Senses and cognition of humans are mainly done by the visual nervous system. Most of the information people absorb from the world all conducted by the visual system. Therefore, visual attention mechanism is very important for exploring the visual system. In this paper, several basic problems of visualization of cellular electrical activity and visual information processing in the central nervous system are reviewed; then, models of visual attention mechanism are systematically reviewed. Finally, application of the visual attention mechanism in medical image segmentation is discussed.