Memory and learning Flashcards
Intrinsic excitability
Number of action potentials a neuron exhibits overtime in response to depolarizing current injections into the neuron.
Synaptic strength
The size of the response in a postsynaptic neuron when a presynaptic neuron has an action potential.
synaptic plasticity
A change in synaptic strength
Changes in intrinsic excitability and synaptic strength can be measured with …
Brain slice recordings
We measure intrinsic excitability by injecting depolarizing current into a neuron and counting …
the number of action potentials it has.
Neuronal excitability is strongly affected by the number of ____ ____ channels on the membrane.
Potassium leak
Neurons with ____fewer/more potassium leak channels are more excitable
Fewer
EPSP (excitatory postsynaptic potentia)
When the postsynaptic response is depolarization
On the presynaptic side, there can be changes in …
The number of vesicles, the filling of vesicles, or the release of vesicles.
On the postsynaptic side, there can be changes in the …
Number of receptors, their sensitivity to neurotransmitters, and their response to neurotransmitter binding.
More neurotransmitter filled ___ on the presynaptic side and more ___ on postsynaptic cause stronger synaptic response.
Vesicles and receptors
Scientists studied the alkyd gill withdrawal reflex and habituation by looking at …
The response of motor neurons to brief puffs of glutamate
Repeated light touches of the siphon _____increases/decreases the magnitude of the gill withdrawal reflex to the point where light touches are ignored. It stops withdrawing its gill.
Decreases
True or false : After habituation, the sensory neuron depolarizes the same amount in response to touch before and after habituation.
True
After habituation, when the sensory neuron spikes, there is a ____smaller/bigger response in the motor neuron.
Smaller
After habituation, on the presynaptic side, there are fewer vesicles (yes/no), less glutamate per vesicle (yes/no). Some vesicles are not being released (yes/no).Fewer vesicles (yes/no)
Yes, no, yes
When a synaptic connection becomes stronger in an enduring manner, the postsynaptic side grows ____ and contains ____ neurotransmitter receptors
Larger and more
Long-term potentiation (LTP)
An enduring (long-term) increase in the connection strength between two neurons (i.e., increased synaptic strength).
LTP an be elicited in reduced preparations (e.g., brain slices) by repeatedly stimulating the inputs to a neuron at a ____low/high -frequency.
High
LTP is often initiated on the ____presynaptic/postsynaptic side (more receptors).
Postsynaptic
The release of retrograde signaling molecules, such as nitric oxide (NO), from ______ membranes triggers complementary changes on the ______ side (e.g., more neurotransmitter released per spike).
Postsynaptic, presynaptic
Long-term depression (LTD)
An enduring (long-term) decrease in the connection strength between two neurons (i.e., decreased synaptic strength).
Repeated ___low/high-frequency stimulation of the inputs to a quiet neuron often causes LTD.
Low
LTD is often initiated on the _____presynaptic/postsynaptic side (fewer receptors).
Postsynaptic
The release of retrograde signaling molecules, such as _______, from postsynaptic membrane triggers complementary changes on the presynaptic side in LTD.
Endocannabinoids
High frequency stimulation (~100 Hz) of afferent inputs often produces LTP. The same number of stimulations at a slower rate (1 Hz) often produces ___.
LTD
LTP and LTD are a function of the number of times the synapse is _____ as well as whether the postsynaptic neuron ____ action potentials at those precise times.
Activated and fired
For LTP to occur, the release of neurotransmitters into the synapse must coincide with a substantial _____hyperpolarization/depolarization of the postsynaptic cell (normally associated with an action potential).
Depolarization
High frequency stimulation of afferent inputs typically causes postsynaptic neurons to ____ (summation of EPSPs)
Spike
Low frequency stimulation is often ______sufficient/insufficient to get postsynaptic neurons to spike
Insufficient
The only synapses we strengthen are the ones releasing _____.
Glutamate
Whether a synapse going to be strengthened or weakened is going to depend on if when the synapse was activated, the postsynaptic cell was also _____ and caused it to spike.
Depolarized
If a cell spikes, what’s going to be strengthened is all the synapses that were ____ when that cell spikes
Active
Glutamate NMDA receptor measures…
The activity of the synapse and the voltage of the postsynaptic cell.
NMDA is a regular _____ glutamate receptor
Ionotropic
What happens when glutamate binds to an NMDA receptor ?
The receptor opens, and positive sodium comes in.
How does the NMDA receptor differ from other ion channels ?
It differs from other ion channels because it’s got a large pore that lets some other ions besides sodium go through, like calcium.
When the NMDA receptor opens, _____ tries to go through and it clogs the pore, which prevents any current flow.
Magnesium
If a molecule of glutamate binds with the NMDA receptor, the calcium channel cannot open because …
The magnesium ion blocks the channel.
he Mg2+ blockade of the NMDA receptor only occurs when the membrane potential of the cell is ______ (< -40mV), like when the cell is at ___.
Hyperpolarized, rest
Calcium (with diffusion ) and sodium can enter the channel when the membrane potential of the cell is slightly ______ (i.e., more positive than -40 mV),
Depolarized
Why is NMDA a coincidence receptor ?
It needs glutamate binding to open, but it also can’t be very hyperpolarized or magnesium will block it.
NMDA receptors play a large role in ____ and memory.
Learning
NMDA receptors are permeable to Na+ and Ca2+ ions, but only when these 2 conditions are met :
- Glutamate is bound to the receptor
- Mg2+ is not clogging the pore (when slightly depolarized membrane potential)
AMPA receptor
The ionotropic glutamate receptor that mediates most of the fast excitatory synaptic currents in the brain. It lets in sodium ions when open, causing EPSPs (excitatory postsynaptic potentials) and membrane depolarization. Most glutamate synapses in the brain contain AMPA and NMDA receptors.
Open, unblocked NMDA receptors are permeable to _____ and _____ ions.
Sodium and calcium
CaMKII
Type II calcium-calmodulin kinase. It is an enzyme that is activated by calcium influx through NMDA receptors.
CaMKII participates in the intracellular signaling cascade that establishes long-term potentiation at glutamate synapses, by increasing the number of ____NMDA/AMPA glutamate receptors in the postsynaptic membrane.
AMPA
For glutamatergic synapses that form on dendritic spines, the strength of the synaptic connection correlates with the ___ of the spine and the number of ____ receptors in it.
Size and AMPA
The size of many spines is constantly fluxed during the day, but some spines are ____
Stable
The learning in association learning is done through more ___AMPA/NMDA receptors
AMPA
Associative long-term potentiation
The increase in synaptic strength that occurs in weak synapses that happen to be active when stronger inputs get the postsynaptic neuron to spike.
Hebb’s rule
Hypothesis proposed by Donald Hebb: The cellular basis of learning involves the strengthening of synaptic connections that happen to be active when the postsynaptic neuron fires an action potential. “Fire together, wire together”
The hippocampus is essential for long term ____ memory and learning.
Conscious
If you strengthen a synaptic connection because it was always active when a cell was spiking, we weaken it by making it always _____ when the cell’s not spiking.
Active
When one synapse gets strong, it maintains its strength by being active when other strong synapses are ____too.
Active
The amount of ____ through the NMDA receptor will determine whether a synapse is useful in association learning
Calcium
