空間巡航之腦動態變化：以EEG探討重新導向之現象

Abstract

在此空間巡航研究中，我們探討了尋找目標物的過程，遇到阻礙並繞路的腦動態之變化，同時觀察使用不同的參考座標(可分為自我中心及他物中心兩種)對重新導航過程之影響。我們建立了一個以城鎮為背景的虛擬迷宮場景，並在每棟完全相同的建築物中，挑選其中的四面牆貼上海報，作為受試者的尋找目標，過程中伴以50%機率出現的路障，迫使受試者必須繞路以到達目的地。實驗中紀錄了腦電波訊號，並利用獨立成份分析(Independent Component Analysis)找出了組成腦電波的各個獨立訊號源並分類，再透過事件相關頻譜擾動(Event-related Spectral Perturbation)觀察腦電波在頻率和時間上的變化。研究成果發現，在遭遇路障時，以自我中心為參考座標者因總是選擇較為固定的路線而有較好的重新巡航表現，其巡航相關之頂葉皮層(Parietal cortex)呈現較弱之抑制現象、對障礙物的突發事件反應較強烈，尤其是在後扣帶皮層(Retrosplenial cortex)的部位，δ與θ頻帶有較明顯的能量上升；反觀以他物為中心者，因其達成路徑較為多元而須到達目標的過程中持續規劃，故路徑規劃的能量較為強烈─尤以後扣帶皮層之α頻帶抑制現象較為明顯，也因此需要較長重新巡航的完成時間。

This study investigated the brain dynamics during searching and detouring based on distinct reference frames. Participants navigated a virtual maze with their proclivity for using an egocentric or allocentric reference frame, and searched for the assigned target for each trial. With the introduction of road blocks, navigators were forced to re-orient and plan detours to reach the goal locations. The Electroencephalography (EEG) dynamics in searching process went through Independent Component Analysis (ICA) and subsequent Event-related Spectral Perturbation (ERSP) analysis with clustering results of the independent components. We found that when encountering an unexpected barrier, Turners, who preferred egocentric reference frame, always chose some fix routes and consequently had better re-navigating performance. Turners had weaker suppression in navigation-related Parietal cortex, and responded stronger to the sudden appearance of barriers. Especially in Retrosplenial cortex, there were significant power increasing in delta and theta bands. On the contrary, Non-Turners, with allocentric reference frame, could plan consistently to achieve the goals for their various paths. As the result, their power in route-planning was stronger, especially the suppression in alpha band of Retrosplenial cortex. This also caused them to spend more time in re-orienting and completing detour.