L20 Vision 1

• What happens in V1?


  Main role = outlines

  Cells are tuned to bars in different positions of the visual field.

  Combination of many neurons = detect edges
• What are simple, complex and hypercomplex cells?


  Simple = responds to a stimulus in one location only

  Complex = responds to a stimulus equally throughout a large area

  Hypercomplex = strong inhibitory area on one end, so can detect location better
• What is the role of V2 & V3?


  About shape

  Reciprocal connections with V1

  Have many complex and hyper complex cells, as well as cells that respond to more complicated patterns e.g. circles
• What are receptive fields?


  Describe the spatial pattern of light to which a cell responds.

  Receptive fields grow more complex across the visual processing stream.
• What is hemianopia?


  Loss of vision in half the visual field.
• What is blindsight?


  Cortical blindness.

  They can still act in some way upon the world they cannot see because the pathway to V5 (motion) is intact.
• What is the role of V4 & V5?

  V4 is important in colour processing, but may be important for aspects of form processing.

  V5 is important for detecting motion.