Task 4- Presentation (Hippocampus)

Question 1

What is the structure of the hippocampus?

Answer 1

• temporal lobe

- 2 interlocked sheets of cells: cornu ammonis and dentate gyrus

Question 2

Afferent vs efferent

Answer 2

• afferent: comes from parahippocampal gyrus, entorhinal gyrus and association areas -> send info and already process
• efferent: send away from hippocampus via divergent pathways –> projects to cortex for storage

Question 3

What are the structures and the entry point of cornu ammonis?

Answer 3

• CA3
• CA1
• entry point: perforant pathway

Question 4

Pathway

Answer 4

Perforant pathway -> Dentate gyrus -> CA3 -> CA1 -> Subiculum

Question 5

Dentate gyrus

Answer 5

• receives input from perforant pathway
• output carried by mossy fibers to CA3
• 1 mossy fibers -> 15 different CA3 cells => sparseness

Question 6

CA3 region

Answer 6

• mossy fibers give direct input
• bit indirect input by perforant pathway
• output: branches in 2 ways –> one recurrent connections back to CA3 and the other branch to Schaeffer collateral
• -> intrinsic, recurrent excitatory system
• -> acts as autoassociative memory

Question 7

What is the advanatge of the recurrent network?

Answer 7

improves recall

Question 8

CA1 Region- input and output

Answer 8

• input by Schaeffer collateral

- sends output back to neocortex

Question 9

Which kind of memory?

Answer 9

• content addressable memories

- must be quick

Question 10

Experiment with rat brain

Answer 10

• typically only 1-5% of neurons in hippocampus active

- without the recurrent network: memory not as good

Question 11

4 stages of info processing in hippocampus

Answer 11

1. Competitive learning in dentate gyrus (related to sparseness)
2. Autoassociation in CA3
3. Competitive learning in CA1
4. Pattern association betw. CA 1 and entorhinal gyrus