Light, Eye, Brain - Terminology Flashcards Preview

PSY247 - Perception Psychologty > Light, Eye, Brain - Terminology > Flashcards

Flashcards in Light, Eye, Brain - Terminology Deck (30):
1

Accommodation

The lens can be stretched to allow focusing of far objects

2

Acuity

Acuity is precision.

3

Astigmatism

- Eyes are rugby ball shaped instead of soccer-ball-shaped
- Different focal lengths for different orientations
E.g. ok for verticle lines but myopic for horizontal lines.

4

Blind spot

Where the optic nerve/ disc leaves the eye. There are no photoreceptors here. Hence, blind spot.

5

Contrast

Relative luminance is constant, regardless of absolute luminance.
E.g. White paper vs. Black paper
A numerical value between 1 and 0. Zero is all grey. One shows a significant difference.
Contrast = (Lmax - Lmin) / (Lmin + Lmax)

6

Cornea

The transparent "window" into the eyeball. A lot of focusing is done by the cornea. Estimates say up to about 2/3rds.

7

Contrast

A measure of the difference between the highest and lowest luminance emitted or reflected from a surface
E.g. White paper vs. Black paper
A numerical value between 1 and 0. Zero is all grey. One shows a significant difference.
Contrast = (Lmin - Lmax) / (Lmin + Lmax)

8

Lens

Clear structure. Enables changing focus using ciliary muscles (stretches and squishes to focus light).

9

Photons

Particles of light.

10

Emmetropia

Appropriate focus. The normal refractive condition of the eye.

11

Extrastriate Cortex

Extrastriate cortical visual areas.
V1 -
V2 -
V3 -
V4 -
V5/MT -
These areas have been associated with processing certain stimuli/ are specialised however they all do a variety of processes.
The deeper the area, the more advanced the specialisation (generally).

12

Focus

Focussing is recombining rays from various directions to form a single point on the imaging surface.

13

Fovea

Fovea or Macula
A central part of the retina with the best resolution.
The part where photoreceptors are most denesly packed.
No blood vessels - they would obscure vision.

14

Ganglion Cells

Recieve electrical impulse from rods and cones.
Have long axons that exit the eyeball via a bundle called the optic nerve.
All of the ganglion cell body is in the eyeball itself.

15

Hyperopia/ Hypermetropia

- Far or long sightedness
- Focal length is too long
- Need convex corrective lenses

16

Lateral Geniculate Nucleus (LGN)

Ganglion cell axons terminate in the Lateral Geniculate Nucleus (LGN).

17

Rods

High sensitivity (low threshold)
Night vision
Pass electrical impulses to ganglion cells

18

Cones

Low sensitivity (high threshold)
Daytime / colour
Pass electrical impulses to ganglion cells

19

Macula

Macula or fovea.
A central part of the retina with the best resolution.

20

Optic disc

Optic disc or optic nerve.
Where the ganglion cell axons leave the eye.
There are no receptors here.
Blind spot.

21

Receptive field

The area in which one ganglion cell receives input from many photoreceptors.
Receptive fields for foveal vision are smaller and more densely packed.
Receptive fields for periphery are larger and less dense.

22

Optic chiasm

Ganglion cell axons cross at the optic chiasm.

23

Partial decussation

Left visual field goes to right LGN.
Right visual field goes to left LGN.
Visual stimulus that lands on the nasal side of the eye will cross to the other side.

24

Retinotopic

Cells next to each other in the brain have retinal receptive fields next to each other in your eye.
The organisation of cells in the brain relates to the organisation of cells in your eye.

25

Striate Cortex

The striate cortex or the primary visual cortex is located in the occipital lobe. LGN projects to it via optic radiations.

26

Refraction

The change in direction of a light ray, as it passes through one transmitting media to another, caused by a change in the velocity of propagation.
E.g. Air vs. Water

27

Interference Pattern

The pattern that is formed when two sets of waves overlap. Producing mutual reinforcement and some locations and cancellation at others.

28

Focal length

The distance from the centre of a lens to its focus.

29

Luminance

A photometric measure of energy emitted or reflected from a light source. Measured in candelas.

30

Reflectance

The proportion of incident light reflected from a surface.