑连接融合分析方法。在中国老龄化的背景下，本项目将为老年人的注意机制提供多视角的新认识，为老年人的认知干预提供新信息，具有重要的科学意义和社会价值。

大脑老化带来脑结构和注意等认知功能的衰退。本项目探索大脑老化对视觉空间选择性注意及对注意相关脑网络的影响及相应机制，并研究相应的脑网络分析方法，以期增进对大脑老化过程中的脑功能和脑结构的认识。围绕项目预设的研究内容，本项目开展多方面的研究并取得进展。..我们首先进行部分试次快事件相关fMRI的空间选择性注意实验，基于Beta序列相关分析的结果显示左右侧枕叶之间和左右侧颞叶之间分别在提示阶段和目标阶段表现出持续性的较显著的功能性连接，这提示左右枕叶和颞叶在空间选择性注意过程中是协同在一起的。我们还进行“空间提示+Go/NoGo任务”脑电实验，研究发现事件相关电位的P3成分在注意条件和非注意条件下的反应抑制中均起重要作用，且额叶中线位置的脑电θ波能量还显著受注意相关的认知过程所调控。..在大脑老化对脑网络的影响方面，我们采用局部一致性方法研究了正常老年被试进行认知训练（每周2次共24次）前后的静息态fMRI数据，结果表明老年被试的局部功能性脑连接的整合水平低于青年被试，接受认知训练的老年被试的局部功能性脑连接的整合水平强于未接受认知训练的老年对照被试，且老年被试在基线阶段的局部脑连接整合水平和其接受教育的年限显著正相关。我们还采用最优控制理论研究大脑老化对脑网络动力学的影响，发现双侧壳核在静息态到运动态的转换中呈现出最强的年龄效应。我们还研究发现非核心脑连接脑损伤可能是超早期无认知下降时的老年脑小血管病的特征，而核心网络损伤可能是由超早期脑小血管病向轻度认知功能障碍转变的标志。..在分析方法方面，我们研究发现基于静默法从功能连接中估计出直接功能连接作为个体的“脑纹”特征能比原始的功能连接获得更好的辨识能力，解释了直接功能连接获得更好辨识力的原因，并揭示大脑的腹侧和背侧注意网络的脑连接在个体化的“脑纹”特征上起重要作用。除此之外，本项目还在动态脑连接和脑状态分析及其应用等方面获得进展。