Dear all,
I hope you are in staying safe.
I'm working on a balanced network consisting of "iaf_cond_exp" neurone model.
I want to have the control over these parameters at the same time:
- increasing the synaptic decay time.
- reducing the synaptic weight.
The goal is to make the area under the synaptic current, constant. So that we know that the only parameter that is affecting on the network, is synaptic delay.
I wonder if you know of any furmula in mathematics or any algorithm, that can help me, making this process automatic. And keeping the area under the curve, a constant value.
Best wishes,
Nosratullah
Dear Nosratullah,
sorry, can you perhaps rephrase your question? It is unclear what you mean by "make the area under the synaptic current constant".
In networks with conductance based synapses, there is no such thing as *the* synaptic current. For conductance based synapses, the current I_ij(t)=g_ij(t)*(V_i(t)-E_j) at synapse j->i is determined by the membrane potential V_i(t) of the target cell i, which, in turn, is affected by the synaptic currents at all synapses of this neuron (for point neurons). As the membrane potential V_i(t) is strongly fluctuating in balanced networks, the synaptic-current responses I_ij(t) triggered by input spikes from neuron j are different (in shape) for each incoming spike, even if the weight and time constant of the conductance kernel are fixed.
You can of course easily preserve the area
A = \int dt g_ij(t) = w_ij * tau
under the exponential conductance kernel
g_ij(t)=w_ij * exp(-t/tau) * H(t)
(with H(t)=Heaviside function) by compensating a change in its amplitude w_ij ("weight") by the time constant tau = A/w_ij. But this won't make I_ij(t) constant.
Best, Tom
On 06.05.20 11:19, Nosratullah M wrote:
Dear all,
I hope you are in staying safe. I'm working on a balanced network consisting of "iaf_cond_exp" neurone model. I want to have the control over these parameters at the same time:
- increasing the synaptic decay time.
- reducing the synaptic weight.
The goal is to make the area under the synaptic current, constant. So that we know that the only parameter that is affecting on the network, is synaptic delay. I wonder if you know of any furmula in mathematics or any algorithm, that can help me, making this process automatic. And keeping the area under the curve, a constant value.
Best wishes, Nosratullah
NEST Users mailing list -- users@nest-simulator.org To unsubscribe send an email to users-leave@nest-simulator.org
-- --- Dr. Tom Tetzlaff Institute of Neuroscience and Medicine (INM-6) Computational and Systems Neuroscience & Institute for Advanced Simulation (IAS-6) Theoretical Neuroscience Jülich Research Centre and JARA Jülich, Germany
phone: +49-2461-61-85166 (office)
http://www.fz-juelich.de/SharedDocs/Personen/INM/INM-6/EN/Tetzlaff_Tom.html
------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------ Forschungszentrum Juelich GmbH 52425 Juelich Sitz der Gesellschaft: Juelich Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Volker Rieke Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender), Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt ------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------
Dear Tom,
Thanks for the time you spent answering my question and Sorry for not including enough details for the question. I added a figure to describe the question. I’m using ‘oaf_cond_exp’ neuron model in a balanced network. I want to change the synaptic decay time while the area under the conductance curve remain a constant value as it has shown in the figure. Mentioning the synaptic conductance as synaptic current was definitely a mistake.
Regards, Nosratullah Mohammadi
On 07 May 2020 AD, at 00:54, Tom Tetzlaff t.tetzlaff@fz-juelich.de wrote:
Dear Nosratullah,
sorry, can you perhaps rephrase your question? It is unclear what you mean by "make the area under the synaptic current constant".
In networks with conductance based synapses, there is no such thing as *the* synaptic current. For conductance based synapses, the current I_ij(t)=g_ij(t)*(V_i(t)-E_j) at synapse j->i is determined by the membrane potential V_i(t) of the target cell i, which, in turn, is affected by the synaptic currents at all synapses of this neuron (for point neurons). As the membrane potential V_i(t) is strongly fluctuating in balanced networks, the synaptic-current responses I_ij(t) triggered by input spikes from neuron j are different (in shape) for each incoming spike, even if the weight and time constant of the conductance kernel are fixed.
You can of course easily preserve the area
A = \int dt g_ij(t) = w_ij * tau
under the exponential conductance kernel
g_ij(t)=w_ij * exp(-t/tau) * H(t)
(with H(t)=Heaviside function) by compensating a change in its amplitude w_ij ("weight") by the time constant tau = A/w_ij. But this won't make I_ij(t) constant.
Best, Tom
On 06.05.20 11:19, Nosratullah M wrote:
Dear all,
I hope you are in staying safe. I'm working on a balanced network consisting of "iaf_cond_exp" neurone model. I want to have the control over these parameters at the same time:
- increasing the synaptic decay time.
- reducing the synaptic weight.
The goal is to make the area under the synaptic current, constant. So that we know that the only parameter that is affecting on the network, is synaptic delay. I wonder if you know of any furmula in mathematics or any algorithm, that can help me, making this process automatic. And keeping the area under the curve, a constant value.
Best wishes, Nosratullah
NEST Users mailing list -- users@nest-simulator.org To unsubscribe send an email to users-leave@nest-simulator.org
--
Dr. Tom Tetzlaff Institute of Neuroscience and Medicine (INM-6) Computational and Systems Neuroscience & Institute for Advanced Simulation (IAS-6) Theoretical Neuroscience Jülich Research Centre and JARA Jülich, Germany
phone: +49-2461-61-85166 (office)
http://www.fz-juelich.de/SharedDocs/Personen/INM/INM-6/EN/Tetzlaff_Tom.html
Forschungszentrum Juelich GmbH 52425 Juelich Sitz der Gesellschaft: Juelich Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Volker Rieke Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender), Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt
NEST Users mailing list -- users@nest-simulator.org To unsubscribe send an email to users-leave@nest-simulator.org
Dear Nosratullah,
thanks for the clarification. As explained in my last email, preserving the area under the exponential conductance kernel (i.e. the one used in iaf_cond_exp) while changing the time constant is straight forward. Scaling the weight w by the inverse of the synaptic time constant tau will do the job. With
w=A/tau
the integral of w*exp(-t/tau)*H(t) is constant and equal to A.
Best, Tom
On 07.05.20 20:40, nosratullah mohammadi wrote:
Dear Tom,
Thanks for the time you spent answering my question and Sorry for not including enough details for the question. I added a figure to describe the question. I’m using ‘oaf_cond_exp’ neuron model in a balanced network. I want to change the synaptic decay time while the area under the conductance curve remain a constant value as it has shown in the figure. Mentioning the synaptic conductance as synaptic current was definitely a mistake.
Regards, Nosratullah Mohammadi
On 07 May 2020 AD, at 00:54, Tom Tetzlaff <t.tetzlaff@fz-juelich.de mailto:t.tetzlaff@fz-juelich.de> wrote:
Dear Nosratullah,
sorry, can you perhaps rephrase your question? It is unclear what you mean by "make the area under the synaptic current constant".
In networks with conductance based synapses, there is no such thing as *the* synaptic current. For conductance based synapses, the current I_ij(t)=g_ij(t)*(V_i(t)-E_j) at synapse j->i is determined by the membrane potential V_i(t) of the target cell i, which, in turn, is affected by the synaptic currents at all synapses of this neuron (for point neurons). As the membrane potential V_i(t) is strongly fluctuating in balanced networks, the synaptic-current responses I_ij(t) triggered by input spikes from neuron j are different (in shape) for each incoming spike, even if the weight and time constant of the conductance kernel are fixed.
You can of course easily preserve the area
A = \int dt g_ij(t) = w_ij * tau
under the exponential conductance kernel
g_ij(t)=w_ij * exp(-t/tau) * H(t)
(with H(t)=Heaviside function) by compensating a change in its amplitude w_ij ("weight") by the time constant tau = A/w_ij. But this won't make I_ij(t) constant.
Best, Tom
On 06.05.20 11:19, Nosratullah M wrote:
Dear all,
I hope you are in staying safe. I'm working on a balanced network consisting of "iaf_cond_exp" neurone model. I want to have the control over these parameters at the same time:
- increasing the synaptic decay time.
- reducing the synaptic weight.
The goal is to make the area under the synaptic current, constant. So that we know that the only parameter that is affecting on the network, is synaptic delay. I wonder if you know of any furmula in mathematics or any algorithm, that can help me, making this process automatic. And keeping the area under the curve, a constant value.
Best wishes, Nosratullah
NEST Users mailing list -- users@nest-simulator.org mailto:users@nest-simulator.org To unsubscribe send an email to users-leave@nest-simulator.org mailto:users-leave@nest-simulator.org
--
Dr. Tom Tetzlaff Institute of Neuroscience and Medicine (INM-6) Computational and Systems Neuroscience & Institute for Advanced Simulation (IAS-6) Theoretical Neuroscience Jülich Research Centre and JARA Jülich, Germany
phone: +49-2461-61-85166 (office)
http://www.fz-juelich.de/SharedDocs/Personen/INM/INM-6/EN/Tetzlaff_Tom.html
Forschungszentrum Juelich GmbH 52425 Juelich Sitz der Gesellschaft: Juelich Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Volker Rieke Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender), Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt
NEST Users mailing list -- users@nest-simulator.org To unsubscribe send an email to users-leave@nest-simulator.org
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