CSB332H1 Lecture Notes - Lecture 14: Ion, Second Messenger System, Ligand-Gated Ion Channel
8 Jun 2018
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Lecture 14 (March 17): Synaptic Plasticity and Learning
**N.B. Mechanism of pre-synaptic specialization for exam
Molecular Bases of non-associative learning
Habituation
• Increase in stimulation of pre-synaptic axon – organism repeatedly exposed to a
stimulus many times → decline in response
• Apply high frequency stimulation in pre-synaptic axon → inactivation of voltage-
gated Ca channels
• High frequency AP stimulation → voltage-gated channels switch to inactivated mode
→ - in exocytosis
• Non-Hebbian – mechanism only occurs in pre-synaptic axon, doesn’t involve activity
of post-synaptic neuron
• Habituation ex. - Have to wait a week when rats arrive to allow them to get habituated
to the test room, there’s a type of rat that isn’t able to habituate go crazy
Mechanisms of learning
• Changes in brain associated with consolidation or with depositing of info to short
term memory to long-term
• New info retained → something has to change in synaptic connectivities that mediate
this info
Long-term potentiation
• Medial most part of temporal lobe – during development, interior part folds onto itself
forming the hippocampus – sea horse shape
• Composed of several sub-fields
• Dentate gyrus receives axons formed by perforant fiber pathway, amygdala, pre-
frontal cortex so that info can be inputed here (memory area → memory generated by
emotion, experience, etc makes sense why it receives info from many parts of the
brain)
• Granular cells – sends axons to hippocampus proper, glutamatergic (excitatory)
• Bundle of axons = Schaffer collateral commissural pathway
Recording long-term potentiation in the hippocampus
• Lower electrode into any cell body – examine changes in post-synaptic potentials
• Excitatory post-synaptic potentials from cell bodies of dentate gyrus
• Perforant fiber pathway – generate action potentials that are in low frequencies under
normal conditions
• Lower stimulating electrode near dentate gyrus → mimic lower firing frequency (no
changes)
• High frequency stimulation (+ # of action potentials arriving at pre-synaptic axons) =
TETANIC STIMULATION aka TETANUS
• Compare magnitude of post-synaptic potential before and after tetanic stimulation
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 14 (march 17): synaptic plasticity and learning. Habituation gated ca channels stimulus many times decline in response: apply high frequency stimulation in pre-synaptic axon inactivation of voltage, high frequency ap stimulation voltage-gated channels switch to inactivated mode. Have to wait a week when rats arrive to allow them to get habituated of post-synaptic neuron. Mechanisms of learning: changes in brain associated with consolidation or with depositing of info to short term memory to long-term, new info retained something has to change in synaptic connectivities that mediate this info. Recording long-term potentiation in the hippocampus normal conditions changes: high frequency stimulation (+ # of action potentials arriving at pre-synaptic axons) = Tetanic stimulation aka tetanus: compare magnitude of post-synaptic potential before and after tetanic stimulation. Early phase: not long-lasting aka not genomic. Late phase: longer-lasting because it recruits genomic mechanism, *ca very important intracellular secondary messenger associated with all forms of learning.
