A Research On Visual Fronto-Parietal Attention Network Based On TMS And FMRI

Visual search is an important way for human beings to receive and process external information,as well as a complex cognitive processing process.Therefore,it is necessary to study visual search.Currently,visual search is mainly controlled by goal-oriented top-down pathway and stimulus-oriented bottom-up pathway.Neuroimaging showed that visual attention was mainly mapped to the fronto-parietal network,with the frontal and parietal lobes as the central brain areas.However,the different brain regions controlled by different pathways and their interactions are still unclear.Therefore,we need to further investigate the attention regulation of the fronto-parietal network.The study used offline cTBS(continuous Theta Burst Stimulation)in Transcranial Magnetic Stimulation(TMS)to stimulate the posterior parietal cortex and used functional Magnetic Resonance Imaging(fMRI)to investigate the regulation of attention of the fronto-parietal network.The paradigms used in this study included pop-out and search tasks.In the pop-out task,the color and the direction of the target stimulus were different from the interfering stimulus,which induced the bottom-up pathway.In the search task,the target stimulus and the interfering stimulus were only in different directions,which induced the top-down pathway.The TMS stimulation site was the right superior parietal lobule(rSPL),which was determined by previous fMRI experiments.In this study,SHAM coil was used as control stimulation.The behavioral study after TMS intervention in this paper showed that compared with SHAM stimulation,the offline cTBS stimulation of rSPL significantly reduced the accuracy of the search task.When the target appeared in the left and right field as another research factor,it was found that the stimulation of rSPL significantly reduced the accuracy in the left and right field under the search task.This study showed that rSPL plays an important role in the top-down pathway and has an impact on both sides of the field.fMRI studies showed that compared with SHAM control group,the stimulation of rSPL significantly reduced the behavioral performance in the top-down pathway when the target appeared in the left field.The fMRI results showed that the bottom-up pathway mainly activated the parietal lobe,and also including bilateral occipital lobe,temporal lobe and angular gyrus.While the top-down pathway mainly activated theparietal lobe,frontal lobe and subcutaneous insula.In addition,ROI analysis showed that after cTBS stimulation of rSPL,the activation intensity of rSPL in the top-down pathway was nearly significantly reduced when the target appeared in the left field,and the contralateral homologous parietal lobule was also significantly inhibited.Furthermore,activated compensation of ipsilateral putamen,medial cingulate and bilateral insula and lateral contribution of bilateral hippocampus in visual search were found.Functional connectivity analysis further demonstrated that after cTBS stimulation of rSPL,the connectivity between rSPL and bilateral medial frontal gyrus and contralateral superior temporal gyrus was enhanced.In summary,the topic selection in this paper expanded the research on attention network,and combined with TMS technology and fMRI technology to accurately explored the regulatory role of the right superior parietal lobule in the fronto-parietal attention network from the spatial dimension.On the one hand,it revealed its important influence in the top-down pathway from behavioral results and neural mechanisms.On the other hand,our study supported the hypothesis of bilateral inhibition in interhemispheric competition and provided new evidence that compensated for related brain regions and functional connections within the hemisphere.