L6 Flashcards
describe Atkinson and Shiffrin’s model of memory
the first 300ms is sensory information
if that sensory information is attended then it goes into your short term memory (20 sec)
if this is reherced then it will go into long term memory
what is distributor processing
Distributor processing is storing information across multiple neurons
what is a cell assembly
particular pattern of activity in a group of interconnected
neurons
Each psychologically significant event, sensation, percept, expectation, memory or thought is the result of what
a cell assembly
what happens during the perception of an event
When you are perceiving an event, it corresponds to particular neurons cell assemblies that are becoming active
when something is in your short term memory, what is happening
Reverberating neural activity in closed-loop circuitry
why do we not store out memories in the way that we store short term memories
because the circuit needs to be active all the time you would run out of neurons and it would also be metabolically expensive
what is long term memory
Long term is when you strengthen the connections between neurons responsible for that particular experience
stronger synapse happen after consolidation meaning that those neurons have an increased potential for activation
how you you recall a memory
you activate the network from when you perceived the event that was that memory
the reactivation of this assembly occurs because of differential synaptic strength
what are Hebbs rules for whether a synaptic connection would strengthened or not
- when neurons fire you strengthen the connection which tends to induce lasting cellular changes that add to its stability (what happens)
- 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. (how it happens)
what is Hebbian learning
When the postsynaptic and the presynaptic cell fire together then the connection between
them is strengthened
(cells that fire together, wire together).
Importantly, this allows for the association of inputs
what is the function of the amygdala
to produce an emotional response
explain how Hebbian learning allows for association of inputs
eg pain has a strong synapse to a neuron that causes you to feel fear.
when you are walking down the beach you see a crab. the neuron activated when you see a carb has a weak synapse to the neuron that causes fear therefore the action potential is not propagated.
however if the crab pinches you both the carb and the pain neuron are going to be activated at the same time and the weak synapse will become stronger
this means that the next time you walk down the beach and you see a crab, the synapse has become stronger so now you the AP will be propogated and you will feel fear
what is long term potentiation (LTP)
the strength of connections which last a long period of time
the bigger the strength of the EPSP the stronger the connection
why does long term potentiation suggest how memory works
you have a phenomenon which can strengthen synapses for a year (or possibly more)
does LTP have Hebbian properties
yes
specific to the pathways that are activated
This allows the nervous system to be very selective and gives you trillions of synapses which can be changed
what receptors are on the postsynaptic neuron that allow for LTP
AMPA subtype of glutamate receptor and NMDA subtype of glutamate receptor
describe the LTP induction mechanism
when glutamate binds to the AMPA receptor it lets Na+ into the cell causing depolerisation of the membrane
Sufficient depolarisation of membrane leads to unblocking of the NMDA channel
Calcium influx leads to LTP induction via downstream changes which increases receptors and then changes protein synthesis that
can induce long-term alterations in the strength of the synapse
describe the AMPA receptor
when glutamate binds it lets Na into the cell
describe the NMDA receptor
the NMDA receptor has a Mg2+ gate
Sufficient depolarisation of membrane leads to unblocking of channel because the inside becomes more positive pushing the +ive charge of the Mg gate out of the way
when this happens and glutamate is bound Ca can enter the cell
what is the critical aspect of the LTP mechanism
it requires a conjunction of presynaptic and postsynaptic activity (Hebbian synapse)
You need a significant depolerisation to get the Mg out of the pore so Ca can get in
This can happen from one big input or lots of small ones
how could you test to see whether LTP has anything to do with memory
Show that blocking LTP prevents memory formation
Show that reversal of LTP produces forgetting
Show that learning leads to LTP-like changes
Show that producing LTP creates false memories or masks existing memories
what is an antagonist of the NMDA receptor
AP5
how does AP5 effect LTP
you need the NMDA receptor for LTPs to occur therefore if the receptor is not working than LTPs cant happen
This is a dose dependent response
what is the Morris water maze
it is a test for memory
it consists of a pool of water with a platform placed in a specific location just under the water so the rats cant see it
a rat is then placed in the water and they swim around until they find the platform. they learn very quickly where the platform is
you would then take the platform out of the water and if the rat spends more time swimming around where the platform was then it shows that they are looking for the platform and they have formed a memory of where the platform was
how could you test to see if AP5 had an effect on memory using the morris water maze
you have a control group and then groups where the dose increases
you find that as the dose increases the time spent in each 1/4 of the pool balances out showing that with very high doses of AP5 that the animal never learns where the platform is
LTP maintenance is dependent on….
protein kinase M zeta (PKMz)
what dose ZIP (Zeta-Inhibitory Peptide) do
it inhibbits PKMz
this reverses the maintenance of late-phase LTP in vivo (it turns off LTP)
this means that when zip is injected the animal forgets what it has learnt
what does zip show
it shows that when a normal action potential is fired there is no change but when zip is injected it dramatically decreases the baseline for EPSP
what does protein kinase M zeta (PKMz) inhibition cause
PKM ζ inhibition abolishes long-term retention of spatial information
what does 2 photon microscopy allow for
the imaging of tissue within a band 1 micron thick and at depths of up to 1 mm inside the brain
when you are looking at a 2 photon microscopy image of a dendrite what are the fuzzy things
dendritic spines
this is where the axon terminals connect to the dendrite
dendritic spine formation can be blocked by which NMDA antagonist
MK-801
why is it important that the number of dendritic spines (connections) are regulated
As you learn more and more information you get more and more strong synapses
This could be dangerous as this is what happens in epilepsie
Also if this is the case what happens if the brain becomes full
what is synaptic scaling
it is a form of homeostasis
This means that there is a continuous process in cell where when you strengthen some synapses you weaken others
