Asymmetrical Frontal-Subcortical Aberrance in ADHD: Empirical Support of a Developmental Network Model

BackgroundThis study empirically tests a theoretical model of ADHD that identifies aberrant frontal-to-subcortical projections--particularly those involving the ventral tegmental area and, consequently, the nucleus accumbens (NAc)--as a core neurobiological vulnerability. The model predicts reduced frontal influence on subcortical structures and group-by-direction interaction effects, especially at the NAc. MethodsStructural and resting-state fMRI data from sixty individuals with ADHD and sixty healthy controls were selected from the ADHD-200 dataset. The cortex was parcellated using MOSI (Modular Analysis and Similarity Measurements). The mean amplitude of low-frequency fluctuations (ALFF) and the mean time series were extracted for each frontal node. Subcortical nuclei--including the caudate, putamen, globus pallidus, NAc, and thalamus--were included in the analyses, with each voxel treated as a neural node. Correlation analyses were performed to examine the relationship between nodal power (ALFF) and nodal degree. Directional metrics were defined as frontal-to-subcortical (F2S) and subcortical-to-frontal (S2F) correlations between nodal strength and nodal power. Group differences and interactions were tested using t-tests and linear mixed-effects (LME) models. ResultsCorrelation and LME analyses revealed a consistent bimodal pattern, with positive F2S and negative S2F associations across all subcortical nuclei, suggesting a directional excitation-inhibition balance. Reduced F2S slopes in ADHD and a significant group-by-direction interaction in the NAc (p = 0.009) supported model predictions. ConclusionsThe proposed developmental model of ADHD was empirically supported.