Note
This documentation is for a development version. Click here for the latest stable release (v0.5.0).
Neuron types¶
These neuron types can be used in any place that Nengo neuron types can be used.

class
nengo_extras.neurons.
SoftLIFRate
(sigma=1.0, **lif_args)[source]¶ LIF neuron with smoothing around the firing threshold.
This is a rate version of the LIF neuron whose tuning curve has a continuous first derivative, due to the smoothing around the firing threshold. It can be used as a substitute for LIF neurons in deep networks during training, and then replaced with LIF neurons when running the network [1].
 Parameters
 sigmafloat
Amount of smoothing around the firing threshold. Larger values mean more smoothing.
 amplitudefloat
Scaling factor on the output. If 1 (default), output rates correspond to LIF neuron model rates.
 tau_rcfloat
Membrane RC time constant, in seconds. Affects how quickly the membrane voltage decays to zero in the absence of input (larger = slower decay).
 tau_reffloat
Absolute refractory period, in seconds. This is how long the membrane voltage is held at zero after a spike.
References
 1
E. Hunsberger & C. Eliasmith (2015). Spiking Deep Networks with LIF Neurons. arXiv Preprint, 1510. https://export.arxiv.org/abs/1510.08829

class
nengo_extras.neurons.
FastLIF
(tau_rc=0.02, tau_ref=0.002, min_voltage=0, amplitude=1, initial_state=None)[source]¶ Faster version of the leaky integrateandfire (LIF) neuron model.
This neuron model is faster than
LIF
but does not produce the ideal firing rate for largerdt
due to linearization of the tuning curves.

class
nengo_extras.neurons.
NumbaLIF
(*args, **kwargs)[source]¶ Numbacompiled version of the LIF model.
 Parameters
 tau_rcfloat
Membrane RC time constant, in seconds. Affects how quickly the membrane voltage decays to zero in the absence of input (larger = slower decay).
 tau_reffloat
Absolute refractory period, in seconds. This is how long the membrane voltage is held at zero after a spike.
 min_voltagefloat
Minimum value for the membrane voltage. If
np.inf
, the voltage is never clipped. amplitudefloat
Scaling factor on the neuron output. Corresponds to the relative amplitude of the output spikes of the neuron.
Utilities¶

nengo_extras.neurons.
spikes2events
(t, spikes)[source]¶ Return an eventbased representation of spikes (i.e. spike times)

nengo_extras.neurons.
rates_isi
(t, spikes, midpoint=False, interp='zero')[source]¶ Estimate firing rates from spikes using ISIs.
 Parameters
 t(M,) array_like
The times at which raw spike data (spikes) is defined.
 spikes(M, N) array_like
The raw spike data from N neurons.
 midpointbool, optional
If true, place interpolation points at midpoints of ISIs. Otherwise, the points are placed at the beginning of ISIs.
 interpstring, optional
Interpolation type, passed to
scipy.interpolate.interp1d
as thekind
parameter.
 Returns
 rates(M, N) array_like
The estimated neuron firing rates.

nengo_extras.neurons.
rates_kernel
(t, spikes, kind='gauss', tau=0.04)[source]¶ Estimate firing rates from spikes using a kernel.
 Parameters
 t(M,) array_like
The times at which raw spike data (spikes) is defined.
 spikes(M, N) array_like
The raw spike data from N neurons.
 kindstr {‘expon’, ‘gauss’, ‘expogauss’, ‘alpha’}, optional
The type of kernel to use. ‘expon’ is an exponential kernel, ‘gauss’ is a Gaussian (normal) kernel, ‘expogauss’ is an exponential followed by a Gaussian, and ‘alpha’ is an alpha function kernel.
 taufloat
The time constant for the kernel. The optimal value will depend on the firing rate of the neurons, with a longer tau preferred for lower firing rates. The default value of 0.04 works well across a wide range of firing rates.