When referencing this material, please cite:
Sweeney KT, McLoone SF, Ward TE. The Use of Ensemble Empirical Mode Decomposition With Canonical Correlation Analysis as a Novel Artifact Removal Technique. IEEE Trans Biomed Eng 60(1):97-105; 2013 (Jan).
Please also include the standard citation for PhysioNet:
This data collection, contributed to PhysioBank by Kevin Sweeney and colleagues at the National University of Ireland in Maynooth, contains examples of functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG) recordings that have been created for evaluating artifact removal methods.
In each such recording, one or two pairs of similar physiological signals have been acquired from transducers in close proximity. (The EEG recordings contain one pair of signals. The fNIRS recordings contain two pairs of such signals, acquired at 690 nm and 830 nm wavelengths.)
In each case, one of the two transducers has not been disturbed, while the other has been manipulated to produce motion artifacts of variable duration within each 2-minute interval of the recording. The motion of the disturbed transducer, and the lack of motion of the other transducer, are documented in each case by simultaneously recorded outputs of 3-axis accelerometers affixed to each transducer. Comparison of the "ground truth" signals obtained from the undisturbed transducer with the intermittently noisy signals obtained from the other transducer reveals high correlation during motion-free intervals and lower correlation during artifact-contaminated intervals. To evaluate the efficacy of artifact-removal methods for "cleaning" the contaminated signals, one may similarly compare the "ground truth" signals with the "cleaned" signals.
The first reference above (Sweeney 2012) describes how these recordings were made in detail, and illustrates their use in evaluation of a wide variety of previously described artifact removal methods. The second reference above (Sweeney 2013) presents a novel method, also evaluated using these recordings.
CSV files
The original data recorded by Sweeney and colleagues are available here within a pair of zip archives in CSV format. Note that the fNIRS (or EEG) signals and the accelerometer signals were recorded simultaneously using independent recording systems; a software-generated trigger signal was recorded by both systems. In order to synchronize the accelerometer signals with the other signals, it is necessary to line up the corresponding transitions in the recorded trigger signals.
Two versions of the trigger signals were produced. In the full version, recorded together with the fNIRS signals and with the accelerometer signals, the trigger signal initially rises to indicate the start of the experiment. The trigger signal transitions to a low value during intervals when motion artifact was produced, and returns to a high level in the clean intervals. The final transition from high to low signals the end of the experiment.
The version of the trigger signal recorded together with the EEG signals includes only the initial rise and final fall (marking the start and end of the experiment); it does not include the intervening transitions marking the noisy and clean intervals of the recording.
The EEG signals and the accompanying trigger signal were digitized at 2048 Hz; the fNIRS signals and their trigger signal, at 25 Hz [*]; and the 3-axis accelerometer signals and their trigger signal, at 200 Hz.
[*] Analysis of the trigger signals in the fNIRS recordings suggests that the actual sampling frequency was slightly slower, and was approximately 24.99305 Hz. This value was used to resynchronize the fNIRS signals with the accelerometer signals in the PhysioBank-compatible versions of these recordings (see below).
fNIRS CSV files
Each of the 9 trials included in fNIRS-csv.zip consists of 2 channels of highly correlated fNIRS data recorded from the pre-frontal cortex. Therefore each trial presents 4 signals (2x690 nm and 2x830 nm recordings). Note: In trials 5 and 8, the 690 nm recordings are poor and were not used in the studies referenced above and below. Columns in the TrialX.csv files represent:
Column 1: Sample index Column 2: Channel 1 : Raw 690 nm intensity : sampled @ 25 Hz Column 3: Channel 1 : Raw 830 nm intensity : sampled @ 25 Hz Column 4: Channel 2 : Raw 690 nm intensity : sampled @ 25 Hz Column 5: Channel 2 : Raw 830 nm intensity : sampled @ 25 Hz Column 6: Trigger data for fNIRS data : sampled @ 25 Hz Column 7: Accelerometer 1 : X-axis : sampled @ 200 Hz Column 8: Accelerometer 1 : Y-axis : sampled @ 200 Hz Column 9: Accelerometer 1 : Z-axis : sampled @ 200 Hz Column 10: Accelerometer 2 : X-axis : sampled @ 200 Hz Column 11: Accelerometer 2 : Y-axis : sampled @ 200 Hz Column 12: Accelerometer 2 : Z-axis : sampled @ 200 Hz Column 13: Trigger data for accelerometer data : sampled @ 200 Hz
EEG CSV files
Each of the 23 trials included in EEG-csv.zip consists of 2 channels of highly correlated EEG data recorded from the pre-frontal cortex. Columns in the TrialX.csv files represent:
Column 1: Sample index Column 2: Channel 1 : Raw EEG : sampled @ 2048 Hz Column 3: Channel 2 : Raw EEG : sampled @ 2048 Hz Column 4: Trigger data for EEG data : sampled @ 2048 Hz Column 5: Accelerometer 1 : X-axis : sampled @ 200 Hz Column 6: Accelerometer 1 : Y-axis : sampled @ 200 Hz Column 7: Accelerometer 1 : Z-axis : sampled @ 200 Hz Column 8: Accelerometer 2 : X-axis : sampled @ 200 Hz Column 9: Accelerometer 2 : Y-axis : sampled @ 200 Hz Column 10: Accelerometer 2 : Z-axis : sampled @ 200 Hz Column 11: Trigger data for accelerometer data : sampled @ 200 Hz
PhysioBank-compatible files
The *.hea, *.dat, and *.trigger files available here were derived from the contents of the CSV files described above. The signals are presented in the same order as for the columns of the original CSV files. The locations of the transitions in the trigger signals were used to resynchronize the data in each recording. The short intervals before the initial rise and after the final fall of the trigger signals were not included in these files. The *.trigger files are annotation files that mark the locations of the transitions in the synchronized trigger signals; R annotations mark rises in the trigger signal, and F annotations mark falls in the trigger (the beginnings of artifact-contaminated intervals). The fNIRS signals were digitally resampled at 200 Hz to match their accompanying accelerometer signals in these records. In the EEG records, the accelerometer signals were digitally resampled at 2048 Hz to match the EEG signals.
Name Last modified Size DescriptionApache/2.4.25 (Debian) mod_auth_pgsql/2.0.3 mod_auth_tkt/2.1.0 OpenSSL/1.0.2u Server at archive.physionet.org Port 80
Parent Directory - fnirs_9.trigger 2014-02-28 15:20 58 motion artifact annotations fnirs_9.hea 2014-02-28 15:20 639 header file fnirs_9.dat 2014-02-28 15:20 2.2M digitized signal(s) fnirs_8.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_8.hea 2014-02-28 15:20 644 header file fnirs_8.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_7.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_7.hea 2014-02-28 15:20 648 header file fnirs_7.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_6.trigger 2014-02-28 15:20 58 motion artifact annotations fnirs_6.hea 2014-02-28 15:20 631 header file fnirs_6.dat 2014-02-28 15:20 2.2M digitized signal(s) fnirs_5.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_5.hea 2014-02-28 15:20 636 header file fnirs_5.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_4.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_4.hea 2014-02-28 15:20 634 header file fnirs_4.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_3.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_3.hea 2014-02-28 15:20 638 header file fnirs_3.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_2.trigger 2014-02-28 15:20 68 motion artifact annotations fnirs_2.hea 2014-02-28 15:20 632 header file fnirs_2.dat 2014-02-28 15:20 2.5M digitized signal(s) fnirs_1.trigger 2014-02-28 15:20 66 motion artifact annotations fnirs_1.hea 2014-02-28 15:20 637 header file fnirs_1.dat 2014-02-28 15:20 2.5M digitized signal(s) fNIRS-csv.zip 2014-02-27 12:31 14M original CSV files eeg_9.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_9.hea 2014-02-28 15:21 492 header file eeg_9.dat 2014-02-28 15:21 21M digitized signal(s) eeg_8.trigger 2014-02-28 15:20 58 motion artifact annotations eeg_8.hea 2014-02-28 15:21 486 header file eeg_8.dat 2014-02-28 15:21 19M digitized signal(s) eeg_7.trigger 2014-02-28 15:20 66 motion artifact annotations eeg_7.hea 2014-02-28 15:20 494 header file eeg_7.dat 2014-02-28 15:20 21M digitized signal(s) eeg_6.trigger 2014-02-28 15:20 58 motion artifact annotations eeg_6.hea 2014-02-28 15:20 486 header file eeg_6.dat 2014-02-28 15:20 19M digitized signal(s) eeg_5.trigger 2014-02-28 15:20 58 motion artifact annotations eeg_5.hea 2014-02-28 15:20 490 header file eeg_5.dat 2014-02-28 15:20 19M digitized signal(s) eeg_4.trigger 2014-02-28 15:20 74 motion artifact annotations eeg_4.hea 2014-02-28 15:20 486 header file eeg_4.dat 2014-02-28 15:20 21M digitized signal(s) eeg_3.trigger 2014-02-28 15:20 66 motion artifact annotations eeg_3.hea 2014-02-28 15:20 486 header file eeg_3.dat 2014-02-28 15:20 21M digitized signal(s) eeg_23.trigger 2014-02-28 15:22 66 motion artifact annotations eeg_23.hea 2014-02-28 15:22 502 header file eeg_23.dat 2014-02-28 15:22 21M digitized signal(s) eeg_22.trigger 2014-02-28 15:22 66 motion artifact annotations eeg_22.hea 2014-02-28 15:22 505 header file eeg_22.dat 2014-02-28 15:22 21M digitized signal(s) eeg_21.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_21.hea 2014-02-28 15:21 508 header file eeg_21.dat 2014-02-28 15:21 21M digitized signal(s) eeg_20.trigger 2014-02-28 15:21 74 motion artifact annotations eeg_20.hea 2014-02-28 15:21 493 header file eeg_20.dat 2014-02-28 15:21 21M digitized signal(s) eeg_2.trigger 2014-02-28 15:20 58 motion artifact annotations eeg_2.hea 2014-02-28 15:20 486 header file eeg_2.dat 2014-02-28 15:20 19M digitized signal(s) eeg_19.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_19.hea 2014-02-28 15:21 504 header file eeg_19.dat 2014-02-28 15:21 21M digitized signal(s) eeg_18.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_18.hea 2014-02-28 15:21 500 header file eeg_18.dat 2014-02-28 15:21 21M digitized signal(s) eeg_17.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_17.hea 2014-02-28 15:21 502 header file eeg_17.dat 2014-02-28 15:21 21M digitized signal(s) eeg_16.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_16.hea 2014-02-28 15:21 503 header file eeg_16.dat 2014-02-28 15:21 21M digitized signal(s) eeg_15.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_15.hea 2014-02-28 15:21 501 header file eeg_15.dat 2014-02-28 15:21 21M digitized signal(s) eeg_14.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_14.hea 2014-02-28 15:21 499 header file eeg_14.dat 2014-02-28 15:21 21M digitized signal(s) eeg_13.trigger 2014-02-28 15:21 66 motion artifact annotations eeg_13.hea 2014-02-28 15:21 501 header file eeg_13.dat 2014-02-28 15:21 21M digitized signal(s) eeg_12.trigger 2014-02-28 15:21 58 motion artifact annotations eeg_12.hea 2014-02-28 15:21 503 header file eeg_12.dat 2014-02-28 15:21 19M digitized signal(s) eeg_11.trigger 2014-02-28 15:21 58 motion artifact annotations eeg_11.hea 2014-02-28 15:21 503 header file eeg_11.dat 2014-02-28 15:21 19M digitized signal(s) eeg_10.trigger 2014-02-28 15:21 58 motion artifact annotations eeg_10.hea 2014-02-28 15:21 503 header file eeg_10.dat 2014-02-28 15:21 19M digitized signal(s) eeg_1.trigger 2014-02-28 15:20 66 motion artifact annotations eeg_1.hea 2014-02-28 15:20 486 header file eeg_1.dat 2014-02-28 15:20 21M digitized signal(s) SHA256SUMS 2014-02-28 18:10 7.7K SHA1SUMS 2014-02-28 18:10 5.4K RECORDS 2014-02-28 09:11 224 list of record names MD5SUMS 2014-02-28 18:10 4.6K EEG-csv.zip 2014-02-27 12:31 145M original CSV files DOI 2015-09-21 13:00 19 ANNOTATORS 2014-02-28 15:48 50 list of annotators