Vision and action

Question 1

Patient DF suffers from agnosia but also exhibits other visual impairments e.g. cannot discriminate between…despite an intact V1. On other hand she does…

Answer 1

A horizontal & vertical pencil. Adjust the orientation of her hand when reaching for a horizontal vs. vertical pencil

Question 2

Can DF draw pictures from memory? Can DF copy pictures?

Answer 2

Yes. No

Question 3

In Milner’s (1991) postal task patient DF can…but not…

Answer 3

Post a card through a slot. Align a card with a slot

Question 4

Patient DF shows size scaling in action but not in representation - what does this mean?

Answer 4

She adjusts her hand grip size appropriately when reaching for different sized shapes but does not when indicating the size of these shapes to others

Question 5

In size scaling experiments X is plotted against Y - what are X and Y? Usually X increases with Y but in the case of DF…

Answer 5

X: width of stimulus (cm), Y: maximum aperture. Y does not change with X

Question 6

In perceptual matching it is interesting that size scaling is still indicated by a motor response but…

Answer 6

can be dissociated from the same motor response when used to reach

Question 7

What type of grasping does vs. does not recruit the perception-for-action pathway? DF therefore shows a deficit in…

Answer 7

Does: immediate, online grasping. Does not: delayed, offline grasping via memory. Delayed, offline grasping

Question 8

Ungerleider & Mishkin (1982) first termed the dorsal & ventral pathways the where & what routes - on what basis did they draw this conclusion?

Answer 8

A lesion to the macaque parietal lobe impairs space perception vs. a lesion to the macaque temporal lobe impairs pattern recognition. Monkeys had to discriminate between un-/rewarded objects/locations

Question 9

Both where and what pathways begin in the ___ lobe

Answer 9

occipital

Question 10

fMRI evidence suggests that the dorsal pathway responds when ___ an object, whereas the ventral pathway responds when ___ to an object

Answer 10

Grasping. Pointing

Question 11

What characterises optic ataxia?

Answer 11

Impaired perception for online action. Intact perception for representation

Question 12

What is the Effron size matching task?

Answer 12

The size scaling task previously described

Question 13

Optic ataxia (Ataxi!) is characterised by impaired ___ grasping but intact ___ grasping despite the latter being more difficult for controls

Answer 13

Immediate, delayed

Question 14

So there is a double dissociation between…&…

Answer 14

visual agnosia & optic ataxia

Question 15

Give 2 conditions in which perception for action is modulated by ventral info & e.g. patients

Answer 15

1) When complex, relative position info is important e.g. DF is impaired at picking up a ten pin bowling ball. 2) When the action is directed towards a familiar object e.g. an optic ataxic patient who more accurately grasped her lipstick than a same-shaped/sized, unfamiliar stimulus

Question 16

The familiarity effect in optic ataxia suggests that the ventral stream is required to use ___ ___ to inform actions

Answer 16

pre-existing knowledge

Question 17

The motor response to visual affordances seems to be mediated by the ventral pathway. What evidence is there for this?

Answer 17

Pps display greater left fusiform gyus activity when objects are positioned correctly for action (interaction) than when not

Question 18

The effect of positioning on LFG activity is greater for ___ pairs of objects & not confined to when objects are ___

Answer 18

Familiar. Attended

Question 19

What is utilisation behaviour?

Answer 19

When a patient automatically obeys a visual affordance despite the contextual inappropriateness of doing so e.g. places the presented glasses on even when he’s already wearing glasses

Question 20

Riddoch (1998) suggests that utilisation behaviour is mediated by visual object properties, finding that

Answer 20

patients made more errors (60% vs. 40%) in a task in which they were required to grasp a mug with their left hand if it was placed on the left & vv, when the side of the mug’s handle afforded the use of the opposite hand