School of Psychology, Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, Ministry of Education Key Laboratory of Brain Cognition and Educational Science, South China Normal University, Guangzhou, Guangdong, China.
Hum Brain Mapp. 2023 Jan;44(1):131-141. doi: 10.1002/hbm.26069. Epub 2022 Sep 6.
Parahippocampal cortex (PHC) is a vital neural bases in spatial navigation. However, its functional role is still unclear. "Contextual hypothesis," which assumes that the PHC participates in processing the spatial association between the landmark and destination, provides a potential answer to the question. Nevertheless, the hypothesis was previously tested using the picture categorization task, which is indirectly related to spatial navigation. By now, study is still needed for testing the hypothesis with a navigation-related paradigm. In the current study, we tested the hypothesis by an fMRI experiment in which participants performed a distance estimation task in a virtual environment under three different conditions: landmark free (LF), stable landmark (SL), and ambiguous landmark (AL). By analyzing the behavioral data, we found that the presence of an SL improved the participants' performance in distance estimation. Comparing the brain activity in SL-versus-LF contrast as well as AL-versus-LF contrast, we found that the PHC was activated by the SL rather than by AL when encoding the distance. This indicates that the PHC is elicited by strongly associated context and encodes the landmark reference for distance perception. Furthermore, accessing the representational similarity with the activity of the PHC across conditions, we observed a high similarity within the same condition but low similarity between conditions. This result indicated that the PHC sustains the contextual information for discriminating between scenes. Our findings provided insights into the neural correlates of the landmark information processing from the perspective of contextual hypothesis.
海马旁回皮层（PHC）是空间导航的重要神经基础。然而，其功能作用仍不清楚。“情境假设”认为 PHC 参与处理地标和目的地之间的空间关联，为解决这个问题提供了一个潜在的答案。然而，该假设之前是通过图片分类任务来检验的，而该任务与空间导航间接相关。到目前为止，仍然需要用与导航相关的范式来检验这个假设。在当前的研究中，我们通过 fMRI 实验来检验这个假设，参与者在三种不同条件下（无地标、稳定地标和模糊地标）在虚拟环境中进行距离估计任务。通过分析行为数据，我们发现稳定地标条件下参与者的距离估计表现有所提高。比较稳定地标与无地标以及模糊地标与无地标对比的脑区活动，我们发现 PHC 在编码距离时是被稳定地标而不是模糊地标激活的。这表明 PHC 是由强烈关联的情境引起的，并编码了距离感知的地标参照。此外，通过比较 PHC 在不同条件下的活动的代表性相似性，我们观察到在同一条件下的相似性较高，而在不同条件之间的相似性较低。这一结果表明 PHC 维持了区分场景的情境信息。我们的发现从情境假设的角度提供了地标信息处理的神经关联的见解。
