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<h1>Read me</h1> <h2>Acquisition</h2> <p>\ Acquisition done in NeuroSpin (CEA, INSERM):\ Commissariat à l’énergie atomique et aux énergies alternatives\ Centre de Saclay\ Bâtiment 145 – P.C. 156\ 91191 Gif-sur-Yvette Cedex\ France\ \ MEG setup:\ - Elekta Neuromag 306, with...\ - 102 MEG magnetometers (MEGXXX1 sensors),\ - 204 MEG gradiometers (MEGXXX2/MEGXXX3 sensors).\ \ Acquisition setup:\ - Acquisition frequency: 1000 Hz\ - Online high-pass filter: 0.10 Hz\ - Online low-pass filter: 330 Hz</p> <h2>Preprocessing</h2> <p>\ MaxFiltering options:\ - Visual bad channels detection and correction (monitored online during acquisition),\ - Automatic bad channels detection and correction (MaxFilter badlimit = 4).\ \ FieldTrip preprocessing options:\ - Epoching between -250 ms an 1 s with respect to stimulus onset,\ - DC filtering: 50, 100 and 150 Hz,\ - Semi-automatic reject of trials with motor artifacts and/or SQUIDs' jumps,\ - Low-pass filter: 30 Hz,\ - Downsampling: 250 Hz,\ - ICA: removing components characteristics of heartbeats, eye-blinks and eye-movements,\ - Epoch demean,\ - Baseline correction (-250 ms to 0 ms with respect to stimulus onset).</p> <h2>Data files</h2> <p>\ "demographics.xlsx": an Excel file specifying the demographic data of the subjects as well as some experimental informations.\ \ "subjectXX.mat": a MATLAB file specifying the MEG data of a single subject.\ - "meg": a structure with:\ - "trial": a N trials x 306 sensors x 321 time-points matrix specifying the MEG amplitude (in Tesla).\ - "time": a 1 x 321 array specifying the time-stamps (from -250 ms to 1 s).\ - "label": a 1 x 306 array specifying the sensors' name.\ - "trialinfo": a N trials x 4 columns matrix with the columns specifying (in order):\ - col. 1: the trial number (in the context of the full experiment),\ - col. 2: the trial number (in the context of the block),\ - col. 3: the block number (1, 2, 3 or 4; see below),\ - col. 4: what was presented (1 for A, 2 for B).\ !!! the total number of trials (N) varies from one subject to another depending on the number of trials that survive the preprocessing procedure.\ - "seq": a 1 x 4 blocks cell array specifying the full (including missing observations in the MEG data due to preprocessing) binary sequence (1 for A, 2 for B, NaN for explicit prediction).\ - "seqidx": a 1 x 4 blocks cell array specifying the indices of sequence observations for which the corresponding MEG activity is available (i.e. trials that survive the preprocessing procedure).</p> <h2>Nomenclature</h2> <p>\ "Block" refers to the experimental conditions (counter-balanced order across subjects):\ - Block 1 (repetition-biased): p(A|B) = 1/3, p(B|A) = 1/3;\ - Block 2 (fully stochastic): p(A|B) = 1/2, p(B|A) = 1/2;\ - Block 3 (alternation-biased): p(A|B) = 2/3, p(B|A) = 2/3;\ - Block 4 (frequency-biased): p(A|B) = 1/3, p(B|A) = 2/3.</p>
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