The cellular basis of learning and memory

Question 1

Difference between STM and Working memory

Answer 1

Working memory emphasises a wider role in cognition (reasoning, comprehension etc.) whereas STM is often taken to imply a more impassive retention of material

Question 2

Modal Model Atkinson and Shiffrin

Answer 2

• One of most influential models of STM
• Divides memory into very short lived sensory registers
• Did not regard their short term store as a phonological system but rather a control system similar to baddley
• In this model information can only get into the long term memory and out of it via the short term memory
• Empirical evidence does not support this
• First neurological patients with reduced digit spans are capable of long term learning
• Patients with limited digit spans to one item are capable of learning and retaining lists of words and learning paired associates
• Second frequent exposure to a stimulus in short term memory is not sufficient to learning e.g. participants are very bad at recalling coins they see many times a day
• Although model incorrect STM is indeed important for LTM

Question 3

Declarative Memory

Answer 3

Memories that can be consciously accessed

Question 4

Non- declarative memory

Answer 4

Memories that can’t be consciously accessed (e.g. procedural memory)

Question 5

Procedural Memory

Answer 5

Refers to memory for skills such as riding a bike. It is not consciously accessible in sense that the contents of the memory are not amendable to report. Evidence suggests that basal ganglia are important for the learning of procedural skills and habits.

Question 6

Korsakoff’s Syndrome

Answer 6

Amnesia from long-term alcoholism

Question 7

Episodic Memory

Answer 7

-Amnesic patients impaired on tests of episodic memory for events on their own life and other types of episode (learning list of words)

Question 8

Wechsler Memory Scale

Answer 8

Contains tests of recall and recognition for verbal and visual material

Question 9

Amnesia

Answer 9

Is clinically defined as poor performance on memory tests relative to that expected based on their IQ scores

Question 10

Environmental Stimuli

Answer 10

Environmental enrichment: the brain grows and changes as a consequence of the environment. (e.g. Bennett et al, 1964; Rosenzweig et al, 1961,1984)

These kinds of evidence suggest that long-term changes in brain structure occur as a result of experience

But, where are memories stored and what are the mechanisms underlying memory formation?

Question 11

Non-associative learning

Answer 11

Non-associative learning – changes over time in the response to a single (repeated) stimulus

Question 12

Associative learning

Answer 12

Associative learning – learning about connections or relationships between events
Associative learning involves relations between events.In classical conditioning – Pavlovian conditioning – a neutral stimulus is paired with another stimulus that elicits a response.
Eventually the neutral stimulus by itself will elicit the response.
Classical Conditioning is a form of associative learning where an association is learned between two previously unrelated stimuli
Operant Conditioning is a form of associative learning where an association is learned between an action and its consequences

Question 13

1) Associative learning: HABITUATION

Answer 13

Habituation – a decreased response to repeated presentations of a stimulus.

Question 14

2) Associative learning

Answer 14

Sensitization – prior strong stimulation increases response to most stimuli.

Question 15

Non-associative learning in Aplysia California

Answer 15

The sea-slug shows a gill withdrawal response when water is squirted at its syphon

Repeated stimulation leads to a decrease in the size of the response
HABITUATION

A small shock to the tail enhances the size of the response to subsequent water squirts
SENSITISATION

Question 16

Engrams

Answer 16

Engrams are distributed throughout the brain i.e. engrams as a property of networks of neurons
Engrams might be distributed according to knowledge domains

Question 17

Storing Information in the Nervous System of Aplysia: Habituation

Answer 17

Results in a change in the synapse between the sensory neurons and the motor neurons.
Sensory neurons fail to excite motor neurons as they did previously.

Question 18

Storing Information in the Nervous System of Aplysia: Sensitisation

Answer 18

Changes at identified synapses include:
Serotonin released from a facilitating neuron blocks potassium channels in a presynaptic neuron.
Prolonged release of 
transmitter from that 
neuron results in prolonged 
sensitization.

Question 19

The synapse as potential mechanism of memory storage

Answer 19

Hebb: Let us assume that the persistence or repetition of a reverberatory activity (or “trace”) tends to induce lasting cellular changes that add to its stability.… When an axon of cell A is near enough to excite a cell 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.
“cells that fire together wire together”
Cell assemblies - ensembles of neurons - linked via Hebbian synapses could store memory traces.

Question 20

Hebbian Synapse

Answer 20

A Hebbian synapse occurs when the successful stimulation of a cell by an axon leads to the enhanced ability to stimulate that cell in the future.
Increases in effectiveness occur because of simultaneous activity in the presynaptic and postsynaptic neurons.
Such synapses may be critical for many kinds of associative learning.

Question 21

Studying how synaptic events underlie more complex learning in vertebrates

Answer 21

Bliss & Lomo (1973) demonstrate Long-term Potentiation (LTP) in the rabbit hippocampus
occurs when one or more axons bombard a dendrite with stimulation (tetanus stimulation).
Leaves the synapse “potentiated” for a period of time and the neuron is more responsive.

Question 22

Specificity

Answer 22

Specificity

only synapses of a cell that have been highly active become strengthened

Question 23

Associativity

Answer 23

Associativity – pairing a weak input with a strong input enhances later responses to a weak input.

Question 24

Storing info at the synapse: Long-term potentiation LTP

Answer 24

Long-term potentiation (LTP) is an activitivity dependent enhancement of synaptic efficacy

Question 25

Storing info at the synapse: Long-term depression LTD

Answer 25

Long-term depression (LTD) is a prolonged decrease in response at a synapse that occurs when axons have been active at a low frequency.
The opposite of LTP

Question 26

LTP (Long term potentiation) in hippocampal neurons occurs as follows:

Answer 26

Repeated glutamate excitation of AMPA receptors depolarizes the membrane.
The depolarization removes magnesium ions that had been blocking NMDA receptors. (NMDA receptor is action is voltage-dependent)
Glutamate is then able to excite the NMDA receptors, opening a channel for calcium ions to enter the neuron.
NOTE that the requirement for both glutaminergic binding at the receptor (i.e. receptor release at the pre-synaptic cell) and depolarisation of the postsynaptic cell (to remove Mg2+ block) lead to specificity

Question 27

Mechanisms of LTP

Answer 27

Entry of calcium through the NMDA channel triggers further changes.
Activation of a protein that sets in motion a series of events occurs.
More AMPA receptors are built and dendritic branching is increased.
These changes increase the later responsiveness of the dendrite to incoming glutamate.

Question 28

Storing Information in the Nervous System

Answer 28

Changes in presynaptic neuron can also cause LTP.
Extensive stimulation of a postsynaptic cell causes the release of a retrograde messenger transmitter that travels back to the presynaptic cell to cause the following changes:
Decrease in action potential threshold
Increase neurotransmitter release of
Expansion of the axons.
Transmitter release from additional sites.

Question 29

Procedural and perceptual (implicit) memory

Answer 29

When given tasks that require visuomotor coordination (drawing around a shape when hand is viewed in mirror) , usually done poorly but improves with practice.
True with amnesia patients thus procedural memory appears to be spared

Question 30

Semantic Memory in Amnesia

Answer 30

At first they appear to retain knowledge of vocab and the world- evidence that semantic memory is intact
Critical at what age information was acquired
Most semantic knowledge learned at first few years of life

Question 31

Consolidation

Answer 31

The process by which moment to moment changes in brain activity are translated into permanent structural changes in the brain

Question 32

Role of prefrontal cortex in LTM

Answer 32

• Traditionally viewed as having a controlling and organising role in relation to cognition rather than storage roll

Question 33

Ventrolateral Prefrontal Region

Answer 33

• Region often activated during memory encoding
• Activated during incidental learning (situations where individuals don’t realise will be tested later)
• Activity in this region predicts subsequent remembering versus forgetting

Question 34

Dorsolateral prefrontal region

Answer 34

• Particularly on the left hemisphere has been associated with selecting from a range of alternatives and is by no means specific to memory tasks
• More widely recognised for playing a role in memory retrieval