ADHD familial loading and abnormal EEG alpha asymmetry in children with ADHD

Abstract

Objective: Abnormal brain laterality (ABL) is indicated in ADHD. ADHD and brain laterality are heritable. Genetic factors contributing to lateralization of brain function may contribute to ADHD. If so, increased ADHD family loading should be associated with greater ABL. Previous studies have shown increased rightward alpha asymmetry in ADHD. We tested whether this was more pronounced in ADHD children with increased ADHD family loading.

Methods: We compared EEG alpha asymmetry at rest and during the Conner's Continuous Performance Test (CPT) in ADHD children with and without ADHD affected parents, and replicated our findings in a second larger sample. The replication study additionally stratified the parent-affected sample by parental persistent versus non-persistent ADHD status, increased spatial resolution of EEG measures, and assessed low versus high-alpha.

Results: Study-1: the parent-affected group showed increased rightward asymmetry across frontal and central regions and reduced rightward parietal asymmetry during an eyes closed (EC) condition, as well as increasing rightward parietal asymmetry with advancing age during the CPT. Study-2 replicated these findings and further delineated influences of low versus high-alpha, recording site, and effects of parental persistent versus non-persistent ADHD status.

Conclusion: Increased ADHD familial loading was associated with increased rightward frontal asymmetry. In contrast, increased rightward parietal asymmetry was associated with reduced ADHD family loading. Frontal results are consistent with an ADHD endophenotype. Parietal results suggest an ADHD adaptive trait prevalent with less ADHD family loading. Age effects indicate a unique developmental course among ADHD children whose parents have non-persistent ADHD.

Copyright 2009 Elsevier Ltd. All rights reserved.

Figures

Figure 1. Study-1 Group Differences in Alpha Asymmetry During EC Condition (adjusted for age and sex)

Group difference for EC EEG alpha asymmetry across frontal (FLI), central (CLI), and parietal (PLI) laterality indices; asymmetry scores > 0= rightward asymmetry; asymmetry scores

Figure 2. Study-1 Scatter Plots of Age Effects on CPT-PLI Alpha Asymmetry in PA− and PA+ groups

Scatter plots of age effects on parietal alpha asymmetry (PLI= parietal laterality index) during the CPT; PA− = ADHD children with no ADHD affected parents; PA+ = ADHD children with at least 1 ADHD affected parent; Pearson correlation analysis of age and the CPT-PLI measure for PA− and PA+ groups are shown.

Figure 3. Study-2 Mean Group differences in Alpha Asymmetry During EC Condition

PA− = ADHD children with no ADHD affected parents; PA+r = ADHD children with at least 1 remitted ADHD parent; PA+p = ADHD children with at least 1 currently affected ADHD parent; error bars show standard error

Figure 4. Study-2 Scatter Plots of Age Effect on Parietal Alpha Asymmetry During the CPT

Age effects on parietal laterality indices; LA = low alpha; HA = high alpha; PA− = ADHD children with no ADHD affected parents; PA+r = ADHD children with at least 1 remitted ADHD parent; PA+p = ADHD children with at least 1 currently affected ADHD parent; pearson correlations between age and parietal laterality indices are shown.