synaptic plasticity
DESCRIPTION
DENT/OBHS 131 Neuroscience. synaptic plasticity. 2009. Learning objectives. Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/1.jpg)
synaptic plasticity
DENT/OBHS 131Neuroscience
2009
![Page 2: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/2.jpg)
Learning objectives
1. Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity
2. Discuss the characteristics that make NMDA receptors coincident detectors cable of initiating associative information storage (Pavlov’s dog)
3. Describe the relationship between NMDA receptors, LTP and behavioral memory
![Page 3: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/3.jpg)
learning & memory in taxi drivers
PET study during recall of London route
(Maguire et al, 1997)
![Page 4: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/4.jpg)
Papez circuit / loop
![Page 5: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/5.jpg)
place cells / maps
some pyramidal cells in the hippocampus (and other parts of Papez circuit) have preferred spatial orientations & place maps
(O’Keefe & Dostrovsky, 1971)
![Page 6: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/6.jpg)
Hebbian learning….in theory
longer term plasticityHebbian learning
Hebb (1949) hypothesized that “ if one neuron frequently takes part in exciting another, some growth process or metabolic change takes place in one or both cells and the strength of their connection increases ”
![Page 7: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/7.jpg)
muscle
motor neuronpre
post
control
muscle
motor neuron
nmj
Synapses are plastic
synapses “remember” previous activity short-term, e.g. post-tetanic potentiation at the nmj
time
![Page 8: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/8.jpg)
Can synaptic plasticity explain learning?
CS (neutral)- no response
US- UR
After pairing:CS- CR
![Page 9: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/9.jpg)
Learning Objective #1
Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity
![Page 10: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/10.jpg)
![Page 11: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/11.jpg)
Long-term potentiation (LTP)
before after
amplitude
time (hrs)
first demonstration of LTP
high-frequency train
rapid induction lasts weeks in vivo
Bliss & Lomo (1973)
![Page 12: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/12.jpg)
properties of LTP
![Page 13: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/13.jpg)
Learning Objective #2
Discuss the characteristics that make NMDA receptors coincident detectors cable of initiating associative information storage (Pavlov’s dog)
![Page 14: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/14.jpg)
cellular mechanisms underlying LTP
inductionmaintenance
![Page 15: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/15.jpg)
AP5
AP5
control
excitatory synaptic transmission
NMDA vs non-NMDA synaptic transmission
![Page 16: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/16.jpg)
LTP depends specifically on NMDA receptor activation
AP5 prevents high frequency-induced LTP
(Collingridge et al, 1983)
![Page 17: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/17.jpg)
what is special about NMDA receptors?voltage-gated channels: voltageligand-gated channels: transmitterNMDA receptors: both
+ - +
+++
- - -
out
in
Mg+
Mg+
![Page 18: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/18.jpg)
NMDA receptor: a molecular switch
co-incidence detector requires both presynaptic
activity (glutamate) and postsynaptic depolarization (relieve Mg block) satisfies Hebbian co-incidence rules explains LTP properties:
![Page 19: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/19.jpg)
how does the NMDA receptor cause a change in synaptic strength?
![Page 20: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/20.jpg)
synaptic transmission is unreliable
increased transmitter releasealtered or new receptorsnew synapses
![Page 21: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/21.jpg)
Johnson & Wu (1995)
hippocampal “integrated circuit”
![Page 22: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/22.jpg)
associative pattern storage
from McNaughton & Morris (1987)
![Page 23: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/23.jpg)
Learning Objective #3
Describe the relationship between NMDA receptors, LTP and behavioral memory
![Page 24: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/24.jpg)
spatial memory task visual task
“Morris” water maze
Morris et al (1990)
NMDA receptor-dependent learning
![Page 25: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/25.jpg)
LTP decay
Castro et al (1989)
LTP and learning
saturation of LTP prevents learning a new spatial task
new learning can occur after LTP decay
![Page 26: synaptic plasticity](https://reader036.vdocument.in/reader036/viewer/2022081418/56816761550346895ddc37a2/html5/thumbnails/26.jpg)
diffuse storage in cortex?
computational theories e.g., Marr (1970’s)
sensory input to neocortex stored by association repetition - association partial pattern recall