Dataset at a Glance
========================

The Active Visual Semantics (AVS) dataset combines MEG and eye-tracking data recorded while
participants visually explored natural scenes, along with structural MRI scans acquired before
the first MEG session. By focusing on active vision, it moves beyond the passive,
fixation-enforced viewing paradigms used in most existing neuroimaging datasets.

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   :widths: 30 70

   * - Participants
     - 5 (see :doc:`methods/participants`)
   * - Sessions
     - 10 MEG + eye-tracking sessions per participant, plus one anatomical session.
       10 runs in ses-01, 14 in ses-02 -- ses-10; 30 trials per run, so 4,080 trials
       (one per scene) per participant
   * - Stimuli
     - 4,080 natural scenes from the Natural Scenes Dataset (NSD), semantically balanced
       (see :doc:`methods/stimuli`)
   * - Task
     - Active viewing (4 s/scene) with a verbal scene-captioning task on 25% of trials
       (see :doc:`methods/semantic_captioning`)
   * - MEG
     - 306-channel Elekta Neuromag TRIUX, 1000 Hz (see :doc:`methods/meg_acquisition`)
   * - Eye tracking
     - EyeLink 1000, 1000 Hz (see :doc:`methods/eye_tracking`)
   * - Fixation epochs
     - More than 200,000 across the dataset. Shipped fixation- and saccade-locked,
       -0.5 to 0.8 s at 500 Hz, with per-epoch metadata
   * - Object labels
     - Per-fixation MS-COCO / COCO-Stuff category labels, 171 categories
       (see :doc:`methods/object_labeling`)
   * - Anatomy
     - Defaced individual T1 plus a ready-to-use FreeSurfer ``SUBJECTS_DIR``
       (cortex only -- source space, BEM, forward solution, coregistration, parcellations)
   * - Release size
     - 22,488 files, 663.1 GiB in total -- but the tree is designed for selective download
       (see :doc:`data_access`)

For the release layout and file formats, see :doc:`dataset/overview`; for known data-quality
caveats, see :doc:`dataset/known_issues`; for how to get the data, see :doc:`data_access`.

What Do I Need?
--------------------

.. list-table::
   :header-rows: 1

   * - Goal
     - Start here
   * - Load MEG + eye-tracking data for an analysis
     - :doc:`package/composer_guide`, :doc:`quickstart`
   * - Understand the acquisition/preprocessing pipeline
     - :doc:`methods/index`
   * - Source reconstruction / population codes
     - :doc:`tutorials/source_reconstruction_population_codes`
   * - Map fixations to scene objects
     - :doc:`methods/object_labeling`, :doc:`examples/cocostuff_object_detection`
   * - Work out which parts of the dataset to download
     - :doc:`data_access`
   * - See example analyses (RSA, encoding, source ERFs)
     - :doc:`analyses/index`
   * - Full function/class reference
     - :doc:`api/index`