基于功能磁共振成像的早期失聪后脑跨模态重塑机制的关键问题研究

发布时间：2018-08-12 20:40

【摘要】：传统观点认为听觉皮层是一个只参与处理听觉信号的单模系统。然而,最近研究发现人脑的听觉皮层可以处理其它感觉刺激,而且这种跨模态活动在早期失聪人群更为明显。然而,早期失聪是否会引起听觉皮层参与非听觉认知活动,以及听觉区如何处理这些认知信号等关键问题却了解甚微。本课题将以早期失聪人群为模型来探讨失去原有功能的听觉皮层跨模态地参与视觉工作记忆任务处理的神经机制。本研究首先假设早期失聪被试的听觉皮层参与处理视觉工作记忆任务并且该皮层的活动能够预测他们工作记忆能力。因此,本研究首先招募41例早期失聪被试和40例年龄与性别相匹配的正常被试来完成包括编码、维持和再认三个阶段的视觉空间延迟再认任务。相比正常对照组,行为学结果表明早期失聪被试在完成工作记忆任务时反应更快。而且,脑激活检测结果表明在工作记忆任务的再认期,早期失聪组双侧颞上回呈现显著性激活,并且激活程度越高,早期失聪组完成工作记忆任务的反应速度更快且更准确。早期失聪组在工作记忆任务维持期的双侧颞上回,以及编码期的右侧颞上回均呈现显著性激活,而且激活程度能够预示早期失聪组更快的完成能力。上述结果都说明早期失聪组听觉相关皮层能跨模态处理视觉工作记忆任务。另外,维持阶段中的听觉皮层激活与开始佩戴助听器年龄成正相关,和终生佩戴助听器年龄比呈负相关,这说明越早或者越长期使用助听器可能抑制听觉皮层的跨模态重塑,并有助于提高佩戴助听器的临床疗效。另外,相比正常对照组,格兰杰因果分析表明早期失聪组从前额叶至颞上回的净信息流显著增强,这意味着自上而下调控机制能更好地解释早期失聪组听觉皮层跨模态激活现象。为了进一步明确早期失聪后跨模态重塑的听觉皮层的自发功能网络组织及其认知特性是否发生改变,本研究引入全脑静息态功能连接分析技术,研究42例早期失聪被试和39例正常对照双侧颞上回的自发功能网络活动的差异,以及功能连接强度与视觉空间工作记忆和数字工作记忆能力的相关性。与正常对照组相比,本研究发现早期失聪被试具有超常的视觉空间和数字工作记忆完成能力。功能连接分析结果表明早期失聪组右侧颞上回与双侧岛叶前部、右侧背外侧前扣带皮层和右侧背外侧前额叶皮层之间功能连接均显著增强。而且,右侧颞上回的功能连接强度与视觉空间工作记忆能力显著相关,这种相关性即使回归掉数字工作记忆的影响仍旧存在。因此,实验结果表明早期听觉剥夺能够增强颞上回的固有功能连接,并且有助于颞上回跨模态参与视觉工作记忆的处理。最后,为了明确早期失聪人群听觉皮层的局部跨模态重塑是否引起全脑大尺度功能和解剖网络的拓扑属性的变化。本研究纳入37例早期失聪被试和33例正常对照,分析解剖网络,功能网络,以及功能-解剖网络耦合等拓扑属性的变化。与正常对照组相比,本研究结果只发现早期失聪组Local节点之间功能连接增加,而Rich-club和Feeder连接未见显著差异。早期失聪组全脑功能-解剖连接耦合强度较正常对照呈现增强的趋势,并且耦合强度与他们开始佩戴助听器年龄呈现显著正相关,而与终生佩戴助听器年龄比呈现显著负相关。这些实验结果表明早期听觉剥夺被试的大尺度脑网络发育基本正常,增强的局部连接强度和功能-解剖连接耦合强度可能有助于早期失聪被试更有效地利用残余的感觉信息。综上,本论文初次尝试早期失聪人群听觉皮层跨模态参与视觉工作记忆的神经机制研究,以早期失聪为典型,从新的角度探讨了大脑工作记忆跨模态重塑机制,在早期失聪被试听觉区域是否发生跨模态重塑以参与和处理视觉空间工作记忆认知活动,早期听觉剥夺是否引起大脑自发功能连接发生代偿,及其对脑解剖与功能网络的影响等关键基础认知神经科学问题提供了基本依据与初步解答。神经可塑性是人脑通过学习和训练方式所具备的一种终生能力。期望本文有助于进一步了解疾病或创伤所引起脑结构与功能的可塑性改变之神经机制,以促进大脑损伤后的康复治疗与认知神经科学的发展。
[Abstract]:The traditional view is that the auditory cortex is a single-mode system that only processes auditory signals. However, recent studies have found that the auditory cortex of the human brain can process other sensory stimuli, and this transmodal activity is more pronounced in early deaf people. In this study, the auditory cortex of early deaf subjects was assumed to be involved in the processing of visual working memory tasks. In this study, 41 subjects with early deafness and 40 age-and gender-matched normal subjects were recruited to perform visual spatial delayed recognition tasks including coding, maintenance and recognition. In addition, brain activation test results showed that bilateral superior temporal gyrus in early deaf group showed significant activation during the recognition period of working memory task, and the higher the activation degree, the faster and more accurate the early deaf group completed the task of working memory. Both the bilateral superior temporal gyrus and the right superior temporal gyrus in the encoding stage showed significant activation during the working memory task maintenance period, and the degree of activation predicted faster completion in the early deaf group. Cortical activation was positively correlated with the age at which hearing aids were first worn, and negatively correlated with the age ratio at which hearing aids were worn throughout life, suggesting that earlier or longer use of hearing aids might inhibit cross-modal remodeling of the auditory cortex and help to improve the clinical efficacy of hearing aids. The net information flow from prefrontal lobe to superior temporal gyrus was significantly enhanced in the deaf group, which means that the top-down regulation mechanism can better explain the transmodal activation of auditory cortex in the early deaf group. In this study, resting-state functional connectivity analysis was used to study the difference of spontaneous functional network activity in 42 subjects with early deafness and 39 normal controls, and the correlation between the intensity of functional connectivity and visual-spatial working memory and digital working memory. The results of functional connectivity analysis showed that the functional connectivity between the right superior temporal gyrus and the anterior bilateral insular lobe, the right dorsolateral anterior cingulate cortex and the right dorsolateral prefrontal cortex was significantly enhanced in the early deafness group. There is a significant correlation between spatial working memory and spatial working memory, even if the effect of digital working memory is returned. Therefore, experimental results show that early auditory deprivation can enhance the intrinsic functional connectivity of the superior temporal gyrus and help the superior temporal gyrus to participate in the processing of visual working memory. In this study, 37 subjects with early deafness and 33 normal controls were included to analyze the changes of topological properties of anatomical network, functional network and functional-anatomical network coupling. It was found that there was an increase in functional connectivity between local nodes in the early deaf group, but no significant difference in Rich-club and Feeder connections. These results suggest that the development of large-scale brain networks in early hearing-deprived subjects is basically normal. Enhanced local connectivity and functional-anatomical coupling may help early deaf subjects to utilize residual sensory information more effectively. The cross-modal involvement of the auditory cortex in the neural mechanism of visual working memory is studied. Taking early deafness as a typical example, the cross-modal remodeling mechanism of brain working memory is discussed from a new perspective. Whether cross-modal remodeling occurs in the auditory region of early deaf subjects to participate in and process the cognitive activities of visual spatial working memory, and whether early hearing deprivation results in it. Neuroplasticity is a lifelong ability of the human brain through learning and training. It is hoped that this paper will help to understand the causes of disease or trauma. The neural mechanism of plasticity changes in brain structure and function promotes the development of rehabilitation therapy and cognitive neuroscience after brain injury.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：R338

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