New light on neurocognitive processes linked to autism and attention deficit and hyperactivity disorder in childhood : studies of eye movements in twins

Abstract

Visual attention and oculomotor response inhibition have been associated with Autism Spectrum Disorder (ASD) and Attention Deficit and Hyperactivity Disorder (ADHD) respectively. The aim of this thesis was to increase our knowledge about these cognitive functions relevant to ASD and ADHD in early infancy and childhood using eye tracking and twin modelling.

Study 1 assessed the relative contribution of genetic and environmental influences to attentional networks and visual disengagement (using the gap overlap task) in a sample of twins from the general population, aged 9-14 years. It also assessed whether visual disengagement was associated with autistic traits. Gaze shift latencies across conditions were driven by shared genetic factors. Additionally, there were unique genetic influences to gaze shift latencies in the gap condition. In line with previous work, autistic traits were found to be heritable. There was no association between visual disengagement and autistic traits. Study 2 investigated the relative contribution of genetic and environmental factors to oculomotor response inhibition (using the antisaccade task) and the degree to which oculomotor response inhibition was associated with ADHD traits in the same twin sample. Oculomotor response inhibition in the form of premature anticipatory eye movements was heritable and associated to parent rated inattentive traits. This association was partially due to shared genetic factors. Study 3 investigated how visual disengagement relates to other cognitive developmental processes and behaviors, socioeconomic status and biological sex in early infancy. Gaze shift latencies in the overlap, baseline and gap conditions, of the Gap Overlap task, differed as a function of socioeconomic status and sex. No other associations between visual attention and developmental measures were observed.

Thus, in summary, while these findings do not support neither a phenotypic nor a genetic link between visual disengagement and ASD, they support such association between oculomotor response inhibition and inattention (a core component of ADHD). Finally, these findings highlight the influence of sociodemographic factors on individual differences in visual attention in early infancy, thus underscoring the importance of understanding all sources of variation in attentional functions in childhood.