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  • 學位論文

時間預期性對工作記憶表徵神經狀態的調節

Temporal Expectation Modulates Neural States of Working Memory Representations

指導教授 : 郭柏呈
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摘要


過去研究指出在工作記憶維持階段將注意導引至特定的記憶表徵有益於延 遲反應的行為表現,最近的研究發現提示個體預期記憶項目的出現時間也能幫 助工作記憶表現。然而,時間預期是否會調節工作記憶表徵仍不清楚。本研究 使用腦磁圖儀探討對記憶測試出現時間的預期,是否能夠調控記憶維持階段特 定項目的工作記憶表徵。我們在受試者進行工作記憶作業時提供了回溯線索與 額外視覺刺激,且在呈現回溯線索後操控兩種時間預期狀況 – 高度可預期與低度 可預期。我們首先發現高度可預期相較於低度可預期對行為表現的助益。我們 接著使用多變量型態分析法,估計 Mahalanobis distance 解譯工作記憶維持階段的 神經表徵,我們發現在低度可預期時,被回溯線索指示的記憶項目相較於沒有 被指示的項目有更好的解譯表現。我們也檢驗了呈現回溯線索後 alpha 波(8-12 Hz)的側化與非側化效果,發現兩種時間預期的狀況引起等量的 alpha 側化,相 對於低度預期,高度預期會使 alpha 波的強度降低。透過訊號源重建,我們發現 時間預期所引發的 alpha 波下降源自於左前額葉與左頂葉。最後,高度與低度預 期在 alpha 側化強度上的差異與預期所增進行為上的反應時間差異呈現了顯著的 相關,顯示當 alpha 側化強度在高度與低度預期的差異越大時,則反應時間也越 快。這些結果為時間預期對維持工作記憶表徵神經型態的調節提供了新穎的證 據。

並列摘要


Previous evidence has revealed that directing attention towards relevant information held in working memory (WM) during the maintenance interval can benefit subsequent responses. Recent studies showed that cueing observers to the time that memory items to occur can also benefit WM performance. However, it remains unclear whether anticipatory attention can modulate WM representations. In this study, we investigated whether anticipating the memory test could modulate item-specific prioritisation during WM maintenance with magnetoencephalography (MEG). Participants performed a retro-cueing WM task with visual impulse. We manipulated the post-cueing intervals to be high or low temporal expectancy. First, we showed behavioural benefits for the trials with high expectancy compared to those with low expectancy. Next, we employed a multivariate pattern analysis approach by estimating Mahalanobis distance metric to decode the content-specific patterns during the delay. We found greater decoding performance for the cued items relative to the uncued items for the low expectancy condition. Moreover, we tested the lateralised alpha effect and non-lateralised alpha effect after the retro-cue presentation. We observed a similar alpha lateralisation for both temporal expectancy conditions. We further showed a decrease of alpha power for high relative to low temporal expectancy during maintenance. Our source reconstruction analysis showed the involvements of the left prefrontal and parietal cortices in alpha attenuation for anticipating memory test. Finally, we showed a positive correlation between behavioural performance and lateralised alpha power over posterior brain regions comparing high and low expectancy, suggesting the greater the lateralisation the faster the response time. Together, this study provides novel evidence for anticipatory modulation on WM representations.

參考文獻


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