5. Mechanisms of Learning and Memory

Question 1

define learning

Answer 1

the strengthening of responses or the formation of new responses to stimuli due to repetition or practice

Question 2

what 2 model organisms are used to study learning and memory

Answer 2

aplasia and drosophila

Question 3

what is declarative memory

Answer 3

knowledge about facts and there meaning

Question 4

how is declarative memory recalled

Answer 4

consciously

Question 5

what is non-declarative memory

Answer 5

knowledge about how to perform something

Question 6

how is non-declarative memory recalled

Answer 6

unconsciously

Question 7

what are the two types of non-declarative memory

Answer 7

associative or non-associative

Question 8

name two types of non-associative learning

Answer 8

habituation and sensitisation

Question 9

define habituation

Answer 9

the decrease in response to a benign stimulus through repeated presentation of the stimulus

Question 10

define sensitisation

Answer 10

the enhanced response to multiple different stimuli after presentation with a noxious or intense stimulus

Question 11

give an example of sensitisation

Answer 11

dripping tap - mega annoying

Question 12

what is associative learning

Answer 12

classical conditioning - where the association between two stimuli is learned

Question 13

what is aplysia

Answer 13

sea snail

Question 14

what is the natural predator of aplysia

Answer 14

spiny lobster

Question 15

how do aplasia protect themselves

Answer 15

close their gill and syphon and eject a cloud of ink that contains chemicals

Question 16

what is the purpose of the chemicals secreted by aplasia in the gill-syphon reflex

Answer 16

aimed to repel and confuse the lobster

Question 17

what happens after a sea snail is attacked once

Answer 17

it is sensitised to future responses - becomes more alert

Question 18

describe the nervous system of aplysia

Answer 18

• no brain = just a collection of ganglia
• contains large identifiable nerve cells which can have their electrical activity recorded

Question 19

how many large nerve cells in aplysia

Answer 19

20,000

Question 20

describe the process of short term memory formation in aplysia

Answer 20

1. serotonin binds to receptors of sensory neurons
2. activates adenyl cyclase which produces cAMP
3. increased cAMP increases the synaptic strength of the sensory to motor neuron connection (short term facilitation)
4. 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

Question 21

describe the mechanism for long-term memory formation in Aplysia

Answer 21

1. neurotransmitter release and short term strengthening of synaptic connections
2. equilibrium is reached between kinase and phosphatase activity
3. retrograde transport from the synapse to the nucleus
4. activation of CREB nuclear transcription factors = gene expression
5. newly synthesised gene products are captured by the synapse = local protein synthesis at active synapses
6. synaptic growth and the formation of new synapses
7. process continues - equilibrium is reached…

Question 22

what type of neurons carry information about aversive stimuli to MB

Answer 22

DA

Question 23

what type of neurons carry information about appetitive stimuli to MB

Answer 23

octopaminergic neurons

Question 24

describe the molecular process of aversive olfactory conditioning

Answer 24

1. Conditioned stimulus (odor) is presented to the MB by the projection neurons
2. Pls secrete Ach at the synapse = voltage-dependent calcium channels open
3. influx of calcium = calmodulin production which activates adenyl cyclase
4. AC produces cAMP
5. unconditioned stimulus (electric shock) is presented to Kenyon cells by PPL1/PPL2ab neurons which release DA onto MB neurons
6. dopamine receptor activation = increase in cAMP via alpha subunit of g-protein coupled to adenyl cyclase
7. simultaneous activation of CS and US pathways = MB encode the CS/US temporal coincidence.

Question 25

describe the molecular process involved in appetitive olfactory conditioning

Answer 25

1. the same conditioned stimulus pathway is activated in the Kenyon cells (PN Ach release = Ca2+ influx = AC = cAMP)
2. US information is conveyed via octopamine release onto the MB neurons that stimulate AC
3. coincident application of CS and US = sub additive increase in postsynaptic cAMP.

Question 26

does dopamine have a role in appetitive olfactory conditioning

Answer 26

yes - but the role is not clear
we only understand that octopamine is definitely released onto MB cells

Question 27

what happens when you microinject CRE oligonucleotides into sensory neurons co-cultured with motor neurons

Answer 27

CREB cannot bind and activate genes = prevents protein expression

this selectively blocked long term facilitation

Question 28

what is apCREB2

Answer 28

a creb repressor that contributes to the LTF process

Question 29

what happens in anti-apCREB2 antibodies are injected into sensory neurons of aplysia

Answer 29

when there is a single pulse of serotonin, it is able to induce long term facilitation lasting days as well as short term facilitation

Question 30

why are aplysia a good model organism

Answer 30

their neurons are large and easy to identify, this means we can record individual neuron activity