Lecture 5

Question 1

What is learning?

Answer 1

Strengthening of responses or formation of new responses to stimuli due to repetition or practice

Question 2

What is non-declarative or implicit learning and memory?

Answer 2

Knowledge about how to perform something

Implicit learning and memory can be associative or non-associative

Question 2

What is memory?

Answer 2

Storage and retrieval of knowledge gained through learning

Question 2

What are the two forms of non-associative learning and memory

Answer 2

Habituation - Decrease in response to a benign stimulus through repeated presentation of the stimulus

Sensitisation - Enhanced response to multiple different stimuli after presentation with a noxious or intense stimulus

Question 2

What is declarative or explicit learning and memory?

Answer 2

knowledge about facts or their meaning

Question 3

Associative learning and memory

Answer 3

• Association between two stimuli learned

Classical conditioning: Pavlov’s paradigm
Food is unconditioned stimulus
Bell is conditioned stimulus

When bell us paired with food, the bell becomes able to elicit salivation, and is now the conditioned response

Question 4

What do invertebrate neuromodulation studies indicate?

Answer 4

Forms of implicit memory involve experience-dependent modulation of synaptic strength and structure.

Question 5

Short term memory

Answer 5

Lasts minutes

Involves covalent modifications of pre-existing proteins at synapse by kinases

Question 6

Intermediate term memory

Answer 6

Last minutes

New protein synthesis (not mRNA synthesis)

Question 7

Long term memory

Answer 7

Last days, weeks, or longer

Requires CREB-mediated gene expression

Also requires new mRNA and protein synthesis

Question 8

Neuromodulation in Aplysia

Answer 8

Natural predator is spiny lobster

Respond to attack by closing gill and syphon, ejects ink containing chemicals that confuse and repel lobsters - behaviour controlled by simple reflex circuit

Following an attack, sea snail sensitized to future attacks

Sensitization to attack involves modulation of synapses at sensory neurons

Question 9

Aplysia nervous system

Answer 9

20,000 large, identifiable nerve cells

Individual neurons identified and electrical activity recorded

Neural circuits controlling behaviour have been identified

Behaviour most extensively studied is gill and syphon-withdrawal reflex

Answer 10

Tacticle stimulus on siphon activates sensory neuron 1

Question 11

Cellular mechanisms of short and intermediate term memory formation in Aplysia

Answer 11

1. Serotonin released in vivo or applied to cultured neurons - binds to cell surface receptors of sensory neurons
2. Binding activates adenyl cyclase - Promotes cAMP production
3. Increased cAMP leads to shirt term sensitisation - Increased synaptic strength of sensory to motor neuron connection (short term facilitation)
4. Short term facilitation is partially due to enhanced glutamate release
5. Short term facilitation accompanied by an increase in neuron excitability due to certain K+ channel depression
6. Changes in cAMP and Ca levels regulate activity of kinases and phosphatases - Controls duration and strength of synpatic efficiency changes

Question 12

What molecules are involved in short and intermediate-term synaptic plasticity in Aplysia

Answer 12

Presynaptic PKA

Presynaptic calcium and CamKII

Presynaptic PKA

Postsynaptic calcium and CamKII

Recruitment of pre- and possibly postsynaptic molecules to new sites

Results in enhanced neurotransmitter release from sensory neurons

Question 13

Cellular mechanism in long-term memory formation in Aplysia

Answer 13

• Neurotransmitter release and short-term strengthening of synaptic connections
• Equilibrium between kinase and phosphatase activities at synapse
• Retrograde transport from synapse to nucleus
• Activation of nuclear transcription factors
• Activity-dependent induction of gene expression

Question 14

Cellular mechanisms of long-term memory formation in Aplysia

Answer 14

chromatin alteration and epigenetic changes in gene expression

synaptic capture of newly synthesized gene products

local protein synthesis at active synapses

synaptic growth and the formation of new synapses

activation of pre-existing silent synapses

The location of these events moves from the synapse to the nucleus and then back to the synapse.

Question 15

Classical (associative) olfactory learning and memory in Drosophila

Answer 15

• Learning contingency between odor and an aversive or appetitive stimulus
• Requires activity of molecules that can integrate 2 types of sensory information
• Form of adenyl cyclase performs integration function in mushroom body neurons of fly brain
• Dopaminergic neurons carry info about aversive stimuli and octopaminergic neurons about appetitive stimuli to MB neurons
• GABAergic neurons control ability to learn via inhibitory inputs