【作者】 于庆宝；

【导师】 唐一源；

【作者基本信息】 大连理工大学 ， 神经信息学， 2009， 博士

【摘要】 在功能磁共振成像(functional Magnetic Resonance Imaging,fMRI)的研究中,人们不仅关心哪些脑区会在相应的任务中激活,而且对脑激活网络的功能连通性更加感兴趣。语言加工和表象都属于人类的高级认知功能,对这两种认知过程中的脑加工模式进行深入研究具有深刻意义。尽管人们已经揭示了这两种认知任务中所激活的脑区,但关于各脑区间的功能连通性研究鲜有报道。心理旋转是一种表象变换,它是空间认知的一个重要方面。近年来,性别差异成为心理旋转领域中的研究热点。大量研究表明男性在心理旋转任务中的表现好于女性,一些研究发现心理旋转任务的脑激活也有性别差异,但是关于导致这种性别差异的原因人们还没有得到一致的结论,甚至还没有人研究经典的三维心理旋转中事件相关电位(Event-related Potential,ERP)的性别差异。针对以上问题,本文进行了以下研究:1.利用fMRI技术和WICA(Within-condition Interregional Covariance Analysis)方法建立了汉真字和汉假字加工过程中由右额下回(BA9)、左额中回(BA6)、左梭状回、右梭状回构成的神经系统的功能连通模型。结果发现:虽然四个感兴趣区在两种任务下都有激活,但是它们的功能连通模式不同,尤其是右梭状回,它在两种任务中与其他脑区之间的功能连通模式截然不同。这说明在汉真字和汉假字的加工过程中,脑内可能有着不同的信息加工模式,右梭状回可能在汉字字形加工中起到重要作用。2.利用fMRI技术和低频相干分析方法,采用事件相关设计,探讨了字符视觉表象任务中脑网络的功能连通性,结果发现:左额下回(Inferior Frontal Gyrus,IFG)、左顶上叶(Superior Parietal Lobule,SPL)和左楔叶(Cuneus,CUN)两两之间有着很强的功能连通,而左梭状回(Fusiform Gyrus,FUS)同其他三个脑区之间的连通性都很弱。这些结果部分的支持Kosslyn提出的关于表象的理论并初步揭示了视觉表象任务中各脑区间的功能相互作用。3.前人研究表明,心理旋转任务会用到客体工作记忆系统。本文采用先后呈现提示刺激和目标刺激的范式来探讨工作记忆的负荷是否会影响心理旋转中的性别差异,有三种实验任务:①无效提示的数字旋转;②有效提示的数字旋转;③有效提示的PMA(Primary Mental Abilities)图形旋转。结果发现:对无效提示的数字旋转任务,反应时和正确率在性别之间都无显著差异;对有效提示的数字旋转任务,正确率在性别之间无显著差异,而反应时的性别差异边缘显著;对有效提示的PMA图形旋转任务,正确率在性别之间无显著差异,但反应时有显著的性别差异。这说明工作记忆的负荷可能会影响心理旋转中的性别差异。4.对经典的三维心理旋转任务中ERP(Event-related Potential,ERP)的性别差异进行了研究。行为结果表明:反应时没有性别差异,正确率有显著的性别差异,男性表现明显好于女性。ERP结果表明:在顶叶区的电极,刺激出现后900-1000 ms的时间窗内,旋转100度与旋转50度相比波幅有负向漂移;在右额叶电极,600-700和800-900 ms时间窗内也发现了与旋转角度有关的波幅成分;同时,只在右额叶电极400-700 ms时间段发现了波幅的性别差异。这些结果表明,三维心理旋转中的性别差异发生在任务加工过程较早的阶段,可能包括旋转过程之前的刺激感知和辨识的认知过程。更多还原

【Abstract】 Researchers not only concern which areas are activated but also pay attention to functional connectivity among brain regions in studies using fMRI(functional Magnetic Resonance Imaging).Language processing and imagery are cognitive functions of human being.It is meaningful to investigate neural mechanisms of them.Brain regions which are activated during tasks involved language processing and imagery are found by neuroimaging studies.However,studies which examined functional connectivity among brain areas during cognitive tasks involved language and imagery are sparse.Mental rotation,which is one type of image transformation,is an important aspect of spatial cognition.Recently,sex differences became a hot point in studies of mental rotation.A number of studies found men performed better than women in mental rotation tasks.Some studies even found sex differences of brain activation during mental rotation.However,there are still debates about the factors which cause this sex differences.There is even no study examined sex differences of ERP(Event-related Potential) effects during the classical three-dimensional mental rotation task.In view of those issues,this dissertation implemented the following studies:1.FMRI and WICA(Within-condition Interregional Covariance Analysis) method are used to investigate functional connectivity pattern of the neural system consisted of right inferior frontal gyrus(BA9),left middle frontal gyrus(BA6),left fusiform gyrus and right fusiform gyrus during processing Chinese character and Chinese pseudo-character.The results indicate connectivity patterns especially the patterns between right fusiform gyrus and the other three areas are different during processing character and pseudo-character,although all of the four areas are activated underlining both conditions.These results suggest different patterns of information processing are used for processing Chinese character and Chinese pseudo-character and right fusiform gyrus may play important role in Chinese orthography.2.Low frequency coherence analysis and event-related fMRI are used to investigate functional connectivity of brain network during character imagery.The results indicate left IFG(Inferior Frontal Gyrus),left SUP(Superior Parietal Lobule) and left CUN(Cuneus) have strong connectivity between them,whereas the functional connectivity between left FUS (Fusiform Gyrus) and any of the other three areas is weak.These results partly support the imagery theory advanced by Kosslyn and primarily reveal functional interactions among brain regions during visual mental imagery.3.Previous studies indicate image is stored in object working memory system during mental rotation.Successive presentation paradigms are used to investigate if working memory load affects sex differences in mental rotation.Three tasks are designed:①number rotation with useless cue;②number rotation with cue;③PMA(Primary Mental Abilities) figure rotation with cue.Analysis of variance of repeated measures results indicate that:for the task of number rotation with useless cue,neither accuracy nor response time had significant differences between sexes;for the task of number rotation with cue,the accuracy had no significant difference between sexes while the response time had marginal significant difference between sexes;for the task of PMA figure rotation,the accuracy had no significant difference between sexes while the response time had significant difference between sexes. These results suggest working memory load could affect sex differences in mental rotation.4.Sex differences of ERPs during the classical three-dimensional mental rotation task are investigated.Results of behavioral data indicate response times have no significant difference between sexes,whereas accuracy had significant difference between sexes.Mental rotation related ERP effects were observed 900-1000 ms post-stimulus at parietal electrodes and 600-700 as well as 800-900 ms post-stimulus at right frontal leads,respectively.Sex differences,however,were observed already 400-700 ms post-stimulus at right frontal electrodes.These findings suggest that sex differences during three-dimensional mental rotation occurred in relatively early cognitive processing stages presumably including perception and identification of stimuli instead of mental rotation itself.更多还原