CSB332H1 Lecture Notes - Lecture 13: Synaptic Plasticity, Temporal Lobe, Episodic Memory

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Published on 11 Aug 2012
School
UTSG
Department
Cell and Systems Biology
Course
CSB332H1
CSB332H1S L13/14; Feb. 27, 2012
Synaptic Plasticity & Learning and Memory
Synaptic Modifications in Cultured Hippocampal Neurons: Dependence on
Spike Timing, Synaptic Strength, and Postsynaptic Cell Type
The Journal of Neuroscience, December 15, 1998, 18(24):10464-
10472
Guo-qiang Bi and Mu-ming Poo
Spike-Timing Dependent Synaptic Plasticity (STDP)
Instead of inducing LTP w high-freq presynaptic stimulation, spike-
timing protocols use lower-freqs w paired pre- & postsynaptic activity
(+)ve spike-timing interval: EPSP arrives before postsynaptic AP is
fired
(-)ve spike-timing interval: EPSP arrives after postsynaptic AP is fired
Pair pre & postsynaptic act pots during induction
Decide ahead of time what protocol to use, can choose from 2
intervals:
Positive spike-timing intervals induce LTP
o Pair Pre & Post activity
o (pair EPSPs w postsynaptic Act Pot)
o Regulate timing interval, uses dif ones
Negative spike timing intervals induce LTD
o Reverse order of pairing, Post then Pre
o Can get another act pot during repolarization phase
LTP & LTD can also be
induced by low freq (1-10Hz)
coincident pre- & postsynaptic
activity
B: want to assess strength of
synapse on own, at low freq,
record for about 15min,
dotted line = avg current
amplitude (30pico amps)
o (+)ve spike timing
interval, 5-10-15ms
interval
o On avg, all pts now
above baseline, so
induced LTP
C: avg of many expts, overall
have increase in current
amplitude
o Have no change w
control
Bi & Poo 1998
STDP w (-)ve spike-timing
intervals induces LT
Post then Pre, same timing,
about 10ms interval
Get decrease in amplitude
(LTD)
Summary figure:
Critical window for induction of
synaptic potentiation & depression.
%age change in EPSC
amplitude at 20-30 min
after repetitive
coincident spiking (60
pulses at 1 Hz) plotted
against spike timing.
Spike timing defined by
time interval (t) btwn
onset of EPSP & peak of
postsynaptic act pot
during each cycle of
repetitive stimulation, as
illustrated by the traces
above.
Spiking-timing windows importance of timing in dif brain structures
Each expt like before is summarized as one data pt
Ex. -10ms: Post then Pre 20% decrease in amplitude
Asymmetry sits right at 0 pt of spike-timing interval
o So if induce btwn 0 & 20ms on avg increase synapse strength;
but if reverse pairing depression
o So can get LTP & LTD w same freq of act pots but what matters is
if Pre is before Post
o So Hebb is right, when Cell A fires (+)ve EPSP repeatedly at Cell B
(to summate) LTP
Can use for glutaminergic & gaba-ergic synapses w computations to
predict brain reaction
o Can also use for artificial intelligence & prosthetics; ex. cochlear
implants
LTP induction: similar mech as titanic induction, difference is how we
get the membrane depolarization
o Now the postsynaptic act pot removes the Mg block
LTD induction: Ca influx much lower, dif signal cascade that
dephosphorylates AMPARs
The Woman Who Could Not Forget (not required)
http://www.youtube.com/watch?v=SoxsMMV538U&feature=related
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Document Summary

Synaptic modifications in cultured hippocampal neurons: dependence on. Spike timing, synaptic strength, and postsynaptic cell type. The journal of neuroscience, december 15, 1998, 18(24):10464- Instead of inducing ltp w high-freq presynaptic stimulation, spike- timing protocols use lower-freqs w paired pre- & postsynaptic activity (+)ve spike-timing interval: epsp arrives before postsynaptic ap is fired (-)ve spike-timing interval: epsp arrives after postsynaptic ap is fired. Pair pre & postsynaptic act pots during induction. Decide ahead of time what protocol to use, can choose from 2 intervals: Positive spike-timing intervals induce ltp: pair pre & post activity, regulate timing interval, uses dif ones. Negative spike timing intervals induce ltd (pair epsps w postsynaptic act pot: reverse order of pairing, post then pre, can get another act pot during repolarization phase. Post then pre, same timing, about 10ms interval. Critical window for induction of synaptic potentiation & depression.

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