Precision Imaging for Intraindividual Investigation of the Reward Response

The reliance of fMRI research on between-person comparisons is limited by low test-retest reliability and an inability to explain within-person processes. Intraindividual studies are needed to understand how changes in brain functioning relate to changes in behavior. Here, we present open data and analysis of a novel intensively sampled fMRI study. This precision imaging dataset includes 44 sessions acquired across four participants at a twice-weekly rate. In each session, participants completed multiple reward-related tasks, mood and alertness ratings, and a behavioral mood manipulation. We examined how the reward response reflects between-person or within-person variance. Trial-level models suggested dramatically more trials than typically collected are needed to maximize reliability within runs and individuals. Test-retest reliability of the reward response was very low and not explained by measurement error, suggesting low power for between-person comparisons without large amounts of data. At an intraindividual level, mood and alertness explained up to 37% of the intraindividual variance of the anticipatory reward response. Finally, we found that while reliability or brain-behavior associations were not improved by multi-echo denoising, a multivariate reward signature had stronger intraindividual behavioral associations than a univariate anatomical mask. Together, results suggest that the BOLD reward response is not a stable trait-like marker, but moderated by state-like factors. More broadly, BOLD activation to reward tasks-and likely other fMRI tasks-presents substantial opportunity for within-person study to complement the traditional focus on between-person study. We conclude with a discussion of considerations for intensive longitudinal neuroimaging designs.