Voluntary saccades in attention-deficit/hyperactivity disorder: Looking into the relationship between motor impairment and Autism Spectrum Disorder symptoms

- Participants with ADHD-CT had hypermetric saccades and main sequence alterations.
- Pattern of saccade deficits is consistent with cerebellar dysfunction in ADHD-CT.
- ADHD-CT and ASD symptoms were associated with greater ocular motor impairment.
- Results are preliminary and further research with larger sample sizes is needed.

Although there is little overlap in core diagnostic criteria for ADHD and Autism Spectrum Disorder (ASD), ASD symptoms are estimated to co-occur in children with ADHD in 20-50% of cases. As motor control deficits are common to both disorders, we investigated the impact of ASD symptoms on ocular motor control in children with Attention Deficit Hyperactivity Disorder-Combined Type (ADHD-CT), using a cued saccade paradigm sensitive to cerebellar ocular motor impairment in ASD. Basic saccade metrics (latency, velocity and accuracy), trial-to-trial variability, and main sequences relationships (saccade velocity for a given amplitude) were assessed, for 14 males with ADHD-CT and 14 typically developing (TD) males (aged 8-14, IQ > 80). Our results revealed that saccade profiles of the ADHD-CT group showed a pattern of hypermetria and altered main sequence. As the cerebellum is crucially involved in the regulation of saccade parameters, we propose that this pattern of deficit in ADHD-CT is consistent with the widely reported morphological abnormalities in ocular motor vermis (cerebellar lobules VI-VII) in ADHD-CT and ASD.