Compare evoked responses for different conditions

In this example, an Epochs object for visual and auditory responses is created. Both conditions are then accessed by their respective names to create a sensor layout plot of the related evoked responses.

# Authors: Denis Engemann <denis.engemann@gmail.com>
#          Alexandre Gramfort <alexandre.gramfort@inria.fr>

# License: BSD-3-Clause

import matplotlib.pyplot as plt
import mne

from mne.viz import plot_evoked_topo
from mne.datasets import sample

print(__doc__)

data_path = sample.data_path()

Set parameters

meg_path = data_path / "MEG" / "sample"
raw_fname = meg_path / "sample_audvis_filt-0-40_raw.fif"
event_fname = meg_path / "sample_audvis_filt-0-40_raw-eve.fif"
tmin = -0.2
tmax = 0.5

#   Setup for reading the raw data
raw = mne.io.read_raw_fif(raw_fname)
events = mne.read_events(event_fname)

#   Set up amplitude-peak rejection values for MEG channels
reject = dict(grad=4000e-13, mag=4e-12)

# Create epochs including different events
event_id = {"audio/left": 1, "audio/right": 2, "visual/left": 3, "visual/right": 4}
epochs = mne.Epochs(
    raw, events, event_id, tmin, tmax, picks="meg", baseline=(None, 0), reject=reject
)

# Generate list of evoked objects from conditions names
evokeds = [epochs[name].average() for name in ("left", "right")]

Opening raw data file /home/circleci/mne_data/MNE-sample-data/MEG/sample/sample_audvis_filt-0-40_raw.fif...
    Read a total of 4 projection items:
        PCA-v1 (1 x 102)  idle
        PCA-v2 (1 x 102)  idle
        PCA-v3 (1 x 102)  idle
        Average EEG reference (1 x 60)  idle
    Range : 6450 ... 48149 =     42.956 ...   320.665 secs
Ready.
Not setting metadata
288 matching events found
Setting baseline interval to [-0.19979521315838786, 0.0] s
Applying baseline correction (mode: mean)
Created an SSP operator (subspace dimension = 3)
4 projection items activated
    Rejecting  epoch based on MAG : ['MEG 1711']
NOTE: pick_channels() is a legacy function. New code should use inst.pick(...).
Removing projector <Projection | Average EEG reference, active : True, n_channels : 60>
    Rejecting  epoch based on MAG : ['MEG 1711']
NOTE: pick_channels() is a legacy function. New code should use inst.pick(...).
Removing projector <Projection | Average EEG reference, active : True, n_channels : 60>

Show topography for two different conditions

colors = "blue", "red"
title = "MNE sample data\nleft vs right (A/V combined)"

plot_evoked_topo(evokeds, color=colors, title=title, background_color="w")

plt.show()

Estimated memory usage: 10 MB