The glutamatergic cycle is essential in modulating memory processing by the hippocampal circuitry. Our combined proton magnetic resonance spectroscopy (¹H-MRS) and task-based functional magnetic resonance imaging (fMRI) study (using face-name paired-associates encoding and retrieval task) of a cognitively normal cohort of 67 healthy adults (18 ApoE4 carriers and 49 non-ApoE4 carriers) found altered patterns of relationships between glutamatergic-modulated synaptic signalling and neuronal activity or functional hyperaemia in the ApoE4 isoforms. Our study highlighted the asymmetric left–right hippocampal glutamatergic system in modulating neuronal activities in ApoE4 carriers versus non-carriers. Such brain differentiation might be developmental cognitive advantages or compensatory due to impaired synaptic integrity and plasticity in ApoE4 carriers. As there was no difference in myoinositol levels measured by MRS between the ApoE4 and non-ApoE4 subgroups, the mechanism is unlikely to be a response to neuroinflammation.

中文翻译：

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ApoE 亚型受试者认知控制的左右海马不对称谷氨酸能调节与神经炎症无关

谷氨酸能循环对于调节海马电路的记忆处理至关重要。我们的组合质子磁共振波谱 ( ¹H-MRS) 和基于任务的功能磁共振成像 (fMRI) 研究（使用面部名称配对关联编码和检索任务）对 67 名健康成人（18 名 ApoE4 携带者和 49 名非 ApoE4 携带者）的认知正常队列进行了研究谷氨酸能调节的突触信号与神经元活动或 ApoE4 同种型中功能性充血之间关系模式的改变。我们的研究强调了左右海马谷氨酸能系统在调节 ApoE4 携带者与非携带者的神经元活动方面的不对称。由于 ApoE4 携带者的突触完整性和可塑性受损，这种大脑分化可能是发育认知优势或补偿性的。由于 ApoE4 和非 ApoE4 亚组之间通过 MRS 测量的肌醇水平没有差异，