Functional Data

Functional MRI (fMRI) data acquired during experimental tasks in the LAION-fMRI dataset.

Overview

The dataset includes BOLD (Blood Oxygen Level Dependent) functional MRI data acquired while participants performed visual perception tasks.

fMRI Acquisitions

Acquisition Parameters

Sequence Details:

Sequence type: Gradient-echo Echo Planar Imaging (GE-EPI)
Field strength: 3 Tesla
TR (Repetition Time): 2.0 seconds (or as specified in JSON)
TE (Echo Time): 30 ms (or as specified)
Flip angle: 90° (or as specified)
Voxel size: 2.5 x 2.5 x 2.5 mm³ (or as specified)
Matrix size: 80 x 80 (or as specified)
Number of slices: 36-48 (or as specified)
Slice orientation: Axial
Phase encoding: Anterior-Posterior (or as specified)
Multiband acceleration: If applicable

Coverage:

Whole brain coverage
Optimized for visual cortex

File Organization

Functional data structure:

sub-01/
└── func/
    ├── sub-01_task-nback_run-01_bold.nii.gz
    ├── sub-01_task-nback_run-01_bold.json
    ├── sub-01_task-nback_run-01_events.tsv
    ├── sub-01_task-nback_run-02_bold.nii.gz
    ├── sub-01_task-nback_run-02_bold.json
    ├── sub-01_task-nback_run-02_events.tsv
    └── ...

File Components

BOLD data (*_bold.nii.gz):

4D NIfTI file

Metadata (*_bold.json):

Acquisition parameters and timing information

{
    "TaskName": "visual_categorization",
    "RepetitionTime": 2.0,
    "EchoTime": 0.03,
    "FlipAngle": 90,
    "SliceTiming": [0, 0.5, 1.0, 1.5],
    "PhaseEncodingDirection": "j",
    "EffectiveEchoSpacing": 0.000495,
    "TotalReadoutTime": 0.03915
}

Events (*_events.tsv):

Trial timing and experimental conditions

onset       duration        trial_type      stimulus_id     response_time   accuracy
0 0.5     face    stim_0001       0.823   1
5 0.5     scene   stim_0045       0.912   1
2        0.5     object  stim_0123       0.0     0
8        0.5     face    stim_0002       0.756   1
1        0.5     scene   stim_0048       0.892   1
7        0.5     object  stim_0126       0.634   1
3        0.5     baseline        n/a     n/a     n/a
9        0.5     face    stim_0005       0.801   1

Events metadata (*_events.json):

Descriptions of the events file columns

{
    "onset": {
        "LongName": "Event onset time",
        "Description": "Time in seconds from the start of acquisition when the event begins",
        "Units": "seconds"
    },
    "duration": {
        "LongName": "Event duration",
        "Description": "Duration of the stimulus presentation",
        "Units": "seconds"
    },
    "trial_type": {
        "LongName": "Trial type",
        "Description": "Category or type of stimulus presented in this trial",
        "Levels": {
            "face": "Human face stimulus",
            "scene": "Natural or indoor scene stimulus",
            "object": "Object stimulus",
            "baseline": "Fixation or rest period"
        }
    },
    "stimulus_id": {
        "LongName": "Stimulus identifier",
        "Description": "Unique identifier for the specific stimulus image presented, references stimuli.tsv"
    },
    "response_time": {
        "LongName": "Response time",
        "Description": "Time in seconds from stimulus onset to participant response. 0 indicates no response or missed trial",
        "Units": "seconds"
    },
    "accuracy": {
        "LongName": "Response accuracy",
        "Description": "Whether the participant's response was correct",
        "Levels": {
            "1": "Correct response",
            "0": "Incorrect response or miss",
            "n/a": "No response required for this trial type"
        }
    }
}