Department of Psychology, Center for Neuroscience, University of California, Davis, California 95618, USA.
Hum Brain Mapp. 2013 May;34(5):1070-87. doi: 10.1002/hbm.21494. Epub 2012 Jan 16.
Previous studies suggest the importance of medial temporal lobe, areas of parietal cortex, and retrosplenial cortex in human spatial navigation, though the exact role of these structures in representing the relations of elements within a spatial layout ("allocentric" representation) remains unresolved. Hippocampal involvement, in particular, during memory processing is affected by whether a previously formed representation is employed in a novel fashion ("flexible" usage) or in a manner comparable with how it was encoded originally ("rigid" usage). To address whether brain systems are differentially involved during flexible vs. rigid utilization of a pre-existing allocentric representation, subjects encoded the position of six different target buildings relative to a centrally located landmark building in a virtual city seen from an aerial view. They then actively searched for the locations of these target buildings using the landmark (rigid retrieval) or using a previously shown target building in a novel fashion (flexible retrieval) while undergoing fMRI. Activations in posterior superior parietal cortex and precuneus were greater during more rigid than flexible forms of allocentric retrieval while activation in the hippocampus decreased linearly over blocks during flexible allocentric retrieval. A functional connectivity analysis further revealed significant interactions between hippocampus and these parietal areas during flexible compared with rigid allocentric retrieval. These results extend previous models of the neural basis of spatial navigation by suggesting that while the posterior superior parietal cortex/precuneus play an important role in allocentric representation, the hippocampus, and interactions between hippocampus and these parietal areas, are important for flexible utilization of these representations.
先前的研究表明内侧颞叶、顶叶皮层区域和后扣带回在人类空间导航中的重要性，尽管这些结构在表示空间布局内元素关系（“以自我为中心”的表示）方面的确切作用仍未解决。特别是，海马体在记忆处理过程中的参与取决于先前形成的表示是以前所未有的方式（“灵活”使用）还是与最初编码的方式相似（“刚性”使用）。为了确定在灵活和刚性使用预先存在的以自我为中心的表示时，大脑系统是否有差异参与，研究对象在从空中视角看到的虚拟城市中，将六个不同目标建筑物的位置相对于一个位于中心的地标建筑物进行编码。然后，他们在 fMRI 检查过程中使用地标（刚性检索）或以前以新颖方式显示的目标建筑物（灵活检索）主动搜索这些目标建筑物的位置。在更刚性的以自我为中心的检索中，后上顶叶皮层和楔前叶的激活大于更灵活的以自我为中心的检索，而在灵活的以自我为中心的检索中，海马体的激活在线性上随块减少。功能连接分析进一步显示，在灵活的以自我为中心的检索与刚性的以自我为中心的检索相比，海马体与这些顶叶区域之间存在显著的相互作用。这些结果通过表明后上顶叶皮层/楔前叶在以自我为中心的表示中起着重要作用，而海马体以及海马体与这些顶叶区域之间的相互作用对于灵活利用这些表示很重要，从而扩展了空间导航神经基础的先前模型。
