To see and not to see

Question 1

Right hemisphere is better at ;

Answer 1

• Spatial judgements
• Recognizing (matching) faces. (fusiform face area is also more prominent in the right hem).
• Perceptual Organization

Question 2

Callosotomy

Answer 2

Split brain procedure

Question 3

Hemianopia

Answer 3

Unilateral V1 lesions.

So only one half of the visual field is lost.

Question 4

What is the reason behind blind-sight patients above chance level success in detecting direction and motion ?

Answer 4

Even though they don’t consciously perceive anything because they have hemianopia they are above chance level at detecting direction and motion. This is because the pathway from optic nerves to superior colliculus and pulvinar, then MT neurons and posterior parietal cortex is still intact.
But if superior colliculus and V1 lesioned : no response from MT neurons, no success at these tasks.
When superior colliculus is intact but patient has hemianopia : weaker responses from MT neurons but still neuons are direction selective.

Question 5

Blind-sight

Answer 5

The dissociation between the conscious percept, and actual abilities.

Question 6

Super blind-sight

Answer 6

Bilateral V1 lesions, but people and monkeys still behave normally, so they still avoid obstacles etc..).

Question 7

The argument about dorsal, ventral streams being conscious or unconscious :

Answer 7

Because of blindsight patients, dorsal stream was thought to responsible from unconscious visually guided action. Because even though patients report not seeing anything consciously, they still avoided obstacles.
However when MT neurons of the monkey were stimulated, monkey made saccadic eye movement indicating he perceived the motion in that direction, even though the actual motion was in the opposite direction.
So MT neurons also corresponds to our ‘conscious perception’.
This is all about were you put the boundry for what counts as conscious and what counts as unconscious.

Question 8

Unconscious Priming

Answer 8

Even though you don’t consciously perceive the prime (because of metacontrast masking for instance) still the prime effects your reaction time.
You are faster at reacting in congruent tasks with the prime than in incongruent tasks.

Question 9

Continous Flash Supression :

Answer 9

Two different images are shown to eyes. One is a very strong image with all kinds of different colours and motion and this image masks the other image. But neverthless this continous flash supression experiments shows that actually many of the complex processes are made pre-consciously.
For instance attactivenessi emotional expression, familiarity of the faces etc.. are processed pre-consciously.
Continous Flash Supression experiments show that we have very complex analysis of things before they enter into our awareness.

Question 10

Problems faced by continous flash supression and masking experiments :

Answer 10

Subjective and objective invisibility.
When something should be called unconscious? when it is subjectively invisible (so we say we don’t see it but in the forced choice task we are still above chanc) or when it is objectively invisible (forced choice tasks are not above chance level?)
Objective invisibility further experiences difficulties with the ‘what to ask’ problems because based on what you ask such as discrimination vs localization etc.. answers differ. So based on what you ask whether things are visible or invisible chances.

Question 11

Bistable Stimuli

Answer 11

Stimulus remains contstant, yet conscious percept switches spontaneously. (similar to binocular rivarly)