Hey Andreas,
Neurons run in single-target-out mode due to the hardware gating. So your pop_src's neuron spikes are either excitatory, OR inhibitory.
Greets
bjoern
-----Original Message-----
From: Spikey neuromorphic system - User [mailto:[log in to unmask]] On Behalf Of Andreas Stoeckel
Sent: Samstag, 26. März 2016 00:02
To: [log in to unmask]
Subject: Neurons cannot target both excitatory and inhibitory synapses
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Dear Spikey developers,
to get a better feeling for the behaviour of the Spikey system I ran
an experiment which measured the neuron "tuning curves", i.e. their
mapping from input to output fire rate.
To do so I've generated a test spike train which is sent from a
population of SpikeSourceArrays to a population of neurons. Half of
the neurons (every second neuron) also receives a bias input from a
constantly spiking SpikeSourceArray, and should receive the test spike
train via inhibitory synapses [2].
The curious behaviour I observed is the following: as soon as a
SpikeSourceArray is targeted both at excitatory and inhibitory
synapses (of different target neurons), only inhibitory connections
are made.
I wrote a small PyNN test script which reproduces this behaviour, you
can find it at [1].
Is this a known restriction? If not, I'll gladly open a bug ticket.
Cheers,
Andreas
[1] https://gist.github.com/astoeckel/6b252f3ce955f6393586
[2]
https://github.com/hbp-sanncs/cypress/blob/408bdc34437ef901386424380ba4b76617b5a77f/examples/measure_tuning_curves.cpp
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