GIGA-CRC In-Vivo Imaging, University in Liège, Liège, Belgium; PsyNCog, Faculty of Psychology, University in Liège, Liège, Belgium.
GIGA-CRC In-Vivo Imaging, University in Liège, Liège, Belgium.
Neurobiol Aging. 2019 Jan;73:135-144. doi: 10.1016/j.neurobiolaging.2018.09.021. Epub 2018 Sep 22.
Unitization, the capacity to encode associations as one integrated entity, can enhance associative memory in populations with an associative memory deficit by promoting familiarity-based associative recognition. Patients with Alzheimer's disease (AD) are typically impaired in associative memory compared with healthy controls but do not benefit from unitization strategies. Using fragmented pictures of objects, this study aimed at assessing which of the cognitive processes that compose unitization is actually affected in AD: the retrieval of unitized representations itself, or some earlier stages of processing, such as the integration process at a perceptual or conceptual stage of representation. We also intended to relate patients' object unitization capacity to the integrity of their perirhinal cortex (PrC), as the PrC is thought to underlie unitization and is also one of the first affected regions in AD. We evaluated perceptual integration capacity and subsequent memory for those items that have supposedly been unitized in 23 mild AD patients and 20 controls. We systematically manipulated the level of perceptual integration during encoding by presenting object pictures that were either left intact, separated into 2 fragments, or separated into 4 fragments. Subjects were instructed to unitize the fragments into a single representation. Success of integration was assessed by a question requiring the identification of the object. Participants also underwent a structural magnetic resonance imaging examination, and measures of PrC, posterior cingulate cortex volume and thickness, and hippocampal volume, were extracted. The results showed that patients' perceptual integration performance decreased with the increased fragmentation level and that their memory for unitized representations was impaired whatever the demands in terms of perceptual integration at encoding. Both perceptual integration and memory for unitized representations were related to the integrity of the PrC, and memory for unitized representations was also related to the volume of the hippocampus. We argue that, globally, this supports representational theories of memory that hold that the role of the PrC is not only perceptual nor mnemonic but instead underlies complex object representation.
单元化，即将联想编码为一个整体的能力，可以通过促进基于熟悉度的联想识别，增强联想记忆缺陷人群的联想记忆。与健康对照组相比，阿尔茨海默病（AD）患者的联想记忆通常受损，但他们不会受益于单元化策略。本研究使用物体的碎片化图片，旨在评估构成单元化的认知过程中，哪一个在 AD 中实际受到影响：是单元化表示本身的检索，还是一些更早的加工阶段，例如在知觉或概念表示阶段的整合过程。我们还旨在将患者的物体单元化能力与他们的边缘系统前回（PrC）的完整性联系起来，因为 PrC 被认为是单元化的基础，也是 AD 中最早受影响的区域之一。我们评估了 23 名轻度 AD 患者和 20 名对照组的知觉整合能力和随后对那些被认为已经单元化的项目的记忆。我们通过呈现完整的、分成 2 个片段的或分成 4 个片段的物体图片，系统地在编码过程中操纵知觉整合水平。要求参与者将片段整合为单个表示。通过要求识别物体的问题来评估整合的成功。参与者还接受了结构磁共振成像检查，并提取了 PrC、后扣带皮层体积和厚度以及海马体体积的测量值。结果表明，患者的知觉整合表现随着碎片化程度的增加而下降，无论在编码时知觉整合的需求如何，他们对单元化表示的记忆都受到损害。知觉整合和对单元化表示的记忆都与 PrC 的完整性有关，对单元化表示的记忆也与海马体的体积有关。我们认为，总体而言，这支持了记忆的代表性理论，即 PrC 的作用不仅是知觉的，也不仅是记忆的，而是基础复杂的物体表示。
