Research On Brain Plasticity And Gut Microbiota Change Induced By RTMS In Patients With Cognitive Impairment And Depression After Stroke

Post-stroke cognitive impairment(PSCI)exhibits high incidence,and often coexists and interacts with post-stroke depression(PSD),seriously inhibiting the neurological rehabilitation and resulting in worse long-term outcomes.More evidence-based medical evidence is crying for the efficacy of repetitive transcranial magnetic stimulation(rTMS)on PSCI and PSD.Therefore,this dissertation intends to verify the efficacy of high frequency rTMS(HF-rTMS)over the left dorsolateral prefrontal cortex(DLPFC)on PSCI with or without PSD,and explore the underlying mechanisms from the brain plasticity and gut microbiota by using multimodal MRI imaging and 16 S r RNA gene sequencing technology based on the "Microbiome-Gut-Brain Axis".The contents are shown as follows:1.For the effects of rTMS on the brain activities in patients with post-stroke comorbid cognitive impairment and depression(PSCCID),true and sham rTMS were given to rTMS group and Sham group respectively.The alterations of the regional homogeneity(Re Ho)and amplitude of low-frequency fluctuations(ALFF)values of regions of interest(ROIs)were analyzed based on resting-state functional magnetic resonance imaging(rs-f MRI)data.The results showed cognition,depression,daily living ability and P300 were improved in both groups after treatment,while greater improvements were observed in the rTMS group.The rTMS group presented sevral brain regions with increased or decreased Re Ho and ALFF compared with its own pre-intervention and the Sham group,among which the regions with increased Re Ho and ALFF were mainly located in the stimulation side while the decreased ones were mainly located in the contralateral side.The increased Re Ho value in the left orbital gyrus and ALFF value in the left Heschl's gyrus were correlated with cognition and depression scores.Our results indicate that the neurophysiological underpinnings of HF-rTMS over the left DLPFC on the PSCCID patients are associated with enhancement of brain activities of the ipsilateral regions related to cognitive and emotional processing and weakness of brain activities of the contralateral regions through interhemispheric inhibition(IHI).2.For the effects of rTMS on functional connectivities(FCs)within the default mood network(DMN)in PSCCID patients,twenty widely used DMN nodes(ROIs)were selected to constructed a 20*20 connection matrix for FC analyses relying on the rs-f MRI data.The results showed that the connection strength of left temporal pole(Temp P)/ left parahippocampal cortex(PHC)and right lateral temporal cortex(LTC)/right retrosplenial cortex(Rsp)in the rTMS group were enhanced compared with its own pre-intervention and that in the Sham group,and the both FC values were positively correlated with mini-mental state examination(MMSE)scores.In addition,the rTMS group had more stronger FCs within the DMN than the Sham group.The nodes of these FCs were closely related to cognitive and emotional processing,and some of the enhanced FCs were correlated with the P300 latency and amplitude.Therefore,it is speculated that after HF-rTMS stimulation over the left DLPFC,enhanced FCs within the DMN serves as a compensatory functional recombination to promote cognitive and depressive recovery.3.For the effects of rTMS on the whole-brain functional network topology in PSCCID patients,rs-f MRI data was used to construct a whole-brain resting-state functional network through a complex brain network analysis based on graph theory,using the regions of prior brain template(BNA246)as nodes and the functional connections between regions as sides.The alterations in the topological organization at different levels were analyzed.The findings: after intervention,the rTMS group showed increased regions with higher nodal properties than the Sham group,meanwhile sevral regions with lower nodal properties.Part of those altered regions were correlated with scores of cognition and mood.Connectional properties analysis showed more enhanced connections in the participants after rTMS stimulation compared with the Sham group,especially in the left hemisphere.Modular properties analysis suggested that there were differences in the total connection strength among different modules between the two groups after intervention.These results reveal the complexity of the topological reorganization of the functional network,which may simultaneously involves nodal,connectional and modular properties,to compensate the destruction of the topological organization after stroke through the combination of the separation and integration effects.4.For the effects of rTMS on gray matter density(GMD)in PSCCID patients,the high-resolution T1 MR image was used to analyze GMD changes in brain regions based on voxel-based morphometry(VBM).The findings: the rTMS group presented sevral brain regions with increased GMD compared with its own pre-intervention and the Sham group,mainly locating in the stimulated hemisphere.Among those regions,GMD of the left middle temporal gyrus(caudal area)and cingulate gyrus(caudal area)were positively correlated with MMSE,GMD of the left middle temporal gyrus(caudal area),inferior parietal lobule(caudal area)and cingulate gyrus(caudal area)was positively correlated with Montreal cognitive assessment(Mo CA),GMD of the left precuneus(medial area)was negatively correlated with Hamilton depression rating scale(HAMD).Our results indicate that the clinical improvements following HF-rTMS over the left DLPFC in PSCCID are associated with GMD increase of cognition and depression related areas,which compensates for the damage of local structure and related functions after stroke through the rebuilding of brain structures.5.In consideration of the uncertain of gut microbiota alterations after stroke,the characteristics of gut microbiota dysbiosis in PSCI patients were firstly explored before revealing the microbiome regulation mechanisms of rTMS.Based on 16 Sr RNA gene sequencing technology,the difference of gut microbiota composition among patients with/without cognitive impairment after stroke(PSCI/non-PSCI)and healthy controls was determined.And the correlation between distinct bacteria and cognition was analyzed.The findings: at the phylum level,the Actinomycetes in the PSCI group was significantly increased.At the genus and species levels,among these increased bacteria in the PSCI group,the Anaerostipes hadrus was negatively correlated with the Mo CA scores,while the Bifidobacterium was positively correlated with the blood uric acid.The Bifidobacterium,Lactobacillus gasseri and Anaerostipes hadrus could distinguish PSCI from non-PSCI in stroke patients(AUC=0.785/0.792/0.750,P<0.05).Our results suggest that cognitive impairment after stroke is related to the disturbance of the gut microbiota,which could provide new clues for the related mechanisms of PSCI improvement.6.For revealing the intestinal underpinnings of rTMS on the PSCI patients,true and sham rTMS were given to rTMS group and Sham group respectively,and then observed the changes of gut microbiota composition.The findings: the rTMS group presented more progress in cognition(MMSE and Mo CA scores)than the Sham group.The Beta diversity of gut microbiota between the two groups tended to increase.The relative abundance of the Patescibacteria in the rTMS group was significantly lower than pre-intervention,and the Fusobacteriota deceased approximately 100-fold in the rTMS group relative to the control group,and the both phyla were negatively correlated with MMSE and Mo CA.At the genus and species levels,the altered genera/species in the rTMS group compared with its own pre-intervention and the Sham group were mainly belonged to Firmicutes,followed by Bacteriodetes,Proteobacteria,Patescibacteria,etc.Among these distinct genera/species,there was more ones with decreased relative abundance(24/35)and less ones with increased relative abundance(11/35).The distinct genera/species correlated with cognitive function were mainly that had decreased relative abundance,and the Bacteroides?nordii with decreased relative abundance and the Bacteroides?salyersiae with increased relative abundance demonstrated the strongest correlation with the cognition scores.Therefore,it is speculated that HF-rTMS over the left DLPFC may affect the intestinal flora composition through the "Microbiome-Gut-Brain Axis" to produce clinical effects,and further studies are needed to verify the specific pathways of Gut-Brain interaction.