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Outline

Effect of Stochastic Synapatic and Dendritic Dynamics on Synaptic Plasticity in the Visual Cortex and Hippocampus . 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

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Outline

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  1. Effect of Stochastic Synapatic and Dendritic Dynamics on Synaptic Plasticity in the Visual Cortex and Hippocampus

  2. Outline - Overview - Methods - Results

  3. 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

  4. Methods Calcium dependent plasticity model - Shouval et al. 2002 - 5 assumptions listed

  5. Methods Assumption 1: Level of [Ca] in synaptic spine determines the signe and magnitude of synaptic plasticity.

  6. 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 calculated

  7. 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 equation

  8. Methods Assumption 4: Short-term Synaptic Plasticity. - Vesicle release probability - Synaptic Depression, in visual cortex - Synaptic Facilitation, in hippocampus

  9. Methods Assumption 5: BPAP can also become depressed, recovers exponentially after a spike.

  10. 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 modelled

  11. 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 occurring

  12. Results Stochastic vs Deterministic (VC) - p0 = vesicle release - pF = failure

  13. Results STDP dependence on frequency

  14. Results Hippocampal data - main difference highlighted in model is synaptic facilitation

  15. Results Hippocampal Data, cont.

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