The Rotman Research Institute, Baycrest, Toronto, Canada.
University of Toronto, Canada.
J Cogn Neurosci. 2021 Aug 1;33(9):1976-1989. doi: 10.1162/jocn_a_01722.
The ventromedial prefrontal cortex (vmPFC) is involved in diverse cognitive operations, from inhibitory control to processing of semantic schemas. When accompanied by damage to the basal forebrain, vmPFC lesions can also impair relational memory, the ability to form and recall relations among items. Impairments in establishing direct relations among items (e.g., A is related to B, B is related to C) can also hinder the transitive processing of indirect relationships (e.g., inferring that A and C are related through direct relations that each contain B). Past work has found that transitive inference improves when the direct relations are organized within an existing knowledge structure, or schema. This type of semantic support is most effective for individuals whose relational memory deficits are mild (e.g., healthy age-related decline) rather than pronounced (e.g., hippocampal amnesia, amnestic mild cognitive impairment). Given that vmPFC damage can produce both relational memory and schema processing deficits, such damage may pose a particular challenge in establishing the type of relational structure required for transitive inference, even when supported by preexisting knowledge. To examine this idea, we tested individuals with lesions to the mPFC on multiple conditions that varied in pre-experimental semantic support and explored the extent to which they could identify both previously studied (direct) and novel transitive (indirect) relations. Most of the mPFC cases showed marked transitive inference deficits and even showed impaired knowledge of preexisting, direct, semantic relations, consistent with disruptions to schema-related processes. However, one case with more dorsal mPFC damage showed preserved ability to identify direct relations and make novel inferences, particularly when pre-experimental knowledge could be used to support performance. These results suggest that damage to the mPFC and basal forebrain can impede establishment of ad hoc relational schemas upon which transitive inference is based, but that appealing to prior knowledge may still be useful for those neurological cases that have some degree of preserved relational memory.
腹内侧前额叶皮层（vmPFC）参与了多种认知操作，从抑制控制到语义图式的处理。当与基底前脑损伤同时发生时，vmPFC 损伤还会损害关系记忆，即形成和回忆项目之间关系的能力。在建立项目之间的直接关系（例如，A 与 B 相关，B 与 C 相关）方面的障碍也会阻碍间接关系的传递处理（例如，通过每个包含 B 的直接关系推断 A 和 C 相关）。过去的研究发现，当直接关系组织在现有的知识结构或图式中时，传递推理会得到改善。这种类型的语义支持对关系记忆缺陷较轻的个体（例如，与年龄相关的健康衰退）最有效，而不是明显的缺陷（例如，海马体遗忘症，轻度认知障碍遗忘型）。鉴于 vmPFC 损伤既可以产生关系记忆缺陷又可以产生图式处理缺陷，即使在预先存在的知识支持下，这种损伤也可能对建立传递推理所需的关系结构类型构成特别挑战。为了检验这一观点，我们在多个条件下测试了 mPFC 损伤的个体，这些条件在实验前的语义支持方面有所不同，并探讨了他们能够识别先前研究过的（直接）和新颖的传递（间接）关系的程度。大多数 mPFC 病例表现出明显的传递推理缺陷，甚至表现出对预先存在的直接语义关系的知识受损，这与图式相关过程的中断一致。然而，一个 mPFC 损伤更靠后的病例表现出识别直接关系和进行新推理的能力保持完好，尤其是在可以利用预先存在的知识来支持表现的情况下。这些结果表明，mPFC 和基底前脑的损伤会阻碍基于传递推理的临时关系图式的建立，但对于那些具有一定程度保留关系记忆的神经病例，诉诸先前的知识可能仍然有用。
