Effect of presentation rate on auditory processing in Rett Syndrome: ERP study

Abstract

Abstract Rett Syndrome (RS) is a rare neurodevelopmeтtal disorder characterized by mutations in the MECP2 gene. Patients with RS have severe motor abnormalities and are often unable to walk, use hands and speak. The preservation of perceptual and cognitive functions is hard to assess, while clinicians and care-givers point out that these patients need more time to process information than typically developing peers. Here we examine neurophysiological correlates of auditory processing in RS as a function of presentation rate. From previous literature we knew that auditory event-related potential (ERP) is increased with prolongation of interstimulus interval (ISI). We presented a repetitive stimulus (1000Hz) at three different ISI of 900 ms, 1800 ms, and 3600 ms in children with RS and their typical development peers (TD) aged 2.5–16 years while recording 28-channels electroencephalogram, EEG. The amplitude of N1 and P2 components of event-related potential (ERP) was smaller at ISI 900 than at longer ISIs in both groups, pointing out that the basic mechanism of adaptation in the auditory system is preserved in Rett Syndrome. At the same time the latency of these components was significantly delayed in the RS than in TD. Moreover, late components (P2 and N2) were drastically reduced in Rett Syndrome irrespective of the ISI, suggesting a severely affected mechanism of integration of upcoming sensory input with memory. Based on these ERP measures it was possible to differentiate RS from TD with great accuracy (0.922 ± 0.047), being maximal with shortest ISI, supporting its implication as potential output measures in clinical trials as well as pointing to the diminishing of the neurophysiological differences between RS and TD with slowing down the presentation rate.