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Open Imaging Index
MRI Brain

Probability Decision-making with Ambiguity (ds004917)

Probability Decision-making Task with ambiguity

Structural, diffusion and task fMRI from healthy young adults choosing between gambles with known or partly hidden odds, collected to study how the parietal cortex handles ambiguity; a second group has EEG during parietal TMS.

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Overview

This OpenNeuro dataset comes from a Chilean study on how people decide when the odds of a reward are only partly known. Participants picked one of two options, each shown as a reward amount and a coloured bar giving its probability. In half of the trials a grey mask covered 40 to 80 percent of the bars, so the true odds were ambiguous. A 2026 Data in Brief article describes the release. Snapshot 1.0.1 (May 2024) is the current version, released under a CC0 waiver.

Composition

There are 53 healthy adults aged 18 to 31 (27 female, 26 male), recruited through social media. 52 of them have T1- and T2-weighted anatomical scans. Of these, 45 also have diffusion MRI and 38 have one task fMRI run of the decision game; 37 have both. A separate EEG session with transcranial magnetic stimulation (TMS) holds 24 people, and one of them has no MRI at all. The overlap between the fMRI and EEG groups is small (nine people in participants.tsv, ten in the Data in Brief text).

Acquisition

All MRI was acquired on one Siemens Skyra 3T at Clínica Alemana de Santiago. The anatomical scans are a 1 mm MPRAGE T1-weighted and a 1 mm 3D SPACE T2-weighted image. Diffusion uses 30 directions at b = 1000 s/mm² plus b = 0 images, 2 mm voxels, with three repetitions. The fMRI run is echo-planar BOLD with 3 mm voxels and a TR of about 2.4 s, covering 40 trials. A field map is included for most subjects. The EEG session used a 64-channel BrainAmp system while paired TMS pulses hit the right intraparietal sulcus, the right posterior parietal cortex or the vertex just before each feedback, over 240 trials.

Annotations

There are no image labels. Events files list stimulus codes, choices, reaction times, the hidden fraction of the bar, the true and visible probabilities and, for the EEG session, which TMS target was active. participants.tsv gives age, sex and which data types each person has.

Known limitations

  • The sample is small, young and from one site.
  • Only about ten people have both fMRI and EEG-TMS data, which limits cross-modal analyses within subjects.
  • The female/male split in Table 2 of the Data in Brief article (27/26 for the 52-person MRI session) does not match participants.tsv, which gives 26/26 for those with MRI.

Cohort

Aggregate numbers from the sources below. Bars are relative to the 53 subjects.

Sex

  • Female 27 51%
  • Male 26 49%

sex in participants.tsv of the ds004917 BIDS repository (CC0), columns age, sex, T1w, T2w, dwi, func, eeg

Modality

  • MRI 52 98%

Table 1 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Condition

Groups can overlap

  • Healthy control 53 100%

Section 4.2 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Scanner vendor

  • Siemens Healthineers 52 98%

Section 4.3.1.1 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Country

  • Chile 53 100%

Specifications table in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Age

mean 24.1 ± 3.8, median 24, range 18 to 31

0
10
20
30
40
42
18-1920-2930-39

age in participants.tsv of the ds004917 BIDS repository (CC0), columns age, sex, T1w, T2w, dwi, func, eeg; Table 2, Section 4.2 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Contrast / sequence

Groups can overlap

  • T1-weighted 52 98%
  • T2-weighted 52 98%
  • Diffusion-weighted 45 85%
  • BOLD fMRI 38 72%

Table 1 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Field strength

  • 3 T 52 98%

Section 4.3.1.1 in Figueroa-Vargas et al. 2026, A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity, Data in Brief

Contrast combinations

How many subjects have exactly each set of contrasts.

T1wT2wdwiboldSubjects with exactly this set
37
8
6
1

anat/dwi/func NIfTI files in File listing and JSON sidecars of the ds004917 BIDS repository (CC0), NIfTI files counted per subject folder, sidecar fields Manufacturer, ManufacturersModelName, MagneticFieldStrength and InstitutionName

License and access

Our reading of the license, not legal advice. Before you use the data, read the original license and confirm that your use is allowed. We take no responsibility for how you use a dataset. Full disclaimer

Access
Open download

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Access page

Creative Commons Zero 1.0 Universal

Public domain dedication. Do anything with the data, including commercial use, without asking and without having to give credit.

dataset_description.json of snapshot 1.0.1 states "License" CC0.

Original license text Version read: 1.0 Checked 2026-10-07

What you can do

  • Yes
  • Yes
  • Yes
  • Yes
  • Yes

What you can share

  • Yes
  • Yes
  • Yes

What you must do

  • No
  • Share alike No
  • No
  • No
  • Manuscript review No
  • Release code No
  • Return results No
  • Delete after use No

Limits

  • No
  • Location limits No

Citation

Figueroa-Vargas A, Valdebenito-Oyarzo G, Martínez-Molina MP, Zamorano F, Billeke P. A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity. Data in Brief 65, 112535 (2026). doi:10.1016/j.dib.2026.112535. Also cite Valdebenito-Oyarzo G et al. The parietal cortex has a causal role in ambiguity computations in humans. PLOS Biology 22, e3002452 (2024). doi:10.1371/journal.pbio.3002452

@article{figueroavargas2026,
  title={A comprehensive multimodal MRI and EEG-TMS dataset on the impact of parietal cortex inhibition on decision-making under ambiguity},
  author={Figueroa-Vargas, Alejandra and Valdebenito-Oyarzo, Gabriela and Mart{\'i}nez-Molina, Mar{\'i}a Paz and Zamorano, Francisco and Billeke, Pablo},
  journal={Data in Brief},
  volume={65},
  pages={112535},
  year={2026},
  doi={10.1016/j.dib.2026.112535}
}
@article{valdebenitooyarzo2024,
  title={The parietal cortex has a causal role in ambiguity computations in humans},
  author={Valdebenito-Oyarzo, Gabriela and Mart{\'i}nez-Molina, Mar{\'i}a Paz and Soto-Icaza, Patricia and Zamorano, Francisco and Figueroa-Vargas, Alejandra and Larra{\'i}n-Valenzuela, Josefina and Stecher, Ximena and Salinas, C{\'e}sar and Bastin, Julien and Valero-Cabr{\'e}, Antoni and Polania, Rafael and Billeke, Pablo},
  journal={PLOS Biology},
  volume={22},
  pages={e3002452},
  year={2024},
  doi={10.1371/journal.pbio.3002452}
}

Sources

Every number on this page comes from one of these documents. Each chart names the table or page it is taken from. The raw numbers are in stats.csv.