Memory And Learning

Question 1

What are the two stages of learning and memory?

Answer 1

1. The acquisition of a short term memory
2. The consolidation of a long term memory

Question 2

What is physical modification of the brain because by?

Answer 2

Incoming sensory information

Question 3

Define memory consolidation

Answer 3

Is the process by which some experiences, held temporarily by transient modifications of neurons, are selected for permanent storage in long term memory

Question 4

Describe the flow of sensory information into long term memory

Answer 4

Sensory experience - (memory acquisition) - short term memory - (memory consolidation) - long term

Question 5

What is the IT area involved in?

Answer 5

Visual area and an area involved with memory

Lesions = propagnosia

Question 6

Define prospagnosia

Answer 6

A selective amnesia for familiar faces that can result from damage to the infertemporal cortex in humans

Question 7

What is stimulus activity?

Answer 7

Response with a barrage of action potentials to the presentation of some but not all stimuli

Example, IT neurons

Question 8

Define distributed memory

Answer 8

The concept that memories are encoded by widespread synaptic modifications of many neurons, not by a single synapse or cell

Question 9

What is graceful degradation

Answer 9

The slow removal of neuronal networks

Representations tend to blend together as neurons are lost, such that one memory gets confused with another

Question 10

What was found on studies about snail memory storage ?

Answer 10

Simple forms of learning were accompanied by changes in the strength of synaptic transmission between sensory neurons and motor neurons

Question 11

What brain region is critical for memory formation?

Answer 11

Hippocampus

Question 12

What are the two thin sheets of neurons in the hippocampus?

Answer 12

1. Ammon’s horn
   
   • CA3 and CA1
2. Dentate’s GYRUS

Question 13

Describe the trisynaptic circuit

Answer 13

1. Entorhinal cortex - dentate gyrus (perforant path) synapses
2. DENTATE GYRUS - CA3 (mossy fibre) synapses
3. CA3 - CA1 (Schaffer collateral) synapses

Question 14

Define tetanus

Answer 14

A brief burst of high-frequency stimulation (typical 50-100 stimuli at a rate of 100/sec)

Question 15

Define input specificity

Answer 15

A property of synapse plasticity that ensure that modifications induced by stimulation of one input onto a neuron do not spread to other unstimulated so puts on the same neuron

Question 16

What does tetanus cause?

Answer 16

A modification of the stimulated synapses so they are more effective

Question 17

What are the remarkable features of plasticity?

Answer 17

1. Induced by brief tetanus
2. Longevity

Question 18

What is a requirement for LTP?

Answer 18

Synapses are active at the same time that the postsynaptic CA1 neuron is strongly depolarised

Question 19

What is necessary for depolarisation with tetanus require?

Answer 19

1. Synapses must be stimulated at frequencies high enough to cause temporal summation of EPSPs.
2. Enough synapses must be active simultaneously to cause significant spatial summation of EPSPs.

Question 20

How are excitatory synaptic transmission in the hippocampus mediated?

Answer 20

Glutamate through the NMDA receptor due to the release of Ca2+ as it signals when presynaptic and postsynaptic elements are active at the same time

Question 21

How is LTP inducted inhibited?

Answer 21

Rises in Ca2+ as it activates two protein kinases: protein kinase C and calcium-calmodulin-dependent protein kinase (CaMKII), which cause phosphorylation of the AMPA receptors to increase ionic conduction of the channel or the insertion of new AMPA receptors

Question 22

Define BCM theory

Answer 22

A theory proposing that synapses are bidirectionally modifiable. Synaptic potentiation results when presynaptic activity correlates with a strong postsynaptic response, and synaptic depression results when presynaptic activity correlates with a weak post synaptic response.

Question 23

What is a key assumption of the BCM theory?

Answer 23

That synapses will undergo synaptic weakening instead of LTP when they are active at the same time the postsynaptic cell is only weakly depolarised by other inputs.

Question 24

Define long term depression

Answer 24

A long lasting decrease in the effectiveness of synaptic transmission that follows certain types of conditioning stimulation

Question 25

What two rules govern bidirectional plasticity?

Answer 25

1. Synaptic transmission occurring at the same time as a strong depolarisation of the post synaptic neuron causes LTP of the active synapses
2. Synaptic transmission occurring at the same time as a weak or modest depolarisation of the post synaptic neuron causes LTD of the active synapses.

Question 26

Define spike timing-dependent plasticity

Answer 26

Bidirectional modification of synaptic strength induced by varying the relative timing of the presynaptic and postsynaptic spikes

Question 27

At the Schaffer collateral - CA1 synapse, describe the two distinct forms of homosynaptic LTD.

Answer 27

1. Activation of the NMDA receptor
2. Activation of the G-coupled metabotrophic glutamate receptors

Question 28

What is the difference between LTP and LTD?

Answer 28

LTP is putting phosphate groups on

LTD is taking them off

LTP and LTD appear to reflect the bidirectional regulation of both the phosphorylation and the number of postsynaptic AMPA receptors

Question 29

Define metaplasticity

Answer 29

Activity dependent modification of the rules of synaptic plasticity

Question 30

When is LTP and LTD favoured?

Answer 30

LTP - more NR2B-containing receptors are expressed at the synapse

LTD - more NR2A- containing receptors are expressed

Question 31

When are NR2A levels high andNR2B levels low?

Answer 31

High cortical activity

Question 32

Describe denervation supersensitivity

Answer 32

Widespread response of neurons to the loss of synaptic input

Question 33

Define synaptic scaling

Answer 33

A cell wide adjustment of synaptic strengths in response to a change in the average firing rate of the post synaptic neuron

Question 34

Why is phosphorylation as a long term memory consolidation mechanism an issue?

Answer 34

1. Not permanent
2. Protein molecules are not permanent

Question 35

What induces LTP in CA1

Answer 35

Entry of calcium into the postsynaptic cell and the activation of CaMKII

Question 36

Describe the structure of CaMKIII

Answer 36

Ten subunits arranged in a rosette pattern

Each unit has two parts attached like a hinge. Two parts are the catalytic region (phosphorylation ) and regulatory region.

Question 37

How does regulation of CaMKIII occur

Answer 37

When hinge is closed, there is no available second messenger and the catalytic region is covered by the regulatory region. Open when second messenger present. Removal = closed

After LTP, hinge stays slightly open and continues phosphorylation.

Question 38

Define molecular switch hypothesis

Answer 38

The idea that protein kinases can be switched on by auto phosphorylation to a state in which they no longer require the presence of a specific second messenger to be active. Such persistently active kinases may hold the memory of an episode of strong synaptic activation.

Question 39

What is the role of ZIP

Answer 39

Inhibits protein kinase m zeta resulting in erasing LTP and memories established many days prior.

Cause dephosphorylation - erasing memory trace

Question 40

What are the two forms of CREB?

Answer 40

CREB-2: represses gene expression when it binds to CRE

CREB-1: activates transcription, but on,y when it is phosphorylated by protein kinase A.