A Functional Magnetic Resonance Image Study About Sustained Attention After The Influence Of Repetitive Transcranial Magnetic Stimulation

Background Sustained attention,also known as the stability of attention,refers to focus one’s attention on certain object or activity for a long period of time.Currently,in psychology,Rapid Visual Information Processing(RVIP)task is a kind of classical paradigm that could be used to assess the ability of human sustained attention.Sustained attention is so important for our daily work,industrial operation,aging etc.At the present,studies about sustained attention have made great progress in psychology and cognitive neuroscience.While there is no such effective way that can change even enhance the ability of sustained attention.Repetitive Transcranial Magnetic Stimulation(r TMS)is a noninvasive neuromodulatory tool,which can be used to stimulate the brain by generating induced current almost without any pain,resulting in the alteration of physiological process and psychological process.The effect of alteration could be enhancing certain cognitive function or inhibiting certain cognitive function.Traditionally,high frequency r TMS was thought to be associate with enhanced effects,while low frequency inhibited effects.Usually the changed effects could last for a period of time.Functional Magnetic Resonance Imaging(f MRI)is a noninvasive brain activity detection tool that can be used to observe brain signal instantaneously.The combined technique of r TMS and f MRI could observed the brain activity after r TMS intervention.Our goal is to explore the effects about r TMS on sustained attention both in neurological and behavioral level.Methods A 2x2 Anova design was used to assess the high-frequency r TMS effects on sustained attention.38 normal college students were recruited.We divided the 38 participants averagely into two groups.One is sham group,which will receive sham r TMS session.Another one is high frequency group,which will receive real stimulation.The detailed parameters of r TMS are listed below: frequency = 20 Hz,duration = 2.5s,inter-train interval = 28 s,90% Motor Threshold(MT),number of total pulses = 1200.The Rapid Visual Information Processing task was selected for assessing the ability of human sustained attention.For behavioral data analysis,we firstly performed inner group paired t test and then did the analysis of variance(ANOVA)between groups.For functional image data analysis,firstly,we did the General Linear Model(GLM)on the 1st-level analysis for single subject.Then we performed inner group paired t test and ANOVA between groups.Results(1)At p < 0.05 level,high frequency r TMS shows no significant effects about mean reaction time of RVIP task.For reaction accuracy,only one factor shows significance.(2)The classical activation of sustained attention and working memory are verified in one sample t test in certain process of each group.We perform ANOVA between sham TMS group and high frequency r TMS group.At p = 0.05 level,we do a Alpha Sim Simulink to calculate the minimal voxel size to avoid the false positive effects.And the number is 389.The activated regions of contrast between sustained attention task and open-eyes rest task: bilateral precuneus(cluster size of the left is 447,the right is 507),left superior parietal lobe(cluster size = 401),right middle frontal lobe(cluster size = 413),left cerebellum(cluster size = 989).All the activation regions are negative.The contrast of 2-back working memory task between open-eyes rest task shows no activated brain region.The activated regions of contrast between 2-back working memory task and sustained attention task: left cerebellum(cluster size = 429).The activation is positive.The results of the above three comparisons were realized first by simple cognitive subtraction,and then by a second comparison between high frequency group and sham group.Given all that steps taken to analyze f MRI data,the final results would not show the classical pattern of sustained attention or working memory.Our goal was to discuss the effects of r TMS.Conclusion Our study shows no significant alteration effects of high frequency r TMS on sustained attention behavioral performance.But for neuroimaging level,r TMS shows a inhibited effectsboth on task-negative brain network and task-positive brain network.Our study doesn’t show any evidence that 20 Hz r TMS could enhance the ability of sustained attention due to lack of enough sample.