Schmidt hippocampus 4

Question 1

What implications can we make with the stored place cell sequence?

Answer 1

e.g. activation of A leads to activation of B then C as it is imprint into the CA3 network
may be related to remembering a sequence, completing a pattern or planning
This sequential activation exists in the hippocampus

Question 2

What does a velocity graph show?

Answer 2

Looks at temporal sequences and indicates points of movement and increased neural activity so would show different place cells organised according to where they are on the track

Question 3

What can you see before movement occurs?

Answer 3

That all the cells are active within 250ms and becoming active in a specific order = forward replay
The order of this activation reflect the path the animal will take

Question 4

What can you see when the animal reaches the end of the path?

Answer 4

Reverse replay, a sequence of place cell activation reflects the most recently visited area and backwards from there

Question 5

What are the current research questions?

Answer 5

1. How can replay work in both directions?

2. What is the functional role of replay?

Question 6

What happens when the animal chooses the correct path?

Answer 6

It reaches the food and there is a release of dopamine which is important in reward processing and leads to association between the recently visited sequence and food reward. 
This hypothetically(!) weakens the association with further away places

Question 7

What is the potential relation of hippocampal firing patterns to different stages of memory?

Answer 7

Storage: during the traversal of place fields the corresponding sequence is then stored into the CA3 network
Recall: there is reactivation of place cell sequences before and after the actual traversal
Consolidation: reactivation of place cell sequences and transfer to other brain regions - also during sleep

Question 8

What did Lee and Wilson (2002) find?

Answer 8

Replay of place cell activity during sleep corresponding to the same order of activation as during the task

Question 9

What is mental time travel?

Answer 9

The ability to recollect specific past episodes and anticipate future needs and motivational states

Question 10

How is mental time travel characterised in humans?

Answer 10

By 2 features of consciousness (Tulving, 2005):

1. The ability to re-experience past events and pre-experiencing possible future events
2. The awareness of being the owner of memories and forethoughts

Question 11

What is a problem with studying mental time travel?

Answer 11

Not accessible for empirical studies in animals as there are no accepted behaviour markers for consciousness
- But an alternative approach would be to focus on the behavioural criteria for episodic cognition without a requirement of conscious experience (Clayton et al., 2003)

Question 12

What is future planning?

Answer 12

The prospective aspect of episodic-like cognition

It occurs independent of the current motivational state and includes a novel action

Question 13

What are the 3 criteria for future planning?

Answer 13

1. Content: anticipating what will happen, when and where based on previous experience
2. Structure: what-when-where components bound together
3. Flexibility: interaction with semantic knowledge

Question 14

What did an experiment with birds show about future planning?

Answer 14

They were given peanuts and worms to cache, aware that they preferred the worms. The worms go off relatively quickly compared to the peanuts though.
At 4hrs they were given access and went for the worms as they prefer them
However at 124 hrs when given access again, the worms had gone off and they used their semantic knowledge to choose to eat the peanuts - have to think about what will have happened between 4 and 124 hours

Question 15

How do we study the underlying neural processes of food caching?

Answer 15

A new paradigm was developed to study the storage and recall of episodes in jackdaws
Involved a hexagonal arena of different touch screens with feeders where visual stimuli can be presented and respond to by touching the screen
Coloured dots appear and the bird has to touch the dot then is tested on the sequence/locations of dots
Can look directly at what-when-where episodes e.g. colour, location, order of sequence

Question 16

What can be done with this paradigm?

Answer 16

Can use wireless recordings during the task performance to see if there are sparse representations in the hippocampus, any phase precession during storage and whether there is sequence replay during recall?
But it will probably take a couple of years before we can answer these questions