Topic 8 Colour

Question 1

What are the three parameters used to define the colour of an object and what do they mean?

Answer 1

1) Hue: the actual colour
2) Saturation: vividness of the colour (amount of colour relative to white)
3) Brightness: light intensity

Question 2

In order to process colour, the human visual system uses 3 broadband detectors rather than many narrowband ones, what is the advantage of such an approach?

Answer 2

Number of cells.
A narrowband system requires too many cells to process all colours at all locations in the retina and hence the ability to see fine detail would be impaired.

Question 3

What are the two types of colour mixing, what is the major difference between them, and give examples of each type?

Answer 3

1) Additive mixing (more light in the mixture than in the components)
2) Subtractive mixing (less light in the mixture than in the components)

Example:
Adding all the spectral colours together:
Perceive white by additive mixing
Perceive black by subtractive mixing

Question 4

If you added all the spectral colours together in an additive-colour mix, what colour what you get, what if you did the same in subtractive colour mix? Why are the two resultant colours different?

Answer 4

1) Get white in additive mix:
white is the sum of the components
2) Get black in subtractive mix:
light is removed by adding colour, so black which is common to all components remains

Question 5

What are metamers?

Answer 5

Physically different stimuli that are perceived as identical.

Question 6

Can a monochromatic system provide the basis for perceiving colour? Why?

Answer 6

No.
It cannot discriminate colour.
It only has one type of receptor and can only see differences in intensity.

Question 7

Can a dichromatic system provide the basis for perceiving colour? Why?

Answer 7

Yes, but having deficit in colour perception. The system may compare relative amount of firing (ratio of activity).

Question 8

In a dichromatic system, what is the neutral point and what is the consequence of it?

Answer 8

Neural point is at a crossover point of the two response curves, where two kinds of cones are equally excited, giving the same kind of response as white light, therefore light of a single wavelength is perceived as white.

Question 9

What is the trichromatic theory of colour perception?

Answer 9

Colour perception based on the relative activity of three receptor types.
3 primaries are needed to match all colours.

Question 10

What is the opponency model of colour perception?

Answer 10

Colour vision is mediated by three opponent mechanisms

Question 11

Explain how both models are correct?

Answer 11

Opponent pairing states how the three cone types are combined.

Question 12

What is meant by the concept of a colour-blind processing system?

Answer 12

A processing mediated only by the M(magnocellular) system which is only luminance sensitive and cannot use colour info.

Question 13

How could you test whether a system, e.g. motion or stereo processing, are colour blind and what are the disadvantages of the various experimental techniques?

Answer 13

1) Isoluminance approach: remove all luminance info from the stimulus, leaving only colour info.
1. impossible to totally remove luminance info
2. this luminance cue may signal depth or motion, and it may differ to that signalled by colour.
2) Alternative approach: have the stimuli contain both colour and luminance info, but define the luminance info.

Question 14

Describe the three main colour spaces used to define colour.

Answer 14

1) CIE space: based upon colour matching studies and hence the trichromatic theory.
2) Perceptual colour space: based upon colour appearance studies.
3) Cone space: based upon the response of the cones.

Question 15

What is one of the main uses of the CIE colour space, i.e. what can it predict?

Answer 15

Predicting colour mixtures. The mixture of any 2 colours will lie along the straight line connecting the two compon.

Question 16

Describe the various types of retinal-based colour blindness and discuss whether it is accurate to call them colour blind.

Answer 16

Monochromats are the only colour blindness that can’t perceive colours.
Dichromats actually are colour deficit, not really colour blindness because they see colours. One of the cone photopigments is missing.

Question 17

What are the two main colour tests?

Answer 17

Farnsworth-Munsell 100 Hue test

Ishihara test

Question 18

What is amnesia and what are the two different types of it?

Answer 18

A loss of memory (forgetfulness).
Retrograde: loss of memories prior to an event;
Anterograde: inability to form new memories.

Question 19

Who is HM?

Answer 19

The most famous research subject in the history of brain study.

Question 20

Why did he need surgery and what was removed?

Answer 20

HM had seizures.

Amygdala, most of hippocampus, and some surrounding cortex from both temporal lobes.

Question 21

What impact did that have on his memory, what memories were impaired and what were not?

Answer 21

He had anterograde amnesia but not retrograde amnesia.

He lost ability to form new declarative memory, but could retrieve old memories and form nondeclarative memory.

Question 22

What studies implicate the hippocampus in encoding declarative long-term memories?

Answer 22

London taxi drivers have larger hippocampus.

H.M. having anterograde amnesia about declarative memory.

Question 23

What findings indicate that the hippocampus is not involved in the storage of most memories?

Answer 23

H.M. could retrieve memories consolidated before his surgery.

Question 24

What information do place and grid cells in hippocampus process?

Answer 24

1) Place cells: Encoding selective spatial locations.

2) Grid cells: Encoding latitude and longitude info, active at intersection point.

Question 25

What is a mirror task, and what were HR’s pattern of results on this task? What did it tell us about his memory ability?

Answer 25

Mirror-tracing task: drawing patterns by looking at its image in the mirror.

HR’s performance improved as practice repeated.

He had ability of nondeclarative skill learning.

Question 26

What cortical region is involved in learning skills?

Answer 26

Basal ganglia
Motor cortex
Cerebellum

Question 27

What is classical condition? What is common experimental task used to study it? What brain area is involved in establishing classical conditioning?

Answer 27

Learning an association between an initially neutral stimulus comes to predict an important event.
Eye-blink reflex.
Cerebellum.

Question 28

What is instrumental or operant conditioning?

Answer 28

A stimulus and response learning. The likelihood that an act (instrumental response) will be performed depends on the consequences (reinforcing stimuli) that follow it.

Question 29

Why can aromas be so evocative?

Answer 29

Olfaction (sense of smell) is part of the limbic system. Olfactory bulb is next to and provides input to the amygdala.

Question 30

What cortical region is involved in encoding emotive memories?

Answer 30

Amygdala

Question 31

What disorder can occur due to over activation of this area when forming memories?

Answer 31

PTSD

Question 32

What are some treatments for PTSD aimed at reducing the emotive impact of the memories?

Answer 32

Use a blocker and get the person to recall the memory to weaken the emotional experience of the event.

Question 33

What is an engram?

Answer 33

Physical changes in the brain that underlie a LTM, also called a memory trace.

Question 34

List the two main types of cellular changes that have been linked to the encoding of memories and given an example of each.

Answer 34

1) Structural:
e. g. greater connections between cells
2) Physiological:
e. g. greater neurotransmitter release

Question 35

Describe the rat study that showed that the richness of the environment could affect the structure of the brain.

Answer 35

Rats were placed in three different environments (IC, SC & EC). Compared to IC (occasionally SC), EC rats have a heavier and thicker cortex with more dendritic branches.

Question 36

What is long term potentiation? (LTP)

Answer 36

The postsynaptic neurons respond to normal levels of presynaptic activity. The synapses strength is increasing (i.e. become stronger and more effective).

Question 37

What is the evidence that LTP can play a role in memory formation?

Answer 37

1) Correlational observation:
time course of LTP is similar to the time course of memory formation
2) Somatic intervention experiments:
pharmacological treatments that interfere with basic physiological processes that contribute to LTP tend to impair learning
3) Behavioural intervention experiments:
training an animal in a memory task can induce LTP in the brain.

Question 38

What memory tasks reliably show an impairment with aging?

Answer 38

1) Conscious recollection that rely primarily on internal generation of the memory
2) Working memory
3) Ability to form new episodic and declarative memories
4) Some decrease in spatial memory

Question 39

What memory tasks are typically not affected by aging?

Answer 39

1) Cued memory tasks

2) Existing memories like autobiographical and semantic

Question 40

What neural changes are linked to memory impairments with aging?

Answer 40

1) Impairments in encoding and retrieval
2) Loss of neurons and /or connections
3) Problems with cholinergic neurotransmission

Question 41

What are the ways to minimise memory impairments with aging?

Answer 41

1) Favourable environments
2) Engaging in complex and intellectually stimulating activities
3) Having a partner with high cognitive status

Question 42

What are Nootropics

Answer 42

Drugs that aim to enhance cognitive function, including memory