Developmental Progression of Inhibitory Control and Flexible Problem-Solving among Infants with Histories of Preterm...

Inhibitory control during visually guided reaching allows for the development of flexible problem-solving in healthy infants born at term. Inhibitory control is often impaired among older children born preterm, but the developmental trajectory of inhibitory control in infants born preterm is not well understood. The objective of this study was to evaluate the developmental trajectory of inhibitory control on the Object Retrieval Task in infants born preterm.

This was a cross-sectional study including a convenience sample of infants born preterm (less than 37 weeks), who were evaluated at corrected ages 5-6, 7-8, 9-10, 11-12, 13-15, and 16-18 months. Children born preterm with additional diagnoses of congenital anomalies, known genetic disorders, focal stroke, neoplasm, or maternal HIV exposure or children in the care of the state were excluded. Children in each of the age-groups were asked to retrieve a toy from a Plexiglas box with an opening on one side. The orientation of the opening was rotated over three trials, and the visually guided reach patterns were scored based on methods used by Diamond. Visually guided reach patterns ranged from perseverative hitting of the box to immediately reaching through the box opening. Analysis consisted of Fischer's exact tests to compare categorical measures, Jonckheere-Terpstra tests to compare ordinal measures, F test from general linear models to compare continuous measures and ordinal logistic regression to assess the association between brain injury and reach patterns.

The majority of infants born preterm in corrected age-groups of 5-6, 7-8, and 9-10 months perseveratively hit the box regardless of the orientation of the opening. This pattern of predominant immature visually guided reaching persisted at 12 months corrected age in this cohort of infants born preterm, with 75% participants demonstrating an immature reach with the box opening at the front and to the left and 88% demonstrating this with the box opening to the right.

In this cohort of preterm infants, developmental progression of inhibitory control and progression of visually guided reaching did not follow the same developmental trajectory observed in full term typically developing infants previously documented by Diamond (1994). While 100% of typically developing infants born at term in Diamond's cohort demonstrated inhibitory control and mature visually guided reach patterns by age 12 months, 75% of participants in our cohort of infants born preterm continued to demonstrate a predominance of immature visually guided reach patterns. This study demonstrates identification of early impairments in inhibitory control using a resource-conscious, low-cost, and brief neurobehavioral assessment tool. This provides a window for early interventions to limit problems in executive dysfunction at school age and beyond.