Memory Flashcards

1
Q

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

A

learning = acquisition of info/skills

memory = storage of learned info

recall = reacquisition of stored info

the engram = physical embodiment of a memory

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2
Q

what are the 2 independent memory systems?

A
  1. procedural - implicit

2. declarative - explicit

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3
Q

what is procedural memory?

A
  • 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
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4
Q

what is declarative memory?

A
  • available to conscious mind
  • can be encoded in symbols and language
  • e.g. speaking/communicating knowledge
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5
Q

what is explicit memory?

A
  • memory that can be consciously recalled

- e.g. recalling riding a new bike

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6
Q

what is implicit memory?

A
  • memory that cannot be consciously recalled

- e.g. learning to ride a bike

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7
Q

what are the 3 types of implicit memory?

A
  1. Procedural memory
  2. classical conditioning e.g. Pavlov’s dogs
  3. Priming - when one stimulus influences the response to subsequent stimuli
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8
Q

what are the 3 types of memory duration?

A
  1. immediate memory = few seconds
  2. short-term memory = seconds/minutes
    - working memory
  3. long-term memory = days/months/years
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9
Q

how is the temporal lobe involved in memory?

A
  • electrical stimulation of the temporal lobe causes hallucinations and recollection of past events
  • important in generating long-term memory
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10
Q

what are epileptic seizures?

A

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

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11
Q

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

A
  • intelligence, personality and long-term memory in tact
  • epileptic seizures stopped
  • extreme anterograde amnesia - couldn’t acquire new memories
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12
Q

what are the important brain structures involved in memory?

A
  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
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13
Q

how is the hippocampus involved in memory?

A
  • 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
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14
Q

what are the mechanisms of memory?

A

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

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15
Q

what is the Hebbian synapse concept?

A
  • 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
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16
Q

what is Long-Term Potentiation (LTP)?

A

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

  • in hippocampus
  • synaptic plasticity was studied between CA3 presynaptic and CA1 postsynaptic neurons
17
Q

what is post-tetanic LTP?

A
  • 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
18
Q

what is paired LTP?

A
  • 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
19
Q

what is Long-Term Depression (LTD)?

A

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

  • in hippocampus
  • if presynaptic neurons are stimulated at low frequency, amplitude of EPSP decreases
20
Q

what are the characteristics of the Aplysia californica snail?

A
  • 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
21
Q

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

A
  • 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)
22
Q

what is the long-term sensitisation of the snail?

A
  • repeated pairing of siphon touch and tail pinch causes long-term withdrawal reflex
23
Q

what are the characteristics of LTP, LTD and aplysia?

A
  • 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
24
Q

how does LTP occur?

A
  • a postsynaptic event involving Ca2+

- trafficking of AMPA receptors to the postsynaptic membrane