새로운 환경에 익숙해짐에 따라 나타나는 인간 해마의 뇌파 역할 연구

Abstract

The hippocampus plays a key role in the encoding and retrieval of information related to novel environments during spatial navigation. However, the neural basis for these processes in the human hippocampus remains unknown because it is difficult to directly measure neural signals in the human hippocampus. This study investigated hippocampal neural oscillations involved in encoding novel environments during spatial navigation in a virtual environment. Seven epileptic patients with implanted intracranial hippocampal depth electrodes performed three sessions of virtual environment navigation. Each session consisted of a navigation task and a location-recall task. The navigation task consisted of eight blocks. In each block the participant navigated to the location of four different objects and was instructed to remember the location of the objects. After the eight blocks were completed a location-recall task was performed for each of the four objects. Intracranial electroencephalography data were monitored during the navigation tasks. Theta (5–8 Hz) and delta (1–4 Hz) oscillations were lower in the first block (novel environment) than in the eighth block (familiar environment) of the navigation task, and significantly increased from block one to block eight. By contrast, gamma (31–50 Hz) oscillations were higher in the first block than in the eighth block of the navigation task, and significantly decreased from block one to block eight. Furthermore, comparison of the sessions with the higher recall performance (lower error between identified and actual object location) and the lower recall performance revealed that gamma and high-gamma (51–100 Hz) oscillations significantly decreased from block one to block eight only in sessions with high recall performance. These findings indicate that low-frequency (delta and theta) oscillations were associated with memory encoding of spatial novelty and that the interaction of high- (gamma and high-gamma) and low-frequency oscillations was important for successful encoding of spatial novelty.