Spike with shape

Support
1

Description of problem

HI,

I’m working on a analog circuit implementation of lif neuruons. Meanwhile, I’m considering using brian to simulate it. The analog neuron, which is essentially a leaky integrator, can be modeled simply by an ode. However, the spike cannot be an ideal impulse, it’s more like a rectangle waveform. in brian2, the spike is more like a event, which triggers other state variables. Is there any way to implement spike with shapes?

Thanks.

Minimal code to reproduce problem

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Expected output (if relevant)

Actual output (if relevant)

Full traceback of error (if relevant)

2

Hi,

I had a similar problem and I solved it by kinda “hacking” Brian.
Check this out:

C, gL, EL  = 200*pF, 4*nS, -70*mV
eqs = ('dV/dt = (gL * (EL-V) + I) / C  :volt \n'
       'I  :amp')

neuron = NeuronGroup(1, model=eqs, threshold= 'V>-40*mV', method='euler',
                     reset ='V = 30*mV', refractory=4*ms)
neuron.V = -70*mV

second_reset = Synapses(neuron, neuron, on_pre='V=-50*mV', delay=0.5*ms)
second_reset.connect(j='i')

Instead of using a single reset value, I introduced a second reset with a self-synapse.
When Vth is crossed, the voltage goes to 30 mV and after a delay of 0.5 ms it goes
to the “normal” reset at -50 mV. I don’t know if this is the best way to achieve more realistic
spikes, but for me, it works well. Also by adjusting the delay you can calibrate the “half amplitude”
of your spikes.

I hope I helped :blush:

3

I think you might also be able to do the same thing with custom events: https://brian2.readthedocs.io/en/stable/advanced/custom_events.html