Learning and memory Flashcards
Declaritive memory
available to the conscious mind and can be encoded in symbols and language
Explicit memory
memory that can be consciously recalled
Implicit memory
memory that cannot be consciously recalled
What are the three types of implicit memory?
procedural memory
classical conditioning
priming
Advantages of using simple systems to study memory (snails, worms insects)
complicated nervous systems but stereotypic and large axons which are easier to record from
temp dependence allows switching on and off of neurons/genes
Habituation
decreased amplitude of response due to repeated stimulus
Sensitisation
increased amplitude of response
What are two examples of simple forms of memory?
habituation
sensitisation
Aplysia gill withdrawal reflex
gill withdrawal reflex caused by touch or water jet
habituation casued by repeated stimulus
sensitisation caused by tail/head pinch or shock, involves presynaptic input from sensory neurons with serotonin and g protein action
Associative learning
very pavlovian like
weak siphon touch paired with strong shock meaning response is much bigger than before and more long term
timing is critical for shock being associated to stimulus
Why does a shock stimulus along with siphon touch give a bigger response?
calcium influx from L29 which is the extra neuron that detects noxious stimuli
happens at the same time as sensory neuron depolarisation so there is much more cyclic AMP and PKA produced
Hebbian synapse
coordinated activity of a presynaptic terminal and a postsynaptic neuron strengthening the synaptic connections between them
What type of memory is the hippocampus particularly involved in?
spatial
Hippocampal pathway
entorhinal cortex > dentate gyrus > CA3 > CA1 > output via fornix and subiculum
Where does long term potentiation usually occur in the memory pathway?
CA3 to CA1 synapses
What is the long term potentiation phenomenom?
high frequency sitmulus causes amplitude of EPSPs to become bigger
How does LTP show cooperativity and sensitivity?
shows input sensitivity as it only acts on the synpases that are activated
shows cooperativity as it allows two pathways converging on the same target to be strengthened if fired together
3 types of glutamate receptor
NMDA
APMA
mGlu
Where could the cooperative characteristics of LTPs come from?
may be a result of NMDA receptors as they have a voltage dependent Mg2+ block which requires indirect pre-activation by a seperate depolarising input
What are the two stages LTP can be split into?
early and late
OR induction and expression
Early stage LTP NMDA activation
increase in Ca2+ conc
activation of calmodulin kinase II which phosphorylates itself into stable active conformation to then phosphorylate other proteins
AMPAfication
increase in the number of AMPA receptors on the postsynaptic terminal
Late stage LTP
lasts much longer and requires protein synthesis so takes much longer
How could cAMP signalling be critical in late stage LTP?
cAMP activates protein kinase A which activates other proteins and phosphorylates proteins inside the nucleus
binds to CRE which then acitvates promoter, leads to expression of genes that change synapse
What are the effects of inhibition of LTP?
inhibits some memory formation so must be somewhat involved but only for some and isn’t sufficient on its own
some memory enhancing drugs increase LTP
Mutations of what pathways affect aspects of learning?
CaMKII
NMDARs
cAMP
Long term depression
related to memory and is the opposite of LTP
decreases the synaptic gain when memories are formed
What parts of the brain are important for LTD?
cerebellum
hippocampus