Background Attention Deficit Hyperactivity Disorder (ADHD) is the most prevalent childhood neurodevelopmental disorder. It shares some genetic risk with Autism Spectrum Disorder (ASD), and the conditions often occur together. Both are potentially associated with abnormal glutamate and GABA neurotransmission, which can be modelled by measuring the synaptic activity in the retina with an electroretinogram (ERG). Reduction of retinal responses in ASD has been reported, but little is known about retinal activity in ADHD. In this study, we compared the light-adapted ERGs of individuals with ADHD, ASD and controls to investigate whether retinal responses differ between these neurodevelopmental conditions. Methods Full field light-adapted ERGs were recorded from 15 ADHD, 57 ASD (without ADHD) and 59 control participants, aged from 5.4 to 27.3 years old. A Troland protocol was used with a random series of nine flash strengths from −0.367 to 1.204 log photopic cd.s.m−2. The time-to-peak and amplitude of the a- and b-waves and the parameters of the Photopic Negative Response (PhNR) were compared amongst the three groups of participants, using generalised estimating equations. Results Statistically significant elevations of the ERG b-wave amplitudes, PhNR responses and faster timings of the b-wave time-to-peak were found in those with ADHD compared with both the control and ASD groups. The greatest elevation in the b-wave amplitudes associated with ADHD were observed at 1.204 log phot cd.s.m−2 flash strength (p < .0001), at which the b-wave amplitude in ASD was significantly lower than that in the controls. Using this measure, ADHD could be distinguished from ASD with an area under the curve of 0.88. Conclusions The ERG b-wave amplitude appears to be a distinctive differential feature for both ADHD and ASD, which produced a reversed pattern of b-wave responses. These findings imply imbalances between glutamate and GABA neurotransmission which primarily regulate the b-wave formation. Abnormalities in the b-wave amplitude could provisionally serve as a biomarker for both neurodevelopmental conditions.

Our memories are made of detailed sensory information representing the puzzle pieces of our personal past. The type of memory integrating sensory features is referred to as relational memory. The main objective of this study was to investigate whether relational memory is affected in children with autism spectrum disorder (ASD) since altered relational memory may contribute to atypical episodic memory observed in ASD. We also examined the association between perceptual style and relational memory abilities. Children with ASD (n = 14) and typically developed (TD) children (n = 16, 9-15 years old) completed a memory task with three conditions: two single-feature conditions measuring memory for objects and locations, and one relational memory condition measuring memory for objects and their locations combined. The Children's embedded figures test was administered to measure perceptual style. The ASD group selected more incorrect stimuli (false alarms) than the TD group, resulting in a lower proportion of correctly recognized targets across all memory conditions. The ASD group did not display a more local perceptual style than the TD group. However, perceptual style was associated with improved memory abilities across conditions. Our findings indicate that the overall memory performance of children with ASD is less stable, leading them to more incorrect responses than TD children. This may be due to the executive demands of the memory tasks, rather than specific impairments in memory binding.