Standard deviation of source activity

By default, all generated waveforms (but not the ones explicitly provided by the user) are normalized to have a standard deviation (SD) of 1 nAm. If necessary, this value can be modified using the base_std argument when initializing the SourceSimulator:

from meegsim.simulate import SourceSimulator

sim = SourceSimulator(src, base_std=1e-8)    # 10 nAm

Normalization also means that the SD of activity will be the same for all added sources by default. However, in real data this does not always hold. For example, alpha power is usually higher in parieto-occipital areas. Therefore, we also provide an option to configure the SD of activity for each source when adding them:

sim.add_point_sources(
    location=...,
    waveform=...,
    std=5,                # 5 times stronger than by default
)

Note

Local adjustment of SNR will have priority over the provided value of SD. The adjustment of the SD is mainly designed to be used in combination with the global adjustment of SNR (the default option).

The SD can also be set for all candidate source locations at once using an instance of mne.SourceEstimate. If the source locations are generated randomly, the SD will be adjusted according to the actual location of the source.