Hippocampus Flashcards
What type of memory is the Hippocampus responsible for?
Declarative memory (facts + verbals knowledge) and spatial maps.
Neil is extraordinary bad at all sport, would damage to the Hippocampus explain this?
No, the Hippocampus is not responsible for learning motor skills. Neil should get his Cerebellum looked at.
Are all long term memories stored in the Hippocampus?
No, experiments have shown that long term memories can be stored outside the Hippocampus.
The Hippocampus has a role in spatial memory, is the encoding complete or sparse?
Sparse
Auto-associative memory are patterns representing memory. Explain what recall is with regards to associative memory.
You are able to complete the pattern when you are only give part of it.
E.g
You are repeatedly shown:
B W B W B W B W
then you are shown:
B W ? W B W B W
You would be able to finish the partially completed pattern
Give an example of when/how Hebbian plasticity occurs in the Hippocampus.
A pattern comes in to the input of the Hippocampus EC and takes the path:
EC —-> DG —-> CA3 —-> CA1—->EC (back to the start)
If EC and CA3 repeatedly have the same pattern their synapses will strengthen, eventually the synapses are strong enough for the signal to go directly from EC to CA3, bypassing DG.
Give an example of Recall working in the Hippocampus
Considering the fundamental pathway in the Hippocampus:
EC —-> DG —-> CA3 —-> CA1—->EC (back to the start)
EC starts off with ‘1010’.
It keeps receiving the signal ‘1111’ from CA1, this is its trigger to resend ‘1010’. Over time, the synapse conveying this pattern combination has strengthened. So when EC receives ‘1110’, this is enough to recall the ‘1111’ pattern, and so EC is triggered, sending off the 1010 signal.
If patterns share subpatterns, the connections for these subpatterns become very strong. What is the problem with this?
If part of the sub pattern is present in a new signal, the neuron may recall the rest of the pattern. This can dominate other elements, potentially losing patterns, resulting in erroreneous completion.
What is the key conclusion drawn from the the fact overlap causes patterns to be lost?
Auto-associative networks are not able to effectively store anything except random patterns. (No correlation between patterns). Hence why they have not yet proved useful in machine learning.
What is the significance of having a large eta in the Hippocampus?
Allows for fast learning, after a small number of presentations.
What are the two key phases of the Hippocampus?
1 - Learning phase
2 - Retrieval phase
How does the Hippocampus switch between its two phases?
The level of stimuli is different, there is higher activity in the learning phase.
This heightened activity is able to excite the learning pathway that goes via DG.
