Exam 4: Learning and Memory Pt 2 - Plasticity Flashcards
how the brain learns and remembers
plasticity
ability to change both synaptic connections and functional properties of neurons in response to stimuli and experience alters effects on what neurons?
postsynaptic
- changes likelihood of action potentials
Hebb’s Rule
when 2 neurons are repeatedly activated together, their synaptic connection will become stronger
- neurons that fire together, wire together
engrams
memory traces in the brain
synapses that are enhanced by coincident activity between pre and postsynaptic neuron - could act together to store memory traces
hebbian synapses
what are the synaptic changes that underlie simple forms of learning
long-term potentiation (LTP)
what are the 2 types of glutamate receptors in LTP
NMDA and AMPA
NMDA glutamate receptors
ionotropic
- Ca and Na ion channel - when glutamate binds it opens
Mg2+ ion blocks channel pore at rest
AMPA glutamate receptor
ionotropic
- Na ion channel
NMDA receptors - what ejects the Mg from the ion channel to allow glutamate to bind
when the cell becomes depolarized!
Upon glutamate binding to NMDA receptors…
- glutamate stimulation of AMPA receptors depolarizes the membrane, releasing Mg from NMDA receptors
- channel opens and Ca enters
calcium entering cell activates second messenger cascades responsible for…
LTP
the influx in Ca activates intracellular enzymes that cause changes in postsynaptic AMPA receptors: (3)
- existing receptors move to the active synapse
- increased conductance of ions
- more receptors produced
when a postsynaptic cell is strongly stimulated it releases ________ that travels back across the synapse to enter the ________
retrograde transmitter
presynaptic neuron
- if gas no transporter is needed
what does the retrograde transmitter ensure?
more glutamate will be released from the presynaptic neuron and further strengthen the synapse
LTP requires what 2 events
- activation of synapses
- depolarization of the postsynaptic membrane
LTP induced structural changes
- change in size/shape of dendritic spines
(thin to fat) - new dendritic spines
(old spines may form perforated spines or multiple spines)- 2 synapses produced as result
what is LTP necessary for?
long term retention of information
where does LTP occur?
hippocampal formation
- hippocampus, dentate gyrus, CA1-3, hippocampal gyrus (entorhinal cortex, subiculum, parahippocampal gyrus)
during normal activity, glutamate released at synapses in CA1 activates only _____ receptors
AMPA
changes in _____ are responsible for acquisition of a conditioned response also involve LTP
lateral amygdala
AMPA receptors move into the postsynaptic density in response to the learned association between _____ and ______
a tone and footshock
what are AMPA neurons increased between
lateral amygdala neurons and axons that provide auditory input
what do you need to strengthen a response
coactivation of auditory and amygadala
long term depression (LTD)
opposite of LTP
- weakening synapses (decreases efficacy of synapse)
LTD leads to long term _____ in excitability of a neuron to a particular synaptic input
decreases
LTD results from
low frequency stimulation while postsynaptic neuron is hyperpolarized or slightly depolarized
- dec glutamate, dec NMDA activation , dec strength
characteristics of LTD (3)
- dec glutamate release from presynaptic neuron
- NMDA dependent, but diff type than LTP
- removal/dec in number of AMPA receptors on dendritic spines
