Cortical markers of excitation/inhibition balance are associated with sensory responsivity from infancy in longitudinal cohorts enriched for autism and ADHD

Autism and ADHD are characterised by atypical sensory responsivity, and this may be driven by alterations in the balance of cortical excitation to inhibition (E/I). Studies in early development are required to establish the primary of effects. We utilised data from a prospective longitudinal cohort of infants with and without a family history (FH) of autism and/or ADHD (N=151; 55% male, 83% white). We extracted electroencephalography (EEG) metrics of E/I balance at 5, 10 and 14 months; the aperiodic exponent of the slope of the power spectrum (‘1/f’). Models estimated correlated latent growth curves of parent-reported hyper and hypo-responsivity between 10 – 36 months. Analyses tested associations between developmental trajectories of sensory responsivity and FH, parent-rated neurodevelopmental traits at 3 years and E/I balance. Results showed that FH-autism was associated with steeper increases in parent-reported hyper-responsivity between 10 to 36 months, whereas FH-ADHD was associated with steeper increases in hypo-responsivity. Higher hypo-responsivity at 10-month baseline was associated with both autistic and ADHD traits at 3 years. A steeper slope of hypo-responsivity predicted ADHD traits at 3 years. Neither the baseline or slope of hyper-responsivity was associated with FH-ADHD, or autistic or ADHD traits at 3 years. Males displayed higher baseline hypo-responsivity. Aperiodic exponent values at 5 and 10, but not 14 months, were associated with hyper-responsivity. Results suggest that hypo-responsivity in infancy may be an indicator of later autism and ADHD outcomes. Alterations in E/I balance may contribute to early differences in sensory responsivity and thus could represent a useful target for intervention development.