The white matter in the brain provides a bridge for communication and information exchange with gray matter. The amount, length, and network structure of white matter affect brain information transmission, and spatial navigation as an advanced cognitive function is no exception. This study systematically analyzes fiber bundle connections' network structure and structural characteristics. The results show that the small worldness of the two networks is more significant than 1, which indicates that the two networks have high clustering, short distance, and small worldness. In other words, in healthy young people, spatial navigation networks are economical and support complex spatial navigation. This also shows that the two groups can achieve optimal balance in functional integration and separation of information processing, consistent with the study by Sharma[28]. Eg is the total efficiency of information transmission between all nodes through multiple paths; increasing Eg means less interference in information transmission and robust synchronization between different cortical regions. In this study, Eg is consistent with other studies on the relations hippocampus(HIP) between global efficiency and the cognitive ability of brain networks; that is, global efficiency is an essential predictor of working memory performance[29].
When assessing differences in an individual's ability to navigate, significant changes in cortical functions are localized rather than whole-brain. To further differentiate differences in spatial navigation capabilities, we use node efficiency to estimate the activity of local brain regions and examine the brain regions that play a crucial role in structural networks based on Hub nodes. The results show a statistical difference in nodal efficiency between the two groups in 16 brain regions, but the differences between the nodes have not been studied. However, there is much agreement that spatial navigation functions are performed by a core network dominated by the medial temporal lobe and expanded area composed of the parietal lobe and the frontal lob[28, 30]. The core network region is the cerebral cortex, primarily responsible for spatial navigation functions, including hippocampus(HIP), entorhinal cortex(EC), parahippocampal gyrus(PHG), retrosplenial complex(RSC), and thalamus(THA). There have been few studies on the expansion of the network area in the past. More and more research has focused on the role of the parietal lobe and frontal lobe in spatial navigation, speculating that the parietal lobe is involved in spatial image and directional decision-making, while the frontal lobe is involved in sensory information processing during navigation[3, 6, 31]. In more than half of the 16 different brain regions, hippocampus༈HIP༉, parahippocampal gyrus(PHG), Left Insula(INS), fusiform gyrus (FFG), heschl gyrus(HES), superior temporal gyrus (STG),temporal pole:superior temporal gyrus(TPOsup) and temporal pole: middle temporal gyrus (TPOmid) were located in the core area. It is shown that the GN group spatial navigation core region nodes have better connectivity and communication efficiency[32]. Previous studies on spatial positioning have focused on the medial temporal lobe but have tended to ignore the importance of extended regions such as the frontal-parietal lobe[33]. We found that there were differences in the nodes of the bilateral superior frontal gyrus(SFG), middle frontal gyrus(MFG), and cingulate gyrus(CG), especially the middle frontal gyrus (MFG), and Right median cingulate and paracingulate gyri (DCG.R). Some studies have observed the discharge sequence of cells and found that hippocampal activity driven by the anterior cingulate gyrus(ACG) increases episodic memory. The prefrontal cortex can reduce the interference of other signals to the hippocampus༈HIP༉ in spatial orientation tasks. Although the frontal lobe node is not the core area of spatial navigation, it can assist the core area in carrying out multiple cognitive processes related to spatial navigation, such as target planning, decision-making, memory, coding, and so on[4, 5]. However, the occipital lobe is not classified as the core and extended region of spatial guidance. Recent studies have verified that the occipital lobe perceives the spatial position and judges the sources and characteristics of the external environment through optical transmission[34]. The occipital nodes in the Left calcarine fissure and surrounding cortex(CAL.L) (0.45 ± 0.03 vs 0.43 ± 0.03,p = 0.02) and Right middle occipital gyrus(MOG.R) (0.40 ± 0.03 vs 0.38 ± 0.03,p = 0.04) were significantly different between the two groups. There is no statistical difference between the two groups' number and efficiency of Hub nodes. These nodes are located in areas associated with spatial navigation function[12], contrary to the result of Sharma[28]. Sharma found that people with better spatial orientation had more hub nodes. Speculate the reason:1 there is no difference between the two groups in the critical nodes of spatial navigation information processing, indicating that the two groups of subjects can communicate efficiently between different structures through these key node[35]. 2 this study is male, excluding gender differences.
To summarize, this study constructs individual structural networks based on DTI technology to explore their structural network connection mode differences. Overall efficiency shows that both groups of structural brain networks were small-world. In contrast, the PN group had a lower topological nature, meaning brain networks could not transmit and process information. Local node efficiency reflects the spatial localization ability of critical regions of the brain. It provides a quantitative analysis method for differentiating the differences in brain tissue structure of different spatial navigation abilities groups, which benefits the selection of particular occupational groups. It also provides a critical imaging basis for the early prevention of spatial disorientation.