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# -*- coding: utf-8 -*-
"""
.. _ex-fnirs-artifacts:
==========================================
Visualise NIRS artifact correction methods
==========================================
Here we artificially introduce several fNIRS artifacts and observe
how artifact correction techniques attempt to correct the data.
"""
# Authors: Robert Luke <mail@robertluke.net>
#
# License: BSD-3-Clause
# %%
import os
import mne
from mne.preprocessing.nirs import (optical_density,
temporal_derivative_distribution_repair)
# %%
# Import data
# -----------
#
# Here we will work with the :ref:`fNIRS motor data <fnirs-motor-dataset>`.
# We resample the data to make indexing exact times more convenient.
# We then convert the data to optical density to perform corrections on
# and plot these signals.
fnirs_data_folder = mne.datasets.fnirs_motor.data_path()
fnirs_cw_amplitude_dir = os.path.join(fnirs_data_folder, 'Participant-1')
raw_intensity = mne.io.read_raw_nirx(fnirs_cw_amplitude_dir, verbose=True)
raw_intensity.load_data().resample(3, npad="auto")
raw_od = optical_density(raw_intensity)
new_annotations = mne.Annotations([31, 187, 317], [8, 8, 8],
["Movement", "Movement", "Movement"])
raw_od.set_annotations(new_annotations)
raw_od.plot(n_channels=15, duration=400, show_scrollbars=False)
# %%
# We can see some small artifacts in the above data from movement around 40,
# 190 and 240 seconds. However, this data is relatively clean so we will
# add some additional artifacts below.
# %%
# Add artificial artifacts to data
# --------------------------------
#
# Two common types of artifacts in NIRS data are spikes and baseline shifts.
# Spikes often occur when a person moves and the optode moves relative to the
# scalp and then returns to its original position.
# Baseline shifts occur if the optode moves relative to the scalp and does not
# return to its original position.
# We add a spike type artifact at 100 seconds and a baseline shift at 200
# seconds to the data.
corrupted_data = raw_od.get_data()
corrupted_data[:, 298:302] = corrupted_data[:, 298:302] - 0.06
corrupted_data[:, 450:750] = corrupted_data[:, 450:750] + 0.03
corrupted_od = mne.io.RawArray(corrupted_data, raw_od.info,
first_samp=raw_od.first_samp)
new_annotations.append([95, 145, 245], [10, 10, 10],
["Spike", "Baseline", "Baseline"])
corrupted_od.set_annotations(new_annotations)
corrupted_od.plot(n_channels=15, duration=400, show_scrollbars=False)
# %%
# Apply temporal derivative distribution repair
# ---------------------------------------------
#
# This approach corrects baseline shift and spike artifacts without the need
# for any user-supplied parameters :footcite:`FishburnEtAl2019`.
corrected_tddr = temporal_derivative_distribution_repair(corrupted_od)
corrected_tddr.plot(n_channels=15, duration=400, show_scrollbars=False)
# %%
# We can see in the data above that the introduced spikes and shifts are
# largely removed, but some residual smaller artifact remains.
# The same can be said for the artifacts in the original data.
# %%
# References
# ----------
#
# .. footbibliography::
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