Flashcards in Plasticity Deck (25):
What is functional decomposition?
Determining which functions a system needs to have and then integrating them in such a way as to produce a desired result.
How was the synapse postulated?
It was postulated by Charles Sherrington based on the fact that reflexes took longer than they should based on the known nerve conduction speeds at the time.
How does myleination affect membrane capacitance? Leakage?
Myleination decreases membrane capacitance, allowing for faster conduction speeds. It also prevents leakage, improving the axon's length constant.
What is the axon's length constant?
The axons length constant is the time it takes for the initial injected current to reduce to 37% of its initial value by passive current flow alone.
What are dendritic spines?
These are typically sites for excitatory synapses.
How was aplysia typically studied (in what form)?
As a semi-intact preparation, with most of the flesh cut away but the nerves and gills and sensory receptors still intact.
What does the change in EPSP amplitude in aplysia mainly come from?
Increased neurotransmitter release at the presynaptic terminal.
Where does the mechanism for aplysia's sensitization occur?
The PKA and everything is in the sensory neuron, which ultimately causes the action potentials of the sensory neuron to become longer.
How do you make sure aplysia is sensitized for more than a few minutes or hours?
You give it the same stimuli pair multiple times within a short timeframe.
What molecules does the NMDA receptor let in?
All positive ions (K+, Na+, Ca2+), but for its LTP features Ca2+ influx appears to be particularly important.
What is "caged glutamate" and how was it used?
This molecule is glutamate that is initially unusable (in a cage), but this cage can be opened by a laser to allow for the glutamate to be use. Caged glutamate was used to show that dendritic spines can physically grow by selectively releasing it at the spines.
How do we know proteins are synthesized at dendrites?
Because dendrites have some free ribosomes near them.
How do we know dendritic protein synthesis is important for LTP?
Because when dendritic protein synthesis is blocked, LTP is not stabilized. These proteins are likely CaMKII and activity-related cytoskeletal protein (ARC).
When is more Arc protein produced?
Arc transcription is upregulated in the nucleus after a period of increased neuronal activity.
How do we know Arc is necessary for LTP?
Blocking Arc synthesis hinders LTP stabilization.
What does zeta inhibitory peptide do? How?
When applied to synapses after LTP has induced, it erases the potentiation. It may do this by interfering with protein kinase M zeta (PKM-zeta), an anzyme that enhances synaptic transmission through AMPA receptors.
Is PKM-zeta necessary for LTP?
No, knockout mice for PKM-zeta still are capable of LTP and still have many forms of learning.
How are epigenetic changes involved in LTP?
Drugs that prevent de-acetylation of histones can convert induced LTP into stabilized LTP and make some memories more persistent.
Do cerebellar granule cell parallel fibers contain NMDA receptors?
No, but they do contain metabatrobic glutamate receptors that involve IP3 and the subsequent release of Ca2+ ions from intracellular stores, which activates protein kinase C, which can remove AMPA receptors.
How do we know neuronal scaling can happen?
In cells cultured in TTX, the EPSCs (excitatory post-synaptic currents) were higher than control neurons, and in cells cultured in bicuculine, EPSCs were lower. This probably involves the insertion or removal of AMPA receptors.
How does dendritic spine turnover relate to learning?
The capacity for learning appears to relate to a high degree of dendritic spine turnover, while the act of learning stabilizes these spines to turn over less.
Can axons sprout new collaterals in the adult brain? How do we know?
Yes, because an experiment done with air puffs and mice involved the sprouting of new axon branches that terminated in the deep cerebellar nuclei from neurons in the pons.
What are varicosities?
Likely sites of axonal neurotransmitter release.
How does acetylcholine relate to plasticity?
In the mouse auditory cortex, acetylcholine release paired with stimulus presentation is sufficient to generate plasticity.