Lecture 8 - Hippocampus, Memory and Synaptic Plasticity Flashcards
1
Q
Why do we use rodents for research?
A
- Quick to learn
- Hippocampus is easy to see
- Human hippocampus is similar to rats
2
Q
Describe Rats’ hippocampus
A
- Made of 3 regions:
- Dentate Gyrus: receives most info from rest of cortex
- Info comes from perforant path and is received from granule cells
- Info is passed onto CA3 and CA1 region via Schaffer collateral pathway where it is projected
- Network above is coherent and easy to follow.
- Electrodes can be placed to artificially create/measure activity
3
Q
Describe place cells in the hippocampus
A
- Certain cells respond to certain areas in the env
- Place electrodes in CA1 region (output) and record movement of rat
- Individual CA1 cells would fire when rat was in a specific location
- Encoding where the rat is in relation to its broader env
- Place cells fire at peak rate when animal is in a specific location
4
Q
What does a Cognitive Map do?
A
- Places you in a local env and broader env
- Allows visualisation
- Thought place cells create a cog map
5
Q
What is the morris water maze?
A
- Used to assess spatial learning in rats
- Rat cannot see through the water. There is a submerged platform
- Rat needs to swim to find the platform in a min
- If not found, they are placed on platform before retrying
- Location learnt by trial 8 = can go directly
6
Q
What measures are used in morris mazes?
A
- Time taken to find platform: should get faster
- Take platform out and measure time spent where platform was
- Should spent most time swimming in a specific quadrant where platform prev was (hippocampal lesions show no preference)
7
Q
What is the role of hippocampus in morris mazes
A
- rats with hippocampal lesions: selective lesion/placebo operation/no operation
- placebo/no operation are very fast at navigating to platform
- hippocampal lesion = slower and don’t get as fast = spatial learning impaired = but they get faster when learning = used different techniques rather than spatial
- To ensure gross impairment e.g motor things are not affecting it, a pole is used as a cue, all rats navigated = not spatial info
8
Q
What did Donald Hebb do?
A
- Cells that fire together wire together
- Co-occurrence is a physiological necessity for learning and memory
- If one cell is activated, it sets off other cells that have previously fire together (repeated exposure = greater connection between neurones)
9
Q
What was hippocampal circuitry?
A
- Info travels in via perforant path to Dentate Gyrus, CA3 region, CA 1 region
10
Q
What was the experiment to do with hippocampal circuitry?
A
- Stimulate axon in perforant path and recording activity in dentate gyrus
- Single low intensity current delivered to perfroant path, response recorded = determines baseline of dentate gyrus
- High stimulation to induce potentiation (also called tetanic stim)
- Low intensity is tested again
- Cells in dentate gyrus act as if they are receiving high stim
- Long term affects: can measure month after and will see high response in cell
11
Q
What are the key properties of Long-Term Potentiation? (LTP)
A
- Long term: via rats and above study
- Only occurs when firing of pre-synaptic neuron is followed by firing of post-synaptic neuron
12
Q
What is the induction of Synaptic LTP
A
- Pre-synaptic neuron (Perforant) releases glutamate that binds to AMPA receptor
- Opens receptor and influx of positive ions to depolarise cells
- NMDA receptors are blocked by a Mg ion, thought to be critical in LTP
13
Q
How are NMDA receptors used for LTP?
A
- When cell depolarises, positive charges oppose
- Mg leaves NMDA and unblocks
- Glutamate can now bind
- Allows Ca ions to flow into cell causing cascade reaction
- Inserts more AMPA receptors into Post-synaptic neurone
- Next neurone is stimulated more easily by same amount of glutamate.
14
Q
What causes long term depression?
A
When neurones do not communicate over time
