Bipolar EEG dataset - music

Dataset setting out to investigate neural responses to continuous musical pieces with bipolar EEG. Analysis code (and usage instructions) to derive neural responses to the temporal fine structure of the stimuli is on Github. The EEG data processed to this end is provided here, as well as the raw data to enable different analyses (e.g. slower cortical responses).

# Introduction

This dataset contains bipolar scalp EEG responses of 17 subjects listening to continuous musical pieces (Bach's Two-Part Inventions), and performing a vibrato detection task.

Naming conventions:

- The subject IDs are EBIP01, EBIP02 ... EBIP17.
- The different conditions are labelled to indicate the instrument that was being attended: fG and fP for the Guitar and Piano in quiet (Single Instrument (SI) conditions), respectively; and fGc and fPc for Competing conditions where both the instruments are playing together, but where the subjects should be selectively attending to the Guitar or Piano, respectively (Competing Instrument (CI) conditions).
- An appended index from 2 to 7 designates the invention that was played (index 1 corresponds to the training block for which no EEG data was recorded). Note that this index does not necessarily corresponds to the order in which the stimuli were played (order was pseudo-randomised).

For example, the EEG file named EBIP08_fGc_4 contains EEG data from subject EBIP08 performing the competing instrument task (CI condition), attending to the guitar (ignoring the piano), and the stimulus that was played was the invention #4.

# Content

The general organisation of the dataset is as follow:

data
 ├─── behav              folder containing the behavioural data
 ├─── EEG                           folder containing the EEG data
 │   ├─── processed
 │   └─── raw
 ├─── linearModelResults            folder containing the results from the analysis code
 └─── stimuli                                                folder containing the stimuli
     ├─── features
     ├─── processedInventions
     └─── rawInventions

This general organisation is the one expected by the code. The location of the data folder and/or these main folders can be personalised in the functions/+EEGmusic2020/getPath.m function in the Github repository. The architecture of the sub-folders in each of these folders is specified by the functions makePathEEGFolder, makePathFeatureFiles and makePathSaveResults. The naming of the files within them is implemented by makeNameEEGDataFile and makeNameEEGDataFile (all these functions being in functions/+EEGmusic2020).

- The behav folder is structured as follow:

behav
 ├─── EBIP02
 │     ├─── EBIP02_keyboardInputs_fGc_2.mat    file containing variables:
 │     │     ├─── timePressed                                key press time (in seconds, relative to stimulus onset)
 │     │     └─── keyCode                                       ID of the keys that were pressed
 │     └─── ...
 ├─── ...
 ├─── vibTime
 │     ├─── vibTime_2.mat                                 file containing variables:
 │     │     ├─── idxNoteVib                           index (in the MIDI files) of the notes in which vibratos were inserted
 │     │     ├─── instrumentOrder                 order of the instruments in idxNoteVib and vibTiming variables
 │     │     └─── vibTiming                             timing of vibrato onsets in the track (in s)
 │     ├─── ...
 └─── clickPerformance_RT_2.0.mat                file containing behavioural results for all subjects (FPR, TPR, etc.):

instrumentOrder indicates to what instrument each column of idxNoteVib and vibTiming refers to. The data for EBIP01 missing due to a technical error.

- The EEG/raw folder contains unprocessed EEG data for all subjects, and files indicating the order in which the inventions were played. It is structured as follow:

EEG
 ├─── raw
 │     ├─── EBIP01
 │     │     ├─── EBIP01_EEGExpParam.mat                file containing variables:
 │     │     │    ├─── conditionOrder                     whether this subject started by listening to the guitar or piano
 │     │     │    └─── partsOrder                             order in which the inventions were presented to this subject
 │     │     ├─── EBIP01_fGc_2.[eeg/vhdr/vmrbk]  raw EEG data files
 │     │     ├─── ...
 │     ├─── ...

The conditionOrder variable can assume two values: either {'fG','fP'} indicating the subject started by listening to the guitar or {'fP','fG'} indicating the subject started by listening to the piano. The partsOrder variable is a 2 x 6 matrix containing the indices (2 to 7) of the inventions that were played, ordered in the presentation order. During the first block, the instrument conditionOrder{1} was attended, and the invention # partsOrder(1,1) was played. During the second block, the instrument conditionOrder{2} was attended, and the invention #partsOrder(2,1) was played, etc.

Each EEG files contains 3 channels: 2 are the bipolar electrophysiological channels, and one (labelled Sound) contains a recording of the stimuli that were played and that was simultaneously recorded at the same sampling rate as the EEG data (5 kHz) by the amplifier through an acoustic adapter. The files also contain triggers that indicate the beginning and end of the stimuli (labelled S 1 and S 2 respectively). The sound channel and triggers can be used to temporally align the EEG data and stimuli.

The EEG/processed folder contains processed EEG data for all subjects, as required for the analyses carried out in the code. It is organised as follow:

EEG
 ├─── processed
 │     └─── Fs-5000                                sampling rate
 │           └─── HP-130                      processing that was applied
 │           │     ├─── EBIP01
 │           │     │     ├─── ...   processed EEG data files
 │           │     ├─── ...
 │           └─── noProc
 │                 ├─── ...

This structure is specified by the makePathEEGFolder function, and the file names by makeNameEEGDataFile. In the files in the noProc folder, the EEG data was simply aligned with the stimuli, but is otherwise unprocessed. Events were added to mark stimulus onset and offset (labelled stimBegin and stimEnd). In the other folders, the EEG data was furthermore high-pass filtered at 130 Hz (HP-130).

- The linearModelResults folder contains the results from the linear model analyses:

linearModelResults
 └─── Fs-5000                                sampling rate
 │     └─── HP-130                      processing of the EEG data
 │     │     └─── LP-2000        processing of the stimulus feature
 │     │           ├─── ...    result files
 │     ├─── ...

This structure and file names are specified by the makePathSaveResults function.

- The rawInventions folder contains the orignal data that was used to construct the stimuli:

rawInventions
 ├─── invent1                                                  invention index
 │     ├─── invent1_60bpm.mid                 MIDI file
 │     ├─── invent1_60bpm_guitar.wav  guitar track
 │     └─── invent1_60bpm_piano.wav    piano track
 │
 ├─── ...

In this folder (and only in this folder), the numbering of the inventions differs from the one otherwise used throughout. The correspondence is as shown below:
   Raw invention #  |  Feature, etc. #
   1, 2, 3, 4         ->  1, 2, 3, 4
   7, 8, 9             ->   5, 6,7

- The processedInventions contains invention waveforms that have been transformed. The instrument and invention index are indicated by a suffix in the file names ('G': guitar, 'P': piano). 'zv' indicates that the vibratos were replaced by zeros. 'noOnset30ms' indicates that the onset of the notes was suppressed in a 30 ms window.

- The features folder contains specific features of the stimuli for use in the models:

features
 └─── Fs-5000                                  sampling rate of the feature
       └─── LP-2000                     processing of the feature
             ├─── waveform      feature name (here: stimulus waveform)
             │     ├─── ...    feature files
             └─── WNO                Waveform No Onset (stimulus waveform with note onsets removed)
                   ├─── ...

The naming convention is as highlighted above for the processedInventions folder. SI conditions correspond to 'G' & 'P' files, and CI conditions to 'PG' files. In the latter case, 'fG' indicates the attended instrument is the guitar and 'fP' the piano.
These files notably contain the variables attended and ignored that contains the feature for the attended and ignored instruments (the ignored field is only present in the CI conditions).
Note that a pair of two files corresponding to the same invention in a CI condition ('PGfG' & 'PGfP') effectively contain the same information with the attended and ignored variables flipped.