This page is a reference documentation. It only explains the class signature, and not how to use it. Please refer to the user guide for the big picture. nilearn.glm.second_level.SecondLevelModel

class nilearn.glm.second_level.SecondLevelModel(mask_img=None, target_affine=None, target_shape=None, smoothing_fwhm=None, memory=Memory(location=None), memory_level=1, verbose=0, n_jobs=1, minimize_memory=True)[source]

Implementation of the General Linear Model for multiple subject fMRI data

mask_imgNiimg-like, NiftiMasker or MultiNiftiMasker object, optional

Mask to be used on data. If an instance of masker is passed, then its mask will be used. If no mask is given, it will be computed automatically by a MultiNiftiMasker with default parameters. Automatic mask computation assumes first level imgs have already been masked.

target_affine3x3 or 4x4 matrix, optional

This parameter is passed to nilearn.image.resample_img. Please see the related documentation for details.

target_shape3-tuple of integers, optional

This parameter is passed to nilearn.image.resample_img. Please see the related documentation for details.

smoothing_fwhmfloat, optional

If smoothing_fwhm is not None, it gives the size in millimeters of the spatial smoothing to apply to the signal.

memorystring, optional

Path to the directory used to cache the masking process and the glm fit. By default, no caching is done. Creates instance of joblib.Memory.

memory_levelinteger, optional

Rough estimator of the amount of memory used by caching. Higher value means more memory for caching. Default=1.

verboseinteger, optional

Indicate the level of verbosity. By default, nothing is printed. If 0 prints nothing. If 1 prints final computation time. If 2 prints masker computation details. Default=0.

n_jobsinteger, optional

The number of CPUs to use to do the computation. -1 means ‘all CPUs’, -2 ‘all CPUs but one’, and so on. Default=1.

minimize_memoryboolean, optional

Gets rid of some variables on the model fit results that are not necessary for contrast computation and would only be useful for further inspection of model details. This has an important impact on memory consumption. Default=True.


This class is experimental. It may change in any future release of Nilearn.

__init__(mask_img=None, target_affine=None, target_shape=None, smoothing_fwhm=None, memory=Memory(location=None), memory_level=1, verbose=0, n_jobs=1, minimize_memory=True)[source]

Initialize self. See help(type(self)) for accurate signature.

fit(second_level_input, confounds=None, design_matrix=None)[source]

Fit the second-level GLM

  1. create design matrix

  2. do a masker job: fMRI_data -> Y

  3. fit regression to (Y, X)

second_level_input: list of `FirstLevelModel` objects or pandas

DataFrame or list of Niimg-like objects.

Giving FirstLevelModel objects will allow to easily compute the second level contrast of arbitrary first level contrasts thanks to the first_level_contrast argument of the compute_contrast method. Effect size images will be computed for each model to contrast at the second level.

If a pandas DataFrame, then they have to contain subject_label, map_name and effects_map_path. It can contain multiple maps that would be selected during contrast estimation with the argument first_level_contrast of the compute_contrast function. The DataFrame will be sorted based on the subject_label column to avoid order inconsistencies when extracting the maps. So the rows of the automatically computed design matrix, if not provided, will correspond to the sorted subject_label column.

If list of Niimg-like objects then this is taken literally as Y for the model fit and design_matrix must be provided.

confoundspandas DataFrame, optional

Must contain a subject_label column. All other columns are considered as confounds and included in the model. If design_matrix is provided then this argument is ignored. The resulting second level design matrix uses the same column names as in the given DataFrame for confounds. At least two columns are expected, “subject_label” and at least one confound.

design_matrixpandas DataFrame, optional

Design matrix to fit the GLM. The number of rows in the design matrix must agree with the number of maps derived from second_level_input. Ensure that the order of maps given by a second_level_input list of Niimgs matches the order of the rows in the design matrix.

compute_contrast(second_level_contrast=None, first_level_contrast=None, second_level_stat_type=None, output_type='z_score')[source]

Generate different outputs corresponding to the contrasts provided e.g. z_map, t_map, effects and variance.

second_level_contraststr or array of shape (n_col), optional

Where n_col is the number of columns of the design matrix. The string can be a formula compatible with pandas.DataFrame.eval. Basically one can use the name of the conditions as they appear in the design matrix of the fitted model combined with operators +- and combined with numbers with operators +-*/. The default (None) is accepted if the design matrix has a single column, in which case the only possible contrast array((1)) is applied; when the design matrix has multiple columns, an error is raised.

first_level_contraststr or array of shape (n_col) with respect to

FirstLevelModel, optional

In case a list of FirstLevelModel was provided as second_level_input, we have to provide a contrast to apply to the first level models to get the corresponding list of images desired, that would be tested at the second level. In case a pandas DataFrame was provided as second_level_input this is the map name to extract from the pandas dataframe map_name column. It has to be a ‘t’ contrast.

second_level_stat_type{‘t’, ‘F’}, optional

Type of the second level contrast

output_typestr, optional

Type of the output map. Can be ‘z_score’, ‘stat’, ‘p_value’, ‘effect_size’, ‘effect_variance’ or ‘all’. Default=’z-score’.


The desired output image(s). If output_type == 'all', then the output is a dictionary of images, keyed by the type of image.

fit_transform(X, y=None, **fit_params)

Fit to data, then transform it.

Fits transformer to X and y with optional parameters fit_params and returns a transformed version of X.

Xarray-like of shape (n_samples, n_features)

Input samples.

yarray-like of shape (n_samples,) or (n_samples, n_outputs), default=None

Target values (None for unsupervised transformations).


Additional fit parameters.

X_newndarray array of shape (n_samples, n_features_new)

Transformed array.

generate_report(contrasts, title=None, bg_img='MNI152TEMPLATE', threshold=3.09, alpha=0.001, cluster_threshold=0, height_control='fpr', min_distance=8.0, plot_type='slice', display_mode=None, report_dims=(1600, 800))[source]

Returns HTMLDocument object for a report which shows all important aspects of a fitted GLM. The object can be opened in a browser, displayed in a notebook, or saved to disk as a standalone HTML file.

The GLM must be fitted and have the computed design matrix(ces).

A fitted first or second level model object.
contrastsDict[string, ndarray] or String or List[String] or

ndarray or List[ndarray]

Contrasts information for a first or second level model.


Dict of contrast names and coefficients, or list of contrast names or list of contrast coefficients or contrast name or contrast coefficient

Each contrast name must be a string. Each contrast coefficient must be a list or numpy array of ints.

Contrasts are passed to contrast_def for FirstLevelModel (nilearn.glm.first_level.FirstLevelModel.compute_contrast) & second_level_contrast for SecondLevelModel (nilearn.glm.second_level.SecondLevelModel.compute_contrast)

titleString, optional

If string, represents the web page’s title and primary heading, model type is sub-heading. If None, page titles and headings are autogenerated using contrast names.

bg_imgNiimg-like object, optional

Default is the MNI152 template (Default=’MNI152TEMPLATE’) See The background image for mask and stat maps to be plotted on upon. To turn off background image, just pass “bg_img=None”.

thresholdfloat, optional

Cluster forming threshold in same scale as stat_img (either a t-scale or z-scale value). Used only if height_control is None. Default=3.09

alphafloat, optional

Number controlling the thresholding (either a p-value or q-value). Its actual meaning depends on the height_control parameter. This function translates alpha to a z-scale threshold. Default=0.001

cluster_thresholdint, optional

Cluster size threshold, in voxels. Default=0

height_controlstring or None, optional

false positive control meaning of cluster forming threshold: ‘fpr’ (default) or ‘fdr’ or ‘bonferroni’ or None Default=’fpr’.

min_distancefloat, optional

For display purposes only. Minimum distance between subpeaks in mm. Default=8mm.

plot_typeString. [‘slice’, ‘glass’], optional

Specifies the type of plot to be drawn for the statistical maps. Default=’slice’.

display_modestring, optional

Default is ‘z’ if plot_type is ‘slice’; ‘ ortho’ if plot_type is ‘glass’.

Choose the direction of the cuts: ‘x’ - sagittal, ‘y’ - coronal, ‘z’ - axial, ‘l’ - sagittal left hemisphere only, ‘r’ - sagittal right hemisphere only, ‘ortho’ - three cuts are performed in orthogonal directions.

Possible values are: ‘ortho’, ‘x’, ‘y’, ‘z’, ‘xz’, ‘yx’, ‘yz’, ‘l’, ‘r’, ‘lr’, ‘lzr’, ‘lyr’, ‘lzry’, ‘lyrz’.

report_dimsSequence[int, int], optional

Default is (1600, 800) pixels. Specifies width, height (in pixels) of report window within a notebook. Only applicable when inserting the report into a Jupyter notebook. Can be set after report creation using report.width, report.height.

report_textHTMLDocument Object

Contains the HTML code for the GLM Report.


Get parameters for this estimator.

deepbool, default=True

If True, will return the parameters for this estimator and contained subobjects that are estimators.


Parameter names mapped to their values.


Set the parameters of this estimator.

The method works on simple estimators as well as on nested objects (such as Pipeline). The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.


Estimator parameters.

selfestimator instance

Estimator instance.