From The Eye To The Cortex

From The Eye To The Cortex

1. Two types of receptor cells known as rods and cones

   • Cones are used for colour vision and sharpness of vision. There are 125 million rods concentrated in the outer regions of the retina
   • Rods are specialised for vision in dim light. There are many differences between rods and cones such as the retinal ganglion cell receives input from only a few cones but hundreads of rods
     • Retinal Ganglion Cells: retinal cells providing the output signal from the retina

2. Retinopy: The notion that there is mapping between receptor cells in the retina and points on the surface of the visual cortex

   • Each eye has its own optic nerve and the two optic nerve meet at the optic chaism
     • Axons from the outer halves of each retina proceed to the hemisphere on the same side. Whereas those from the inner halves cross over and go on to the other hemisphere
       • As a result each side of the visual space is represented with opposite brain hemispheres
         • Signals then proceed along two optic tracts within the brain. One ttact contains signals from the left half of the eye and the other contains signals from the right half
           • After the optic chiasma, the optic tract proceeds to the LGN which is a part of the thalamus. Nerve impulses finally reach the V1 in the primary visual cortex within the occipital lobe at the back of the head before proceeding to the v2 area

3. Processing Information From The Environment

   • -Stimulus enters the eye
     • Reception: Photoreceptors in the retina detect light
       • Transduction: Light is converted from electromagnetic energy to electrochemical
         • Transmission: sent to brain via optic nerve
           • Received in the visual cortex and organisation and interpretation occurs in that area