Outline Overview Methods Results Overview Paper seeks to present a model to explain the many mechanisms behind LTP and LTD in the visual cortex and hippocampus main focus being the implementation of a stochastic model and how it compares to the deterministic model ID: 592232
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Slide1
Effect of Stochastic Synapatic and Dendritic Dynamics on Synaptic Plasticity in the Visual Cortex and Hippocampus Slide2
Outline
- Overview
- Methods
- ResultsSlide3
Overview
Paper seeks to:
- present a model to explain the many mechanisms behind LTP and LTD in the visual cortex and hippocampus
- main focus being the implementation of a stochastic model and how it compares to the deterministic modelSlide4
Methods
Calcium dependent plasticity model
- Shouval et al. 2002
- 5 assumptions listedSlide5
Methods
Assumption 1: Level of [Ca] in synaptic spine determines the signe and magnitude of synaptic plasticity. Slide6
Methods
Assumption 2: Primary Source of calcium influx is through NMDA Receptors.
- double exponential model used to model NMDA current.
- Calcium concentration rate is derived from the NMDA current calculatedSlide7
Methods
Assumption 3: Back Propagating Action Potential (BPAP) contributes to Ca influx
- BPAP - backpropagation spike sent to the dendrites of a firing neuron
- double exponential equationSlide8
Methods
Assumption 4: Short-term Synaptic Plasticity.
- Vesicle release probability
- Synaptic Depression, in visual cortex
- Synaptic Facilitation, in hippocampusSlide9
Methods
Assumption 5: BPAP can also become depressed, recovers exponentially after a spike. Slide10
Methods
Stochastic Implementation
- finite pool of presynaptic vesicles
- modified implementation of Paired-Pulse Depression and Paired-Pulse Facilitation to change release theshhold
- stochastic postsynaptic receptor binding/opening of channels not modelledSlide11
Results
Stochastic vs Deterministic Pulses
- Deterministic model displays
2nd pulse of varying
magnitude
- stochastic model has 2nd
pulse of the same magnitude,
but with less chance of occurringSlide12
Stochastic vs Deterministic (VC)
- p0 = vesicle release
- pF = failure
ResultsSlide13
Results
STDP dependence on frequencySlide14
Results
Hippocampal data
- main difference highlighted in model is synaptic facilitationSlide15
Results
Hippocampal Data, cont.