neurons
Information is represented in connections between _____
ex: Faces are represented by the activity of sets of neurons in the fusiform gyrus (in inferior temporal lobe).
Seeing a familiar face causes reactivation of the same network of neurons that were act
fusiform
Faces are represented by the activity of sets of neurons in the______ gyrus (in inferior temporal lobe).
Seeing a familiar face causes reactivation of the same network of neurons that were active when the face was first seen
Hebb's Law
neurons that fire together, wire together
The more often neuron A stimulates a connected neuron B that immediately fires, the more efficient A becomes at stimulating B.
plastic
A synapse is _____ if it can change the strength with which it affects its neural target.
presynaptic, postsynaptic
Changes in synapse can be:
______(increased neurotransmitter release)
_______(effectiveness of receptors)
or both
more nt release cause more receptors
info
Structural changes at the synapse may provide long-term storage.
New synapses could form, or some could be eliminated with training.
Training might also lead to synaptic reorganization.
Glutamate
Take a neuron that has both NMDA and AMPA receptors.
______ first activates AMPA receptors.
NMDA receptors do not respond until enough AMPA receptors are stimulated and the neuron is partially depolarised.
NMDA receptors at rest have a magnesium ion (Mg2+
Mg
NMDA receptor inactive because of block by ___ ion
...
The large Ca++ influx activates certain protein kinases - enzymes that catalyze phosphorylation.
CaM =calmodulin - activates CaM Kinase
CaMK affects AMPA receptors:
Phosphorylates (activates) receptors in dendritic spines
Moves receptors from the interior
kinases
Add a phosphate group to a molecule
Enzymes that catalyze the transfer of phosphate groups from ATP to acceptor molecules.
info2
Calcium ions are extremely important intracellular messengers that activate many enzymes by altering their conformation.
One of these enzymes is calmoduline (CaM), which becomes active when four calcium ions bind to it.
It then becomes Ca2+/calmodulin, th
info 3
The activated protein kinases also trigger protein synthesis.
Kinases phosphorylate and activate the transcription factor cAMP Responsive Element-binding Protein (CREB).
CREB binds to cAMP responsive elements in DNA promoter regions.
CREB changes the tran
phosphorylation
Addition of a phosphate group.
The transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.
cAMP
CREB binds to ____ responsive elements in DNA promoter regions.
CREB
changes the transcription rate of genes.
a transcription factor that causes the manufacturing of more receptors.
CaMK
_______ is one of the few enzymes NECESSARY for modulating long-term synaptic changes.
activated by calmodulin
Phosphorylation of target protein
...
Activated adenylate cyclase manufactures cyclic adenosine mono-phosphate (cAMP), which in turn catalyzes the activity of another protein, kinase A (or PKA).
In other words, there is a typical cascade of biochemical reactions which can have many different
CaM kinase II
has a unique mechanism of activation that allows its activity to persist even after the transient calcium signal has faded.
other enzyme activated by Ca2+/calmodulin, has a property that is decisive for the persistence of LTP: it can phosphorylate itself!
Long-term potentiation
a stable and enduring increase in the effectiveness of synapses
Synapses behave like Hebbian synapses:
Tetanus drives repeated firing
Postsynaptic targets fire repeatedly due to the stimulation
Synapses are stronger than before
Tetanus
a brief increase of electrical stimulation that triggers thousands of axon potentials
After tetanus, EPSPs remain high.
(excitatory postsynaptic potential)
EPSP
excitatory postsynaptic potential
A temporary depolarization of the postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell
retrograde
Induction of LTP activates a _______ signal for the presynaptic neuron to release more transmitter.
the ability of the post-synaptic neuron to affect the pre-synaptic neuron by sending ________ messengers such nitric oxide or arachidonic acid to the pre-s
summary
Activation of NMDA receptor introduces Ca++, which binds with calmodulin (CaM) to CaMKII.
CaMKII phosphorylates GluR1&4 subunits of AMPA receptor to increase its channel conductance.
CaMKII leads to the insertion of AMPA receptors into the postsynaptic me
summary 2
Stimulation triggers transcription of immediate early genes (e.g. CREB, zif268) by
(a) proteins transported from synapse to nucleus
or (b) back-propagated spikes.
CREB binds to the cAMP-dependent response element (CRE) in the promoter region of responsive
protein synthesis
The formation of LTM requires _____ _____
It occurs in two waves - about 1 hour after training, and at about 5 to 8 hours after training.
Inhibitors of protein synthesis at these stages prevent LTM formation.
info 4
what does it mean strengthening a synapse?
Making the synaptic connections become more effective
How?
The effect of the pre-synaptic neuron on the postsynaptic neuron increases (post-synaptic potentials)
Increased probability of the post-synaptic neuron t
NO
More glutamate release (pre-synaptic change
___ gas flows back to the pre-synaptic neuron (retrograde messenger)
Depends on Ca2+ (by CAMKII) and other second messengers
Perforated synapses
the production of new synapses
Structural changes in dendritic spines
Early LTP (several hours)
Early LTP (several hours)
More AMPA receptors (post-synaptic change)
Ca2+ activates CaMKII (a protein kinase - enzyme that catalyzes phosphorylation)
CaMKII affects AMPA receptors:
Phosphorylates receptors in dendritic spines
Moves receptors from the inte
Long-lasting LTP (more than several hours)
Long-lasting LTP (more than several hours)
Protein synthesis
Chemical messengers go to the nucleus and activate genes that code for the proteins needed to build receptors Maintenance of memory for a long time