Response inhibition is an essential executive function necessary for achieving behavioural and cognitive goals. In this study, we therefore examine whether tissue-specific qMRI metrics (R1, R2*, QSM) in the inhibitory network predict individual differences in Stop-Signal-Reaction-Time (SSRT) in healthy adults. To measure each participant’s stopping ability, we used the Stop-Signal task (SST). 7T MRI scans were used to acquire microstructural properties by measuring qMRI metrics (R1, R2*, QSM). We used the cognitive modelling approach to gain a deeper understanding of the response latency. 

Finally, we conducted Bayesian Kendall's τ correlations between each brain region of interest-metric pair and SSRT. We found no significant correlations across any inhibitory region of interest and metric (R1, R2*, QSM) combinations. All our Bayes Factors ranged from anecdotal to moderate in favour of the null hypothesis (H₀). Our results open an interesting discussion about microstructural properties that are either not pathologically observable in the healthy population or fall within a narrow effect size range, making them harder to detect. Our study shows an important development in the study of the microstructural properties of the inhibitory network in the healthy population, encouraging rethinking of study protocols and procedures.