L13 Brain circuits I

Question 1

two types of recognition

Answer 1

recall and familiarity

Question 2

what is the justification for functional heterogeneity of MTL

Answer 2

• convergence of different inputs
• differences and similarities in neural architecture
• different kinds of memory representations and resultant retrieval properties
• differences in encoding and retrieval processes
  BASICALLY DIFFERENT INPUTS, DIFFERENT OUTPUTS EVERYTHING DIFFERENT BUT CONNECTED, MUST BE HETEROGENEITY

Question 3

what does the heterogeneity model propose?

Answer 3

• different memory processes (algorithms)
• lesions should impair recollection and familiarity somewhat selectively
• activation patterns should differentiate recollection and familiarity

Question 4

what is the model against heterogeneity? what does it propose?

Answer 4

The Unitary model:
- it is not recognition memory processes that distinguish MTL components
- hippocampal lesions should impair recollection recollection and familiarity somewhat equivalently
- activation patterns should show similar MTL engagement across recollection and familiarity

Question 5

diff tests for recollection and familiarity

Answer 5

• R/K test
• Source memory test (corners)
• Item recognition
• Associative recognition

Question 6

pattern separation?

Answer 6

• Responsibility of hippocampus - recollection
• reason you know where your bike is locked every day at same general location
• patterns that overlap in PRC/PHC are spread out i hippocampus

Question 7

strength and weaknesses of lesion studies

Answer 7

strength:
- provides info on critical role played by a region
weakness:
- patient variability ad group size - no 2 patients the same
- resolution and other limitation of MRI
- limited to lesion site - opportunistic lesions

Question 8

YR

Answer 8

case study:
- bilateral hippocampal damage
- memory task for objects with similar foils, testing pattern separation/completion
- therefore testing hippocampal function according to the heterogeneity model
- could encode details and difference (familiarity), couldn’t do yes/no task
- evidence that hippocampus critical for recollection task

Question 9

evidence against YR conclusion?

Answer 9

Bayley et al 2008:
- in support of unitary view
- tested 5 patients w/ hippocampal damage, also impaired on Y/N task
- argued that difference reported is due to task difficulty not selective role of hippocampus (60 items)

Question 10

why might familiarity support some forms of associative memory?

Answer 10

domain dichotomy view - perhaps info binds together in MTL early on

Question 11

what reasons may hippocampal patients differ on measures of familiarity?

Answer 11

• different amounts of hippocampal sparing
• undetected extra-hippocamapl damage in cases with impaired familiarity
• re-organisation of brain function

Question 12

what area of brain was looked at as an opportunity for research?

Answer 12

• fornix
• always damaged when removing colloid cyst
• Damage to hippocampal circuit selectively impairs recollection for a variety of information, while leaving familiarity intact

Question 13

what side does fornix study support

Answer 13

heterogeneity model