Research Of The Regulation Effect Of Transcranial Alternating Current Stimulation On Vigilant Attention

Vigilant attention refers to the ability to self-sustain mindful,conscious processing of stimuli whose repetitive,non-arousing qualities,would otherwise lead to habituation and distraction by other stimuli.Vigilance decrement can result in a decline in mission performance and may even lead to task failure.Therefore,it is particularly important to study the neural mechanisms of vigilant attention and how to modulate the level of vigilant attention.In attention-related tasks,the time-frequency characteristics of the electroencephalogram(EEG)in theta band between the posterior midfrontal cortex(pMFC)and the lateral prefrontal cortex(LPFC)play a vital role,but whether those features correlate with vigilant attention remains unknown.In addition,transcranial alternating current stimulation(tACS)has been proved to regulate neural oscillations in specific frequency bands of the brain so that multiple cognitive functions can be modulated,however,few studies have shown that it can regulate vigilant attention.Based on mentioned above,the following two hypotheses are presented: 1)The time-frequency characteristics(including phase synchronization and time-frequency power)of theta band between pMFC and LPFC closely correlate to the level of vigilant attention.2)tACS of theta band can regulate theta-band time-frequency characteristics of the brain,and then modulate vigilant attention.To evaluate these two research hypotheses,two experiments were designed in this research.The results and conclusions are as follows:1)Experiment 1 mainly analyzes the relationship between different vigilance levels and EEG time-frequency characteristics.It was found that the higher the level of vigilant attention was,the earlier the phase synchronization occured in the theta band,the higher the synchronization and the time-frequency power were.On the other hand,the lower the level of vigilant attention was,the later the phase synchronization occured in the theta band,the lower the synchronization and the time-frequency power were.The results demonstrated that the time-frequency characteristics(including phase synchronization and time-frequency power)of theta band between pMFC and LPFC closely correlate to the level of vigilant attention.2)Experiment 2 mainly investigates the regulation effect of 6Hz tACS on EEG frequency characteristics and vigilant attention.The results showed that the reaction time was significantly reduced in the middle of the stimuli(5 minutes to 10 minutes of after stimulation begins),but the reaction time did not show any significant changes in other time periods,compared with the pseudo-stimulus.The phase synchronization of theta band was significantly decreased and the time-frequency power did not change significantly in the true stimulation group compared with the pseudo-stimulation group.It was demonstrated that theta-band tACS can regulate the phase synchronization of the corresponding frequency band after the stimulation,whereas it has no significant effects on the time-frequency power.At the same time,it can significantly reduce the reaction time and enhance the level of vigilance during the mid-stimulation,but has no significant effects on the reaction time and the level of vigilance after stimulation.In conclusion,this study shows that transcranial alternating current stimulation has a certain regulation effect on EEG frequency characteristics and levels of vigilant attention,which lays the theoretical and experimental basis for the practical application of transcranial alternating current stimulation on vigilant attention.