| Aphasia refers to an impairment of language,because of the damage of language central areas in brain cortex(dominant hemisphere)and resulting in impaired language understanding and expression ability.The most common aphasia is the aphasia caused by stroke in dominant hemisphere,which is also called post-stroke aphasia(PSA).Many structural and functional neuroimaging techniques have been widely used to study the language damage,recovery and neurophysiological mechanism of PSA.However,alterations of brain function and the characteristics of the structural change in patients with PSA are still not clear.The fusion of multimodal brain imaging methods is needed in in-depth study.This study applied multimodal imaging methods of three-dimensional T1 imaging,diffusion tensor imaging(DTI)and functional magnetic resonance imaging(fMRI)data to detect the altered brain functional and structural characteristics in patients with aphasia.The study may give new neuroimaging insights in clinical diagnosis and evaluation of the objective index.The main contents are as follows:(1)Aiming at studying the change of local synchronization in resting state in PSA,we investigated the altered intrinsic local synchronization using regional homogeneity(ReHo)on PSA(n = 17)and age-and sex-matched healthy controls(HCs)(n = 20).We examined the correlations between the abnormal ReHo values and the aphasia severity and language performance in PSA.Compared with HCs,the PSA patients exhibited decreased intrinsic local synchronization in the right lingual gyrus,the left calcarine,the left cuneus,the left superior frontal gyrus(SFG),and the left medial of SFG.The local synchronization(ReHo value)in the left medial of SFG was positively correlated with aphasia severity(r = 0.55,P = 0.027)and the naming scores of Aphasia Battery of Chinese(r = 0.66,P = 0.005).This result indicated the neurophysiological mechanism of PSA may be attributed to the abnormal alterations of local synchronization in the brain regions aforementioned.(2)We focused on the possible local functional activity changes and altered functional connections in these regions in PSA patients.By combining amplitude of low-frequency fluctuations(ALFF)and inter-regional functional connectivity(FC)using resting-sate functional MRI,we examined the alterations of locally regional and remote inter-regional network cerebral functions in aphasia.In total,17 patients with PSA who had undergone stroke in the left hemisphere and age-and sex-matched healthy controls(n = 20)were enrolled in this study.The patients showed significantly increased intrinsic regional activity mainly in contralateral mesial(hippocampus/ parahippocampus),temporal and extra temporal cortices,and increased inter-regional FC between right hippocampus and right fusiform gyrus.The results suggested contralateral widespread inter-regional neural network responsible for compensatory insufficient left hemisphere language capacities.We also found decreased ALFF in lingual gyrus and frontal cortices of dominant hemisphere,indicating impairments of language and semantic network.The changes in intrinsic regional brain activity and associated remote functional connectivity network would provide valuable information for better understanding the pathophysiological mechanisms of aphasia.(3)We focused on exploring the changes of the local brain structure and the corresponding abnormal brain functional connectivity changes in PSA patients.We investigated specific regions with gray matter volume(GMV)abnormality in patients with PSA(n=17)and age-and sex-matched healthy controls(HCs)(n=20)using voxel-based morphometry.In addition,we examined whether there was a link between abnormal gray matter and altered interregional FC.Furthermore,we explored the correlations between abnormal interregional FC and clinical scores in aphasic patients.We found significantly increased GMV in the right superior temporal gyrus,right inferior parietal lobule(IPL)/supramarginal gyrus(SMG),and left middle occipital gyrus.Decreased GMV was found in the right caudate gyrus,bilateral thalami in PSA patients.Patients showed increased remote interregional FC between the right IPL/SMG and right precuneus,right angular gyrus,and right superior occipital gyrus;while reduced FC between the right caudate gyrus and supplementary motor area,and dorsolateral superior frontal gyrus.Moreover,iFC strength between the left middle occipital gyrus and the left orbital middle frontal gyrus was positively correlated with the performance quotient.We suggested that GMV abnormality contributes to interregional FC in PSA.These results may provide the structural and functional imaging evidence for the pathogenesis of PSA.(4)Aiming at the individual identification problem of the brain functional network characteristics in the whole brain connection mode in PSA,the present study used whole-brain functional connectivity-based multivariate pattern analysis to distinguish PSA patients from controls.Here,17 patients with PSA and 20 age-and sex-matched healthy controls were enrolled.We used functional connectivity pattern and linear support vector machine to classify two groups.The results showed that the accuracy of classification reached to 86.5%,sensitivity reached to 76.5%,and specificity reached to 95.0%.In addition,consensus connections were mainly located in the fronto-parietal,auditory,sensory-motor,and visual networks.Furthermore,the right rolandic operculum contributed the highest weight.We suggested that whole-brain functional connectivity could be used as a potential neuromarker to distinguish PSA patients from controls.(5)We focused on the fiber connection damage in the ventral and dorsal language pathways in PSA patients.The whole brain unbiased tract-based spatial statistics method was applied to analyze the possible changes of fiber connection in PSA comparing to healthy controls(HCs).Eighteen patients with acute aphasia and age-,gender-,and education-matched HCs underwent language assessment and DTI scanning.WM integrity(fractional anisotropy)for both groups was quantified using whole brain unbiased tract-based spatial statistics method,and the relationship between WM integrity and clinical features in PSA was assessed by linear correlation analyses.The aphasic patients showed decreased WM integrity in the left inferior fronto-occipital fasciculus/inferior longitudinal fasciculus(IFOF/ILF)and the left uncinate fasciculus,which represented components of ventral language pathway;and the left superior longitudinal fasciculus(SLF),which related to dorsal language pathway.In addition,WM integrity of the left IFOF and SLF showed positive correlations with aphasia quotient,performance quotient,and cortical quotient,respectively.These findings suggested that impaired WM integrity in both language pathways not only contributed to language performance,but also to general cognitive status.We suggested that aphasia involves a breakdown of multiple connections of dorsal and ventral streams that directly contributes to language deficits.Damage to these dual-streams may serve as a neuromarker for PSA. |
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