Remap MEG channel types

In this example, MEG data are remapped from one channel type to another. This is useful to:

• visualize combined magnetometers and gradiometers as magnetometers or gradiometers.

• run statistics from both magnetometers and gradiometers while working with a single type of channels.

# Author: Mainak Jas <mainak.jas@telecom-paristech.fr>

# License: BSD-3-Clause
# Copyright the MNE-Python contributors.

import mne
from mne.datasets import sample

print(__doc__)

# read the evoked
data_path = sample.data_path()
meg_path = data_path / "MEG" / "sample"
fname = meg_path / "sample_audvis-ave.fif"
evoked = mne.read_evokeds(fname, condition="Left Auditory", baseline=(None, 0))

First, let’s call remap gradiometers to magnometers, and plot the original and remapped topomaps of the magnetometers.

# go from grad + mag to mag and plot original mag
virt_evoked = evoked.as_type("mag")
fig = evoked.plot_topomap(ch_type="mag")
fig.suptitle("mag (original)")

# plot interpolated grad + mag
fig = virt_evoked.plot_topomap(ch_type="mag")
fig.suptitle("mag (interpolated from mag + grad)")

Now, we remap magnometers to gradiometers, and plot the original and remapped topomaps of the gradiometers

# go from grad + mag to grad and plot original grad
virt_evoked = evoked.as_type("grad")
fig = evoked.plot_topomap(ch_type="grad")
fig.suptitle("grad (original)")

# plot interpolated grad + mag
fig = virt_evoked.plot_topomap(ch_type="grad")
fig.suptitle("grad (interpolated from mag + grad)")

Estimated memory usage: 0 MB