multimeter – Sampling continuous quantities from neurons

Description

Most sampling use cases are covered by the multimeter, which allows to record analog values from neurons. Models which have such values expose a recordables property that lists all recordable quantities. This property can be inspected using GetDefaults on the model class or GetStatus on a model instance. It cannot be changed by the user.

>>> nest.GetDefaults('iaf_cond_alpha')['recordables']
['g_ex', 'g_in', 't_ref_remaining', 'V_m']

The record_from property of a multimeter (a list, empty by default) can be set to contain the name(s) of one or more of these recordables to have them sampled during simulation.

mm = nest.Create('multimeter', 1, {'record_from': ['V_m', 'g_ex']})

The sampling interval for recordings (given in ms) can be controlled using the multimeter parameter interval. The default value of 1.0 ms can be changed by supplying a new value either in the call to Create or by using SetStatus on the model instance.

nest.SetStatus(mm, 'interval': 0.1})

The recording interval must be greater than or equal to the simulation resolution, which defaults to 0.1 ms.

Warning

The set of variables to record from and the recording interval must be set before the multimeter is connected to any neuron. These properties cannot be changed afterwards.

After configuration, a multimeter can be connected to the neurons it should record from by using the standard Connect routine.

neurons = nest.Create('iaf_psc_alpha', 100)
nest.Connect(mm, neurons)

To learn more about possible connection patterns and additional options when using Connect, see the guide on connection management.

The above call to Connect would fail if the neurons would not support the sampling of the values V_m and g_ex. It would also fail if carried out in the wrong direction, i.e., trying to connect the neurons to mm.

Note

A pre-configured multimeter is available under the name voltmeter. Its record_from property is already set to record the variable V_m from the neurons it is connected to.