Executive function and language: a behavioural and functional near-infrared spectroscopy study in 23 normally hearing children and one deaf child with cochlear implants.

Introduction: Emerging evidence suggests that neurocognitive processes, notably executive function (EF), should be considered important contributors to the observed variability in language outcome in both normally hearing (NH) and deaf children. Neural correlates of EF have potential clinical value, especially for infants and young children, in whom behavioural assessments can be unreliable. Methods: In the current study, we aimed to examine cortical correlates of EF in NH children aged 4-6 years old using functional near-infrared spectroscopy (fNIRS), a non-invasive, neuroimaging technique. In 23 NH children we measured activity in superior temporal and prefrontal cortex bilaterally whilst participants performed a behavioural EF task. Results: A significant association between the amplitude of EF-evoked cortical activation overlying the left dorsolateral prefrontal cortex and language performance was observed in NH children. To demonstrate that fNIRS is feasibly capable of measuring cortical responses specifically to behavioural EF in paediatric cochlear implant (CI) recipients, we also present the data for one deaf child aged 4.3 years with (CIs) who underwent the same simultaneous behavioural EF tasks and fNIRS imaging as the NH children. Discussion: The current results not only highlight the importance of higher-order top-down EF processes in language development, but they also demonstrate potential for fNIRS to provide cortical correlates of EF performance. Future applications of this technology could not only help explain variability in language outcome in both NH children and deaf children with CIs but also facilitate earlier intervention, such as EF rehabilitation strategies, where required at an earlier stage in a child's life.