A Cross-species Brain Atlas Study Of The Fusiform Gyrus

The fusiform gyrus is an important area on the ventral temporal lobe.Recent studies have indicated that the fusiform gyrus plays an important role in advanced cognitive functions such as language and facial recognition.In addition,in studies on facial recognition in macaque and chimpanzee,there is no evidence that the fusiform gyrus is involved in this function.Therefore,exploring fusiform gyrus structural and connectivity asymmetries from an evolutionary perspective has important implications for explaining the origin of human-specific function.Using multimodal magnetic resonance imaging data,a cross-species brain atlas of the fusiform gyrus was established.For each species,we investigated the asymmetry of the subregions of the fusiform gyrus in search of alterations in the brain during evolution.The main results of this thesis are as follows:1.A cross-species brain atlas of the fusiform gyrus was established.In this thesis,using the MRI data from 27 chimpanzees and 8 macaques,spectral clustering algorithm was used to divide the fusiform gyrus of chimpanzee and macaque into three subregions based on connectivity information.The three subregions of the fusiform gyrus of chimpanzees are arranged in order in the anterior-posterior direction,namely anterior subregion,middle subregion and posterior subregion;the three subregions of the fusiform gyrus of macaques are arranged in a triangular shape,namely anterior subregion,posteromedial subregion and posterolateral subregion.Previous studies have divided the fusiform gyrus of humans into three subregions,namely anterior subregion,posteromedial subregion,and posterolateral subregion,which are similar to the macaque arrangement pattern.Taken together,we have obtained a cross-species brain atlas of the fusiform gyrus.2.We investigated asymmetry in the cross-species brain atlas of the fusiform gyrus.For humans,in order to seek the connection between the asymmetry of brain regions and the known functional asymmetry,this thesis calculated the asymmetry of each subregion of the fusiform gyrus from three perspectives: structure,functional connectivity,and structural connectivity.For each species,in order to seek changes in the brain during evolution,using probabilistic tractography,we investigated the structural connectivity asymmetry of each fusiform gyrus subregion(including structural connectivity between subregion and whole brain,structural connectivity between subregion and target region).This thesis found leftward asymmetry in the posteromedial subregion of human fusiform gyrus,which may be related to the asymmetry of human language function,and leftward and rightward asymmetry in the posterolateral subregion of human fusiform gyrus,which may indicate that it is related to various asymmetric functions such as emotion and language.The strength of the asymmetry in the anterior subregion is weaker.This thesis also found leftward asymmetry in the posteromedial subregion of macaque fusiform gyrus and leftward and rightward asymmetry in the posterolateral subregion of macaque fusiform gyrus.Chimpanzees showed almost no asymmetry.In addition,the macaque and human fusiform gyrus shared the same asymmetric pattern,which may be related to simple social communication functions.In conclusion,the fusiform gyrus of humans and macaques has to some extent similarity in division and asymmetry,which indicates the homology of macaque and human brains,and has value for further research on the origin of human advanced cognitive functions.