The Role of Anterior Nuclei of the Thalamus: a Subcortical Gate in Memory Processing. An Intracerebral Recording Study.

Abstract Objective To study the involvement of the posterior medial cortex (PMC), the anterior nuclei of the thalamus (ANT), and the hippocampus in the processes of encoding and recognition during visual and verbal (auditory) memory tasks. Methods We studied intracerebral recordings in epilepsy-surgery candidates using depth electrodes implanted in the retrosplenial cingulate, precuneus, cuneus, lingual gyrus, and hippocampus and in patients with pharmacoresistent epilepsy who underwent deep brain stimulation (DBS) of the ANT with depth electrodes implanted bilaterally in the ANT. We recorded the event-related potentials (ERPs) evoked by visual and verbal memory encoding-recognition tasks. Results In the hippocampus, ERPs were elicited in the encoding and recognition phases in both visual and verbal modalities. In the PMC and ANT, ERPs were recorded in both the encoding and recognition visual tasks; in the verbal modality, they were recorded in the recognition task, but not in the encoding task. In the visual and verbal recognition tasks, the ERPs (P300-like potentials) in the ANT preceded the P300-like potentials in the hippocampus. Conclusions The PMC and the ANT are modality dependent in memory processing. ERPs are elicited by memory recognition, but they are not elicited by verbal encoding memory processing in the PMC and ANT. The PMC appears to be involved in higher-order top-down cognitive activities as well as in more basic, rather bottom-up activities. The ANT is a structure in the memory pathway that processes memory information before the hippocampus. We suggest that the ANT has a specific role in memory processes, especially memory recognition, and that memory disturbance should be considered in patients with ANT-DBS and in patients with ANT and PMC lesions. ANT is well positioned to serve as a subcortical gate for memory processing in cortical structures. Key words: event-related potentials (ERPs), P300 like potentials, memory, posterior medial cortex (PMC), hippocampus, stereoelectroencephalography (SEEG), deep brain stimulation (DBS), anterior nuclei of the thalamus (ANT)

摘要
研究目的：探讨后内侧皮层（posterior medial cortex, PMC）、丘脑前核（anterior nuclei of the thalamus, ANT）与海马体在视觉及言语（听觉）记忆任务的编码与再认过程中的作用机制。
研究方法：本研究纳入拟接受癫痫手术的患者，采用植入于压后扣带回、楔前叶、楔叶、舌回及海马体的深部电极开展颅内脑电记录；同时纳入接受双侧丘脑前核深部脑刺激（deep brain stimulation, DBS）的药物难治性癫痫患者，记录视觉与言语记忆编码-再认任务所诱发的事件相关电位（event-related potentials, ERPs）。
研究结果：在海马体中，视觉与言语两种记忆模态的编码及再认阶段均可诱发出事件相关电位。在后内侧皮层与丘脑前核中，视觉任务的编码与再认阶段均可记录到事件相关电位；而言语模态下，仅在再认任务中可记录到电位变化，编码阶段未诱发电位。在视觉与言语再认任务中，丘脑前核的类P300电位出现时间早于海马体的类P300电位。
研究结论：后内侧皮层与丘脑前核在记忆加工中存在模态依赖性。后内侧皮层与丘脑前核的事件相关电位可由记忆再认诱发，但言语编码记忆加工无法诱发出此类电位。后内侧皮层似乎既参与高阶自上而下的认知活动，也参与更为基础的自下而上加工过程。丘脑前核是记忆通路中位于海马体之前的记忆信息处理结构。本研究提示，丘脑前核在记忆加工尤其是记忆再认过程中发挥特异性作用，因此接受丘脑前核深部脑刺激的患者，以及存在丘脑前核与后内侧皮层病变的患者，需警惕记忆障碍风险。丘脑前核可作为皮层结构记忆加工的皮层下门户。
关键词：事件相关电位（event-related potentials, ERPs）、类P300电位、记忆、后内侧皮层（posterior medial cortex, PMC）、海马体、立体脑电图（stereoelectroencephalography, SEEG）、深部脑刺激（deep brain stimulation, DBS）、丘脑前核（anterior nuclei of the thalamus, ANT）