The Eye- Lecture 1

Question 1

Pupil

Answer 1

Controls amount of light let into eye

Question 2

Retina

Answer 2

Where transduction occurs by photoreceptors- Rods and Cones

Question 3

Rods

Answer 3

Respond to intensity and brightness

Question 4

Cones

Answer 4

Respond to colour and works best in bright conditions

Question 5

3 Types of cone cells

Answer 5

Short cones- Responsive to blue light wavelength
Medium - Responsive to green light wavelength
Long - Responsive to red light wavelenth

Question 6

What is colour blindness?

Answer 6

Due to change in the number of cones that an individual has of each type

Question 7

Fovea

Answer 7

Where visual processing is most in detail (cones are primarily in the fovea right at centre of retina)

Question 8

Optic Nerve

Answer 8

Axons of magnocellular and parvocellular cells form the optic nerve and leave through the blindspot- transfer of info from eye to brain

Question 9

Different retinal cells

Answer 9

Photoreceptors- rods and cones
Bipolar cells
Ganglion cells

Question 10

Bipolar cells

Answer 10

act directly or indirectly to transmit signals from the photoreceptors to the ganglion cells.

Question 11

Ganglion cells

Answer 11

Receives visual information from photoreceptors via intermediate neuron- bipolar cells

Question 12

Magnocellular pathway

Answer 12

Rod cells join M cells which forms the Magnocellular pathway

Question 13

Parvocellular Pathway

Answer 13

Cone cells join P cells which forms the Parvocellular pathway

Question 14

Parallel processing

Bishop (1933)

Answer 14

At each step of visual processing there are lots of parallel neurons in each layer (with lateral connections between them).
Found three different classes of axons found in the optic nerve process different sensory qualities related to vision

Question 15

Hierarchical Processing

Answer 15

there is a transfer of information from the eye to the brain.
Each step involves some image processing and computation that builds on the last

Question 16

Receptive fields of V1 receptors

Answer 16

Photoreceptors have receptive fields. They respond to light in point A but not point B.

Question 17

Example of retinotopic organisation and receptive fields

Answer 17

Anatomically adjacent photoreceptors responded to physically adjacent points of light.

Question 18

Retinotopic organisation

Answer 18

axons from specific regions of the retina project to a specific area of the lateral geniculate nucleus (LGN) and also the occipital cortex.

Question 19

Lateral Geniculate Nuclues

Answer 19

multilayered structure that receives input from both eyes to build a representation of the contralateral visual hemifield.

Question 20

Hubel and Wiesel 1981

Answer 20

Micro-electrode recording in cats- found a retinotopic map in V1
Also that the cells in V1 are sensitive to orientation as well
Different cells respond to specific orientations of stimulus by firing a burst of action potentials

Question 21

Laminar architecture of V1 cortex

Answer 21

6 layers of cells
Input goes to layer IV (4)
Outputs from layers II/III (2/3)

Question 22

After V1…

Answer 22

V2 > V3 > V3A
Where there is an increase of receptive field size as we move up the visual hierarchy
And- increasing specialisation of function

Question 23

V2

Answer 23

Relay station which sends parvocellular inputs along ventral stream and magnocellular inputs along the dorsal stream

Question 24

Ventral visual stream

Answer 24

gets parvocellular inputs and generates conscious representations of object shape and identity

Question 25

Dorsal visual stream

Answer 25

gets magnocellular inputs and generates unconscious representations of object location and motion- rapid action control like returning a tennis serve

Question 26

Leslie Ungerleider

Answer 26

Pioneer in Ventral and Dorsal stream research and exploration

Question 27

Milner and Goodale (1995)

Answer 27

Carried out famous neuropsychological work on patients with dorsal and ventral stream lesions

Question 28

V5

Answer 28

Early part of the dorsal stream
Neurons in this region are sensitive to motion in their receptive field
Damage causes akinetopsia- motion blindness

Question 29

V4

Answer 29

Early part of ventral pathway
Sensitive to colour and shape
Damage causes Achromoatopsia- colourless world

Question 30

Beckers and Hömberg (1992) AK

Answer 30

Akinetopsia induced by TMS of V5 area in humans