左側後頂葉腦區於情節記憶提取之功能性角色：電生理、腦磁波與經顱直流電刺激之研究;The functional roles of the left posterior parietal cortex in episodic retrieval: EEG, MEG, and tDCS studies

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Title:	左側後頂葉腦區於情節記憶提取之功能性角色：電生理、腦磁波與經顱直流電刺激之研究;The functional roles of the left posterior parietal cortex in episodic retrieval: EEG, MEG, and tDCS studies
Authors:	陳乃鳳;Chen, Nai-Feng
Contributors:	認知與神經科學研究所
Keywords:	左側後頂葉腦區;情節記憶;經顱直流電刺激;事件相關腦電位;腦磁波;left posterior parietal cortex;episodic memory;tDCS;ERP;MEG
Date:	2020-05-21
Issue Date:	2020-06-05 17:40:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	近年來腦造影研究持續發現左側後頂葉腦區與情節記憶提取之間存在關聯性，並指出左側後頂葉內的子區域對於記憶提取歷程有不同功能性的貢獻。然而，頂葉受損的病人其來源記憶表現並無明顯缺失，神經心理學的研究並不支持情節記憶提取需要左側後頂葉的參與假設。本研究將以腦電波與非侵入性經顱直流電刺激檢驗左側後頂葉是否涉及情節記憶提取的功能，此外，亦將使用腦磁波來源定位技術進一步探究左側後頂葉內不同子區域於記憶提取的功能性表現。實驗一探討左側後頂葉與情節記憶提取間的因果關係。結果顯示，陰極電刺激削弱情節記憶表現，此結果提供左側後頂葉與情節記憶提取間存在因果關係的支持性證據。實驗二延續實驗一的發現，藉由紀錄事件相關腦電位，進一步檢驗左側後頂葉是否涉及重拾記憶(recollection)的運作歷程。結果顯示，相較於接受假性電刺激，陰極電刺激會降低左側頂葉新舊腦電位效果，但中額葉新舊電位效果並未受影響。此電生理結果提供神經元活動方面的證據，亦支持左側後頂葉與重拾記憶歷程間存在因果關聯性之推論。實驗三以腦磁波儀紀錄執行記得/知道記憶判斷(Remember/Know judgment)時相關的腦部活動。結果顯示，記憶熟悉感(familiarity)的相關腦部活動早先發生於背側頂葉；另一方面，重拾記憶的相關腦部活動晚些發生於腹側頂葉。實驗結果提供了記憶熟悉感歷程與重拾記憶歷程間時序與解剖位置上皆互相獨立的證據。總結以上實驗發現，本研究顯示，左側後頂葉與情節記憶提取間存在因果關聯性，且頂葉內不同區域涉及情節記憶提取的不同認知運作歷程。;Recent functional neuroimaging studies consistently revealed the association between the left posterior parietal lobe (LPPC) activities and episodic retrieval, and reflected distinct subregions of the LPPC contributes differently to retrieval processing. In contradiction to the abundant neuroimaging evidence, patients with parietal lesions exhibited intact memory performance when tested with the source memory task. Given these inconsistent findings, the role played by the LPPC in memory retrieval remains unclear. Therefore, this thesis aimed to address the issue of whether the LPPC is necessarily involved in episodic retrieval, and investigate the functional significances of the subregions in the LPPC. The first two experiments were carried out to examine the causal role of the LPPC in episodic retrieval. The third experiment was carried out to investigate the functional heterogeneity in LPPC. In Experiment Ι, transcranial direct current stimulation (tDCS) was employed to interfere with the neural excitability of the LPPC during memory retrieval. Participants were randomly assigned to the anodal or the cathodal stimulation group and engaged in three source memory tests on three separate days. The results showed that source memory accuracy decreased significantly when participants in the cathodal group received stimulation over the LPPC scalp region in comparison to the sham stimulation and the control stimulation condition, supporting the claim that the LPPC is causally related to episodic memory retrieval. Following the casual evidence observed from the first experiment, Experiment Π was designed to further validate whether the LPPC is involved in the recollection process, in which event-related potentials (ERPs) were recorded during the retrieval right after direct current stimulation applied. The results demonstrated that cathodal stimulation decreased the left-parietal old/new ERP effect in comparison to the sham condition. In contrast, the mid-frontal old/new ERP effect remained unaffected across three stimulation conditions. These findings suggested that LPPC supports the recollection process in episodic retrieval. In Experiment Ш, to examine the underlying parietal neural substrates of episodic memory, participants performed modified confidence Remember/know judgments in the Magnetoencephalography (MEG) scanner. The MEG source estimation data revealed distinct temporal and spatial profiles of recollection- and familiarity-related processes. Specifically, recollection-related activities were found in the left ventral parietal regions in the later time window, whereas familiarity-related activities were observed in the left dorsal lateral parietal regions in the early time window. These results supported the hypothesis that recollection and familiarity are functionally distinct mechanisms and indicate the heterogeneous functions of LPPC subserve memory retrieval. In conclusion, the experiments in this thesis provided supportive evidence that the LPPC is indeed causally involved in episodic retrieval and reflected different memory functional roles of the subregions within the LPPC.
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