Anodal TDCS Over The Left Frontal Eye Field Improves Sustained Visual Search Performance

The decrement in vigilance during sustained visual search is a matter of pervasive concern across diverse domains,including enemy aircraft detection,high-speed rail driving,and motor vehicle operation.This is because the loss of visual sustained attention during task execution can significantly impede performance,leading to misjudgment(i.e.,decreased target detection rate)or failure to detect critical information in a timely manner(i.e.,slowed reaction time),which may result in potentially irreparable accident consequences.Therefore,maintaining visual sustained attention is essential for ensuring optimal performance during prolonged,monotonous task execution.Buffering the decrement in visual sustained attention is a critical area of psychological research.Transcranial direct current stimulation(tDCS),a safe,portable,inexpensive,and noninvasive brain stimulation technique,has shown significant promise in enhancing cognitive functions such as perception and attention in numerous studies.Therefore,this study mainly focused on the effects and underlying mechanism of anodal tDCS in enhancing visual sustained attention.As one of the main brain area of the dorsal attention network(DAN),the frontal eye field(FEF)plays an important role in sustained attention.Previous research has suggested that the use of tDCS to modulate the excitability of FEF can enhance the performance of visual sustained attention.However,the cognitive mechanism underlying the improvement effects remains unclear,and it is uncertain whether these effects can be sustained after stimulation,particularly for complex cognitive tasks.Thus,the first aim of this study is to investigate the cognitive mechanism underlying the enhancement of visual sustained attention during and after anode tDCS over the left frontal eye field(1FEF).Furthermore,previous studies have exclusively examined the enhancement effect of stimulation at the behavioral level,with the neural mechanism of this effect remaining unclear.Therefore,the secondary aim of this study is to investigate the neural mechanism of anode tDCS applied over the 1FEF in enhancing visual sustained attention by using electroencephalography(EEG)technology.This study includes two experiments:Experiment 1 aims to explore the cognitive mechanism of transcranial direct current stimulation over the 1FEF to improve visual sustained attention during and after stimulation by detecting the behavioral indicators(such as perceptual sensitivity,response bias,hit rate,false alarm rate,and accuracy rate)of individuals in the visual search task that lasted for 38.8 min.In experiment 2,EEG technology is used to detect the EEG indicators(theta band oscillation and alpha band oscillation)of individuals during the visual search task lasted for 38.8 min to explore the neural mechanism of tDCS over the 1FEF to improve visual sustained attention.The results showed that:(1)At the behavioral level,during anodal tDCS over the 1FEF,performance was significantly improved,as evidenced by increased perceptual sensitivity(d’),hit rate,false alarm rate,and ACC,rather than response bias(β).Furthermore,compared to sham,anodal tDCS resulted in significantly higher d ’in the 9.6 min following stimulation,indicating that the effect could be sustained after stimulation.These findings suggest that anodal tDCS over the 1FEF can effectively enhance individual visual sustained attention,which is related to the regulation of cognitive resources.(2)At the neural mechanism level,during anodal tDCS over the 1FEF,theta band oscillation exhibited a significant increase,whereas alpha band power did not increase significantly for the online effect.For the after-effect,compared to sham,anodal tDCS caused a significant increase in theta power in the 9.6 min following stimulation,while alpha band power did not increase significantly.These results once again confirmed that tDCS may improve visual sustained attention by increasing the speed of regulating attention resources at the neural mechanism level.In summary,the results of this study showed that anodal tDCS over the 1FEF could significantly enhance an individual’s visual sustained attention.This finding revealed the critical role of the 1FEF in visual sustained attention and sheds light on the cognitive neural mechanism underlying this improvement effect.Specifically,the study showed that the improvement was mainly due to the enhancement of attention resource regulation speed rather than arousal level.This study has uncovered the cognitive and neural mechanisms underlying the effectiveness of tDCS over the 1FEF in improving visual sustained attention in healthy individuals.This finding enhances our understanding of the neural mechanism of visual sustained attention as well as the regulation mechanism of tDCS.Moreover,study’s use of tDCS to intervene in visual sustained attention can provide scientific evidence and practical reference for the cognitive enhancement function of tDCS.