Let’s take a break: Head motion during fMRI tasks is reduced in children and adults if data acquisition is distributed across sessions or days

Head motion remains a challenging confound in functional magnetic resonance imaging (fMRI) studies of both children and adults. Most pediatric neuroimaging labs have developed experience-based, child-friendly standards concerning e.g. the maximum length of a session or the date of mock scanner training. However, it is unclear which factors of child-friendly neuroimaging approaches are effective in reducing head motion. Here, we investigate three main factors including (i) time lag of mock scanner training to the actual scan, (ii) prior scan time, and (iii) task engagement in a dataset of 77 children and 64 adults using a multilevel modeling approach. In children, distributing fMRI data acquisition across multiple same-day sessions reduces head motion. Nevertheless, motion increases over the course of a study, especially in older children. In adults, splitting data acquisition into multiple days, but not same-day sessions, reduces head motion. Moreover, motion is reduced after inside-scanner breaks. In both children and adults, motion increases with run length. Our results suggest that splitting up fMRI data acquisition is an effective tool to reduce head motion in general. At the same time, different ways of splitting up data acquisition benefit children and adults.nnHighlightsO_LIIn children, fMRI data acquisition split into multiple sessions reduces head motionnC_LIO_LIHowever, childrens head motion increases over the duration of the studynC_LIO_LIIn adults, fMRI data acquisition split into several days reduces head motionnC_LIO_LIMoreover, adults motion decreases after inside-scanner breaksnC_LIO_LIIn both children and adults, motion increases with run lengthnC_LI