Department of Psychology, York University, Toronto, ON, Canada; Rotman Research Institute at Baycrest Hospital, Toronto, ON, Canada.
Department of Psychology, York University, Toronto, ON, Canada.
Cortex. 2024 Oct;179:191-214. doi: 10.1016/j.cortex.2024.06.020. Epub 2024 Aug 13.
The hippocampus (HPC) is well-known for its involvement in declarative (consciously accessible) memory, but there is evidence that it may also play a role in complex perceptual discrimination. Separate research has demonstrated separable contributions of HPC subregions to component memory processes, with the dentate gyrus (DG) required for mnemonic discrimination of similar inputs and the CA1 subfield required for retention and retrieval, but contributions of these subregions to perceptual processes is understudied. The current study examined the nature and extent of a double dissociation between the dentate gyrus (DG) to discrimination processes and CA1 subfield to retention/retrieval by testing two unique individuals with bilateral damage to the DG (case BL) and CA1 (case BR). We tested BL and BR on a wide range of standardized neuropsychological tests to assess information encoding and retention/retrieval and co-opted many measures to assess perceptual discrimination. Compared to normative data, BL exhibited performance below expectations on most measures requiring perceptual discrimination and on measures of encoding but demonstrated intact retention. Conversely, BR showed no difficulties with perceptual discrimination or verbal encoding but exhibited poor verbal retention, as well as poor encoding and retention of spatial/integrative tasks (e.g., object in a location). These results indicate that, despite its prominent role in memory, the DG is necessary for perceptual discrimination and encoding, whereas CA1 is necessary for retention/retrieval and encoding of spatial information. The pattern of results highlights the critical nature of individual case studies in the nuanced understanding of HPC subfield contributions to different memory processes, as well as the utility of repurposing neuropsychological measures to capture individual differences.
海马体（HPC）以其在陈述性（可有意识获取）记忆中的作用而闻名，但有证据表明它也可能在复杂的知觉辨别中发挥作用。独立的研究已经证明了 HPC 子区域对组成记忆过程的可分离贡献，齿状回（DG）需要对相似输入进行记忆辨别，CA1 子场需要保留和检索，但这些子区域对知觉过程的贡献仍未得到充分研究。本研究通过测试两名双侧 DG（病例 BL）和 CA1（病例 BR）损伤的独特个体，检查了齿状回（DG）与辨别过程和 CA1 子场与保留/检索之间的双重分离的性质和程度。我们使用各种标准化神经心理学测试对 BL 和 BR 进行了测试，以评估信息编码和保留/检索，并采用了许多措施来评估知觉辨别。与正常数据相比，BL 在大多数需要知觉辨别和编码的测试以及在记忆保持方面的测试中表现低于预期，但保留能力完好。相反，BR 在知觉辨别或言语编码方面没有困难，但言语记忆保留能力较差，以及空间/综合任务（例如，位置中的物体）的编码和保留能力较差。这些结果表明，尽管 DG 在记忆中具有突出作用，但 DG 对于知觉辨别和编码是必要的，而 CA1 对于保留/检索和空间信息的编码是必要的。结果模式突出了个别案例研究在深入了解 HPC 子区域对不同记忆过程的贡献方面的关键性质，以及重新利用神经心理学措施来捕捉个体差异的效用。
