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Speech motor control develops gradually as the acoustics of speech are mapped onto the positions and movements of the articulators. In this event-related potential (ERP) study, children and adults aged 4-30 years produced vocalizations while exposed to frequency-altered feedback. Vocal pitch variability and the latency of vocal responses were found to differ as a function of age. ERP responses indexed by the P1-N1-P2 complex were also modulated as a function of age. P1 amplitudes decreased with age, whereas N1 and P2 amplitudes increased with age. In addition, a correlation between vocal variability and N1 amplitudes was found, suggesting a complex interaction between behavioural and neurological responses to frequency-altered feedback. These results suggest that the neural systems that integrate auditory feedback during vocal motor control undergo robust changes with age and physiological development.

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Parent mediated interventions have the potential to positively influence the interactions and developmental outcomes of children with autism spectrum disorder (ASD). However, a range of factors relating to children, parents and caregivers, and study design may impact on outcomes and thus the generalizability of these interventions to the broader community. The objective of this review was to examine factors that may influence the feasibility, appropriateness, effectiveness, and generalizability of parent mediated interventions for children with ASD. We conducted a systematic review, yielding 41 articles. There was substantial variability in the intervention type, intensity, and study quality. Notably, 46 different inclusion/exclusion criteria were reported across studies including factors relating to children's development, access to other services, comorbidities, parental factors, and access to the intervention. Fifteen articles included examination of 45 different factors potentially associated with, or influencing, intervention outcomes including child (e.g., language skills, ASD severity, cognition) and parent (e.g., adherence and fidelity, education) factors. Although there is clear evidence for an increasingly sophisticated (e.g., systematic phased research for some interventions) and diverse (e.g., studies in geographical diverse contexts including low-resource communities) approach to research examining parent mediated interventions, there remains a need for improved study quality and measurement consistency in research, including a detailed examination of factors that may predict, moderate, and mediate intervention effectiveness for children and their parents.Lay Summary: Parent mediated interventions-in which parents adapt their own behavior or deliver interventions to help their children learn-appear to be effective for some children with autism spectrum disorder. In this review, we identified a range of child, parent, and study design factors that may influence intervention outcomes and ultimately the uptake of these approaches in the community. We suggest that research in this area could be further improved by ensuring that studies include diverse groups of children and parents, and by using study designs that help to establish not only if interventions work, but for whom they work best and why.

Speech production requires the combined effort of a feedback control system driven by sensory feedback, and a feedforward control system driven by internal models. However, the factors that dictate the relative weighting of these feedback and feedforward control systems are unclear. In this event-related potential (ERP) study, participants produced vocalisations while being exposed to blocks of frequency-altered feedback (FAF) perturbations that were either predictable in magnitude (consistently either 50 or 100 cents) or unpredictable in magnitude (50- and 100-cent perturbations varying randomly within each vocalisation). Vocal and P1-N1-P2 ERP responses revealed decreases in the magnitude and trial-to-trial variability of vocal responses, smaller N1 amplitudes, and shorter vocal, P1 and N1 response latencies following predictable FAF perturbation magnitudes. In addition, vocal response magnitudes correlated with N1 amplitudes, vocal response latencies, and P2 latencies. This pattern of results suggests that after repeated exposure to predictable FAF perturbations, the contribution of the feedforward control system increases. Examination of the presentation order of the FAF perturbations revealed smaller compensatory responses, smaller P1 and P2 amplitudes, and shorter N1 latencies when the block of predictable 100-cent perturbations occurred prior to the block of predictable 50-cent perturbations. These results suggest that exposure to large perturbations modulates responses to subsequent perturbations of equal or smaller size. Similarly, exposure to a 100-cent perturbation prior to a 50-cent perturbation within a vocalisation decreased the magnitude of vocal and N1 responses, but increased P1 and P2 latencies. Thus, exposure to a single perturbation can affect responses to subsequent perturbations.