Ontogeny of perception of maternal and nosocomial stimuli in infants

Preterm born infants in neonatal units experience unusual sensory inputs that can shape and nurture their developing brains differently from full-term healthy newborn infants. To improve the care of preterm infants and their neurodevelopmental outcomes, we need to understand how the brain functions at different developmental stages and implement this knowledge into clinical care and follow-up programs. An infant’s cortical response to external stimuli can be measured with functional near-infrared spectroscopy (fNIRS). We aimed to analyze how maternal and nosocomial stimuli are processed in the developing cerebral cortex in infants. In paper I, the functional cortical processing of a known face (the infant’s mother) and an unknown face were assessed at six to ten months of age with fNIRS. We found that the infants exhibited an increased brain response when they saw their mother’s face, as compared to the unknown face. In paper II, we aimed to study the regional cortical responses to known and unknown faces, to compare them between infants born extremely preterm and infants born full-term and to correlate them to regional brain volumes. The infants were examined at six to ten months of corrected age using fNIRS. We also performed structural brain magnetic resonance imaging in the preterm group and correlated their regional cortical volumes to their fNIRS responses. The preterm infants had a smaller hemodynamic response in the right frontotemporal area while viewing a face they knew than the full-term born infants. There was a negative correlation between the hemodynamic response in the right frontotemporal cortex and regional grey matter volume in the face processing areas. In paper III, we examined the effects of alien odors on preterm and full-term newborn infants, exploring whether these odors elicit pain, and if oral glucose modulates this pain. We exposed the infants to odorous stimuli from the hospital environment and recorded pain behaviors and cortical activation with fNIRS. We repeated the exposure and measurements after oral glucose administration. Newborn infants exhibited brain responses to both olfactory and nociceptive processing areas from 31 weeks of postmenstrual age and also demonstrated pain behaviors. Oral glucose inhibited pain behaviors and cortical activation. In paper IV, we studied the cortical processing of maternal breast odors in preterm and fullterm newborn infants. Three groups of infants, very preterm, late preterm and full-term, were exposed to their mother’s breast odor and a control odor during fNIRS measurements. Fullterm infants demonstrated bilateral activation of their olfactory cortices following exposure to the maternal breast odor. Late preterm infants and very preterm boys exhibited unilateral cortical activation, unlike very preterm girls. LIST OF SCIENTIFIC PAPERS This thesis is based on the following original articles and manuscript, which will be referred to by their Roman numerals. I. Carlsson J, Lagercrantz H, Olson L, Printz G, Bartocci M. Activation of the right fronto-temporal cortex during maternal facial recognition in young infants. Acta Paediatr, 2008;97:1221-5. II. Frie J, Padilla N, Ådén U, Lagercrantz H, Bartocci M. Extremely Preterm-Born Infants Demonstrate Different Facial Recognition Processes at 6-10 Months of Corrected Age. J Pediatr, 2016. 172: p. 96-102 e1. III. Frie J, Bartocci M, Lagercrantz H, Kuhn P. Cortical Responses to Alien Odors in Newborns: an fNIRS Study. Cerebral Cortex, 2017:1-12 https://doi.org/10.1093/cercor/bhx194 IV. Frie J, Bartocci M, Lagercrantz H, Kuhn P. Ontogeny of cortical perception of maternal breast odors in newborn infants: A fNIRS study -Manuscript CONTENTS