3. From retina to cortex

Question 1

There is inherent ____ in the visual signals our eyes recieve

Answer 1

Ambiguity

Question 2

What is meant by bi-stable perception?

Answer 2

No depth cues leads to visual ambiguity

Question 3

What is the purpose of the following parts of the eye?
1. Pupil
2. Iris
3. Cornea and lens
4. Accommodation

Answer 3

1. Where light enters eye
2. Adjustable aperture, constricts in bright light to make pupil smaller
3. Focuses light on retina
4. Ciliary muscles change shape of lens to bring objects into focus at different distances

Question 4

What are photoreceptors?

Answer 4

Cells with light sensitive photopigments in outer segments

Question 5

What are Rods?

Answer 5

Contain rhodopsin, respond in dim light, none in fovea

Question 6

What are Cones?

Answer 6

Three types with photopigments sensitive to different wavelengths (long, medium, short) - daytime vision

Question 7

What are the different types of cells in the last stage in retinal processing?

Answer 7

• Large parasol ganglion cells
• Small midget ganglion cells
• Cells have ‘receptive fields’ - the part of the retina from which the ganglion cell receives input

Question 8

What are three properties of retinal ganglion processing?

Answer 8

1. Poor at spotting gradual change
2. Good at picking out sharp edges
3. Filters the input for useful info

Question 9

Within the Lateral Geniculate Nucleus (LGN) there are three types of cells. What are they and what do they detect?

Answer 9

1. Magnocellular cells - movement and flicker
2. Parvocellular cells - colour and detail
3. Koniocellular cells - blue-yellow

Question 10

50% of the cortex is dedicated to what?

Answer 10

Vision

Question 11

Prevalence of neutron types is shaped by what early on?

Answer 11

Environmental experience

Question 12

What did Blakemore and Cooper (1970) find when they raised kitten in striped tubes from birth with vertical or horizontal stripes?

Answer 12

5 hours per day in tube
5 months later: no response to orientation not in tube
Recorded from cells in visual cortex: no neurons that respond to orientation absent in tube
Example of neural plasticity, but with a critical period - ‘use it or lose it’

Question 13

What do the following streams of processing process?
1. Dorsal
2. Motor system
3. Ventral
4. Hippocampus

Answer 13

1. Where
2. Movements
3. What
4. Memory

Question 14

Processing of some features (e.g. ____) begins at the ____ and gets more complex ‘____’ in the visual processing stream

Answer 14

edges
retina
higher

Question 15

Cells in different parts of the visual stream are ____ to different features and take in information from a particular ____ ____

Answer 15

selective
receptive field

Question 16

Early levels of visual processing have ____ ____ where each part of the visual field is ____

Answer 16

retinotopic maps
represented