Sensory Coding: Vision

Question 1

Explain the purpose of Rod receptors?

Answer 1

Located in the periphery and are responsible for night vision. These have bad spatial acuity and only require one photon for excitation

Question 2

Explain the purpose of Cone receptors?

Answer 2

Located in the Fovea of the retina and escpecially high concentrated in the Foveaola. They are responsible for spatial acuity and colour vision. These require 100-1000 photons for excitation.

Question 3

What are the function of rhodopsin?

Answer 3

When the photon hits the receptor, rhodopsin is activated. This induces a second messenger cascade that closes the Na+ channels and induces hyperpolarization in the cell. In the dark rhodopsins are inactive and the Sodium channels are always open, leading to large release of glutamate.

Question 4

What is the pathway for creating vision

Answer 4

From Retina -> bipolar cells -> retinal ganglion cells -> LGN in thalamus (here right eye go to the left, left eye go to the right) -> V1 primary visual cortex -> V2 (Colour, orientation, depht and direction) -> Both ventral and dorsal pathway to identify

• Ventral: What
• Dorsal: Where

Question 5

What does the 3 main maps of the V1 show?

Answer 5

Retinotopic map:
- Shows the areas that are excitated in the V1 when showing a series of lines 
and circles (topography)

Orientation selectivity map: Shows the areas that are mainly used for the different orientations

Ocular dominance map: Shows the areas that are dominant when using the right and the left eye