| 摘要: | 注意力和眼球運動準備歷程之間的關係一直是心理學家感興趣的議題之一，Posner等人在1980年運用著名的Posner paradigm 顯示這兩者在功能上的分離，然而負責處理視覺注意力以及眼球運動歷程的神經機制是否分離到目前仍然是一個持續在爭論的議題。由Rizzolatti等人所提出的注意力的前運動理論(the premotor theory of attention) 認為負責視覺注意力以及動作控制的機制為同一個(Rizzolatti, 1983; Sheliga et al., 1994; Sheliga et al., 1995)。 部分來自行為以及腦造影實驗的結果支持了前運動理論的看法(Sheliga et al. 1995, Corbetta et al., 1998)，相反的，來自神經細胞活化紀錄的實驗顯示了負責這兩個機制的大腦區域可能在空間上重疊但在時間向度上是分離的(Hanes and Schall, 1996)。Juan(2008)等人在人類的跨顱磁刺激實驗也觀察到類似的結果，他們發現受試者在執行視覺搜尋作業時有兩個獨立的時間點可以施打跨顱磁刺激有效的延長眼球跳視反應時間。這樣的結果被認為是支持這兩個機制在時間向度上分離的證據。有趣的是，眼球跳視反應時間是一個由許多歷程相加的複合體，因此Juan等人(2008)所觀察到的反應時間延長是否分別代表注意力及眼動準備需要更進一步的探討。本研究試圖結合跨顱磁刺激的實驗以及數學模型以進一步探究這個議題。過去已經有研究者結合跨顱磁刺激以及數學模型探討後頂葉(PPC)在視覺選擇扮演的角色(Hung et al., 2005)。結合這兩種技術探討注意力及眼動準備歷程的關係，本研究是首開先例。 如同Juan等人(2008)的研究，此研究同樣觀察到了眼球跳視產生前施打的跨顱磁刺激會有效的延長眼球跳視反應時間。以數學模型進一步分析的結果顯示，晚期的跨顱磁刺激主要影響的是 。這個數值代表的是Carpenter的Linear Approach to Threshold with Ergodic Rate (LATER) model中的眼動準備歷程，而不會影響代表視覺選擇的 。然而，此研究並沒有觀察到如Juan等人觀察到的早期跨顱磁刺激的效果，可能的原因為我們沒有辦法將那些未經視覺選擇的反應刪除。總結來說，本研究展示了視覺選擇以及眼動準備在時間向度上的部分分離，並進一步提出未來可進一步實行的實驗。The relationship between covert attention and eye movement has been a hotly debated issue among psychologists over a long period of time. In 1980, Posner demonstrated the functional dissociation between covert attention and overt eye movement with the classic orienting paradigm. However, the issue that whether the neural mechanism responsible for covert attention and eye movement is temporally or structural dissociated is still in dispute. The premotor theory of attention (Rizzolatti, 1983; Sheliga et al., 1994; Sheliga et al., 1995) in its strongest form states that the same mechanisms are responsible for controlling action and spatial attention. Whereas some behavioral and neuroimaging studies support the notion of premotor theory (Sheliga et al. 1995, Corbetta et al., 1998), results from single-unit recording and microstimulation experiments suggest the two might overlapped structurally but dissociable temporally(Hanes and Schall, 1996). Recently, Juan et al. (2008) demonstrated that TMS over human FEF can prolong saccade latencies at two distinct time points. The finding was taken as the evidence that supports the dissociation of the two in temporal dimension. However, the prolonged saccade latencies were compounded. To verify whether the prolonged saccade latencies by TMS at two different time points really indicate the dissociation of the two mechanisms, the combination of TMS and model fitting was applied in this study to elucidate the issue. The attempt to combine TMS on human subjects with model fitting has been made on PPC to probe the top-down influence of visual selection (Hung et al., 2005). The combination of TMS over FEF with model fitting is a novel attempt toward the relationship between attention and oculomotor preparation. The late TMS effect was replicated as in Juan et al. (2008), and the results of model fitting reveal that the late TMS effect is mainly acting on , which indicates oculomotor preparation in Carpenter’s Linear Approach to Threshold with Ergodic Rate (LATER) model. The early TMS effect was not replicated. One of the possible reasons could be that the trials without visual selection were not excluded for further analysis as in Juan et al. (2008). In summary, the results of this study show a partial dissociation of attention and oculomotor preparation with TMS at late time point. Further experiments are suggested to probe the effect of TMS at early time point. |
