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Biopsych - Learning (Y2) - Coggle Diagram
Biopsych - Learning (Y2)
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Memory acquisition
Sensory experience -> memory acquisition -> short term memory -> memory consolidation -> long term memory
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Memory consolidation
Phosphorylation as a mechanism of consolidation has two problems -
- Phosphorylation of a protein is not permanent - phosphate groups are removed, erasing memory
- Protein molecules are not permanent - memories tied to changes in individuals, proteins would not survive
Persistently active protein kinases -
- Kinases can become independent of the secondary messenger, which may allow the phosphorylation to continue
- CaMKII is required for LTP induction in CA1
-> Two regions of the phosphorylation of substrate proteins in response to Ca2+ - catalytic region responsible for phosphorylation reaction and the regulatory region
-> After LTP, the regulatory region does not fully shut, and this means the kinase can continue to produce phosphorylation reactions
-> Autophosphorlyating protein kinase keeps this hinge open
-> If initial activation is strong, this will occur faster than the process of dephosphorylation to turn it off - this keeps the postsynaptic AMPA receptors phosphorylated, known as the molecular switch hypothesis
Protein Kinase M Zeta -
- Activity of this maintains changes in synaptic strength by continuing to phosphorylate substrates
- mRNA exists for this kinase at synapses but is not normally translated, but strong synaptic activation triggers a burst of synaptic protein synthesis and new molecules
- Prevents degradation of molecules and therefore memories
Protein synthesis and consolidation - synaptic tagging and capture:
- A new wave of protein synthesis triggered by strong stimulation of one synaptic input to a hippocampal neuron consolidates LTP through weak stimulation of the second
- Weak stimulation tags synapses and allows capture of new proteins synthesised to consolidate LTP
Synaptic homoestasis
Synaptic scaling - synaptic effectiveness that preserves the relative distribution of synaptic weights
- Cutting the nerve to a muscle results in denervation supersensitivity, where electrical excitability and sensitivity to ACh increases
- Mechanisms in synaptic scaling -
-> Ca2+ entering the soma through voltage-gated channels and activation of the calcium-calmodulin-dependent kinase IV (CaMKIV) to regulate gene expression - elevated activity increases gene expression, and this results in insertion of glutamate receptors at synapses, making learning easier