Perception (1-2)

Question 1

Which 2 components of the eye focus light entering the eye?

Answer 1

The cornea and lens.

Question 2

Which part of the eye inverts the image?

Answer 2

The lens.

Question 3

What is the process of light entering and leaving the eye?

Answer 3

• Cornea and lens focus it
• Hits retina
• Leaves via optic nerve

Question 4

What is the retina?

Answer 4

The thin inner surface on the back of the eyeball - it contains the sensory receptors that change light into neural signals.

Question 5

What photoreceptors does the retina contain and how many of each?

Answer 5

• Rods - 120 million

- Cones - 6/8 million

Question 6

What are rods?

Answer 6

Retinal cells that respond to low levels of light

• BLACK AND WHITE PERCEPTION
• nocturnal vision

Question 7

What are cones?

Answer 7

Retinal cells that respond to higher levels of light

- COLOUR PERCEPTION

Question 8

What is transduction?

Answer 8

Transducing external light into a neural signal which allows the brain to interpret the light source.

Question 9

What is the fovea?

Answer 9

The center of the retina.

Question 10

Where are rods generally found?

Answer 10

Heavily concentrated in the periphery/outer edges of the retina. There are none in the fovea.

Question 11

Where are cones generally found?

Answer 11

Very densely packed in the fovea, but also spread out across the rest of the retina.

Question 12

What 6 steps are there in the transmission from the eye to the brain? (starting at the photoreceptors).

Answer 12

1. photoreceptors
2. bipolar cells
3. ganglion cells
4. optic nerve
5. thalamus
6. primary visual cortex.

Question 13

What are bipolar cells?

Answer 13

• They transmit the signals from the photoreceptors to the ganglion cells
• Communicate via graded potentials

Question 14

What 2 ways can the bipolar cell operate?

Answer 14

• Directly

- Indirectly - via the amacrine or horizonal cells).

Question 15

What do we know about ganglion cells? and how?

Answer 15

We know that response characteristics, receptive field layout and size have all been mapped out by studies using single cell recordings (Hartline 1930s, Kuffler 1950s).

Question 16

Roughly how many ganglion cells are there?

Answer 16

2 million.

Question 17

What is the optic chaism?

Answer 17

The point at which nasal information from each eye crosses along the visual pathways.

Question 18

What side does the temporal branch run down and what is this referred to?

Answer 18

The same side - ipsilateral.

Question 19

What side does the nasal branch run down and what is this referred to?

Answer 19

The opposite side - contralateral.

Question 20

What is the function of the lateral geniculate nucleus?

Answer 20

• Located in the thalamus

- The relay center for visual information and is part of the pathway from the optic nerve to the occipital lobe.

Question 21

What are the 2 largest pathways to the brain called? (referring to all species)

Answer 21

• Retinotectal

- Retinogeniculate (most prominant in mammals)

Question 22

At what point do axons along the visual pathway terminate?

Answer 22

At the primary visual cortex (V1) in the occipital lobe

Question 23

What other names are given to the primary visual cortex?

Answer 23

V1, striate cortex, Area 17.

Question 24

What do Hubel and Weisel (1958) say about the types of cells that are in V1?

Answer 24

there are 2 types:

• simple
• complex

Question 25

What do we know about the transferring of infomation from the straite to extrastriate cortex?

Answer 25

• Information flow is not sequential from v1 onwards - ot converges and diverges.
• Processing of information is distributed and specialized in the different areas.