全域或區域地標之虛擬環境中尋路的學習行為與回憶時腦波活動

Abstract

本研究建立一套用來研究人類空間巡行的可調式虛擬實境軟體，此軟體建構很多有用的功能，讓研究者可以設計虛擬空間巡行實驗以探討其行為表現與生理訊號。地標對於找尋目標是一個重要的參考位置，而很少有研究根據地標的特性:全域與區域地標，來探討對於空間巡行的影響，本研究建構只有全域地標或區域地標的虛擬環境，並且研究學習搜尋目標過程中性別的行為差異與使用學習後的記憶去搜尋目標過程中的腦波變化。在學習過程中，本研究使用全面的與深入的量測指標探討性別在規則迷宮中此兩種地標下搜尋目標的績效。全面性指標如校正距離與搜尋時間並沒有全部呈現出男生在空間巡行時的優勢，雖然女生搜尋時花了比較多的時間但是在距離上卻與男生無異。而深入性的指標提供了更多的資訊，女生遠離目標的時間比例較少，停在同一位置的時間比例較多且在不動時旋轉角度的比例較高，顯示出女生有可能先停止再藉由旋轉方向獲得更多的視覺資訊以進行下一步。簡而言之，男生在空間巡行時速度會比女生快，但不一定會比較有效率。 在使用已學習的記憶進行目標搜尋方面，本研究比較了在規則與不規則迷宮中以及全域與區域地標下的腦波EEG能量，並且有系統的將搜尋目標過程分為計劃、搜尋熟悉地點與跟隨腦內已知路徑的階段。額葉theta能量會上升如同文獻一樣，而在搜尋時到達最大之後在跟隨階段則會緩緩下降。在跟隨階段，額葉beta及後面腦區的theta同樣會有能量下降的現象顯示出心理活動的降低及警覺性的提高。而有較大視覺刺激範圍的全域地標比區域地標引發出更大額葉及枕葉的delta能量，不規則迷宮下誘發出較多枕葉gamma能量有可能是因為需要較多視覺訊號的處理。女生顯示出較小的額葉theta能量上升及較多的左邊感知運動區gamma能量下降，支持了女生仰賴更多地標資訊的觀點。

The current study introduced a software framework, FlexNavi (flexible navigation), for studying human navigation. FlexNavi provides many useful functions in virtual spatial navigation for researchers to design their idiosyncratic behavioral or neuroimaging experiments. Landmarks are important spatial information as the reference points for wayfinding. According to the characteristic of landmarks, current study built virtual environment with global or local landmarks, and investigated the gender behavior differences during learning to search targets, as well as analyzed EEG activities during retrieving spatial memory to search targets after learning. During learning, This study assesses gender differences in wayfinding in environments with global or local landmarks by analyzing both overall and fine-grained measures of performance. Both female and male participants were required to locate targets in grid-like virtual environments with local or global landmarks. Interestingly, the results of the two overall measures did not converge: although females spent more time than males in locating targets, both genders were generally equivalent in terms of corrected travel path. Fine-grained measures account for different aspects of wayfinding behavior and provide additional information that explains the divergence in overall measures; females spent less time traveling away from the target location, a higher proportion of time not traversing, and made more rotations when stopping than males did. Rather than unequivocally supporting male superiority in wayfinding tasks, both the overall and fine-grained measures partially indicate that males and females are differentially superior when using global and local landmark information, respectively. To summarize, males moved faster than females but did not necessarily navigate the spatial surroundings more efficiently. Each gender showed different strengths related to wayfinding; these differences require the application of both overall and fine-grained measures for accurate assessment. During retrieving, this study investigated EEG power during two geometric structure mazes (regular and irregular) with global or local landmark types, and systematically divided the navigation processes into planning, searching and cruising stages. The frontal theta power was increase during navigation as result of navigation literatures and reached maximum during searching stage then suppressed during cruising stage. During cruising stage, there were also frontal beta and posterior theta power suppression which would reflect the cognitive status change of mental activity and alertness. Global landmark with extensive stimulus field induced larger delta power of frontal and occipital cluster than local landmark. The larger gamma power of irregular structure may be due to the requisition of more visual processing. The result of female navigation demonstrated smaller increase of frontal theta power and larger decrease of left sensorimotor gamma power, and this would support the gender difference which females rely on more landmark information.