Internally representing the world

  1. What are the main features of the Allocentric frame of reference?
    • Centred on external objects
    • Includes knowledge of our position in space; 'mental maps'
    • Is represented in the HPC, with single neurons representing our position in the world
    • Taxi drivers will use more allocentric FoR, and thus the longer they have been driving for, the higher the vol. of their posterior HPC grey matter (Maguire et al, 2001 [probably])
  2. What are the main features of the egocentric frame of reference, and what are its subdivisions?
    • Centred on the body
    • Eyecentric: objects are coded relative to the centre of gaze.
    • Left intraparietal (IP) area maintains a constant representation of space as the eyes move.
    • Head-centred: hearing.
    • Ventral IP is where headcentred FoR are located
    • Joint-centred: e.g. grasp. Coded in terms of set of joint angles needed to perform movement.
    • Grasp is located in anterior IP, reach in medial IP.
  3. What is spatial neglect?
    • Happens most frequently following stroke damage to the right side of one's brain 
    • In these cases, people are unable to become aware of items to their left
  4. In neglect, why is it wrong to say that people cannot see things on their left?
    • They CAN see things, their photoreceptors work fine, they just lack the cortical representation for what they're seeing 
    • This means it is not retinotopic (i.e. it has brain origin, not eye origin)
    • Eg. someone with spatial neglect will see a whole Navon figure, but will only be able to cross out the non-neglected side of it.
    • They can see it, they just can't act on this
  5. What is the difference between egocentric and allocentric neglect?
    • Allocentric neglect: neglected region is 1 side of an object, regardless of position relative to person
    • Egocentric neglect: neglected region depends on position of object relative to person
  6. What does spatial neglect tell us about internal representation?
    • That we use multiple FoR!
    • Each FoR has separate neural representation (hence why damage doesn't affect all FoR)
    • That FoR are deployed when it is most task-relevant.
  7. What brain region is associated with allocentric neglect when damaged?
    The parietal cortex
  8. Give an example of how different frames of reference are given preference in a day to day task
    • Pick up teapot: Body FOR
    • Pour the tea: Teapot FOR
    • Remember which cup is yours from a different angle: Table FOR
    • FOR are given priority when they are most relevant to the task at hand
  9. How do the main two frames of reference differ for day to day life?
    • Allocentric frames of reference are more efficient descriptions of the stable properties of the world
    • Egocentric frames of reference are useful for representing the world on a moment to moment basis
Card Set
Internally representing the world