| Popis: |
Visual system processes simple object features in early visual areas, and visual features become more complex as visual information is sending to downstream areas. In addition to the feedforward pathway, visual system has abundant feedback connections, whose number is even larger than feedforward ones. This suggests that top-down signal from higher visual areas may strongly affect sensory representation in early visual areas. However, little is known about how top-down signals are generated in higher visual areas and the mechanism by which the sensory representation in early visual areas is modulated. To address these issues, we focus on an experimental study using visual perceptual tasks. We develop a model of visual system which consists of network models of V1, a higher visual area, and a recognition area. Using the model, we show that a top-down pathway from the recognition layer to V1 via the higher area is formed concurrently with the formation of a decision process by reinforcement learning. We also show that tuning modulations of V1 neurons are caused by a top-down influence mediated by the change in long-range horizontal connections of V1 neurons. The results provide crucial insights into understanding the roles of top-down influence in perceptual task. |
