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
目的：探讨后内侧皮层（posterior medial cortex, PMC）、丘脑前核（anterior nuclei of the thalamus, ANT）及海马体在视觉与言语（听觉）记忆任务的编码与识别过程中的作用。
方法：本研究针对拟行癫痫手术的候选患者，采用置入压后扣带回、楔前叶、楔叶、舌回及海马体的深部电极进行颅内脑电记录；同时纳入接受丘脑前核深部脑刺激（deep brain stimulation, DBS）的药物难治性癫痫患者，其双侧丘脑前核均置入深部电极。本研究记录了视觉与言语记忆编码-识别任务所诱发的事件相关电位（event-related potentials, ERPs）。
结果：在海马体中，视觉与言语模态的编码与识别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，视觉任务的编码与识别阶段均可记录到事件相关电位；而言语模态下，仅在识别任务中可检测到电位活动，编码阶段未诱发电位。在视觉与言语识别任务中，丘脑前核的类P300电位（P300-like potentials）出现时间早于海马体的类P300电位。
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。记忆识别可诱发出事件相关电位，但后内侧皮层与丘脑前核的言语编码记忆过程无法诱发电位。后内侧皮层似乎既参与高级自上而下认知活动，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先于海马体处理记忆信息的结构。本研究认为，丘脑前核在记忆加工（尤其是记忆识别）中具有特异性作用，因此对于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，应考虑其可能出现记忆障碍。丘脑前核具备作为皮层结构记忆加工的皮层下门控结构的良好解剖生理基础。
关键词：事件相关电位（ERPs）、类P300电位、记忆、后内侧皮层（PMC）、海马体、立体脑电图（stereoelectroencephalography, SEEG）、深部脑刺激（DBS）、丘脑前核（ANT）