Chapter 25: Molecular Mechanisms of Memory

Question 1

iIdentifying where and how different types of
information are stored

Answer 1

neurobiology of memory

Question 2

Accdg. to (), Memory results from synaptic modifications

Answer 2

Hebb

Question 3

Study of simple invertebrates (Kandel)

molecular mechanisms lead to ()

Answer 3

synaptic plasticity

Question 4

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

not all memories are created equal

Answer 4

memory consolidation

Question 5

virtually () in the nervous system can form am memory of recent patterns of activity

Answer 5

all neurons

Question 6

macaque monkeys can be trained to discriminate images of objects and associate them with a food reward; however, they can lose this ability when lesions are made in the ()

Answer 6

inferotemporal cortex (contains Area IT)

Area IT = both a visual area and an area involved in memory storage

Question 7

selective amnesia for familiar faces (including one’s own) that can result from damage to the inferotemporal cortex in humans

Answer 7

prospagnosia

Question 8

like most cortical neurons, IT neurons typically show the property of ()

Answer 8

stimulus selectivity

Question 9

concept that a memory is represented by a unique pattern or ratio of activity of neuronal activity; no single neuron represents specific memory

Answer 9

distributed memory

Question 10

memory loss: instead of a catastriohic loss of any one memory as a result of damaged neurons, representations tend to blend together as nwueons are lost -> one memory gets confused with another

Answer 10

graceful degradation of memories

Question 11

synapses store memories

the () that leads to memory can be the modification of synaptic weight

Answer 11

physical change

Question 12

Eric Kandel’s study of Aplysia californica showed that simple forms of learning (habituation, sensitization) were accompanied by changes in ()

Answer 12

strength of synaptic transmission between sensory neurons and motor neurons

they were able to dissect many of the molecualr mechanisms that underlie these changes

Question 13

2 traditional views in memory research

Answer 13

1. chain of reactions (Pavlov and Thorndike)
2. flashbulb memory (insight learning)

Question 14

memories formed as APs pass through pathways multiple times -> gradually, pathways are strengthened

Answer 14

chain of reactions

Conditioning

Question 15

“one try learning”; being able to commit something to memory after experiencing it just once

evidence that chains of reactions cannot explain everything about memory formation

Answer 15

flashbulb memory (insight learning)

Question 16

responses to a situation which are followed by a rewarding state of affairs will be strengthened and become habitual
responses to that situation.

Answer 16

Law of Effect (Thorndike)

Question 17

() was thought to explain Flashbulb memory

Answer 17

Hebbian synapses

Question 18

Connections between neurons increase in efficacy in proportion to the degree of correlation between pre- and post-synaptic activity.

“Neurons that fire together, wire together”

“Neurons that aren’t in sync, lose their link”

Answer 18

Hebb’s Rule

Question 19

Hebbian explanation for short term memory: neruons activate each other

Answer 19

reverberation

Question 20

Hebbian explanation for transition into long-term memory: when there are (1) that happen between active neurons, a new (2) is formed

Answer 20

1. metabolic process
2. functional assembly -> changes in synaptic weight

Question 21

pattern completion based on Hebbian response

patterns are completed because synapses are ()

Answer 21

strengthened

Question 22

even though part of the image is given, we can recollect the missing parts from memory

Answer 22

pattern completion

Question 23

1. () studies have shown that associative memories can be stored in a network of neurons using Hebbian learning rule (Hopfield, 1984).
2. () is important.
3. () serve this function in the brain.

Answer 23

1. Neural network
2. Bidirectional connectivity
3. Recurrent collaterals

Question 24

recurrent collaterals are especially present in the () -> epilepsy due to overactivity in this region is very common

Answer 24

hippocampus

Question 25

well-known example of short-term synaptic plasticity in the NMJ

Answer 25

post-tectanic potentiation (PTP)

Question 26

increased response in PTP is due to ()

Answer 26

accumulation of Ca2+

Question 27

brief stimulation resulting in long-lasting response can explain ()

Answer 27

one time learning

Question 28

the hippocampus consists of 2 thin sheets of neurons folded onto each other

Answer 28

1. dentate gyrus 2. Ammon's horn (cornu Ammonis, CA)

Question 29

the entorhinal cortex (major input to HC) sends info to the dentate gyrus of the HC via a bundle of axons called ()

Answer 29

perforant path

Question 30

dentate gyrus neurons give rise to axons called () that synapse on cells in CA3 (division of Ammon's horn)

Answer 30

mossy fibers

Question 31

one of the branches that stem from CA3 neurons is called () -> synapse on CA1 neurons ## Footnote other branch leaves HC via the fornix

Answer 31

Schaffer collateral ## Footnote where the most sophisticated understanding of LTP was found

Question 32

LTP requires Ca2+ entry via (1); to open these, strong depolarization required to overcome (2)

Answer 32

1. NMDA receptors 2. Mg2+ block ## Footnote NMDA receptor: coincidence detector (molecular switch)

Question 33

property in which only the activ inputs show synpatic plasticity

Answer 33

input specificity

Question 34

LTP induction is blocked by (1) and (2)

Answer 34

1. AP5 (NMDA receptor blocker) 2. EGTA (Ca2+ chelating agent)

Question 35

mechanism of LTP in CA1: increased [Ca2+] activates PKC and CaMKII, which in turn cause (3)

Answer 35

1. phosphorylation of AMPA-Rs -> increased membrane conductance 2. Increased number of AMPA-Rs at terminal 3. Formation of new synapses (via formation of postsynaptic dendritic spines)

Question 36

(): synapses will undergo synaptic weakening instead of LTP when they are active at the same time the postsynaptic cell is only weakly depolarized by other input (1982).

Answer 36

BCM theory

Question 37

Bidirectional plasticity of many cortical synapses governed by two simple rules

Answer 37

– Synaptic transmission during strong depolarization of postsynaptic neuron causes LTP. – Synaptic transmission during weak depolarization of postsynaptic neuron causes LTD.

Question 38

LTP can result when the EPSP caused by synaptic glutamate (excitatory) release precedes an AP in the postsynaptic neuron

Answer 38

spike timing-dependent plasticity

Question 39

# Mechanisms of LTD in CA1 Two forms of controllimg homosynaptic LTD at Schaffer collateral–CA1 synapse

Answer 39

– G-protein coupled metabotropic glutamate receptors (mGluRs) – NMDA receptors

Question 40

Rise in () is necessary to trigger LTD.

Answer 40

postsynaptic [Ca2+]

Question 40

() accounts for bidirectional synaptic changes (up or down)

Answer 40

partial block on NMDA-Rs (modest, prolonged elevation of Ca2+)

Question 41

() in the postsynaptic membrane are continually being added and removed (about every ~15 min)

Answer 41

AMPA receptors

Question 42

determine capacity of postsynaptic membrane for AMPA receptors

Answer 42

slot proteins (PSD-95)

Question 43

recent research suggests that the add'l receptors added to membrane during LTP contain ()

Answer 43

GluR1 subunits

Question 44

First evidence of NMDA receptor-dependent processes in memory

Answer 44

Morris experiments using water maze

Question 45

learning induces () in CA1

Answer 45

LTP

Question 46

Homeostatic mechanisms needed to provide stability and keep synaptic weights within useful dynamic range

Answer 46

1. metaplasticity 2. synaptic scaling

Question 47

Unchecked synaptic plasticity could lead to ()

Answer 47

unstable neuronal responses ## Footnote further strengthening of synapses -> all synapses fully potentiated -> lose stimulus sensitivity0

Question 48

- general idea that the rules of synaptic plasticity change depending on the history of synaptic or cellular activity - Adjustments in composition of NMDA receptors

Answer 48

metaplasticity

Question 49

# metaplasticity () increases in response to too much LTP (increased activity); same logic for too much LTD

Answer 49

synaptic modification threshold

Question 50

metaplasticity adjusts (), which determines the properties of NMDA receptors

Answer 50

NR2A/NR2B ratio (subunits in NMDA receptors) ## Footnote more NR2B = favor LTP more NR2A = favor LTD

Question 51

* adjustment of absolute synaptic effectiveness that preserves the relative distribution of synpatic weights * Relative differences in synaptic strengths on a neuron are unchanged, even at the absolute levels go up or down * Occurs over hours to days

Answer 51

synaptic (homeostatic) scaling

Question 52

Other mechanisms needed for long-term consolidation

Answer 52

- Persistently active protein kinases – Protein synthesis

Question 53

# Persistently Active Protein Kinases: (): large increase in [Ca2+] allows autophosphorylation -> maintains "on" state

Answer 53

CaMKII

Question 54

general idea that the an autophosphorylating inase could store information could store information at the synapse

Answer 54

molecular swtich hypothesis ## Footnote in the context of CaMKII and LTP

Question 55

– “() zaps established memories” – Maintains changes in synaptic strength by continuing to phosphorylate substrates

Answer 55

ZIP (PKM-zeta inhibitor)

Question 56

() required during the period of memory consolidation

Answer 56

New protein synthesis ## Footnote when brain protein synthesis is inhibited, training of task is okay but no memory retention when tested days later

Question 57

# Experiments of Julietta Frey and Richard Morris - Weak stimulation endows synapses with a () - Enables them to capture newly synthesized proteins that consolidate LTP

Answer 57

tag

Question 58

with tag, an event that would otherwise be forgotten might be () if it occurs within 2 hours of a momentous event that triggers a wave of new protein synthesis

Answer 58

seared into long-term memory

Question 59

- Functions to regulate expression of neighboring genes (transcription factor) - regulates gene expression required for memory consolidation (fruit fly).

Answer 59

CREB: cyclic AMP response element binding protein

Question 60

– CREB-2 overexpression: (1) – CREB-1 overexpression: (2)

Answer 60

1. represses gene expression, blocks memory consolidation 2. activates transcription, facilitates memory