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Example of the tsodyks2_synapse in NEST

This synapse model implements synaptic short-term depression and short-term f according to 1 and 2. It solves Eq (2) from 1 and modulates U according

This connection merely scales the synaptic weight, based on the spike history parameters of the kinetic model. Thus, it is suitable for any type of synapse that is current or conductance based.

The parameter A_se from the publications is represented by the synaptic weight. The variable x in the synapse properties is the factor that scales the synaptic weight.

Parameters

The following parameters can be set in the status dictionary:

• U - probability of release increment (U1) [0,1], default=0.

• u - Maximum probability of release (U_se) [0,1], default=0.

• x - current scaling factor of the weight, default=U

• tau_rec - time constant for depression in ms, default=800 ms

• tau_fac - time constant for facilitation in ms, default=0 (off)

Notes

Under identical conditions, the tsodyks2_synapse produces slightly lower peak amplitudes than the tsodyks_synapse. However, the qualitative behavior is identical.

This compares the two synapse models.

References

1(1,2)

Tsodyks MV, and Markram H. (1997). The neural code between neocortical depends on neurotransmitter release probability. PNAS, 94(2), 719-23.

2

Fuhrmann G, Segev I, Markram H, and Tsodyks MV. (2002). Coding of temporal information by activity-dependent synapses. Journal of Neurophysiology, 8. https://doi.org/10.1152/jn.00258.2001

3

Maass W, and Markram H. (2002). Synapses as dynamic memory buffers. Neural Networks, 15(2), 155-161. http://dx.doi.org/10.1016/S0893-6080(01)00144-7

import nest
import nest.voltage_trace
import matplotlib.pyplot as plt

nest.ResetKernel()

Parameter set for depression

dep_params = {"U": 0.67, "u": 0.67, 'x': 1.0, "tau_rec": 450.0,
              "tau_fac": 0.0, "weight": 250.}

Parameter set for facilitation

fac_params = {"U": 0.1, "u": 0.1, 'x': 1.0, "tau_fac": 1000.,
              "tau_rec": 100., "weight": 250.}

Now we assign the parameter set to the synapse models.

tsodyks_params = dict(fac_params, synapse_model="tsodyks_synapse")  # for tsodyks_synapse
tsodyks2_params = dict(fac_params, synapse_model="tsodyks2_synapse")  # for tsodyks2_synapse

Create three neurons.

neuron = nest.Create("iaf_psc_exp", 3, params={"tau_syn_ex": 3.})

Neuron one produces spikes. Neurons 2 and 3 receive the spikes via the two synapse models.

nest.Connect(neuron[0], neuron[1], syn_spec=tsodyks_params)
nest.Connect(neuron[0], neuron[2], syn_spec=tsodyks2_params)

Now create two voltmeters to record the responses.

voltmeter = nest.Create("voltmeter", 2)

Connect the voltmeters to the neurons.

nest.Connect(voltmeter[0], neuron[1])
nest.Connect(voltmeter[1], neuron[2])

Now simulate the standard STP protocol: a burst of spikes, followed by a pause and a recovery response.

neuron[0].I_e = 376.0

nest.Simulate(500.0)
neuron[0].I_e = 0.0
nest.Simulate(500.0)
neuron[0].I_e = 376.0
nest.Simulate(500.0)

Finally, generate voltage traces. Both are shown in the same plot and should be almost completely overlapping.

nest.voltage_trace.from_device(voltmeter[0])
nest.voltage_trace.from_device(voltmeter[1])
plt.show()