Long Term Potentiation Flashcards
What is the beginning of the process leading to learning and memory?
The process of glutamate at its receptors - activation of AMPA and NMDA
What do we learn?
Declarative memory - facts and events
Non declarative memory - procedural and classical conditioning - responding to events
What did Donald Hebb suggest?
A hypothesis for how through neuronal networks, the brain can process and store information - how at a cellular level, cells can make memories
What is learning a response too?
Response of the brain to environmental events and involves adaptive changes in synaptic connectivity, which then alters behaviour - plasticity
What was Hebb’s hypothesis?
“When an axon of cell A is near enough to excite a cell B
and repeatedly or persistently takes part in firing it, some
growth process or metabolic change takes place in one or
both cells such that A’s efficiency, as one of the cells firing B, is increased” - cells that fire together, wire together - strengthening and weakening synaptic connections in the brain provides a mean by which learning occurs and memories can be formed
Example of learning and memory event occurring in the hippocampus
Cell A - sensory input from sight of rose
Cell B - sensory input for smell of rose
Cell C - sensory input for smell of onion
Individually stimulation of the hippocampal neuron by just one of these cells may not create a EPSP great enough to fire an AP. When cell A and B are activated together, seeing and smelling the rose, the coincident EPSPs may be big enough to fire an AP. if this association is made repeatedly, cells A and B firing simultaneously, their synapses onto the hippocampal neuron will be strengthened. The strengthening of synapses of cell A and B will be suffice,t so individually they will now cause an EP in the hippocampus. The sight of rose will be associated with the smell of a rose rather than the smell of an onion
What does it mean to be synapse specific?
The strengthening will only work for the things which have been paired together
What do events in the environment therefore cause?
Changes in the synpase
Why do you look at the hippocampus in rats?
Easy to slice a part of the hippocampus and look at what happens - the shape and anatomy means pathways can be easily looked at but has been recorded in most other brain areas too - first area we learnt about LTP
What is the mechanism underlying synaptic strengthening?
Long term potentiation
Bliss and Lomo - LTP
Stimulate Axons on perforate pathway, causing glutamate release, probe it to see what happens in the dentate gyrus - stimulation repetition leads to increase in EPSP
then give high frequency stimulation. let it go back to resting state. then stimulate it again, after HFS, response of neurons have changed, EPSP from a single stimulation is greater that it was before
one HFS can last hours
multiple HFS can last days/months
What does LTP mean?
A persistent increase in synaptic strength following high-frequency stimulation of a chemical synapse
Recording electrical activity
Stimulate cell A, get an EPSP of a certain size
Stimulate B, get an EPSP of a similar size
these are the baseline EPSP
When you do HFS,
get a large EPSP, accumulation of all of them, leads to increase of EPSP
let it go back to baseline, when you stimulate cell A, see an enhanced response, size of EPSP has changed, but B hasn’t changed because it is specific to the synapses being activated during HFS
What is tetanic stimulation?
Repeated stimulation
What are the types of long term potentiation?
Associative
Temporal
