Learning and Memory

Question 1

What is learning?

Answer 1

Learning is the acquisition of new knowledge and skills

Question 2

What is memory?

Answer 2

Memory is the retention of learned information.

Question 3

What is short term working memory?

Answer 3

Short term maintenance of information in memory, and manipulation of the memory in order to achieve an immediate goal. It has a strictly limited capacity and duration. eg. remembering a phone number before dialling. Working memory is needed for more complex tasks eg multitasking

Question 4

What is long term memory?

Answer 4

Memory that can store much more information that the short term memory for a potentially infinite term. The two types are declarative and non declarative long term memory

Question 5

Which part of the brain is important in learning and short term memory?

Answer 5

The pre frontal cortex (primates have large frontal lobe and prefrontal cortex is highly developed). Delayed response task in primates proved it (show monkey food under a bowl, hide it, show again). Large prefrontal lesions seriously degrade performance in these tasks.

Question 6

What do recent experiments show that the pre frontal cortex is important for?

Answer 6

Working memory for problem solving and behaviour planning. Also PET scans show activity when identifying faces and spatial location of faces

Question 7

What is declarative long term memory and what are the two types?

Answer 7

Memories of events/facts and are accessible to the consciousness - can be declared. Episodic: recollection of events and experiences. Semantic: stores ideas and concepts not neccessarily drawn from personal experience eg. common knowledge

Question 8

Which regions of the brain are responsible for declarative memory?

Answer 8

Hippocampus and adjacent cortical regions within the medial temporal lobe.

Question 9

What is anterograde amnesia?

Answer 9

Inability to create new memories however long-term memories are not affected. Happened to HM when hippocampus was removed for treatment of epilepsy. Can learn new skills but couldn’t remember facts or events for longer than a few minutes

Question 10

What is non-declarative memory?

Answer 10

Involving memories manifesting as subconscious behavioural/psychological responses to events/stimuli. It includes several forms of learning that occur during performance of a task

Question 11

What are the different kinds of non-declarative memory?

Answer 11

Skills and habits eg. driving, swimming, riding a bike. The memory depends on the striatum (caudate nucleus and putamen), motor areas of cortex, and cerebellum
Emotional memory/ associations - involve a change in behaviour towards a previously neutral stimulus because of an experience. Depends on amygdala
Conditioned reflexes - depend on cerebellum eg. salivating at the sound of a bell

Question 12

What is retrograde amnesia?

Answer 12

The inability to recall information or events acquired before neurological damage/trauma

Question 13

What is classical conditioning?

Answer 13

Involves training - consistently pairing unconditioned and neutral stimulus to build association.
Before training :
Unconditioned stimulus -> unconditioned response. Conditioned stimulus -> nothing.
After training :
Unconditioned stimulus -> Unconditioned response
Conditioned stimulus -> Conditioned response

Question 14

How was the hippocampus confirmed to be linked with spatial memory?

Answer 14

Rats using Morris water maze. The pool of water is cloudy and just below the surface is a platform that allows the rat to escape. The rat swims around and finds the platform to escape. In a few sessions the rat learns to find the platform using external cues ie position of windows posters etc. Mice with bilateral hippocampal lesions can’t.

Question 15

What does consolidating memory mean? Which regions of the brain are responsible?

Answer 15

Consolidation is the moving of short term memories to long term memories. The memories are mostly stored in the region of the brain related to the experience ie. visual memories in the visual cortex etc. This means that particular forms of memories may require multiple regions of the brain to work in concert

Question 16

What is the basis of memory storage as proposed by Ramon y Cajal and built on by Donald Hebb?

Answer 16

The basis of memory storage resides in the strengthening of connections between neurons in certain key memory regions of the brain. Key event is that pre and post synaptic neurons are both stimulated at the same time for potentiation to occur. “Neurons that fire together, wire together”

Question 17

What is a Hebbian synapse?

Answer 17

A synapse that increases in effectiveness because of simultaneous in pre and post synaptic neurons

Question 18

How did Kandel confirm Cajal?

Answer 18

Showed that memory leads to a strengthening of connections between neurons in the brain. Short term memory leads to an increase in synaptic strength. Long term memory leads to a change in gene expression which leads to the formation of new synapses

Question 19

Describe what is meant by age related memory loss

Answer 19

Age of onset is 40s, region of brain affected is the dentate gyrus, and it can be reversible with intellectual exercise and a good diet.

Question 20

Describe what is meant by Alzheimer’s disease

Answer 20

Age of onset is 65-75, region of brain affected is the entorhinal cortex, and it involves proteins that kill synapses

Question 21

Describe the concept of Long Term Potentiation

Answer 21

Delivering a brief high frequency burst of electrical stimulation (a tetanus) to the perforant pathway produced a long lasting increase in the response recorded in the dentate gyrus

Question 22

What is the perforant pathway?

Answer 22

Begins with input from the entorhinal cortex, travels to the dentate gyrus where it travels to CA3 area of hippocampus via mossy fibres (granule cell axons from dentate), travels via Schaffer collaterals (CA3 pyramidal cell fibres), gets to CA1 neuron

Question 23

How is the experiment to test synapse potentiation performed?

Answer 23

Test impulse given every 10s to establish a baseline (amplitude of EPSP), then a tetanus is given (1+ bursts of >100Hz), then the response to test impulses is measured again. The response is increased and the synapse is potentiated

Question 24

Explain the relevance of the NMDA and AMPA receptors in LTP

Answer 24

Weak stimulation of the postsynaptic neuron opens that AMPA ion channel which conducts NA+. When the signal is strong enough, the membrane is sufficiently depolarised to remove the Mg2+ block from the NMDA ion channel, allowing it to conduct Na+ and Ca2+. Ca2+ activates CAM which activates CAMKII which is an autophosphorylating kinase and is permanently on. It phosphorylates the AMPA receptor, increasing its Na+ conductivity and causes intracellular stores of AMPA to go to the membrane. Also causes retrograde signalling to presynaptic neuron to produce more glutamate.

Question 25

Why does the post-synaptic neuron need to be depolarised at the same time as the pre-synaptic neuron releases glutamate?

Answer 25

Because this will produce a strong enough depolarisation in the post-synaptic membrane that will result in the removal of the Mg2+ block in the AMPA receptor. The tetanus will be an experience during memory formation

Question 26

How is long term potentiation maintained?

Answer 26

The number of synaptic spines (post synaptic enlargements helping to transmit AP to rest of neuron) increases as well as their shape to allow for more efficient connections. May also be the mechanism of consolidation (which requires protein synthesis)

Question 27

What is the evidence for LTP?

Answer 27

Rats with NMDA receptor antagonists performed poorly in the Morris maze test, because LTP requires NMDA receptors. Also, rats perform poorly when they are CAMKII KO. When CAMKII is overexpressed their learning is enhanced