평균크기 처리의 신경생리학적 기제 = Neurophysiological Mechanisms of Ensemble Size Processing

국문 초록 (Abstract)

시각체계는 처리 용량에 한계를 가지고 있다. 이 한계를 극복하는 방법은 망막에 맺히는 시각 정보를 요약하여 표상함으로써 전체 시각 장면을 효율적으로 처리하는 것이다. 이처럼 많은 정보를 요약해서 표상하는 것을 평균 표상(mean representation)이라 한다. 평균 표상을 처리할 때 사용되는 분산주의와 하나의 자극을 처리할 때 사용되는 초점주의가 뇌의 활성화에 차이를 보인다는 연구결과는 존재하지만, 평균크기 자극이 제시된 후 어떠한 처리과정을 거치는지에 대한 연구는 부족하다. 따라서, 본 연구에서는 평균크기 판단 과제를 수행하는 동안 발생하는 뇌파를 관찰하여 평균크기에 따라 조절되는 뇌파 성분이 있는지 보고자 하였다. 실험은 비교자극과 기준자극을 순차적으로 제시하고, 비교자극과 기준자극 중 평균크기가 더 큰 것을 응답하게 하는 평균크기 판단 과제를 실시하였다. 이 때, 비교자극은 평균크기 비율 조건 5가지, 개수 조건 2가지로 이루어진 원 집합이 제시되었고, 기준자극은 평균크기가 2.1°~2.8° 사이인 원 집합이 제시되었다. 실험 결과, 비교자극의 사건관련전위(Event-related potential; ERP)에서 70~100ms, 250~310ms에서 평균크기에 따라 평균 진폭에 유의한 차이가 나타나는 것을 관찰할 수 있었고, 150~180ms에서 평균크기에 따라 부분 영역 지연시간에 유의한 차이가 나타나는 것을 관찰할 수 있었다. 기준자극 분석에서는 70~100ms, 150~180ms, 250~310ms 모두 평균크기에 따라 유의한 차이를 보이지 않았다. 비교자극과 기준자극 ERP 분석만으로는 평균크기 표상이 실제로 반영된 것인지, 전체 면적을 반영하는지 구분하기 어렵기 때문에, 기준자극 반응에서 비교자극 반응을 뺀 차이 뇌파를 분석하였다. 그 결과, 120~160ms 사이에서 평균크기 비율이 커질수록 차이 뇌파의 평균 진폭이 점차 증가하는 것을 관찰할 수 있었고, 200ms 이후에는 평균크기 비율 조건에 따라 차이 뇌파의 평균 진폭에 유의한 차이를 보이는 것을 관찰할 수 있었다. 이러한 결과는 70~100ms에 원 집합의 개별 원에 대한 처리 혹은 전체 면적에 대한 처리가 이루어진 후, 120~160ms에 평균크기에 대한 처리가 이루어지며, 200ms 이후에는 평균크기 판단 과제의 의사결정 처리과정이 반영될 수 있다는 것을 시사한다. 본 연구의 연구결과는 평균크기 처리의 신경학적 처리에 대한 중요한 통찰이 될 것으로 기대된다.

목차 (Table of Contents)

• 국문 요약 ········································································································································· iii
• Ⅰ. 서론 ·············································································································································· 1
• 1. 연구 배경과 목적 ································································································································ 1
• 2. 이론적 배경 ··········································································································································· 3
• 3. 연구 문제 및 가설 ···························································································································· 15
• Ⅱ. 방법 ············································································································································ 16
• Ⅲ. 결과 ············································································································································ 19
• Ⅳ. 논의 ············································································································································ 32
• 참고문헌 ·········································································································································· 36