Principles of function in the visual system

© 2012 Springer-Verlag/Wien. A large fraction of the primate brain, especially of the cortex, is dedicated to the processing of visual information. A complex network of brain structures transforms electrical signals in the eye about local differences in brightness into signals which directly relate to visual perception in higher areas of visual cortex. Using electrical recordings from individual brain cells in animals, we can trace the hierarchical visual pathway from representations of the visual world by spots of lights in the eye to representations of lines and edges in primary visual cortex and more complex representations in higher cortical areas. The primate visual system also processes different visual attributes, like motion direction or colour, in parallel. This is achieved through specific rules that govern connectivity and organisation of neurons in the visual system. The nature of these image transformations directly shapes the perception of the visual world. The close relationship between visual cortical processing and perception has been an important experimental key for neuroscientists to identify brain cells that directly contribute to visual perception. Thus, our current understanding of visual processes is no longer limited merely to representations of the physical stimuli in the outside world.