Bottom-up And Top-down Pathways Of Visual Experts:A Functional Magnetic Resonance Imaging Study

Vision is one of the most important feelings of human beings.More than 80% of human information comes from the visual system.Humans are good at visually recognizing objects in complex environments.The recognition of visual information in the brain relies on two types of visual information processing pathways: bottom-up and top-down pathways.Among them,the bottom-up pathway refers to the visual processing pathway that the brain originates from the input of visual information;the top-down pathway refers to the visual processing pathway that is regulated by the scene information.The study of visual recognition of the bottom-up and top-down pathways helps us to understand the neural mechanisms of humans' visual recognition.Through deliberate training over a long period of time,the trained individual often obtains stable and significantly superior expert skills.Robust behavior often corresponds to a stable visual nerve basis,so academia usually uses experts with certain skills as a robust model to study the brain mechanism of human learning.Plasticity refers to the fact that the structure and function of the nervous system is constantly changing due to factors such as its own or external environment.Changes in the plasticity of the nervous system often result in a corresponding change in behaviour.Neural plasticity is the neural basis of human learning and memory,and makes the acquisition of expert skills possible.Therefore,it is of great significance to study the change of brain plasticity during the acquisition of expert skills.In this thesis,we used the cross-sectional study design and functional magnetic resonance imaging(f MRI)techniques to quantitatively measure the behaviors and centers of the radiologist's visual recognition capabilities to study the changes in brain plasticity that occur from the visual experts' bottom-up and top-down pathways.The main work and innovations are summarized as follows:Firstly,for the radiologist model,we combined the behavioral characteristics of the radiologist's visual recognition and included the three indicators of accuracy,specificity,and confidence in the evaluation criteria.Receiver operating characteristics(ROC)curves were used to specify normalized evaluation indicators.Then we designed and developed a quantification system for radiologist' visual recognition capabilities.Using this system,21 radiologists and 21 controls performed behavioral tests.The experimental data analysis results showed that the radiologist's lesion recognition ability was significantly better than non-radiologist.Secondly,using the radiologist model,we studied the effects of short-term vision training on the visual bottom-up pathway in resting state.We collected the resting state f MRI data of the subjects in the previous study and conducted an independent component analysis(ICA)method to investigate the problem.The data analysis results show that the visual expertise have caused plasticity changes of the visual experts' ventral visual pathways,specifically manifested in the enhancement of intra-regional connectivity of the right fusiform face area(FFA)in the advanced visual network.FFA usually involves the fine recognition of objects.We suggest that the effectiveness of visual information recognition is reflected in the effective connection between the high-level visual cortex and the right FFA.Finally,this study focuses on the effects of short-term visual training on the visual bottom-up and top-down pathways.In this paper,we use the coordinate data of the previous study based on task-state f MRI visual expertise neural mechanism and the differential mapping(SDM)meta-analysis method to quantitatively study the brain activation of visual experts under the visual recognition task.Consistent brain activation intensity and pattern in performing related visual tasks.It was found that the visual experts in the implementation of the relevant visual tasks,the expert group from the bottom-up and top-down access to the core brain area activation intensity was significantly higher than the non-expert group.Further,we found that when visual experts perform related visual recognition tasks,the bottom-up and top-down pathways coexist and work together.Their plasticity changes are reflected not only in the underlying functional brain regions associated with basic visual processing,but also advanced functional brain areas related to memory,attention and semantic processing.