眼睛開闔與光線對人類大腦感覺網路的影響: 靜息態功能性磁振造影之研究

Abstract

靜息態腦功能性磁振造影(Resting-state brain fMRI)在最近幾年受到神經 科學家廣泛的注意。與傳統功能性造影譬如以血液含氧程度為對比的功能性磁 振造影(Blood oxygenation level dependent – functional magnetic resonance imaging, BOLD-fMRI)大不相同的是,靜息態腦功能性造影並不需要額外的刺 激,就能夠取得大腦各個不同反應區域的共振連結,因此除了一般受試者外, 更有機會進一步應用在臨床患者身上。 眼睛開闔雖然是微小的動作,但是對大腦的覺醒,注意力,執行,各種感 覺系統,與預設模式網路都有相當程度的影響。但是過去的文獻比較沒有嚴格 考慮眼睛開闔時光線因素可能造成的影響。本研究針對二十一位右撇子健康受 試者,利用實驗設計觀察受試者在有光線與無光線的環境下,張眼與閉眼兩種 動作對大腦不同注意力網路,感覺網路,以及預設模式網路所產生的變化。 實驗結果顯示眼睛開闔與光線對大腦有不同的作用。在傳統血液動力的結 果分析上,光線對大腦造成前額葉與視覺相關皮質的活化,眼睛開闔則會活化 視丘與視覺相關皮質。至於在功能性連結上,則發現在眼睛閉合的狀態下,不 論有無光線因子的介入,大腦各種感覺網路以及注意力網路皆會產生高度的共 振,至於大腦預設模式網路則相對受較小的影響。

Resting-state brain functional Magnetic Resonance Imaging (rs-fMRI) has acquired intensive attention among neuroscientists in recent years. Compared with traditional blood oxygenation level dependent-fMRI (BOLD-fMRI), rs-fMRI can obtain oscillations—the functional connectivity—between different brain regions without stimulations or tasks. Eyes-closed or eyes-open, though trivial, is critical for stimulus-induced brain activation patterns. However, the previous literature did not consider seriously the possible concurrent confounding effect of the light. In this rs-fMRI study, 21 healthy right-handed subjects were deprived of light for certain experimental sessions, and we aimed to investigate the pure effect of light/dark and eyes-open/closed especially upon attention, sensory and default mode networks of the human brain. Results suggested that light/dark and eyes-open/closed have different roles upon brain. Hemodynamically, light activated prefrontal and visual-associated cortexes; on the other hand, eyes-open activated thalamus and also the visual-associated cortexes. Concerning the functional connectivity, sensory networks including visual, auditory, and somatosensory networks and attention networks encompassing dorsal attention and salience networks were highly coherent during eyes-closed stage regardless of the light. However, the default mode network is relatively more robust to trivial stimuli like eyes-open or eyes-closed than sensory or attention networks are.