This study investigated executive function and sustained attention in preterm and full-term infants at 8 months after expected date of delivery and at 10-11 months chronological age. Executive function and sustained attention emerge in infancy and continues to develop throughout childhood. Executive function and sustained attention is believed to underlie some learning problems in children at school age. Although numerous studies have reported that the overall development of preterm infants is comparable to that of full-term infants at the same corrected age, it is unclear to what extent the development of specific cognitive abilities is affected by prematurity and/or other factors such as medical complications. As preterm infants have a high rate of learning difficulties, it is possible that factors associated with prematurity specifically affect the development of some regions of the brain associated with the regulation of executive function and sustained attention. Thirty-seven preterm infants without identified disabilities, and 74 due date and gender matched healthy bull-term infants, participated in the present study. The preterm infants were all less that 32 weeks gestation and less that 1500 grams birth weight. The current study aimed to examine the effects of maturation and length of exposure to extrauterine environmental stimuli on the development of executive function and sustained attention, by comparing the development of preterm infants with that of full-term infants at both the same corrected age and the same chronological age. All infants were therefore assessed on executive function and sustained attention tasks at 8 months after the expected date of delivery (when preterm infants were actually 10-11 months chronological age). The full-term infants in the study were then reassessed at an age equivalent to the chronological age of their matched preterm infants at the time of the first assessment. The findings of the study showed that preterm infants performed significantly more poorly than full-term infants at both 8 months after the expected date of delivery and 10-11 months chronological age on all measures of executive function and sustained attention. However the difference between preterm and full-term infants at 8 months after expected date of delivery was much less that at 10-11 months chronological age. The results suggested that the effects of maturation are greater that the effects of exposure to extrauterine environmental stimuli on the development of executive function and sustained attention. However, as the performance of the preterm infants was below that of the term infants at the same corrected age, it was necessary to consider whether other factors associated with preterm birth were contributing to this difference. Confounding factors including cognitive abilities and psychomotor skills on the Bayley Scales of Infant Development, infant temperament, maternal education, family socioeconomic status and maternal psychological wellbeing were examined. Statistical analysis of the effects of these factors on the difference between preterm ad full-term infants found that only psychomotor sills significantly affected the differences between preterm and full-term infants of the same corrected age on executive function measures, although not on sustained attention measures. The differences between preterm and full-term infants of the same corrected age remained even when psychomotor skills were taken into consideration; therefore psychomotor skills were not sufficient to fully explain the differences between preterm and full-term infants in the performance of executive function. Consequently, the preterm infants were divided into two subgroups on the basis of (a) low or high medical risk factors, (b) birth weight of less that 1000g versus 1000-1500g, and (c) gestation age of less that 28 weeks versus 28-32 weeks, in order to assess the effects of these variables on the performance of executive function and sustained attention. Medical risk, lower birth weight and lower gestation age were all found to adversely affect performance on executive function, but did not affect the performance on sustained attention tasks. It is argued that these factors may influence the development of specific areas of the brain which govern executive function, and that as the prefrontal regions are particularly immature they may be especially vulnerable to damage or disruption. The fact that these perinatal factors did not contribute to the difference between preterm and full-term infants' performance on sustained attention tasks. This suggests that the deficits of sustained attention in preterm infants may be associated with birth prematurity per se, and that additional complications may not have any further detrimental effect. The three components of executive function (i.e., working memory, inhibition, and planning) did not correlate with each other when only infants with Bayley psychomotor ability scores greater that 85 were included, suggesting that the components of executive function may be discrete abilities which are governed by different parts of the prefrontal cortex. Sustained attention correlated with planning, supporting the suggestion that it may be a cognitive dimension which overlaps with executive function, depending upon the task requirement. Neither executive functio nor sustained attention correlated with the Bayley mental ability and Bayley psychomotor ability scores when infants with scores of less than 85 were excluded. This suggests that executive function and sustained attention measures are independent of general development.
| Identifer | oai:union.ndltd.org:ADTP/264840 |
| Date | January 2003 |
| Creators | Sun, Jing (Jenny) |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Jing (Jenny) Sun |
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