Study Of Sex Differences And Functional Connectivity During Orthography And Imagery Tasks

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:â‘ number rotation with useless cue;â‘¡number rotation with cue;â‘¢PMA(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.