Internally representing the world

Question 1

Define egocentric representation.

Answer 1

Centred on parts of the body, relative to you.

Question 2

Define allocentric representation.

Answer 2

Centred on objects and the external world, e.g. a cognitive map of our environment built up by hippocampal cells (John O’Keefe, 2014).

Question 3

What are the 3 main forms of egocentric representation?

Answer 3

1. Eye-centred
2. Head-centred
3. Joint centred

Question 4

Explain eye-centred representation.

Answer 4

The object is relative to your centre of gaze, creating a frame of reference. E.g. the kitkat is to the left of where you are looking.

Question 5

Define the area LIP.

Answer 5

The laterial intraparietal area is a part of the parietal lobe involved in eye movement. It helps to maintain a consistent representation of visual space as the eyes move around.

Question 6

How does the LIP work?

Answer 6

It changes which part of the retina it derives signals from during a saccade, thus maintaining visual perception.

Question 7

Define a saccade.

Answer 7

Rapid movement of the eye(s) between fixed points.

Question 8

Explain head-centred representation.

Answer 8

The object is perceived relative to where your head is facing. For example sound is perceived in this way.

Question 9

Which area of the brain is involved in head-centred representation?

Answer 9

The area VIP, or ventral intraparietal area within the parietal lobe.

Question 10

Explain joint-centred representation.

Answer 10

Coding is in terms of the set of joint angles necessary to grasp an object.

Question 11

Which area of the brain is involved in joint-centred representation?

Answer 11

There are 2:

1. The area MIP or medial intraparietal area of the parietal lobe
2. The area AIP or anterior intraparietal area

Question 12

What is the MIP concerned with?

Answer 12

Reach

Question 13

What is the AIP concerned with?

Answer 13

Grasp. The AIP is responsible for very specific spatial representation and is closely associated with the premotor area F5.

Question 14

Define spatial neglect.

Answer 14

The loss of representation of a particular frame of reference.

For example when a patient suffers damage to one hemisphere of the brain they are unable to perceive stimuli on the other side of the body. This is called hemispatial neglect. In a stroke the right side of the brain is damaged, thus the patient cannot perceive anything on the left.

Question 15

What are the LIP, VIP, MIP and AIP all referred to as?

Answer 15

Frames of reference or FORs.

Question 16

Define allocentric neglect.

Answer 16

One side of an object is neglected, regardless of its position in relation to the patient. For example if a patient cannot see the left side of an object, it does not matter if that object is to the left/right/in front of the patient, they still will not see the left side of it.

‘Neglect is of one side of an object not of one side of the visual field’

Question 17

Define egocentric neglect.

Answer 17

The neglected region depends on the object’s relation to the patient. For example in hemispatial neglect the whole left side is neglected. Thus placing an object to the left of the patient means they cannot perceive it. Then if you move the same object in front of or to the right of the patient, they will be able to perceive it.

Question 18

Is the manifestation of neglect always the same?

Answer 18

No. It can be within different regions of personal space, e.g. only peripersonal not extrapersonal.

Question 19

Define a) peripersonal and b) extrapersonal space.

Answer 19

a) Personal space that is ‘within arm’s reach’ of an individual
b) Space that occurs outside the reach of an individual

Question 20

Are patients aware of neglect?

Answer 20

Often not. They can accurately report a global stimulus but cannot interact with all of it. For example they can see a shape but can only colour in one side of it.

Question 21

What part of the brain is associated with neglect?

Answer 21

The parietal cortex.

Question 22

In neglect areas of the brain are damaged, thus we might be able to deduce which FORs are involved in tasks. Why is it not that simple?

Answer 22

Multiple FORs are used in combination with each other for almost every task.

Question 23

Sensory inputs are often based on multiple FORs. True or false?

Answer 23

False - often sensory inputs rely on a single FOR, e.g. sight uses eye-centred representation.

Question 24

Information is transferred between FORs as we move around in the world. Why?

Answer 24

Sensory inputs ‘update’ our perception of the world, e.g. when walking along our vision updates our sense of place orientation. This is a shift of eye to allocentric, a shift from vision to navigation.

Question 25

The cells in our brain involved in navigation/orientation are called?

Answer 25

Place cells, discovered by John O’Keefe.