The Visual System

The Visual System

1. Pathways in visual cortex: Axons of LGN project to primary cortex

   • Then axons go to the secondary visual cortex
     • Parallel streams extract more specific dimensions
       • Unresponsive to diffuse light
         • Colour perception V2 and V4
           • Motion Perception V5

2. Reciprocal Connections: Feedback/feed forward connection

   • Higher centres modulation response of lower ones: Top down influences
     • LGN has more feedback from V1 than it sends
       • V1 has more from V2 than it sends

3. Opponent organisation of receptive field: Lateral inhibitory connections create sensitivity to contrast. Stimulation by light of the surround relative to the centre of the receptive field. There is lots of information on absolute intensity of light

4. Basic mechanism of transformation: Convergence of earlier cells in system onto later cells creates receptive fields. Allows responses of earlier cells to be compared