Resting-state Functional Magnetic Resonance Imaging Based Brain Connectomics In Poststroke Aphasia

Focal damage due to stroke usually causes a collection of language disruptions in phonological processing as well as semantic and executive-cognition functions;this condition is called post-stroke aphasia(PSA).These behavioral deficits originate from the disruption of regions local to the lesion site as well as the dysfunction of interconnected remote regions within the language network.Resting-state functional magnetic resonance imaging(rsfMRI)is an emerging method help to reveal network pathology in post stroke aphasia.Previous neuroimaging studies have indicated that structural damage caused by stroke induces disruptions in network coherence which could explain the loss of language function.Herein we focused on brain network-based methods from static and dynamic aspects,such as functional connectivity density,dynamic amplitude of low-frequency fluctuations,and dynamic functional connectivity to characterize different network properties(e.g.integration or segregation)and their relationship in post stroke aphasia。The main contents are listed as follows:1.We used functional connectivity density(FCD)to investigated the integrative features of key nodes in language network in PSA.We compared FCD between individuals with PSA and healthy controls.We then performed Pearson’s correlation analysis on the FCD values from the affected brain regions and the speech scores in the PSA group.Compared with HCs,individuals with PSA showed decreased FCD in the ipsilesional frontal lobe,temporal lobe and basal ganglia.PSA participants also showed increased FCD in the contralesional frontal-pariatal-temporal lobe and basal ganglia.The decreased long-range FCD in the left superior temporal gyrus in PSA participants was positively correlated with the spontaneous speech score.Our findings provide objective imaging evidence of the language functional pathophysiology in PSA.2.This study predicts the impairment of language function after stroke through the dynamic abnormalities of network.We first applied dynamic framework(dynamic segregation obtained from dynamic amplitude of low-frequency fluctuations(dALFF)and dynamic integration obtained from dynamic functional connectivity(dFC))to restingstate functional MRI data from PSA patients,and healthy controls.Compared to the healthy controls,the PSA participants exhibited decreased dALFF and dFC in the ipsilesional frontal and temporal subregions.PSA participants also displayed increased dynamic FC between left temporo-frontal subregions and right homotopic language regions.Furthermore,we found that dALFF in the pars triangularis of the left inferior frontal gyrus was positively associated with aphasia quotient.These findings indicate that language related cortical activity flexibility in PSA is reduced,and the change of local activity flexibility is related to the destruction of ipsilesional network integration,which leads to the loss of corresponding functions.The results of this study provide valuable spatial and temporal information for the alterations of dynamic separation and integration at network-level in PSA participants,and illuminate how dysfunction in flexible activity may underlie language deficits in PSA.