비침습적 경두개 뇌자극술이 정상인의 인지 기능 향상에 미치는 영향

Abstract

[한글]뇌에 입력된 정보를 유지하는 여러 복잡한 과정 중, 입력된 정보를 짧은 시간 동안 유지하여 장기간 기억, 언어 학습 및 실행 기능에 기초가 되는 과정을 작업 기억이라고 한다. 반복 경두개자기자극, 경두개직류자극 같은 비침습적 경두개 뇌자극술은 뇌기능을 조절하기 위한 방법으로 그 효과가 입증되었으며 최근에는 기억 기능을 향상시키기 위한 방법으로 이 두 가지 자극술이 연구되고 있다. 이 두 가지 비침습적인 뇌 자극 방법을 이용하여 기억 기능이 일시적으로 향상 또는 억제된다는 결과가 발표되고 있으나, 기억 기능의 향상을 위한 효과적인 자극 영역, 자극 시간 및 자극 강도에 대해서는 아직 비교 발표된 바 없다. 따라서, 본 연구에서는 정상인을 대상으로 하여 반복 경두개자기자극은 운동 역치의 100%, 10Hz로 1000회 자극하였고, 경두개직류자극은 1mA로 30분 자극하여 작업 기억 능력을 향상시키기 위한 자극 정도 및 효과 지속 시간 등을 알아보고자 하였다.본 연구의 결과는 다음과 같다.1. 반복 경두개자기자극으로 1000회 자극 후, 정답율 및 정확도가 자극 전과 500회 자극 후에 비해 향상되었다(p<0.05).2. 반복 경두개자기자극 효과는 자극 종료 후 30분까지 유지되었다(p<0.05).3. 반복 경두개자기자극에 의해 오답율 및 반응시간은 변화가 없었다.4. 경두개직류자극으로 20분 자극 후, 정답율 및 정확도가 자극 전과 10분 자극 후에 비해 향상되었다(p<0.05). 30분 자극 후에는 20분 자극 후에 비해 정답율 및 정확도가 계속 향상되었다(p<0.05).5. 경두개직류자극 효과는 자극 종료 후 30분까지 유지되었다(p<0.05).6. 경두개직류자극에 의해 오답율 및 반응시간은 변화가 없었다.7. 두 가지 자극을 하는 동안 특이 부작용은 나타나지 않았다.이상의 결과를 통하여 반복 경두개자기자극 및 경두개직류자극은 작업 기억 기능을 향상시키기 위한 효과적이고 안전한 뇌 자극 방법으로 생각되며, 작업 기억 기능을 향상시키기 위해 전전두엽은 효과적인 자극 부위임을 알 수 있었다. 작업 기억 기능의 향상을 위해서는 운동 역치의 100%, 10Hz 로 반복 경두개자기자극을 하였을 때 1000회 자극이 필요하며, 1mA로 경두개직류자극을 하였을 때 20분 이상의 자극이 필요함을 알 수 있었고, 두 자극 종료 후 30분까지 작업 기억 향상 효과가 지속됨을 알 수 있었다.

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Recently, for the enhancement of memory, these two methods are being massively investigated. However, the optimal site of stimulation or dose of stimulation for the enhancement of memory function is not well established. It is also not well investigated how long the stimulation effect is lasted after stimulation. The objectives of this study are to determine the effective stimulation site, dose, and residual effect of rTMS and tDCS for the enhancement of working memory. For these purpose, rTMS with the intensity of 100 % motor threshold and the frequency of 10Hz, and tDCS with 1 mA were applied in the twenty normal persons.The results of this study were as follow;1. After 1,000 pulses of real rTMS, the correct rate and accuracy were improved compared to the baseline and the previous test (p<0.05).2. rTMS effect was maintained for 30 minutes after the end of stimulation (p<0.05).3. The error rate and reaction time were not changed by rTMS.4. After 20 minutes of real tDCS, the correct rate and accuracy were improved compared to the baseline and the previous test (p<0.05). After 30 minutes of real tDCS, the correct rate and accuracy were improved compared to the previous test (p<0.05).5. tDCS effect was maintained for 30 minutes after the end of stimulation (p<0.05).6. The error rate and reaction time were not changed by tDCS.7. Side effect did not occur during or after rTMS and tDCS.With these results, both rTMS and tDCS were considered as effective and safe brain stimulation methods to enhance working memory in normal person. For the enhancement of verbal working memory by tDCS and rTMS, the left prefrontal cortex seemed to be a proper site of stimulation. By tDCS at 1mA, stimulation time more than 20 minutes was required, whereas by 10 Hz rTMS at the intensity of 100 % motor threshold, 1,000 pulses were needed to obtain the positive effect of stimulation.