Synaptic refinement

Question 1

Problems with chemospecificity hypothesis

Answer 1

1- If each neuron-neuron connection requires a different molecular recognition molecule then we would need at least 1013 combinations!
2- If all synaptic connections are hard-wired where is the capacity to LEARN?

Question 2

What supports Weiss’s theory

Answer 2

Ocular dominance columns are organised after birth supports the theory as function is learnt

Question 3

What is the molecular basis of learning?

Answer 3

(post synaptic target neuron)
If A and B fire at the same time = synaptic consolidation (more reward from NGF)
If A and B fire independently = synaptic retraction (one is not trained)

Question 4

What are neurotrophins?

Answer 4

Secreted proteins required for neuronal survival

Question 5

Describe neurotrophin action

Answer 5

Transmitter released from presynaptic terminal
Neurotrophin released from postsynaptic element (retrograde signal i.e reward)

So axon terminals that have been recently active are reinforced through PostS NT release