뇌파의 시간-주파수와 위상 동기화 분석을 통한 기억 인출 과정에서의 뇌 활성화 연구 = A study of brain activity during memory retrieval using the time-frequency and phase synchronization analysis of EEG

다국어 초록 (Multilingual Abstract)

We still do not know the function of brain area, brain activity when cognitive or memory process. Recent advances in neuro-imaging techniques and cognitive neuroscience have enabled us to read out brain activity related to cognitive functions. It is a performance by the non-invasive measuring apparatus such as magnetoencephalography (MEG), positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). In particular, many cognitive studies have employed the EEG technique due to its simplicity, mobility and fine time resolution. Traditional methodologies using EEG have relied on the measurement of event-related potentials (ERPs) or power spectra to identify the neural response to a cognitive process of interest. Another measurement, the spectral analysis using EEG shows change of power by frequency. However, these measurements typically examine the neural correlates of cognitive functions only in individual EEG channels according to the current of time. These results reveal the little emphasis on an organized neural response across the whole brain. Based on the assumption that the connectivity structure across the brain can represent the dynamics of an underlying cognitive process, but it was not a common use in the research of memory task. We particularly investigated the representation of the memory retrieval process through large-scale connectivity. The phase synchronization method was used to statistically evaluate the connectivity between all the pairs of EEG channels. We analyzed the EEG and behavioral data recorded from a memory retrieval task in which fourteen healthy subjects performed a series of a visual navigation task followed by a memory retrieval task in the 3-D virtual environment used beam project and head mounted display (HMD). We found that the overall spectral power decreased while the number of synchronized channels increased in the beta band (12-30Hz). The synchronized channels were mostly located in the occipital and parietal areas in the beginning of the memory retrieval process (~0.25s after stimulus onset), and then migrated to the frontal area in the late stage of process (~1s after stimulus onset). The spectral power at the gamma band increased while the number of synchronization channels showed no significant change during memory retrieval. These results suggest that memory retrieval may induce large-scale synchronizations of the beta rhythms among different brain regions and their topographic pattern may dynamically change during the memory retrieval process.

목차 (Table of Contents)

• 제１장 서론 1
• 1.1 연구 배경 1
• 1.2 관련 연구 5
• 1.1.1 기억 연구의 방법과 특징 5
• 1.1.2 위상 동기화 분석 방법을 이용한 연구 7
• 1.3 논문 목적 9
• 1.4 논문의 구성 10
• 제２장 기억 연구 11
• 2.1 기억의 분류 11
• 2.2 기억의 처리 과정 13
• 2.3 기억 장애: 기억 상실의 종류와 특징 15
• 제３장 3-D 가상 환경을 이용한 기억 연구 실험과 전처리 17
• 3.1 실험 환경과 과정 17
• 3.1.1 3-D 가상 환경의 특징과 활용 17
• 3.1.2 OLD/NEW 이론을 이용한 실험 과정 18
• 3.2 뇌 신호 데이터 수집 및 전처리 20
• 제４장 뇌 활성화의 시간, 공간적 분석 22
• 4.1 스펙트럼 분석 22
• 4.2 위상 동기화 분석 23
• 제５장 결과 25
• 5.1 행동 데이터 분석 결과 25
• 5.2 주파수 대역별 파워 값의 시간에 따른 변화 25
• 5.3 위상 동기화 분석을 통한 채널 간 관련성 파악 42
• 5.4 채널별 동기화 정도의 정량적 분석 44
• 5.5 동기화 정도의 지형학적 표현 46
• 제６장 토의 및 결론 48
• 참고 문헌 52