Abstract

In daily life, we often face decisions where potential outcomes are unclear, creating uncertainty. The complete or partial lack of knowledge regarding outcome probabilities- referred to as ambiguity-poses significant challenges for individuals. While recent studies have linked ambiguity in decision-making to neural activity in the parietal cortex, the precise role of this region and its interactions with other brain areas remain poorly understood. Here, we present a comprehensive dataset on human decision-making under conditions of risk and ambiguity. The dataset includes two experimental sessions. The first one corresponds to the MRI setting, which includes structural MRI (T1-and T2-weighted images, n = 52), diffusion-weighted imaging ( n = 45), and task-based functional MRI ( n = 38). The second session corresponds to the EEG setting combined with inhibitory transcranial magnetic stimulation (TMS), targeting two parietal regions and the vertex ( n = 24). TMS targets were defined from group-level fMRI activations obtained in the first session and then transformed to individual anatomy. Ten participants completed both fMRI and EEG-TMS recordings. This dataset, partially analyzed in previous work, now includes newly acquired and previously unexamined data- such as diffusion-weighted imaging, T2-weighted images- and is fully organized according to the Brain Imaging Data Structure (BIDS) standard. It provides valuable opportunities to investigate the neurobiological decision-making mechanisms under ambiguity, focusing on the parietal cortex. (c) 2026 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/)