Vision

Question 1

Retina

Answer 1

Nerve cells and glia forming a thin, layered structure that lines the back of the eye, including:

Photoreceptors that are light-sensitive sensory cells (rods for low light levels, cones for daylight vision)

Interneurons forming a circuit that extracts salient information from the pattern of photoreceptor responses

Retinal ganglion cells that are the retinal afferents

Question 2

Fovea

Answer 2

A tiny region in the centre of the retina, where the point in visual space that you are directly looking at is focussed, that is structurally adapted for fine detailed vision. Often used as synonymous with “macula”, a more extensive region distinguished by yellow pigmentation.

Question 3

Photopigment

Answer 3

The molecule that captures a photon of light and triggers a change in a photoreceptor’s membrane potential. Consists of a protein, “opsin”, and a light-sensitive chromophore, “11-cis retinal”.

Question 4

Receptive field

Answer 4

Region of the visual image that directly increases or decreases the action potential firing rate of a given cell. The term also encapsulates the pattern of light that is needed in that region to generate this response.

Question 5

Binocular cell

Answer 5

A cell that receives input from both eyes, and hence has matching receptive fields in the two eye fields. These cells contribute to depth perception.

Question 6

Dorsal lateral geniculate nucleus (dLGN)

Answer 6

The thalamic nucleus that relays visual information from the retina to the primary visual cortex, in the pathway that serves perception.

Question 7

Primary visual cortex

Answer 7

Area 17 of the cortex, receives input from the retina via the dLGN and distributes it to many “higher” visual areas for further and more specific processing.

Question 8

Higher visual cortical areas

Answer 8

There are at least 20 identified regions in the primate cortex that contribute to vision, and it has been estimated that up to half of all the cortex may be involved in one way or another. The main cortical areas can be roughly divided between two pathways (Infero-temporal pathway and Parietal pathway)

Question 9

Infero-temporal pathway

Answer 9

Supports our ability to see objects in detail and identify them.

Question 10

Parietal pathway

Answer 10

Supports our ability to understand the location and relationships of multiple objects within our visual field, how they relate to us and therefore how we can interact with them, how they are moving and hence how these relationships are changing.