Precision fMRI reveals that the language network exhibits adult-like left-hemispheric lateralization by 4 years of age.

Left hemisphere damage in adulthood often leads to linguistic deficits, but many cases of early damage leave linguistic processing preserved, and a functional language system can develop in the right hemisphere. To explain this early apparent equipotentiality of the two hemispheres for language, some have proposed that the language system is bilateral during early development and only becomes left-lateralized with age. We examined language lateralization using functional magnetic resonance imaging with two large pediatric cohorts (total n=273 children ages 4-16; n=107 adults). Strong, adult-level left-hemispheric lateralization (in activation volume and response magnitude) was evident by age 4. Thus, although the right hemisphere can take over language function in some cases of early brain damage, and although some features of the language system do show protracted development (magnitude of language response and strength of inter-regional correlations in the language network), the left-hemisphere bias for language is robustly present by 4 years of age. These results call for alternative accounts of early equipotentiality of the two hemispheres for language.

At-home use of app-based mindfulness for children: A randomized active-controlled trial.

Objectives: School-based mindfulness interventions in children have shown benefits to child well-being. Here, we investigated the effectiveness of a remote, app-based mindfulness intervention for promoting well-being in children. Methods: We conducted a randomized controlled trial (RCT) with two control groups to examine the effects of an 8-week mindfulness intervention in U.S. children ages 8-10. We compared pre-post effects between a mindfulness intervention using the Inner Explorer app, and two audiobook control interventions. The 279 children who participated in the interventions were assessed on self-report measures of anxiety and depression symptoms, perceived stress and trait mindfulness and we also collected parental reports. Results: Over 80% of children completed the intervention in each condition. There was evidence for reduced self-perceived stress in children and reduced negative affect in children by parental reports using the mindfulness app, but no significant reduction for anxiety or depression symptoms. In general, between-group effect sizes were small (ds < 0.45). Regular use, defined as at least 30 days of mindfulness practice within the study period, was associated with reduced child negative affect by parental reports, as well as reduced parental stress and child self-perceived stress. Conclusions: These findings suggest that home use of a mindfulness app in young children can have a positive impact on children's emotional well-being if the app is used regularly, specifically for at least 30 days in the 8-week study period. Strategies aimed at promoting regular use of the mindfulness app at home could lead to even better outcomes for children. Preregistration: Preregistered on OSF at https://osf.io/23vax.