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- Title
Low-frequency neuronal oscillations show evidence of heritability and association with performance measures in ADHD.
- Authors
Tye, Charlotte; Rijsdijk, Fruhling; Kuntsi, Jonna; Asherson, Philip; Bolton, Patrick; McLoughlin, Gráinne
- Abstract
Introduction and objective: Increased reaction-time variability (RTV) in ADHD may arise from the inability to appropriately modulate very low-frequency oscillations (VLFOs; <0.05 Hz) of the brain that are observed when the brain is in ‘default-mode’. A lack of sufficient VLFO attenuation or ‘default-mode interference’ during cognitive activity may play a role in attentional lapses that contribute to RTV [3]. Recent studies using EEG to investigate this hypothesis have reported an association between reduced VLFO power and inattention symptom scores and that less rest-to-task VLFO attenuation is associated with ADHD [1]. State-related conditions can affect the transition; if the individual is experiencing little extrinsic motivation, VLFO attenuation would require a larger investment of energetic resources [3]. Therefore it can be hypothesised that default-mode interference in ADHD would decrease when the individual is offered a reward, as extrinsic motivation increases and arousal is optimised. EEG frequency bands consistently demonstrate high heritability, an important criterion for its acceptance as a marker of a disorder, yet this has not yet been investigated in VLFOs. An additional aim of the study is to investigate heritability and genetic overlap between ADHD and VLFOs. Methods: 68 twin pairs were recruited from the twins early development study (TEDS) based on a trajectory analysis of consistently high or low ADHD scores. The fast task [2], a four-choice reaction time task, was administered to measure the effects of arousal consisting of a baseline and a fast-incentive condition combining a fast event rate and rewards. VLFO activity was measured using DC-EEG. Mean absolute power was calculated using fast-Fourier transform (FFT) analysis across sub-delta very low-frequency bands Slow-4 (S4; 0.02–0.06 Hz), Slow-3 (S3; 0.06–0.2 Hz), Slow-2 (S2; 0.2– 0.5 Hz) and Slow-1 (S1; 0.5–1.5 Hz). We will apply structural equation model-fitting using monozygotic (MZ) and dizygotic (DZ) twin pairs ascertained on ADHD scores. The program Mx will be used for maximum likelihood genetic model fitting, using an applied bivariate model, to directly estimate model parameters [additive genetic (A); common environmental (C); and unique environmental effects (E)] from the observed data. Results: Based on previous research (Helps et al. 2010), we combined S4 + S3 and S2 + S1. Preliminary analysis of 60 twin pairs during the completion of the baseline condition of the Fast task suggests significantly higher S3 + S4 power in those with high symptoms scores (M = 0.7140, SD = 1.90) compared to those with low symptom scores (M = -0.3275, SD = 1.74; t = -2.12, p < 0.05). Additionally, significant associations were found between S3 + S4 and mean reaction-time (MRT; r = 0.307, p\0.05) and reaction-time standard deviation (RTSD; r = 0.397, p < 0.01), and between S1 + S2 and MRT (r = 0.376, p < 0.01) and RTSD (r = 0.283, p < 0.05). We will report VLFO patterns during the fast-incentive and rest conditions to assess the effect of arousal on default-mode interference. We will further describe the genetic models for VLFOs based on model-fitting analyses. Discussion: The findings support previous studies reporting increased VLFO power during cognitive activity in ADHD, suggesting that during task completion those with ADHD have increased default-mode interference. Moreover, decreased attenuation of VLFOs during cognitive activity is associated with poor task performance. The implications of heritability will be discussed. Conclusion: These findings strengthen the association between nonoptimal arousal and inattention, and warrant further investigation of the state-related factors that may improve task performance and EEG-indexed arousal using genetically sensitive designs.
- Publication
European Child & Adolescent Psychiatry, 2010, Vol 19, pS90
- ISSN
1018-8827
- Publication type
Article
- DOI
10.1007/s00787-010-0117-5