5. Mechanisms of Learning and Memory Flashcards
define learning
the strengthening of responses or the formation of new responses to stimuli due to repetition or practice
what 2 model organisms are used to study learning and memory
aplasia and drosophila
what is declarative memory
knowledge about facts and there meaning
how is declarative memory recalled
consciously
what is non-declarative memory
knowledge about how to perform something
how is non-declarative memory recalled
unconsciously
what are the two types of non-declarative memory
associative or non-associative
name two types of non-associative learning
habituation and sensitisation
define habituation
the decrease in response to a benign stimulus through repeated presentation of the stimulus
define sensitisation
the enhanced response to multiple different stimuli after presentation with a noxious or intense stimulus
give an example of sensitisation
dripping tap - mega annoying
what is associative learning
classical conditioning - where the association between two stimuli is learned
what is aplysia
sea snail
what is the natural predator of aplysia
spiny lobster
how do aplasia protect themselves
close their gill and syphon and eject a cloud of ink that contains chemicals
what is the purpose of the chemicals secreted by aplasia in the gill-syphon reflex
aimed to repel and confuse the lobster
what happens after a sea snail is attacked once
it is sensitised to future responses - becomes more alert
describe the nervous system of aplysia
- no brain = just a collection of ganglia
- contains large identifiable nerve cells which can have their electrical activity recorded
how many large nerve cells in aplysia
20,000
describe the process of short term memory formation in aplysia
- serotonin binds to receptors of sensory neurons
- activates adenyl cyclase which produces cAMP
- increased cAMP increases the synaptic strength of the sensory to motor neuron connection (short term facilitation)
- enhanced glutamate by the sensory neuron also aids short term facilitation
cAMP level change regulate the activity of kinases and phosphatases to control the duration and strength of synaptic connections
describe the mechanism for long-term memory formation in Aplysia
- neurotransmitter release and short term strengthening of synaptic connections
- equilibrium is reached between kinase and phosphatase activity
- retrograde transport from the synapse to the nucleus
- activation of CREB nuclear transcription factors = gene expression
- newly synthesised gene products are captured by the synapse = local protein synthesis at active synapses
- synaptic growth and the formation of new synapses
- process continues - equilibrium is reached…
what type of neurons carry information about aversive stimuli to MB
DA
what type of neurons carry information about appetitive stimuli to MB
octopaminergic neurons
describe the molecular process of aversive olfactory conditioning
- Conditioned stimulus (odor) is presented to the MB by the projection neurons
- Pls secrete Ach at the synapse = voltage-dependent calcium channels open
- influx of calcium = calmodulin production which activates adenyl cyclase
- AC produces cAMP
- unconditioned stimulus (electric shock) is presented to Kenyon cells by PPL1/PPL2ab neurons which release DA onto MB neurons
- dopamine receptor activation = increase in cAMP via alpha subunit of g-protein coupled to adenyl cyclase
- simultaneous activation of CS and US pathways = MB encode the CS/US temporal coincidence.
describe the molecular process involved in appetitive olfactory conditioning
- the same conditioned stimulus pathway is activated in the Kenyon cells (PN Ach release = Ca2+ influx = AC = cAMP)
- US information is conveyed via octopamine release onto the MB neurons that stimulate AC
- coincident application of CS and US = sub additive increase in postsynaptic cAMP.
does dopamine have a role in appetitive olfactory conditioning
yes - but the role is not clear
we only understand that octopamine is definitely released onto MB cells
what happens when you microinject CRE oligonucleotides into sensory neurons co-cultured with motor neurons
CREB cannot bind and activate genes = prevents protein expression
this selectively blocked long term facilitation
what is apCREB2
a creb repressor that contributes to the LTF process
what happens in anti-apCREB2 antibodies are injected into sensory neurons of aplysia
when there is a single pulse of serotonin, it is able to induce long term facilitation lasting days as well as short term facilitation
why are aplysia a good model organism
their neurons are large and easy to identify, this means we can record individual neuron activity
