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spikes do matter: speed and plasticity” Thomas Trappenberg 1. Generation of spikes 2. Hodgkin-Huxley equation 3. Beyond HH (Wilson model) 4. Compartmental model 5. Integrate-and-fire model 6. Hebbian (asymmetric) learning 7. Population rate models
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”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Jan 05, 2016

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Page 1: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

”When spikes do matter: speed and plasticity”

Thomas Trappenberg

1. Generation of spikes

2. Hodgkin-Huxley equation

3. Beyond HH (Wilson model)

4. Compartmental model

5. Integrate-and-fire model

6. Hebbian (asymmetric) learning

7. Population rate models

Page 2: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Buracas, Zador, DeWeese, Albright, Neuron, 20:959-969 (1998)

Page 3: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Even without much information in spike trains

Spikes do matter !

Even if spikes matter

Rate models are well motivated !

Page 4: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Generation of a spike

Concentration gradient (Nernst equation)

Electrical force

Page 5: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Hodgkin-Huxley equations

Page 6: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Wilson model 1

Equilibrium potential Time constants

Page 7: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Wilson model 2

Na+ leakage and voltage dependent channel

K+ voltage dependent channel with slow dynamic

Ca2+ voltage dependent channel with slow dynamics

K+ dynamic voltage dependent channel (Ca2+ mediated)

Hugh R. Wilson

Simplified Dynamics of Human and Mammalian Neocortical Neurons

J. Theoretical Biology 200: 375-388 (1999)

Page 8: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Compartmental modelling

Neuron (and network) simulators

like NEURON and GENESIS

Cable equations + active channels

Page 9: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Integrate-and-fire neuron (see also spike-response model)

1. Sub-threshold leaky-integrator dynamic

2. Summation of PSPs from synaptic input

3. Firing threshold (spike generation)

4. Reset of membrane potential

Page 10: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

I=8 I=16I=12

Average current-frequency curve (activation,gain,transfer) - function

Page 11: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Poisson input spike trains

Fine-tuning of synaptic weights?

Page 12: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Donald Hebb (1904-1985)

The organization of behavior (1949)

“When an axon of a cell A is near enough to excite cell B or repeatedly or persistently takes part in firing it, some growth or metabolic change takes place in both cells such that A's efficiency, as one of the cells firing B, is

increased.”

Hebbian (asymmetric) learning 1

G.-q. Bi and M.-m. Poo, J. of Neuroscience 18:10464-10472 (1998)

Page 13: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Adapted from Abbott & Nelson, Nature Neuroscience Oct. 2000

Hebbian (asymmetric) learning 2

Page 14: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Hebbian (asymmetric) learning 3

Page 15: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Song & Abbott, Neurocomputing Oct. 2000

Variability control Gain control

Hebbian (asymmetric) learning 4

Page 16: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Van Rossum, Bi, & Turrigiano, J. Neuroscience, Dec. 2000

(Fokker-Planck equation)

Additive vs. Multiplicative rules ?

Hebbian (asymmetric) learning 5

Page 17: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Rate models 1

Page 18: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Rate models 2

1.

2.

3.

4.

• Population of similar neurons (e.g. same input, same time constant, …)

• Independent (e.g. no locking, synchronization, no sigma-pi, …

• Write as integral equation (e.g. use spike response model; see W. Gerstner)

• Mean field theory (e.g. averaging)

• Adiabatic limit (e.g. slow changes)

Page 19: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Rate models 3

Page 20: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Fast processing

Panzeri, Rolls, Battaglia & Lavis, Network: Comput. Neural Syst. 12:423-440 (2001)

Page 21: ”When spikes do matter: speed and plasticity” Thomas Trappenberg 1.Generation of spikes 2.Hodgkin-Huxley equation 3.Beyond HH (Wilson model) 4.Compartmental.

Conclusions

Rate models are now well motivated

Spike models are now well developed

Hebbian plasticity is now better explored

Spikes are important for rapid and robust information processing