【作者】 李志鹏；

【导师】 梁夏；

【作者基本信息】 哈尔滨工业大学 ， 生物医学工程， 2025， 博士

【摘要】 记忆是大脑的核心认知功能之一,其中的情节记忆作为一种独特的记忆类型,对人类自我意识的形成和维持起着重要的作用。海马作为情节记忆的关键脑区,在将新体验转化为长期记忆的过程中发挥了不可替代的作用。然而,在情节记忆的不同阶段,语义和时间背景信息对海马信息处理的具体影响尚不完全明确。同时,提取阶段海马是否存在预测表征及其背后的神经机制,以及各海马亚区在记忆巩固阶段的相互调节机制仍有待深入研究。基于此,本研究利用分类单词列表的延迟自由回忆实验中和睡眠状态下的颅内海马脑电记录,系统探讨了情节记忆编码和提取阶段背景信息对海马信息表征的差异性影响,海马在情节记忆提取阶段的预测功能及其机制,以及海马在情节记忆巩固阶段各个亚区之间的调节关系。在情节记忆的编码和提取阶段,本研究分析了语义/时间背景信息对海马神经表征的影响。结果表明,提取阶段相同-不同语义类别的神经相似性差异明显高于编码阶段,并且这种神经相似性差异与回忆正确率显著正相关。相较于提取阶段,编码阶段的时间-神经表征相似性更强,并且编码阶段的海马时间-神经表征相似性会影响记忆的成功与否。语义/时间背景信息对海马各个频段的神经表征的影响与全频段一致。各个频段的时间-神经表征相似性比较发现:编码阶段delta和theta频段的相似性显著高于其他频段;提取阶段delta频段的相似性显著高于其他频段,alpha频段的相似性显著低于其他频段。这些研究结果表明,语义/时间背景信息在情节记忆编码与提取阶段对海马表征机制的影响具有显著差异。这一结论为深入理解海马在情节记忆中对背景信息的复杂处理机制提供了新的视角。在情节记忆提取阶段,本研究分析了海马的预测功能及其神经机制。研究发现,海马在提取完全正确和近期编码的单词时表现出显著的预测表征,且预测强度随着预测尺度的增大而减弱。在编码阶段,海马未表现出明显的预测表征,但提取阶段的预测相似性与编码阶段显著正相关。此外,情节记忆中的语义和时间背景信息对提取阶段海马的预测表征相似性影响显著。在提取阶段,海马的ripple发生率和同频段连接强度与预测相似性呈正相关关系。这些研究结果表明,海马在情节记忆的提取阶段不仅存在预测表征,其预测强度还受记忆的背景信息和海马内部电生理活动的调节。此研究为理解海马在情节记忆中的预测功能提供了新的证据。在情节记忆巩固的非快速眼动(NREM)睡眠阶段,海马亚区间神经振荡调节关系的研究中发现,NREM睡眠期间,DG/CA3、CA1和SUB三个海马亚区均存在显著的delta和spindle频段的高功率。DG/CA3亚区内部及其与CA1和SUB亚区之间均存在显著的频段水平的delta-ripple耦合,而CA1和SUB亚区则展现出时间精确的事件水平上的delta-spindle和spindle-ripple耦合。研究还发现,海马内部的delta斜率与spindle功率呈线性关系,而ripple则仅在功率达到最大时对delta斜率产生调节作用。这些结果表明,在NREM睡眠期间,海马各亚区不仅通过不同频段的神经振荡实现互补和协同调节,还能有效影响突触强度。这些发现进一步揭示了NREM睡眠阶段海马在记忆巩固中的复杂机制。综上所述,本研究通过分类单词列表的延迟自由回忆实验中和睡眠状态下的颅内海马脑电记录,结合表征相似性分析、频谱分析和耦合分析等方法,深入探讨了海马在情节记忆过程中对背景信息处理、预测表征及记忆巩固的作用。研究结果为理解海马在情节记忆中的背景信息处理机制、海马在情节记忆预测功能中的神经机制,以及睡眠阶段海马内部神经振荡在记忆巩固中的作用提供了新的见解。更多还原

【Abstract】 Memory is a fundamental cognitive function of brain,with episodic memory,a unique form of memory,being essential to the development and maintenance of human self-awareness.Hippocampus,a key brain region for episodic memory,is crucial for the conversion of new experiences into long-term memories.However,the specific impact of semantic and temporal contextual information on hippocampal processing across different stages of episodic memory remains incompletely understood.Additionally,whether predictive representations exist in hippocampus during retrieval,the underlying neural mechanisms of this process,and the regulatory mechanisms among hippocampal subfields during memory consolidation require further investigation.To address these questions,the study utilized intracranial EEG recordings in hippocampus during delayed free recall of categorized word lists task,as well as recordings during sleep,to systematically examine how contextual information at various stages of episodic memory differentially impacts hippocampal representations.The study also explores the hippocampus’s predictive functions during episodic memory retrieval,their underlying mechanisms,and the regulatory interactions among hippocampal subfields during episodic memory consolidation.In examining encoding and retrieval of episodic memory,this study analyzed the impact of semantic and temporal contextual information on hippocampal neural representations.Results revealed significantly higher neural similarity for same versus different semantic categories during retrieval than encoding,positively correlating with recall accuracy.Temporal context exhibited stronger effects during encoding,influencing memory success.Temporal-neural similarity showed distinct frequency band patterns:delta and theta bands were dominant during encoding,while delta band was prominent during retrieval.These findings highlight distinct roles for semantic context during retrieval and temporal context during encoding,offering insights into hippocampal processing mechanisms.During retrieval,this study further investigated the predictive function of hippocampus and its neural basis.Hippocampus exhibited significant predictive representations for fully accurate and recently encoded words,with predictive strength decreasing at larger scales.Predictive similarity during retrieval was positively correlated with encoding,significantly influenced by semantic and temporal context,and modulated by ripple occurrence and within-band connectivity.These results demonstrate the hippocampus’s predictive representation during retrieval,shaped by contextual information and internal electrophysiological activity.During episodic memory consolidation in non-rapid eye movement(NREM)sleep,studies on the regulatory relationships among hippocampal subfields revealed significant delta and spindle power in DG/CA3,CA1,and SUB subfields.Delta-ripple coupling was observed within the DG/CA3 subfield and between DG/CA3 and CA1 and SUB,while temporally precise event-based delta-spindle and spindle-ripple couplings were seen between CA1 and SUB.Additionally,it was found that the delta slope within the hippocampus showed a linear relationship with spindle power,while ripple activity modulated the delta slope only when ripple power reached its maximum.These findings suggest that during NREM sleep,hippocampal subfields achieve complementary and coordinated regulation through distinct frequency oscillations,effectively influencing synaptic strength.This insight advances our understanding of hippocampal neural circuitry during NREM sleep and further elucidates the complex mechanisms of hippocampal memory consolidation.In summary,intracranial hippocampal EEG recordings from delayed free recall of categorized word lists task and from sleep,combining representational similarity analysis,spectral analysis,and coupling analysis,this study offers a comprehensive exploration of the hippocampus’s roles in contextual information processing,predictive representation,and memory consolidation during episodic memory.These findings provide new insights into the hippocampal mechanisms for processing contextual information in episodic memory,the neural basis of predictive function,and the role of internal neural oscillations in hippocampal memory consolidation during sleep.更多还原