Abstract:

Boundaries are obstacles with extended surfaces in the spatial environment and significantly contribute to the spatial navigation of humans and animals. Extensive behavioral literature has revealed that boundary cues contribute more than landmark cues to spatial navigation, in multiple species, which is considered as the superior boundary effect. However, the dynamic developmental process of boundary perception and its underlying neural mechanisms in spatial navigation remain unclear. Therefore, this study reviewed the last decade of research systematically and put forward several possible future directions for boundary-based navigation. On the one hand, we summarized the cognitive developmental mechanisms of boundary-based navigation. Specifically, most reorientation studies have reported that children could reorient successfully by using the geometry of the boundary after they disoriented at 1.5~2 years old, and gradually using the vertical information until they were 3.1~4.7 years old, length information until the age of 4~5, and visual opaqueness information until the age of 5 years old in navigation. On the other hand, a body of neuroimaging studies in adults found that the medial temporal lobe and parietal lobe play different roles in boundary processing. First, the geometry of the boundary and its constituent elements (i.e., vertical structure, length, and angle) are represented in the parahippocampal place area (PPA) and the retrosplenial complex (RSC). Furthermore, although both PPA and RSC could represent the geometry and vertical structure of the boundary, only the PPA was sensitive to changes in boundary length and angle between boundaries. Second, the encoding and retrieval of the boundary-based object’s location were associated with the hippocampus. When the structure of the hippocampus was damaged, boundary-based learning was accompanied by impairments. Third, research on the cognitive neural mechanism of navigational affordance is. The present study first distinguished navigational affordance, the hot topic in spatial navigation, into physical affordance and visual affordance. Recently, functional magnetic resonance imaging studies have shown that the physical affordance for boundaries is represented in the occipital parietal area (OPA) or transverse occipital sulcus (TOS), and the OPA may be mainly responsible for egocentric information representation in spatial navigation. Howver, it’s not yet explored the neural basis of visual affordance for boundaries, which would provide new insights into visual-guided navigation. Together, previous studies preliminarily examined the behavioral and neural basis of boundary-based navigation, which enriched our knowledge and understanding of spatial navigation. However, several issues are unaddressed that should be investigated in future. First, future studies should explore the comprehensive cognitive processes of boundary-based navigation and its development trajectory. A vast cognitive network or computational model to investigate the role of each cognitive function in boundary-based navigation should be considered. Second, further research could explore the functional interaction between the medial temporal lobe and the posterior parietal cortex in boundary-based navigation and its neural developmental changes in children. Third, we could pay attention to the distinctions and associations between the cognitive neural mechanisms of the boundary and geometry center encoding. Forth, further study could investigate specific behavioral and neural impairment of boundary-based navigation in individuals at genetic risk and preclinical Alzheimer’s disease. Finally, we could concern about the boundary influence mechanisms in long-term memory, time estimation, visual space, and social networks.

Key words: boundary, spatial navigation, cognitive development, functional basis, medial temporal lobe