压后皮质在空间导航的作用:认知地图与环境的映射

Retrosplenial Cortex and its Function in Spatial Navigation:From Cognitive Map to Environment

压后皮质在大脑中紧邻胼胝体压部,在空间导航中起到重要作用,但其具体功能尚未明确。目前存在空间更新、地标领航和参照系转换三种观点。本文通过梳理上述观点,认为压后皮质的功能为对认知地图与环境布局进行映射,这种映射功能有助于解释压后皮质在基于认知地图进行导航过程中的激活。未来研究应该关注对压后皮质的功能分区,也要关注压后皮质与不同脑区的连接,这将对进一步理解其功能有重要的意义。

Spatial navigation,an inherent wayfinding process that combines multiple cues to accurately pursue the destination,is considered as an important process referring to the survival and reproduction of humans and animals.For decades,researchers have devoted to studying the neural underpinnings of spatial navigation and detected several brain regions associated with the navigation process,including the hippocampus,entorhinal cortex,and retrosplenial cortex(RSC),etc.The present study focuses on summarizing the function of the RSC in spatial navigation.The RSC includes the region in the posterior of the splenium of the corpus callosum and consists of Brodmann’s Areas 23,29,and 30.Although the engagement of the RSC in spatial navigation and memory formation has been revealed by a sizeable body of studies,there is no consensus as to its precise function in spatial navigation.Previous studies suggested that the function of the RSC in spatial navigation could be explained in three ways,that is,spatial updating,landmark piloting,and reference translation.Spatial updating refers to a dynamic cognitive process that accounts for perceiving changes in the environment during navigation.The fire of head-direction cells when the animal faces a specific direction is considered to engage in the process of spatial updating.Landmark piloting refers to the use of landmarks to orientate and to trace the location of the destination.The main evidence from clinical studies indicates that patients with RSC impairment suffer from a frustration of using landmarks to recall the map even in their familiar environment.Reference translation means a mental process that keeps the spatial information available between egocentric and allocentric reference frames.Animal experiments showed that rats with the RSC lesions were difficult to complete the navigation task requiring switching between multiple reference frames.In the present review,we describe a comprehensive perspective of the RSC function in spatial navigation or the mapping function of the RSC,which means that the RSC builds a cognitive map to the environment to maintain a consistent layout between locations.To describe the rationality of this mapping function,we list three possible reasons as follows.First,spatial updating,landmark piloting,and reference translation show somewhat overlapping with each other which indicates a common process underlying these functions.Second,the graph-like organization of the cognitive map indicates a flexible layout of object locations.The graph-like cognitive map gives the topological relationship of object locations,whereas lack of geographic information like sizes,angles,and distances.Therefore,the cognitive map should be mapped to the environment to afford adequate spatial details in further navigational decisions.Third,the remapping process,a vital mental process in the hippocampus,which is believed to be related to the utilization of the cognitive map,is also found in the RSC.In future study,it will be better(1)using the localizer task to locate the RSC in individual-level,(2)exploring the dynamic properties of the RSC activation by specific experimental designs to improve the ecological validity,and(3)understanding the subfield function of the RSC and its functional connectivity with other brain regions.