Functional MRI Study On Category-Member Generation Task State In Expressive Aphasia Patients After Stroke

Objective:Functional magnetic resonance imaging was performed on patients suffering from expressive aphasia after stroke.The main purpose was to detect the activation feature of brain regions related to expressive language and the state of network connectivity in category-member generation task,and to analyze its relationship with the occurrence and development of expressive aphasia.Subjects and Methods:Fifteen patients(male 14;female 1) suffering from expressive aphasia after stroke and an age-matched control group were recruited in this study,all of them received category-member generation task in an block-design.All the subjects were asked to imagine the words which belong to the category word showed to them.SPM2 was used to process fMRI data.Pre-processing include realign, normalization and smooth.Group analysis was performed with single sample t-test. Intergroup analysis was performed with two sample t-test.Finally,activated mapping was overlapped onto standard MNI template Locations,MNI coordinate and activated intensity of the brain regions were recorded.The greatest activation intensity regions(the posterior part of left lateral inferior frontal gyrus,Broca region included) in the resulting map of normal control group were considered as the seed voxels of the whole brain.Then Matlab7.0 was used to identify the brian areas correlated with ROI.Results:Ten patients were recruited in category-member generation task state scanning after affected factors(head motion,behavioral performance and machine noise) were ruled out.All the ten patients were males mean aged 56.7±8.6 years old;then we selected ten age-matched and sex-matched controls,mean aged 56.2±9.0 years old.The activated regions resulting map in category-member generation task of two groups showed:Positive activated regions of the control group included Broca's area, right Broca homologue area,SMA,left anterior insula,left superior temporal gyrus and left precentral gyrus;PCC,MPFC and right precuneus lobe were significantly deactivated during word generation task.Positive activated regions of the patient group included left middle frontal gyrus,postcentral gyrus,inferior parietal lobule, precuneus lobe,right inferior frontal gyrus,bilaterial precentral gyrus,insula, thalamas,striatum,SMA and cerebellum;bilaterial medial parietal cortices and left precuneus lobe were deactivated during word generation task.The positive activated regions differences of the two groups included the posterior part of left inferior frontal gyrus(controls＞patients);There were no significant differences about other brain areas in two groups(patients＞controls).The functional connectivity resulting map in category-member generation task of two groups showed:The regions positively correlated with ROI in control group included left inferior frontal gyrus,precentral gyrus,insula,superior temporal gyrus, inferior parietal lobule,PCC,superior frontal gyrus,middle frontal gyrus,middle occipital gyrus,middle temporal gyrus,precuneus lobe,cerebellum,right inferior frontal gyrus,middle frontal gyrus,inferior parietal lobule and bilaterial striatum.The regions positively correlated with ROI in patient group included left inferior frontal gyrus,insula,thalamas,inferior parietal lobule,postcentral gyrus,middle frontal gyrus,bilaterial cerebellum,precueus lobe.The differences of the regions positively correlated with ROI in two groups included SMA,right inferior frontal gyrus,middle frontal gyrus,superior temporal gyrus,middle temporal gyrus,precentral gyrus, cerebellum,left superior parietal lobule,precuneus lobe,thalamas,superior temporal gyrus,middle temporal gyrus(controls＞patients);the inferior part of left inferior frontal gyrus,middle frontal gyrus,postcentral gyrus,inferior parietal lobule,right medial frontal gyrus and superior frontal gyrus(patients＞controls).Conclusion:Compared with normal middle-old aged controls,the activation level of the posterior part of left inferior frontal gyrus(Broca area) declined or disappeared in patients with Broca aphasia after stroke in category-member generation task state, which suggest that damage to the expressive language center has led to the occurrence of aphasia.The emergence of language depends on the collaboration features of whole brain language areas.As the expressive language center,Broca area and whole brain function areas constitude the complex neural network for language processing and speech "output".①After stroke,the brain areas that played important role in language function such as SMA,bilateral temporal lobe,left thalamus,precuneus lobe,right Broca homologue area,right cerebelum reduced the positively correlation with ROI,which suggest that expressive language center injury lead to its interruped relations with those important brain regions,with the performance of connectivition loss.②After stroke,the regions around Broca area,left inferior parietal lobule increased the positively correlation with ROI,right Broca homologue area reduced the positively correlation with ROI,which suggest that the regions around Broca area and left inferior parietal lobule play important role in the language restoration of the initial stage.