Hi, Weights are properties of connections (synapses), so you'd set these (e.g. in your Python script) using something like: nest.Connect(spikegenerator, neuron, syn_spec={'weight': 1e3}) This value is then stored in the C++ synapse instance, for example in the static synapse: https://github.com/nest/nest-simulator/blob/2869b6364ccd85edf69246deb12c03c… The neuron obtains the weight from a SpikeEvent from its incoming connection by calling get_weight() on the event here, as you pointed out: https://github.com/nest/nest-simulator/blob/2869b6364ccd85edf69246deb12c03c… The other multiplicative factor, multiplicity, is there to support the possibility for more than one spike to occur at the exact same time; typically this will just be equal to 1. Your understanding of the handle(SpikeEvent&) function is correct; for more documentation about how the buffer works, see the API comments in `nestkernel/ring_buffer.h`. The iaf neuron with alpha synapse is typically theoretically described as a differential equation, but for this particular neuron+synapse combination, there is an easy analytic solution of the differential equation. This means that we don't need a numerical integrator (like GSL provides), but that we can compute the solution directly, which is more efficient and precise. See the references at the bottom of the iaf_psc_alpha model documentation (in the .h file), especially https://doi.org/10.1007/s004220050570 With kind regards, Charl On Wed, Dec 30, 2020, at 13:26, enguang zhou wrote: > Dear Charl, > Thank for your answer. And I am also confused about the code on lines > 345-346, at > https://github.com/nest/nest-simulator/blob/2869b6364ccd85edf69246deb12c03c…. > The line 345 says 'V_.weighted_spikes_ex_ = B_.ex_spikes_.get_value( > lag );', and does that means V_weighted_spikes_ex_ is the weight I set? > > Except the last question, I also want to confirm whether I understand > right to those code on lines 380-395(showed below), which is a handle > invoked by spike event. First, the get_weight() will get the weight I > set, multiplied by something(I don't know what it is, If you can > answer that will be better ). Second the 's' variable will be stored in > buffer by add_value() . Third when execute the code on 345 line(showed > above) of update(), the get_value() will read out the 's' stored by > add_value(). Fourth, does there a differential equation describing the > membrane potential for the iaf_psc_alpha model? I know there are > several neurons have differential equation such as gif_cond_exp > neuron, this is at , > > https://nest-simulator.readthedocs.io/en/nest-2.20.1/models/neurons.html?hi… > > iaf_psc_alpha::handle( SpikeEvent& e ) > { > assert( e.get_delay_steps() > 0 ); > > const double s = e.get_weight() * e.get_multiplicity(); > > if ( e.get_weight() > 0.0 ) > { > B_.ex_spikes_.add_value( e.get_rel_delivery_steps( > kernel().simulation_manager.get_slice_origin() ), s ); > } > else > { > B_.in_spikes_.add_value( e.get_rel_delivery_steps( > kernel().simulation_manager.get_slice_origin() ), s ); > } > } > Thank you again and expect answers from you and anyone else. > Best regards, > Enguang > _______________________________________________ > NEST Users mailing list -- users(a)nest-simulator.org > To unsubscribe send an email to users-leave(a)nest-simulator.org >

Hi Charl, I have a very big problem now again for the iaf neuron(such as iaf_psc_alpha), if I don't know know differential equation for the neuron model, how can I get the derivative about some variable, such as derivative of voltage versus weight. The point is I do need to know the derivative equation of iaf_psc_alpha neuron model to design some algorithm for neural network. For the paper you mentioned, I still can't figure out the exact derivative equation of voltage or voltage state equation. https://link.springer.com/article/10.1007/s004220050570 By the way, At today's meeting, I wanted to ask that but my device had trouble when host asked, haha, so awkward. Hope for your answer or anyone else. Thank you. Enguang