Memory

Question 1

what are the definitions of learning, memory, recall and ‘the engram’?

Answer 1

learning = acquisition of info/skills

memory = storage of learned info

recall = reacquisition of stored info

the engram = physical embodiment of a memory

Question 2

what are the 2 independent memory systems?

Answer 2

1. procedural - implicit

2. declarative - explicit

Question 3

what is procedural memory?

Answer 3

• skills and associations that are largely unavailable to the conscious mind
• e.g. acquired skills which after you practice you can naturally do e.g. riding a bike

Question 4

what is declarative memory?

Answer 4

• available to conscious mind
• can be encoded in symbols and language
• e.g. speaking/communicating knowledge

Question 5

what is explicit memory?

Answer 5

• memory that can be consciously recalled

- e.g. recalling riding a new bike

Question 6

what is implicit memory?

Answer 6

• memory that cannot be consciously recalled

- e.g. learning to ride a bike

Question 7

what are the 3 types of implicit memory?

Answer 7

1. Procedural memory
2. classical conditioning e.g. Pavlov’s dogs
3. Priming - when one stimulus influences the response to subsequent stimuli

Question 8

what are the 3 types of memory duration?

Answer 8

1. immediate memory = few seconds
2. short-term memory = seconds/minutes
   - working memory
3. long-term memory = days/months/years

Question 9

how is the temporal lobe involved in memory?

Answer 9

• electrical stimulation of the temporal lobe causes hallucinations and recollection of past events
• important in generating long-term memory

Question 10

what are epileptic seizures?

Answer 10

when neurons in local, specific areas of the brain fire APs uncontrollably, causing complex sensations and memories

Question 11

what happens when a patient’s temporal lobe is removed? (lobectomy)

Answer 11

• intelligence, personality and long-term memory in tact
• epileptic seizures stopped
• extreme anterograde amnesia - couldn’t acquire new memories

Question 12

what are the important brain structures involved in memory?

Answer 12

1. Prefrontal cortex: working memory
2. Hippocampus: declarative memory
   - converts short to long term memory
3. amygdala: implicit memory
   - multiple, processed sensory inputs i.e. emotional memory and learnt fear
4. cerebellum: procedural memory
   - sensorimotor

Question 13

how is the hippocampus involved in memory?

Answer 13

• 3 layered cortex with inputs from the entorhinal cortex
• outputs to many regions
• enlarged in people with good spatial memory
• hippocampal lesions cause memory loss

Question 14

what are the mechanisms of memory?

Answer 14

long-term storage is distributed across brain regions

reverberating circuits: memory part of a specific population of neurons in the brain

the Hebbian synapse concept: gain of synapses increases/decreases during memory formation
- synaptic plasticity

Question 15

what is the Hebbian synapse concept?

Answer 15

• synaptic strength changes cause an increase in amplitude of EPSP
• facilitation/depression: short-term changes in synaptic strength due to Ca2+ availability or vesicle depletion
• long-term facilitation/depression is sustained

Question 16

what is Long-Term Potentiation (LTP)?

Answer 16

an increase in synaptic strength that lasts over days/weeks:

• in hippocampus
• synaptic plasticity was studied between CA3 presynaptic and CA1 postsynaptic neurons

Question 17

what is post-tetanic LTP?

Answer 17

• high frequency burst of depolarisations on CA3 causes increase in EPSP amplitude
• if a different neuron has the same high frequency depolarisation applied, the EPSP stays the same
• shows that changes in the synapse are at local level and specific to certain cells (CA3 and CA1)
• even if other neurons synapse to CA1, their EPSPs will remain the same

Question 18

what is paired LTP?

Answer 18

• stimulus and depolarisation of CA3 and CA1 at the same time causes change in strength of synpase
• causes increase in amplitude of EPSP
• classical conditioning

Question 19

what is Long-Term Depression (LTD)?

Answer 19

a decrease in synaptic strength that lasts over days/weeks:

• in hippocampus
• if presynaptic neurons are stimulated at low frequency, amplitude of EPSP decreases

Question 20

what are the characteristics of the Aplysia californica snail?

Answer 20

• lacks many neurons so can correlate specific neurons with specific behaviours
• larger neurons than mammalian neurons so easy to study
• has gill-withdrawal reflex: stimulation of areas close to gill (siphon) causes gill to move inwards

Question 21

what is the short-term habituation and sensitisation of the snail?

Answer 21

• repeated gentle stimuli to siphon causes reduced gill-withdrawal as snail releases no danger = habituation
• random tail pinch causes re-established withdrawal reflex which is short term (60 mins)

Question 22

what is the long-term sensitisation of the snail?

Answer 22

• repeated pairing of siphon touch and tail pinch causes long-term withdrawal reflex

Question 23

what are the characteristics of LTP, LTD and aplysia?

Answer 23

• require receptor activation by glutamate or serotonin
• alters synaptic responsivity
• mediated by second messengers
• require protein phosphorylation in early stages and protein synthesis in late stages
• involve pre and post synaptic changes

Question 24

how does LTP occur?

Answer 24

• a postsynaptic event involving Ca2+

- trafficking of AMPA receptors to the postsynaptic membrane