6: The Visual System Flashcards

Question

Scotopic SSC...

Answer 1

Relative brightness of light shone on retina.

Answer 2

When the relative brightness of objects changes due to changes in scotopic and photopic spectral sensitivity.

Answer 3

A process whereby our eyes build on the last 'scan' it makes of the seen environment, enabling us to have a continual perception of our environment.

Answer 4

Any substance that absorb light; in this case, rhodopsin, a red pigment.

Answer 5

It becomes bleached when it absorbs too much bright light, and regains colour in darkness.

Answer 6

A G-protein that responds to light, not neurotransmitters.

Answer 7

Conduct signals from the retinas to the primary visual cortex via the lateral geniculate nuclei in the thalamus. Its system is retinotopic.

Answer 8

Is for the analysis of fovea input.

Answer 9

A channel of communication via RGS pathways. Cones provide most input to these.

Answer 10

A channel of communication via RGS pathways. | Rods provide most input to these.

Answer 11

The most important piece of information in any visual display, as it establishes object separation and their positions.

Answer 12

A.K.A the Chevreul illusion. Stripes used to emphasises differences of a colour along a spectrum.

Answer 13

+ intense light = + ommatidium axon firings = + lateral inhibition Inhibition of rate of firing of surrounding cells.

Answer 14

The area of a visual field of a neuron in which a visual stimulus can influence the firing rate.

Answer 15

Are smaller than in periphery visual components of eye. Supports idea of small area-high acuity.

Answer 16

Meaning their receptive field only accounts for one eye.

Answer 17

Illumination on central region = excitatory. | Illumination on peripheral region = inhibitory.

Answer 18

Illumination on central region = inhibitory. | Illumination on peripheral region = excitatory.

Answer 19

On-off response, receptive fields are rectangular shaped, so respond best to bar-shaped features.

Answer 20

On-off response, except its 'on' and 'off' regions aren't static, enabling continuous response to a stimulus. Good for recognising moving objects.

Answer 21

Determines its preference for the orientation of features, e.g. | / - \ | , horizontal or columnar organisation.

Answer 22

Is a key function in the visual cortex, and contradicts the key assumption that receptive fields are static properties of neurons.

Answer 23

Absence of light.

Answer 24

Intense and equal mixture of a wide range of wavelengths (colours).

Answer 25

Young (1802) - 3 types of colour receptors, and stimulus is perceived in varying ratio by these receptors. - Can be any 3 wavelengths provided that the colours are mutually exclusive. - Supported by findings that there are 3 types of cones that are mutually exclusive.

Answer 26

Hering (1878) - 2 cell classes for colour coding, and another class for brightness coding. - Each class has 2 complementary colour perceptions (red-green, blue-yellow, and black-white for brightness). - Supported by idea that there is no such thing as 'reddish-green' or 'bluish-yellow'.

Answer 27

Most mammals are this, lacking perception of red hues.

Answer 28

Some birds and reptiles are this. Can detect ultraviolet light.

Answer 29

- Tendency to perceive an object as same colour in spite of the major variations occuring in the wavelengths said object reflects. - Trichromatic and Opponent Process theories cannot explain this.

Answer 30

The illumination contains a mixture of short, medium, and long wavelenghts, and that the object is perceived as part of the visual scene.

Answer 31

Land (1977) Object colour is dictated by its reflectance, which is the ratio of different wavelengths of light reflected by its surface.

Answer 32

Fire 'on' when red is on periphery and green is on centre, and 'off' for the reverse.

Answer 33

Peglike, cytochrome, oxidase-rich, dual-opponent colour columns. This supports discovery that visual cortex organisation is largely columnar.

Answer 34

1: Primary visual cortex (V1) <--- Secondary visual cortex information. - The further away from V1 neurons are, the larger their receptive fields are, and the more complex and specific the stimuli they respond to.

Answer 35

Hidden in posterior of the occipital lobes, surrounded by the prestriate cortex.

Answer 36

- An area of blindness induced by V1 damage. - Tested for using the 'perimetry test', which creates a visual map for each eye, which is indicative of areas of damage.

Answer 37

A scotoma in half of one's visual field.

Answer 38

When patients with scotomas can still respond to visual stimuli that pops up in scotomas, even though they don't have any conscious awareness of it.

Answer 39

Is hardiest visual ability when visual damage occurs. Probably because it is one of our most basic perceptual abilities.

Answer 40

Remaining cells of striate cortex are still alive,and there is a sufficient amount of them to continue carrying out visual abilities without conscious awareness.

Answer 41

Visual pathways between secondary visual cortex and visual structure that don't go through V1 are still able to carry out visual abilities as they don't need cognitive awareness.

Answer 42

- Dorsal stream - Ventral stream - Same as sensorimotor system!

Answer 43

V1 ---> dorsal prestriate cortex ---> posterior parietal cortex. This responds to spatial stimuli.

Answer 44

V1 ---> ventral prestriate cortex ---> inferotemporal cortex. This responds to colour, shape, size etc. of stimuli.

Answer 45

Organises roles of the 2 streams as: - Dorsal - where? - Ventral - what?

Answer 46

Organises roles of the 2 streams as: - Dorsal - control of behaviour - Ventral - conscious perception

Answer 47

- Visual agnosia for faces. - Damage to an area of secondary visual cortex that is responsible for face recognition. - Can detect faces, but cannot recognise. - Not just specific to face recognition, but recognition of objects, i.e whose chair/dog/house/car?

Answer 48

- Inability to see movement in smooth progression. - Nefazodone (drugs) can induce temporary akinetopsia. - Damage to middle temporal area of cortex (MT). - MT function is likely the perception of motion.