There is no association between axon diameter or count in the right superior longitudinal fasciculus (SLF) I and II and sustained attention among children with attention/deficit-hyperactivity disorder (ADHD), according to study findings published recently in Cortex.
Researchers conducted a longitudinal fixed-based analysis that included 161 children aged 9 to 14 years (participants with ADHD, n=80; controls, n=81) who had 309 diffusion-weighted imaging scans up to 3 waves across. Participants were recruited from the longitudinal community-based Neuroimaging of the Children’s Attention Project. Cognitive assessments and scans were conducted at the Murdoch Children’s Research Institute, Royal Children’s Hospital in Melbourne, Australia.
Mean fiber density and fiber-bundle cross section was calculated using fixed-based analysis. Omission errors and response time variability on the out-of-scanner sustained attention to response task was used to measure sustained attention. Associations of white matter metrics, group, and age with sustained attention were measured with linear mixed effects models.
No significant differences were noted between participants’ attending 1, 2, or 3 waves in sex, baseline IQ, socioeconomic status, or group (range, P =.418-.926). Equivalent variances between groups in sustained attention measures over the 3 waves were confirmed by Levene test (range, P =.056-.906).
Fewer errors were found in the control group and were associated with greater fiber density in the bilateral SLF I and right SLF II. There was better sustained attention with greater fiber density in the left inferior longitudinal fasciculus (ILF) and right thalamo-premotor pathway in both groups. Greater fiber cross-section in the left SLF I and II and right SLF III were also associated with better sustained attention in both groups.
Researchers noted the consistency of relationship across age span. Participants in the ADHD group had consistently worse sustained attention across all waves for omission errors and response time variability. Increasing age was associated with better sustained attention in both groups. There were no differences between girls and boys in sustained attention.
Limitations of the study include the fact that fiber cross section differences may be more subtle than density effects and heterogeneity in cognitive functioning for ADHD
Researchers conclude, “Greater capacity for information transfer across the SLF was associated with attention maintenance in 9-14-year olds regardless of diagnostic status, suggesting white matter macrostructure may also be important for attention maintenance. White matter and sustained attention associations were consistent across the longitudinal study, according with the stability of structural organization over this time.”
Thomson P, Vijayakumar N, Fuelscher I, Malpas CB, Hazell P, Silk TJ. White matter and sustained attention in children with attention/deficit-hyperactivity disorder: a longitudinal fixel-based analysis. Cortex. Published online October 7, 2022. doi:10.1016/j.cortex.2022.09.006