於虛擬實境空間巡行中大腦腦波變化之研究

Abstract

過去許多研究發現壓部後皮質在空間認知活動中扮演很重要的角色,其功能 包含提供「他物中心」空間定向時必要的資訊。然而這些研究大多是核磁共振的 腦造影研究為主,而後壓皮質在空間定向時的腦波變化,以及相關的腦波聯結網 路尚未明瞭。因此,本研究探討以「自我中心」和「他物中心」參考坐標系在空 間定向時,後壓皮質以及其他腦區的腦波變化及腦聯結網路狀態。 本研究以虛擬實境模擬的空間場景,讓實驗者進行路徑整合的空間活動,並 在實驗中,量測及觀察實驗者的腦波反應。在實驗中所量測到的腦波訊號,透過 獨立成份分析,以及時域頻域轉換來觀察不同頻帶不同腦區的腦波變化。此外, 本研究也以格蘭傑因果分析法來觀察大腦腦區之間的互動與聯結狀態。研究結果 顯示出,在進行路徑整合時,額葉皮質的θ腦波能量會上升,而腦前區的前扣帶 皮質、背外側前額葉皮質的θ腦波相互聯結成有效性網路。另外在腦後區的運動 區皮質、頂葉皮質、視覺區皮質、壓後皮質都觀察到α波的變化和聯結網路。當 受試者使用自我中心參考坐標系時,額葉皮質的θ波能量會顯著性的更為增加。 而他物中心者在後壓皮質,和視覺區皮質,頂葉皮質會發現α波的連結網路。不 僅如此,壓後皮質的α波能量還能預測,他物中心受試者的行表現好壞。 本研究的結果明確的指出,後壓皮質在的空間導航中扮演重要的功能。並進 一步發現後壓皮質在他物中心機制的大腦聯結網路和腦波變化。未來的研究,能 以此結果,衡量他物中心者的表現,並進一步協助實驗者訓練並增進空間導航能 力,減少迷向的發生。

Studies on spatial navigation reliably demonstrate that the retrosplenial complex (RSC) is crucial for allocentric information process for a translation function by transform egocentric spatial information into allocentric spatial reference frames (SRF) and vice versa. However, most of these studies are imaging studies. High temporal resolution measures such as electroencephalography (EEG) are missing. Besides, the interaction between RSC and other brain cortex for spatial navigation remains unclear. Thus, this study investigated the function of the RSC in spatial navigation with high temporal resolution and causal relation between RSC and other regions of navigational network. High-resolution EEG signals were recorded during a path integration task to analyze spectral perturbations during navigation based on allocentric and egocentric SRF. EEG signals were decomposed by independent component analysis (ICA) and subsequently time-frequency transformation to investigate the EEG modulation for reference frame-specific orientation processes. Granger causality flows between brain sources was measured using direct short-time directed transfer function (sdDTF). Our results showed that navigation involved areas including the parietal, motor, and occipital cortices with dominant perturbations in the alpha band and theta modulation in frontal cortex. Causal connectivity was found between the anterior cingulate cortex and left prefrontal cortex in theta band and between the motor, parietal and occipital cortices and RSC in alpha band. Egocentric navigation revealed stronger theta increased in the prefrontal cortex. In contrast, allocentric navigation engaged an occipital-pareitao-RSC alpha network. The RSC revealed strongest causal flow during orientation changes. Moreover, allocentric participants revealed ii performance-related alpha desynchronization and synchronization in the 12-14 Hz band in the RSC. The results support the role of RSC for translating egocentric spatial information into allocentric reference frames. The results also suggest RSC directly provides information on heading changes in humans.