ABSTRACT
Word in noise identification is facilitated by acoustic differences between target and competing sounds and temporal separation between the onset of the masker and that of the target. Younger and older adults are able to take advantage of onset delay when the masker is dissimilar (Noise) to the target word, but only younger adults are able to do so when the masker is similar (Babble). We examined the neural underpinning of this age difference using cortical evoked responses to words masked by either Babble or Noise when the masker preceded the target word by 100 or 600 ms in younger and older adults, after adjusting the signal-to-noise ratios (SNRs) to equate behavioural performance across age groups and conditions. For the 100 ms onset delay, the word in noise elicited an acoustic change complex (ACC) response that was comparable in younger and older adults. For the 600 ms onset delay, the ACC was modulated by both masker type and age. In older adults, the ACC to a word in babble was not affected by the increase in onset delay whereas younger adults showed a benefit from longer delays. Hence, the age difference in sensitivity to temporal delay is indexed by early activity in the auditory cortex. These results are consistent with the hypothesis that an increase in onset delay improves stream segregation in younger adults in both noise and babble, but only in noise for older adults and that this change in stream segregation is evident in early cortical processes.
ABSTRACT
Child executive functions (cognitive flexibility, inhibitory control, working memory) are key to success in school. Cortisol, the primary stress hormone, is known to affect cognition; however, there is limited information about how child cortisol levels, parenting factors and child care context relate to executive functions in young children. The aim of this study was to examine relationships between child cortisol, parenting stress, parent coping, and daycare quality in relation to executive functions in children aged 3-5 years. We hypothesized that (1) poorer executive functioning would be related to higher child cortisol and higher parenting stress, and (2) positive daycare quality and positive parent coping style would buffer the effects of child cortisol and parenting stress on executive functions. A total of 101 children (53 girls, 48 boys, mean age 4.24 years ±0.74) with complete data on all measures were included. Three saliva samples to measure cortisol were collected at the child's daycare/preschool in one morning. Parents completed the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P), Parenting Stress Index (PSI), and Ways of Coping Questionnaire (WCQ). The Early Childhood Environment Rating Scale - Revised (ECERS-R) was used to measure the quality of daycare. It was found that children with poorer executive functioning had higher levels of salivary cortisol, and their parents reported higher parenting stress. However, parent coping style and quality of daycare did not modulate these relationships. Identifying ways to promote child executive functioning is an important direction for improving school readiness.
