4.2. The Data Object#

4.2.1. Description#

This is the object that traverses the steps of the pipeline. It is indeed a dictionary of dictionaries. The first level of keys are the data types and a special key named meta that contains all the information on the data object including source and previous transformation steps.

The second level of keys are the actual data. So far, there are two keys used:

  • path: path to the file containing the data.

  • data: the data loaded in memory.

The Data Grabber step will only fill the path value. The data value will be filled by the DataReader step, if it is one of the possible file types that the datareader can read.

A point to note is that you never directly interact with the data object but it’s important to know where and how the object is being manipulated to reason about your pipeline.

4.2.2. Data types#

Name

Description

Example

T1w

T1w image (3D)

Preprocessed or Raw T1w image

BOLD

BOLD image (4D)

Preprocessed/Denoised BOLD image (fmriprep output)

BOLD_confounds

BOLD image confounds (CSV/TSV file)

Confounds that can be applied to the BOLD image.

VBM_GM

VBM Gray Matter segmentation (3D)

CAT output (m0wp1 images)

VBM_WM

VBM White Matter segmentation (3D)

CAT output (m0wp2 images)

fALFF

Voxel-wise fALFF image (3D)

fALFF computed with CONN toolbox

GCOR

Global Correlation image (3D)

GCOR computed with CONN toolbox

LCOR

Local Correlation image (3D)

LCOR computed with CONN toolbox