Neural mechanisms of learning

Question 1

What type of neural firing supports memory

Answer 1

1. increased sensitivity of post synaptic neuron
2. increased level of neurotransmitter
   or both

Increased excitability of post synaptic potential

Question 2

APLYSIA

Answer 2

Abdominal ganglia- memory or learning through habituation
If you tap the gill its withdrawn into the body of the animal
If continue to stimulate then it becomes habituated and the response is inhibited

Like tuning out a tap dripping

The circit that mediates this response can be located
- sensory neuron on the skin, directly connects to a motor neuron that activated the withdrawal response
although the motor neuron is still working it no longer fires in response to the fireing of the sensory neuron

Question 3

Habituation

Answer 3

Shows short term and long term memory.

this habituation can last for days.

Question 4

Short term habituation

Answer 4

Quantal analysis- measures amount of neurotransmitter released by presynaptic neuron.
This found that after training the amount of excitedry neurotransmitter released is much lower.

LTP- supports learning through strengthening connections
Decreased strength mediated DIFFERENT kind of learning.

Question 5

Long Term habituation

Answer 5

• showed that there was fewer synaptic connections in long term memory of aplysia
  Protein synthesis is required for this

Question 6

Kandells SLUG conclusion

Answer 6

1. habituation not caused by damage to cells
2. decrease in neurotransmitter released by the sensory neuron (short term)
3. these changes are specific to the pathways being trained
4. Long term habituation is caused by changes to the physical structure of network
   HOMOSYNAPTIC DEPRESSION - pathway specific

Question 7

different forms of learning

Answer 7

LTP - calcium surge = ampa receptors
short term habituation - neurotransmitter released less
HOMOSYNAPTIC depression - fewer connections between sensory neuron and the motor neuron - requires protein synthesis

Question 8

sensitization

Answer 8

Another form of learning- opposite to habituation.
Response increased as a product of learning
heightened arousal - mild electric shock - gill withdrawal response occurs for longer
more shocks - long term memory

SYSTEM WIDE CHANGE

Question 9

sensitization at cellular level (spike broadening)

Answer 9

the action potential, the high sensitization shock depolarizes the motor neuron, leading to the activation of a SUBORDINATE unit which releases seretonin to the presynaptic terminal for the sensory neuron.
This closes potassium channels in the sensory neurons membrane.
This allows for more calcium into the sensory neuron which enhances the release of neurotransmitter.
After being exposed to seretonin the sensory neuron when stimulated now releases much more neurotransmitter than before

therefore the motor neuron reaches the firing threshold faster.

SYSTEM WIDE

Question 10

Long term sensitization

Answer 10

like with habituation long term sensitization results in an increase of connections between sensory and motor neurons

Question 11

summary

Answer 11

Erik kandel showed for the first time that learning can derive from synaptic strength using aplysia on a cellular level.