|前額葉上內側 （pre-supplementary motor area, Pre-SMA）是抑制控制中相當重要的腦區。先前的研究表明，pre-SMA的介入可能會影響反應選擇及增強抑制性能之間的聯繫。非侵入性腦刺激是研究大腦區域與行為表現之間因果關係的重要技術。Joundi等人(2012) 和Leunissen等人（2022 年）使用 Go/Nogo作業和傳統的停止信號作業分別對於pre-SMA進行beta (20 Hz) 跨顱交流電刺激並觀察運動行為結果的變化。他們認為抑制能力隨著beta功率的增加而增加。此研究旨在更全面地討論beta跨顱交流電刺激應用於pre-SMA後的變化，包括對行為表現、N1及N2分別於電刺激之前與之後的差異以及希爾伯特-黃轉換的功率帶差異之變化。
30名學生在正式實驗期間進行了三次選擇性停止信號作業，在第二次的選擇性停止信號作業期間進行了1mA電流的beta跨顱交流電刺激。參與者需要在不犧牲準確性的情況下，對於指示盡快地透過力鉗 (grip-force) 做出反應或是抑制他們的行為。行為結果表明，刺激介入後，力量的恢復能力變差。在停止條件下，不成功停止的反應力量及力量速率，和不成功停止試驗中反應力量較大的錯誤回應率會隨著停止信號出現的時間長度增加而增加，這表示停止信號延遲的時間越長反應的力量會更大。希爾伯特-黃轉換 (Hilbert-Huang Transform; HHT, Huang et al. (1998)) 的結果表明，比較不同條件的結果之下，theta (2.8Hz~6.4Hz) 在進行反應的準備期間存在較低功率差，在運動反應期間存在較高功率差。繼續進行指令在延遲信號較短的條件中，跨顱交流電刺激之前與之後，運動區域的beta功率差和alpha (6.4Hz~13.5Hz) 功率差在進行運動反應的期間增加。在停止刺激條件出現之前，跨顱交流電刺激之後的成功停止反應與不成功停止反應之間beta功率差降低。同時，alpha和theta功率的變化也與較差的運動表現有關。事件相關模式於N1的結果也表明跨顱交流電刺激的介入會導致抑制能力下降。
;Background: The pre-supplementary motor area (pre-SMA) plays an important role in inhibition control, where previous studies suggest that intervention of pre-SMA likely affects the connection amid response selection and enhanced inhibitory performance. Non-invasive brain stimulation is an important technology to investigate the causal link between brain areas and behavioral performance. Joundi et al. (2012) and Leunissen et al. (2022) used the go/no-go task and the conventional stop signal task to investigate the motor change with tACS stimulation over pre-SMA with beta oscillation separately. They suggested that inhibitory ability increases with beta power increases. The current study aims to provide a more comprehensive discussion of the tACS intervention with beta oscillation over pre-SMA, including the difference between stimulation for behavior performance, N1 and N2 components and the power band change with Hilbert Huang Transform (HHT).
Method: Thirty students (12 females / 18 males) were recruited from National Central University, Taiwan. Three sessions of the selective stop signal tasks were conducted during the formal experiment, and intervention of beta tACS with 1mA current was conducted during the second session of selected stop signal tasks. Participants were required to inhibit their preparation response or respond with the force pincher with their thumb and index fingers as fast as possible without sacrificing accuracy, following instructions.
Results: The behavioral result shows that the ability of the force to recover after peak force alignment became poorer with stimulation intervention. In the stop condition, the peak force and peak force rate of unsuccessful stop and trial numbers of the full USST were increased followed by increased SSDs (stop signal delays), which means that the larger force is followed by a longer stop signal delay. The HHT result shows that theta power decreases with time during response preparation, and increases with time during motor response, beta and alpha power increases during motor response around the motor area in CSD1 (continue go signal delay-shortest one) between different tACS stimulation sessions. The beta power difference decreased between the successful stop and unsuccessful stop conditions before stop stimulus onset, yielding poorer performance after tACS intervention. Increased alpha and theta power during poor motor performance with poorer inhibition is also consistent with previous research findings. The Event Related Mode (ERM) result shows that for the N1 component, the ability of the inhibition decreases after tACS intervention.
Conclusion: In our study, we not only provide the change of behavioral performance after stimulation but also that of the electrophysiological power difference during the selective stop signal task. The beta, alpha and theta power difference decreases during response preparation with increases during motor response. These patterns of results suggest that the difference change for beta, alpha, and theta power band were highly correlated with inhibition ability change. Our findings show that tACS intervention reduces the ability of inhibitory control, although different from previous findings (i.e., tACS enhances the ability of inhibitory control, (e.g: Joundi et al. (2012) ; (Joundi et al., 2012); Leunissen et al. (2022)), our study may provide a more complete and comprehensive preparatory and executive period before inhibitory control information.