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Neuroscience from molecules to behaviour > Neural mechanisms of Learning and Memory: an introduction > Flashcards

Neural mechanisms of Learning and Memory: an introduction Flashcards

1
Q

What is the core concept of molecular mechanisms underlining neuroplasticity?

A

Synaptic Plasticity

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2
Q

Name an influential scientist to the field of neuroplasticity

A

Donald Hebb (1904-1985)

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3
Q

Define Hebbian Learning

A

Efficiency of synapses between neurons increases has a correlation with the similarity in activity between the pre and post-synaptic neurons.

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4
Q

What is a Hebb synapse?

A

When an axon of cell A id near enough to excite B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased.

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5
Q

What is thinking in terms of neuroplasticity?

A

The sequential activation of sets of cell-assemblies

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6
Q

Neuroplasticity can lead/has been related to which higher functions?

A

Memory and learning

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7
Q

What are the three postulates of Hebb’s Theory?

A
  • Hebbian learning
  • Cell Assemblies
  • Phase sequence
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8
Q

Define Hebbian learning

A

The idea that efficiency of synaptic connections between neurons is positively correlated with the temporal and quantitative repeated excitatory activity between the pre- and post-synaptic neuron.

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9
Q

Define cell assemblies

A

A cluster of neurons that tend to be active together, this firing can be persistent and this firing is a type of memory.

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10
Q

Describe the story of HM?

A
  • bicycle accident at 9
  • led to the onset of epileptic seizures
  • removal of parts of both right and left medial temporal lobes
  • resulting in cessation of seizures but anterograde amnesia
  • he was still able to learn new motor skills but could not remember learning them.
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11
Q

What are the types of memories?

A
  • Implicit
  • Explicit
  • Knowing how
  • Knowing what
  • Declarative
  • Non declarative
  • Long term
  • Short term
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12
Q

Define implicit memory

A

More automatic and reflexive

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13
Q

Define explicit memory

A

Involves conscious remembering of the past

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14
Q

Define knowing how memory

A

Memory without record

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15
Q

Define knowing what memory?

A

Memory with record

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16
Q

Define LT memory

A

Long term memory is memory that is encoded to last more than approx. 30 seconds

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17
Q

Define ST memory

A

Short term memory is memory with a duration lasting between 7 seconds to 30 seconds

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18
Q

Which type of memory was affected in HM?

A

Long-term declarative memories

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19
Q

Which structure was later on discovery to be located in the areas of the right and left MTLs?

A

The Hippocampus (Ammon’s Horn or Cornu Ammonus)

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20
Q

What are the four anatomical regions of the hippocampus?

A

CA1, CA2, CA3 and CA4

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21
Q

Which structures are included in the parahippocampal formation?

A
  • hippocampus
  • parahippocampal gyrus
  • dentate gyrus
  • fornix
  • located under the lateral ventricles
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22
Q

What is the assumed function of the Hippocampus?

A

Responsible in the conversion of short term declarative memories to long term declarative memories

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23
Q

What are the areas comprising the parahippocampal gyrus?

A
  • the entorhinal cortex

- subiculum

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24
Q

Describe the case of Clive Wearing

A
  • contracted viral encephalitis that damaged the hippocampus

- he was unable to form long lasting memories

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25
Q

What is the name of the two scientists who drew the neural circuitry of a rat’s hippocampus?

A

Santiago Ramon y Cajal

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26
Q

To which system does the hippocampus belong to?

A

The limbic system

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27
Q

State the cell types involved in the trisynaptic circuit?

A

The three major cell groups involved are:

  • CA1 pyramidal cells
  • CA3 pyramidal cells
  • Granular cells (Dentate gyrus)
28
Q

Describe the trisynaptic hippocampal circuit

A

Axons of the Perforant pathway, arising from the Entorhinal Cortex in the parahippocampal gyrus, synapse with Granule cells of the Dentate gyrus. Granule cells use mossy fibers to transmit the signal to the CA3 pyramidal cells, which is then sent to the CA1 pyramidal cells via the Schaffer collaterals.

29
Q

State the main synapses of the trisynaptic circuit of the hippocampus

A

Synapse 1
- From the Entorhinal cortex to the
Dentate gyrus via the perforant pathway.

Synapse 2
- From the Dentate gyrus to the CA1 pyramidal cells via the mossy fibers

Synapse 3
- From the CA3 pyramidal cells to the CA1 pyramidal cells via the Schaffer collaterals.

30
Q

What are the two main output sources of the hippocampal trisynaptic circuit?

A

Fornix
bundle of nerve fibers that act as a major output tract of the hippocampus.

Entorhinal cortex
gray mater structure, main gateway of communication between the parahippocampal area and the neocortex.

31
Q

Explain the connectivity of the subiculum

A

The most inferior part of the hippocampus, main output. Projects to:
Entorhinal Cortex, amygdala, nucleus accunbens, and other brain regions.

32
Q

What is the importance of the Dentate gyrus?

A

Formation of new episodic memory, high rates of adult Neurogenesis

33
Q

What are the main modulators and mediators of EPSPs in the hippocampal formation?

A

glutamate and ionotropic glutamate receptors

34
Q

What technique is used to measure current (EPSC)?

A

Voltage clamping

voltage is held at a specific potential in order for current to be measured.

35
Q

Is glutamate the main NTM in all animals?

A

In arthropods and other insects it is not important for the CNS but it is important for neuromuscular transmission.
It is pertinent in the CNS for mammals but important in the periphery of other animals.

36
Q

What are the forms of glutamate receptors?

A

Ionotropic
- ligand gated ion channels, fast excitatory neurotransmission
Metabotropic
- GPCRs, involve second messenger pathways to influence ionotropic channels, slower longer term signals

37
Q

What are the types of metabotropic glutamate receptors identified in humans?

A 
mGluR1
mGluR2
mGluR3
mGluR4
mGluR5
mGluR6
mGluR7
mGluR8
38
Q

What are the two major types of ionotropic glutamate receptors?

A
  1. Non-NMDA type receptors
    - AMPA
    - Kainate
  2. NMDA type receptors
39
Q

What does NMDA stand for?

A

N-methyl-D-aspartate

40
Q

What does AMPA stand for?

A

Alpha-amino-3-hydroxy-5-methyl-4-isoxalonw propionic acid

41
Q

What other molecules can bind to activate AMPARs and NMDARs?

A

Muscarine, nicotine.

Are exogenous and can selectively activate specific ionotropic Glu receptors.

42
Q

How was the first ionotropic Glu receptor identified and how?

A

1989, Isolation of rat cDNA (in a library). Then selecting some cDNA sequences and inject them into Xenopus oocytes (not responsive to glutamate). If the oocyte (with the cDNA) can respond to Glutamate then that would narrow down the number of cDNA responsible for the sequencing of an ionotropic Glutamate receptor.

43
Q

What are the AMPAR types?

A

GluR1
GluR2
GluR3
GluR4

44
Q

What are the NMDAR types?

A 
GluR5
GluR6
GluR7
KA1
KA2
45
Q

Are all ionotropic Glutamate receptor genes responsive to glutamate?

A

No, there are also delta receptors that are not responsive to Glu.

46
Q

What is the topology of the ionotropic glutamate receptors?

A

Three transmembrane helices plus pore loop. Extracellular N terminus and intracellular C terminus (comes inside because of the pore loop).

47
Q

How was the topology of the ionotropic Glu receptor identified?

A

Glycosilation by designing a protein that could not undergo glycosilation and removing the 5 glycosilation sites from the receptor domains.

48
Q

On which side of the cell does glycosilation occur?

A

Extracellularly

49
Q

Which part/domain of the ionotropic Glu receptor is the binding region?

A

The N terminal (extracellular) the longest part

50
Q

What is the function of the p-loop and where is it located?

A

Forms the lining of a pore that forms a channel for cations. Between transmembrane helices 1 and 2.

51
Q

How many subunits are necessary for the formation of an ionotropic Glu receptor?

A

Tetrameric, two dimers coming together. Identified by X-ray

52
Q

What is the structure of the majority of the GluR in the central nervous system?

A

GluR2 heteromer included in the overall structure of most GluRs.

53
Q

What is the most abundant ionotropic glutamate receptor subunit?

54
Q

What is the effect of GluR2 subunits in AMPARs?

A

GluR2 make AMPARs impermeable to Calcium ions.

55
Q

Why are majority of AMPARs impermeable to Calcium ions?

A

Because of the presence of GluR2 subunits in the channel structure.

56
Q

What is the Glur1-4 ratio/concentration in the fore brain?

A

There is a higher concentration of [GluR1-2] and lower concentrations of [GluR3-4]

57
Q

Why are AMPARs the major mediators of fast EPSPs or EPSCs?

A

It is due to a net influx of sodium ions

58
Q

What technique can be used to identify the expression of GluRs?

A

In situ hybridization

59
Q

What are the principle neurons of the cerebellar cortex?

A

Purkinje fibres

60
Q

On which side of the synapse can kainate receptors be found?

A

Both pre and postsynaptically

61
Q

Explain in terms of synaptic location where mossy fibers and hippocampal CA1 and CA3 pyramidal cells are located?

A

Mossy fibres are located presynaptically (from granule cells of the DG to the, CA3 pyramidal cells located postsynaptically.

62
Q

Present evidence for the origins of of ionotropic Glu receptors?

A

They did not originate from the NS, they were adopted by the Nervous System.

  • Share little similarities with ligand gated ion channels in the nicotinic ACh/GABA/Glycine family.
  • They evolvedindependently
  • nicotinic ACh/GABA/Glycine family are only found in animals.
  • genes encoding ionotropic GluRs have been found in plants.
63
Q

What function was discovered for ionotropic GluRs in insects?

A

Ionotropic Glu receptor-like proteins function as mediators of olfactory transduction in insects.

64
Q

What is the name of the ancient cyanobacterial Glutamate receptor?

65
Q

What is the difference between GluR0 and GluR2 receptor subunits?

A

The bacterial sub unit lacks the third transmembrane domain.

Neuroscience from molecules to behaviour (5 decks)

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