Differences between late preterm and full-term infants: comparing effects of a short bout of practice on early reaching behavior

This study compared the effects of a short bout of practice on reaching behavior between late preterm and full-term infants at the onset of goal-directed reaching. Twelve late preterm infants and twelve full-term infants received reaching practice based on a serial schedule. Late preterm and full-term infants were assessed in 3.3±1.4 and 2.6±1.0 days after the onset of goal-directed reaching in two measures in a single day: immediately before practice (pre-test) and immediately after practice (post-test). During the assessments, the infants were placed in a baby chair and a rubber toy was presented at their midline within reaching distance for 2 min. Between assessments, the infants received practice of toy-oriented reaching in 3 activities repeated for approximately 4 min. The activities were elicited in a pre-established serial sequence and were applied by a physical therapist. During the pre-test, late preterm infants presented lower range of proximal adjustments, greater proportion of reaches with semi-open hand, and greater proportion of reaches without grasping than the full-term infants. During the post-test, late preterm infants presented greater motor variability of proximal adjustments, but explored and selected distal control and grasping outcomes less compared to the full-term group. Differences in reaching and gross motor behavior between late preterm and full-term infants can be found at the age of reaching onset. Practice provided new opportunities for late preterm infants to improve perception-action coupling to reach; however, relative to full-terms, they seemed less advanced in benefiting from the experience for more refined manual tasks.