W6 - Reality

Question 1

Does detecting modulations in colour rely in output of local/distributed neurons

Answer 1

Not due to single neural characteristic. Distribution representation rather than relying on output of local/individual neurons

Question 2

What are the 2 evidences to suggest that detecting colour modulation is part of a distributed representation

Answer 2

1. ) Psychophysical sensitivity to chromatic stimuli far better than that of any individual neuron
2. ) Different neural expansions in Magnocellular and Parvocellular pathways from retina to V1

Question 3

Evidence that colour modulation is part of a distributed network: psychophysical sensitivity chromatic stimuli > neuronal senstivity

Answer 3

More sensitive= lower threshold level needed to identify stimulus.

Question 4

M and P Pathways to Retina Cortex

Answer 4

M Pathways involved in luminance
P Pathways involved in colour
- Both are anatomically distinct

Question 5

M pathway in Retical Cortical Expansion

Answer 5

Retina: Larger receptive field than P
LGN: 1-to-1 relationship between retina and LGN
V1: Principle point of expansion

Question 6

P pathway in Retical Cortical Expansion

Answer 6

Retina: Lesser receptive field than P
LGN: Principle point of expansion
V1: Little (not 1-to-1) relationship between LGN and V1

Question 7

Is there more feedback between: V1 to LGN, or LGN to V1

Answer 7

More feedback between V1 to LGN

Question 8

Study about M and P pathways

Answer 8

Studies in motion in purely chromatic stimuli (no luminance) reveal strange behaviour consistent with spatiotemporal interaction prior to motion extraction.

• More slowly
• Reliance on luminance for motion detection.

Question 9

fMRI study about M and P Pathways

Answer 9

Cardinal tuning in V1

> Represents some kind of feedback, unlike the single cones of retina, whole V1 has cardinal representation.

Question 10

Why is there more feedback from V1 to LGN?

Answer 10

Mediating factor on Parvocellular activity, and then feed back into V1

Question 11

V4 vs V1

Answer 11

V4: Sense of Colour (taking into account cortex)
V1: Threshold & Hue

Question 12

Why is there difference between representation of colour and that of cardinal space

Answer 12

May be due to feedback from cortex and strong connections between LG and cortex
> Basic sense of colour is not well predicted by basic properties represented by cones.

Question 13

Colour discrimination: between vs within categories

Answer 13

Discrimination between categories is easier than discrimination within categories.

Question 14

Is colour vision categorical/continous? Cropper (2013) study

Answer 14

Discrimination vs Categorization Task (Without colour names):

Discrimination: Highly accurate performance (i.e., responding ‘same’ only when the test colour was very similar to the reference colour)

Categorization: Everyone their own categorical structure and much as the broader
> No categorical boundary effect

Question 15

What does the discrimination v categorisation task by cropper (2013) suggest

Answer 15

We still lack a predictive and quantitative model of how we see simple visual stimuli.

Question 16

What is syneaesthesia

Answer 16

Involuntary conjoint perception across two modalities

Question 17

Is synaesthesia objective?

Answer 17

No. It is a subjective experience/unique and consistent

Question 18

What is the most common syneaesthesia

Answer 18

Colours (70%)

Question 19

How do hallucinogens work

Answer 19

Mimicking active group on neurotransmitter serotonin (5H-T), which is associated with mood, sleep, appetite, psychosis.

Increasing 5H-T = Increase cortical activity = reduce inhibition

Question 20

What happens when inhibition is reduced and cortical activity is increased in system

Answer 20

Visual and auditory hallucination

Question 21

How do hallucinogens affect simple visual tasks?

Answer 21

Affects motion detection

- Disruptions in integrating simple isolated vectors to a
coherent representation (Biological motion, flow fields, structure from motion)

Question 22

Study: Carter et al. (2004) Motion Perception and Psilocyblin. What were the 2 tasks & results

Answer 22

1. Right motion contrast sensitivity
   - 2 alternative choice
   - Rigid
   - Can do with basic motion detector
2. Motion Integration sensitivity
   - 2 alternative choice
   - Non Rigid
   - Basic motion detector must be integrated into global precept

> Only affected in Task 2. Therefore, Psilocyblin affected integration and failure to inhibit.

Question 23

What is relationship between hallucinogenics and schizophrenia

Answer 23

Same psychosis - In SZ patents, simple visual task requiring less integration led to better performance (due to context)

Question 24

Study: Dakin et al. (2005) Contrast of central disk and SZ patients. Results

Answer 24

Controls: Stronger contextual suppression > More vulnerable to ‘contrast’ illusion > Less accurate at judging contrast where contrasts disrupts judgement

SZ: Weaker contextual suppression > Less vulnerable to ‘contrast’ illusion > More accurate at judging contrast since contrasts does not disrupt judgement

Question 25

Schizotypy (at high levels, mirrors SZ) and hallcinations

Answer 25

High positive schizotypy (wild day dreams, etc) linked to having hallucination-like visual experienes

Question 26

Study: Partos, Cropper, & Rawlings (2016): Schizotypy and image meaning. Study and findings

Answer 26

Present random array of white dots and instructed dots show something meaningful > Individuals on higher psychoticism, neuroticism, and hallucination-proneness perceived more meaningful images of complex nature of dots > High positive schizotypy score = Increased tendency to perceive complex meaning in random visual noise.