Long Term Potentiation and Learning Flashcards
There must be something that changes in the nervous system when we…
The stability of learning must….
The long-standing idea is that these changes occur at the level of the…
Another was to describe learning is….
learn
change something physically in the brain
synapses
synaptic plasticity…the brain changes…like moulding clay.
The Hebbian synapse is a theory about synaptic plasticity describing how ________ can be ________ during learning. Firstly, neurons that are for ________ significant events (eg: food) are ________.
connections
strengthened
biologically
hardwired
Hebbian Synapse
Neurons for biologically significant events (USs) are _____-______ connections controlling behaviour (thanks to genes)
Eg: neurons coding for food can directly excitate neurons producing salivation.
However, there are also other synapses that are ______ connections and not ________ neurochemically (but they exist ______). They have similar output structures, and are strengthened through ______.
This strengthening occurs by both these pathways being activated __________ while the output is being activated by the US. The CS input is ______, while the US input is _______. Now, the CS can produce a response __________.
“neurons that fire together, wire together”
This is known as ______ ________ learning.
hard-wired
latent
effective
physically
learning
simultaneously
weak
strong
independently
simple associative
Most of the evidence for simple associative learning has come from the _________. It contains 3 regions (_____, _____, and ____). It’s architecture makes experiments in this area quite easy. When you want to study plasticity, you want to see whether connections can ______ (can they become ______), so you have to measure the inputs and outputs. Luckily, in the hippocampus, these inputs are _________.
Inputs to the hippocampus come in from the _______ path (from entorhinal cortex). They are ________ glutamatergic neurons. they synapse onto ______ cells. The actions of these granule cells bundle into the ______ fibres that passes through CA3 region of hippocampus. These fibres connect onto the ________ cells in this region. Another set of these fibres pass through the ________ collaterals and connect onto the pyramidal cells in the _____ region.
hippocampus
CA1
CA2
CA3
change
stronger
segregated
perforant
granule
mossy
excitatory
pyramidal
schaffer
CA1
What is Long-Term Potentiation?
A model for neural mechanisms of learning
What are the 3 steps of LTP?
What does it result in?
Step 0: Weakly stimulate pre-synaptic input (eg: perforant path). This causes little or no activity in post-synaptic neurons (eg: dendate gyrus)
Step 1: Strongly stimulate (with high frequency) pre-synaptic input to cause a long-lasting increase in sensitivity of post-synaptic neurons
Step 2: Weakly stimulate pre-synpatic input - this now produces action potential in post-synaptic cells.
–> Weak stimulation is now more effective at producing a response
Dose dependency of LTP
Activity in the hippocampus is often matched to ______ frequency (5Hz), so they probably like this kind of frequency.
So, instead of delivering continuous HFS, it can be delivered as bursts of ______ frequency (______ burst stimulation, TBS), and this has been shown to be just as good as _______ stimulation. This is much more _________ as you are getting the same result with fewer pulses.
Further, the duration of LTP depends on the number of ______ ______ stimulations given.
theta
theta
theta
continuous
efficient
theta burst
What 3 characteristics make LTP a good model of learning?
- Persitence
- Synaptic specificity
- Associativity
Characterisitcs of LTP
Persistence is very important for LTP as endurance is an important part of any ____-_____ memory model. Sometimes it can last for days or weeks!
But, it can be ________, but it’s hard to mesure because the animal has to be able to move around and you can’t be too sure the _______ don’t move, and it has to be done in-vivo.
long-term
insufficient
electrodes
Characterisitcs of LTP
Synaptic-specificty is important for this model as it has to be shown that there is no increase in ______ to any other ___-_______ outputs (EVEN for the same pathway). It has to be specific for a certain set of _______.
This is good because memories are _______. In the brain, certain synapses are specific for certain _______.
sensitivity
pre-synaptic
synapses
specific
memories
Characteristics of LTP
Associativity is important as you have to be able to see the potentiation ________ across synapses under certain conditions. For this, you have to have one synapse ______ stimulated while the other is _______ stimulated.
This is very similar to the ______ synapse model. So LTP demonstrates this very nicely (how CS response can be strengthened when activated simultaneously to US response)
transferred
weakly
strongly
Hebbian
Long Term Depression is…
The opposite of LTP
- they’ve found that plasticity is bi-directional
- Low-frequency stimulation (LFS) can REDUCE synaptic efficiancy
- similar experiments (normalising response to 100%, then deliver LFS, and found synapses not as sensitive to stimulation
High Frequency Stimulation produces _______, and Low Frequency Stimulation produces ________.
potentiation
depression
LTP - common mechanisms
SO if LTP is a good model of learning, then the _______ for the two should be the same. There should be _______ between changes in LTP and changes in _______.
Eg: age-related decline can be seen in LTP and learning (takes more trials to learn vs takes more stimulation bursts to produce LTP)
same
correlations
learning
LTP - common mechanisms
Is it possible to get saturation in LTP? If so, does this affect the ability to learn?
Yes,
Yes, it has been shown that saturation in LTP resulted in learning deficits in rats in the morris water maze task
