Learning and memory

Question 1

Explain what is short term and long term memory

Answer 1

Short term involves the short-term maintenance of information in memory and sometimes manipulation of that memory to achieve an immediate goal

Longterm can store much larger quantities of information for unlimited duration

Question 2

What are the two types of long term memory

Answer 2

Declarative for facts or events and non-declarative memory (not accessible to consciousness)

Question 3

what is the delayed response task and what does it suggest

Answer 3

1. A monkey was first shown food being placed in a well below one of two identical covers in a table.
   
   2. A delay period followed, during which the animal could not see the table.
   3. Finally, the animal was allowed to see the table again and received the food as a reward if it chose the correct well.

This suggest that frontal lobe is important for learning and memory as prefrontal lesions degraded performance in this task

Question 4

What method can be used to show that prefrontal lobe demonstrated working memory activity

Answer 4

positron emission tomography (PET)

Question 5

What does declarative long term memory depends on (brain structure)

Answer 5

activity in hippocampus and adjacent cortical region within the medial temporal lobe

Question 6

What are the two types of declarative memory

Answer 6

episodic memory for events and semantic for facts

Question 7

what does episodic memory includes

Answer 7

involves memory of events and ability to learn store and retrieve information about personal experience

Question 8

what does semantic

memory includes

Answer 8

• involves the knowledge of facts that have been learned, but of which the source of the original information is typically not known

Question 9

What is anterograde amnesia

Answer 9

○ loss of the ability to create new memories after the event, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.

Question 10

What is non-declarative memory

Answer 10

• involves memories that manifest as subconscious behavioural or physiological responses to events or stimuli

Question 11

Describe classical conditioning

Answer 11

1. The dog’s food is the unconditioned stimulus because no training is required to elicit a response (salivation)
   
   2. The second stimulus is one that does not normally elicit a response (i.e. no salivation) - neutral stimulus
   3. Training consisted of repeatedly pairing the presentation of the meat with the sound of the bell
   4. After many of these pairings, the meat was withheld and the animal salivated to the sound of the bell alone. The dog had learned an association with between the sound (conditioning stimulus) and the presentation of meat (unconditional stimulus)

Question 12

What is spatial memory and how can it be tested

Answer 12

• Form of memory responsible for the recording of information about one’s environment and spatial orientation
can be tested using morris water maze

Question 13

Explain the morris water maze

Answer 13

1. In this test, a rat is placed in a pool filled with cloudy water.
   
   2. Submerged just below the surface in one location is a small platform that allows the rat to escape the water.
   3. When a rat is placed in the water and the first time, it will swim around until it bumps into the hidden platform and will then climb on to it.
   4. Normally, within a few sessions, rats learn the location of the platform using cues external to the tank, i.e. posters on the walls, the door, etc., and on subsequent trials waste no time swimming straight to it.
   5. Rats with a bilateral hippocampal lesion fail to learn the location of the platform.

Question 14

What is Hebbian synapse

Answer 14

synapse that increase in effectiveness because of simultaneous acitivity in pre-synaptic and post-synaptic neurons

Question 15

Describe the different kinds of summation

Answer 15

temporal summation if stimulation repeated within a short interval. Spatial summation if activation by multiple synapses. Spatial summation, inhibitory synapses also contribute to the sum, in the opposite direction: they hyperpolarise the neuron, therefore contrasting the generation of a epsp (d).

Question 16

Describe the structure of hippocampus

Answer 16

• two sheets of 3-layered cortex (the more evolutionarily ancient type, orarchicortex), wrapped around each other
  
  • layout of the cells and their connections is such that slices can be cut and kept in vitro for several hours with the synapses still functioning

Question 17

Describe the pathway in hippocampus

Answer 17

1. The main input into the hippocampus is theperforant pathfrom theentorhinal cortex; these fibres end with a synapse on to the granule cells of thedentate gyrus
   
   2. The axons of the granule cells form themossy fibres
   3. which synapse with the pyramidal neurons ofarea CA3
   4. These in turn send fibres calledSchaeffer collaterals
   5. to the pyramidal neurons ofarea CA1.

Question 18

function of long term potentiation

Answer 18

to produce a long lasting increase in signal transmission between the two neurons recorded in dentate gyrus

Question 19

what is used to induce LTP

Answer 19

○ Burst of high frequency electrical pulses or tetanus
§ Tetanus - brief burst of high frequency electrical impulses, typically at 100Hz for 1 sec to induce LTP in the hippocampus

Question 20

Action of AMPA

Answer 20

they are glutamate receptors and channel for Na+ and when glutamate binds, it opens a channel for Na+ and postsynaptic neuron will depolarise and fire action potentia l

Question 21

action of NMDA

Answer 21

they are glutamate receptors and channels for Na+ and ca2+/. However channels are normally blocked by magnesium ion. When membrane is depolarised, Mg2+ block is lifted and channel open

Question 22

How do NMDA receptors initiate LTP

Answer 22

Presynaptic release of glutamate;

2. Binding of glutamate to AMPA causes post-synaptic depolarisation and release of Mg2+ from NMDA receptors;
3. Activation of NMDA receptors causes Ca2+ to enter the post-synaptic cell;
4. Ca2+ mediated plasticity promotes movement of more AMPA receptors to the post-synaptic membrane;
5. Subsequent stimulation causes an enhanced post-synaptic response.

Question 23

Evidence of LTP in memory

Answer 23

1. The hippocampus and other brain structures key to memory formation also exhibit LTP.
   2. Both LTP and learning require NMDA receptors
      • Richard Morris tested spatial memory of rats by pharmacologically modifying their hippocampus using an NMDA receptor antagonist
   3. Both LTP and learning require CaMK-II
   4. Both LTP and learning require protein synthesis in long term
   5. Number of synapses appear to increase with both LTP and learning

Question 24

Action of calcium in strengthening of synapse

Answer 24

the activation of protein kinase c (PKC) and calcium-calmodulin dependent protein kinase II (CaMK-II) increase the effectiveness of AMPA receptors and promotes the recruitment of new AMPA receptors to the post-synaptic membrane.
• CaMK-II is an autophosphorylating kinase – it phosphorylates itself, thus becoming persistently active.
Phosphorylation increases conductance of the receptors

Question 25

Importance of LTP

Answer 25

• LTP constitutes a good molecular model for the physiological changes occurring in the brain during learning
  
  • key to our understanding of synaptic plasticity
  • Understand on how brain stores information

Question 26

What is habituation

Answer 26

means that after repeated stimulations, the gill response decreases.

Question 27

What is sensitisation

Answer 27

means after administering a strong stimulus to another part of the body resulted in an exaggerated gill withdrawal response to a stimulus that was hardly provoking a reaction

Question 28

What is a possible mechanism for sensitisation

Answer 28

The image on the left shows that the L29 sensory neuron releases serotonin (5-HT); the serotonin receptor on the axon terminal of the siphon sensory neuron has a 5-HT receptor coupled with a G-protein, which in turn activates adenylyl cyclase to produce more cAMP. cAMP activates PKA. The image on the right shows that PKA phosphorylates a K+ channel, blocking it. If you think back to the dynamics of the action potential you will remember that the K+ current is repolarising, therefore blocking the K current prolongs the depolarisation of the terminal. This results in increased calcium entry and increased neurotransmitter release: the synapse has become more responsive to the sensory stimulus.