Inhibitory processes in people with Williams syndrome and Down syndrome

AbstractBackground: Research on inhibitory processes in neurodevelopmental disorders (NDDs) is essential, as these mechanisms constitute the neurocognitive substrate of executive functions such as self-control, emotional regulation, and behavioural adaptation, processes that are fundamental for personal autonomy and social inclusion. These mechanisms are particularly vulnerable in populations with NDDs associated with intellectual disability, such as Williams syndrome (WS) and Down syndrome (DS). Although executive deficits in these syndromes are well documented, the specific profile of impairment across different inhibitory components (perceptual, cognitive, and motor) remains fragmented. A precise delineation of the impairment profile for each of these components is indispensable for advancing the understanding of the cognitive bases of these disorders and for developing specific evidence-based intervention programmes.Methods. The sample consisted of four groups of 27 participants each: an experimental group with WS, an experimental group with DS, and two control groups (CG) of individuals with typical development (TD), each individually matched to one of the clinical groups. To examine cognitive and motor inhibition processes, two inhibition tasks were administered: the Day–Night task and the Go/No-go task, respectively.Results. In the Day–Night task, the WS group showed significantly lower performance in interference conditions than both the DS group and its matched CG, whereas the overall performance of the DS group did not differ from its CG. In the Go/No-go task, both the WS and DS groups committed a higher proportion of omission errors (associated with inattention) than their respective CG, with the DS group showing a higher proportion than the WS group. However, the difference in the proportion of commission errors (associated with impulsivity) between the clinical groups was not significant.Conclusions. Results from the Day–Night task indicate cognitive inhibition difficulties in the WS group, whereas no clear evidence of such difficulties was observed in the DS group. The Go/No-go task results suggest that both WS and DS groups may present deficits in sustained attention, while their motor inhibitory capacity does not show clear evidence of impairment.Keywords: Executive functions; cognitive inhibition; motor inhibition; Williams syndrome; Down syndrome