PT - JOURNAL ARTICLE AU - Nakuci, Johan AU - Yeon, Jiwon AU - Xue, Kai AU - Kim, Ji-Hyun AU - Kim, Sung-Phil AU - Rahnev, Dobromir TI - Quantifying the contribution of subject and group factors in brain activation AID - 10.1101/2022.08.01.502338 DP - 2023 Jan 01 TA - bioRxiv PG - 2022.08.01.502338 4099 - http://biorxiv.org/content/early/2023/09/05/2022.08.01.502338.short 4100 - http://biorxiv.org/content/early/2023/09/05/2022.08.01.502338.full AB - Research in neuroscience often assumes universal neural mechanisms, but increasing evidence points towards sizeable individual differences in brain activations. What remains unclear is the extent of the idiosyncrasy and whether different types of analyses are associated with different levels of idiosyncrasy. Here we develop a new method for addressing these questions. The method consists of computing the within-subject reliability and subject-to-group similarity of brain activations and submitting these values to a computational model that quantifies the relative strength of group- and subject-level factors. We apply this method to a perceptual decision-making task (N=50) and find that activations related to task, reaction time (RT), and confidence are influenced equally strongly by group- and subject-level factors. Both group- and subject-level factors are dwarfed by a noise factor, though higher levels of smoothing increases their contributions relative to noise. Overall, our method allows for the quantification of group- and subject-level factors of brain activations and thus provides a more detailed understanding of the idiosyncrasy levels in brain activations.Competing Interest StatementThe authors have declared no competing interest.