Abstract
Atypical brain function in attention-deficit/hyperactivity disorder (ADHD) has been identified using both task-activation and functional connectivity fMRI approaches. Recent work highlights the potential for another measure derived from functional neuroimaging data, brain signal variability, to reveal insights into clinical conditions. Higher brain signal variability has previously been linked with optimal behavioral performance. At present, little is known regarding the relationship between resting-state brain signal variability and ADHD symptom severity. The current study examined the relationship between a measure of moment-to-moment brain signal variability called mean-square successive difference (MSSD) and ADHD symptomatology in a group of children (7–12 years old) with (n = 40) and without (n = 30) a formal diagnosis of ADHD. A categorical analysis comparing subjects with and without a clinical diagnosis of ADHD showed no differences in MSSD between groups. A dimensional analysis revealed a positive relationship between MSSD and overall ADHD symptom severity and inattention across children with and without an ADHD diagnosis. Specifically, this positive relationship was found in medial prefrontal areas comprising the default mode network. These results demonstrate a link between intrinsic brain signal variability and ADHD symptom severity that cuts across diagnostic categories, and point to a locus of dysfunction consistent with previous neuroimaging literature.
Highlights
Attention-deficit/hyperactivity disorder (ADHD) is characterized by a lack of attention, impulsivity, and hyperactivity and affects ∼11% of young individuals aged 4–17 years old (Visser et al, 2014)
Significant relationships with mean-square successive difference (MSSD) were found for ADHDindex and attention-deficit/hyperactivity disorder (ADHD)-inattentive symptom severity scores across children with and without an ADHD diagnosis (Figure 1)
The cluster-corrected results demonstrated that higher scores on the ADHD-index measure were related to increased MSSD in the dorsal medial prefrontal cortex (MPFC) and ventral MPFC, while higher scores on the ADHD-inattentive measure were associated with greater MSSD in the ventral MPFC
Summary
Attention-deficit/hyperactivity disorder (ADHD) is characterized by a lack of attention, impulsivity, and hyperactivity and affects ∼11% of young individuals aged 4–17 years old (Visser et al, 2014). Brain Variability and ADHD Symptoms periods in a task-based fMRI paradigm is more prevalent in younger compared with older adults (Garrett et al, 2010) These increases in BOLD signal variability were found in frontal, parietal, temporal, and subcortical brain areas. Intrinsic BOLD signal variability in resting-state fMRI data has been shown to generally decrease for most areas of the brain across the lifespan and increase within the insula and ventral temporal cortex (Nomi et al, 2017). These studies demonstrate how intrinsic BOLD signal variability measures can identify meaningful differences between and across subject populations
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