Does hunger affect spontaneous behavior in preterm neonates? A new coding scale

During the last decades, the systematic study of spontaneous motor activity within the earliest developmental stages has come to play a pivotal role in the assessment of preterm and term newborns (Prechtl et al., 1989; Thelen, 2000). In full-term neonates, a few pioneering studies highlighted a short-term relation between hunger and coordination of spontaneous movements (Rochat et al., 1988; Blass et al., 1989, Lew and Butterworth, 1995), limited to nutrition-related motor patterns. The present study aims to replicate these findings with regard to preterm neonates, as well as to test the broader hypothesis that appetite would work as a motivational condition that modulates different classes of – non necessarily feeding-related – behaviors. In order to do that we implemented a new coding scale, assembling 21 behavioral categories originally described in fetuses, preterm and full-term newborns by de Vries (1982), Prechtl (1985), Kurjak et al. (2003), Einspieler et al. (2008) and Wolff (1987) and reconceptualising them on the basis of the Facial Action Coding System (FACS) by Ekman and Friesen (Ekman and Friesen,1978; Ekman, Friesen & Hager, 2002), adapted for neonates and infants by Harriet Oster (Baby FACS, 2009). Both of these methods have shown a documented reliability in the detection of individual units of facial actions in the first months of life as well as in very low gestational age neonates. In a first pilot phase, we included 10 preterm neonates, between 33-42 weeks postmenstrual age (M = 36.90, SD = 3.178). Two video recordings were performed, respectively preceding and following feeding. The analysis of video recordings was performed frame by frame independently by two expert coders in behavioral micro-analysis. Data analysis were conducted on the frequency of occurrence per minute calculated for each of the 21 motor patterns. Statistical contrasts conducted by using the nonparametric Friedman test showed that neonates exhibited more frequently STARTLE (p = .034), HEAD ROTATION (p = .011), and DISTRESS (p = .002) before feeding than after feeding. In addition, with the aim of contrasting the youngest and the oldest neonates both between and within, the sample has been split into two groups based on postmenstrual age at the time of testing. Statistical analyses performed by the Mann-Whitney U test did not show significant differences between the two groups neither before nor after feeding. Instead, within contrasts revealed that both groups showed more frequently DISTRESS (p = .025, respectively) in the before feeding condition compared to the after feeding condition, but also that only the oldest group exhibited a greater occurrence of MOUTHING MOVEMENTS (p = .025) and HEAD ROTATION (p = .025) before compared to after feeding. If confirmed, these findings would support the thesis that hunger plays a motivational role even for preterm neonates, not only for strictly feeding-related behaviors. On the methodological side, the new scale we adopted seems sensitive enough to record subtle differences in the spontaneous behavior of preterm neonates.