Intact sleep-dependent memory consolidation of auditory statistical learning among young adults with ADHD

Background Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder commonly linked to deficits in executive function. However, some theoretical frameworks propose that ADHD may also involve disruptions in cognitive mechanisms central to statistical learning, such as predictive processing and implicit learning. Moreover, abnormal sleep electroencephalography in ADHD raises the possibility of altered sleep-dependent memory consolidation of statistical learning. Aim Here we examined how individuals with ADHD acquire and consolidate statistical regularities in auditory input, with specific focus on the role of sleep in memory consolidation. Participants were passively exposed to sequences of tones organized according to probabilistic rules of varying complexity and subsequently tested on their recognition of novel tone sequences that conformed to the learned statistical structure. Immediate and delayed recall tests were conducted, with a subset of participants completing the delayed test after a 12-hour interval that included nocturnal sleep, whereas others were tested following a 12-hour interval of daytime wake. This design enabled us to examine how sleep influences the generation of long-lasting statistically structured input in ADHD. Results Statistical learning performance significantly deteriorated following an interval of daytime wake but remained stable after a night of sleep, indicating that sleep has a protective effect on memory consolidation of statistical regularities. Importantly, participants with ADHD were capable of learning and consolidating statistical structures at the same level as controls. Conclusions These findings indicate that not all forms of learning and not all sleep-dependent mechanisms are affected in ADHD, highlighting the importance of distinguishing between different learning and memory processes in this population.