Predict single trial activity from a continuous variable. A single-trial regression is performed in each sensor and timepoint individually, resulting in an Evoked object which contains the regression coefficient (beta value) for each combination of sensor and timepoint. Example also shows the T statistics and the associated p-values.
Note that this example is for educational purposes and that the data used here do not contain any significant effect.
(See Hauk et al. (2006). The time course of visual word recognition as revealed by linear regression analysis of ERP data. Neuroimage.)
Set parameters and read data
raw_fname = data_path + '/MEG/sample/sample_audvis_filt-0-40_raw.fif' event_fname = data_path + '/MEG/sample/sample_audvis_filt-0-40_raw-eve.fif' tmin, tmax = -0.2, 0.5 event_id = dict(aud_l=1, aud_r=2) # Setup for reading the raw data raw = mne.io.read_raw_fif(raw_fname) events = mne.read_events(event_fname) picks = mne.pick_types(raw.info, meg='mag', eeg=False, stim=False, eog=False, exclude='bads') # Reject some epochs based on amplitude reject = dict(mag=5e-12) epochs = mne.Epochs(raw, events, event_id, tmin, tmax, proj=True, picks=picks, baseline=(None, 0), preload=True, reject=reject)
Opening raw data file /home/ubuntu/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. Current compensation grade : 0 145 matching events found Created an SSP operator (subspace dimension = 3) 4 projection items activated Loading data for 145 events and 106 original time points ... Rejecting epoch based on MAG : [u'MEG 1711'] Rejecting epoch based on MAG : [u'MEG 1711'] 2 bad epochs dropped
names = ['intercept', 'trial-count'] intercept = np.ones((len(epochs),), dtype=np.float) design_matrix = np.column_stack([intercept, # intercept np.linspace(0, 1, len(intercept))]) # also accepts source estimates lm = linear_regression(epochs, design_matrix, names) def plot_topomap(x, unit): x.plot_topomap(ch_type='mag', scale=1, size=1.5, vmax=np.max, unit=unit, times=np.linspace(0.1, 0.2, 5)) trial_count = lm['trial-count'] plot_topomap(trial_count.beta, unit='z (beta)') plot_topomap(trial_count.t_val, unit='t') plot_topomap(trial_count.mlog10_p_val, unit='-log10 p') plot_topomap(trial_count.stderr, unit='z (error)')
Fitting linear model to epochs, (10812 targets, 2 regressors) Done
Total running time of the script: ( 0 minutes 8.638 seconds)