Cortical Responses to Alien Odors in Newborns: An fNIRS Study

Abstract

Very preterm (VPT) infants are exposed to odors released by healthcare products, triggering the trigeminal and olfactory subsystems. Irritation of the nasal mucosa induces pain in adults. We examined whether preterm and full-term (FT) newborns perceived trigeminal odors at different cortical levels, whether these odors elicit pain, and if oral glucose modulates this pain. We performed 44 recording sessions in newborn (15 VPT infants, 12 VPT infants at term-equivalent age, and 17 FT infants) following exposure to trigeminal/olfactory stimuli from the hospital environment. We repeated the exposure after oral glucose administration. We recorded cortical activation in the olfactory, frontal, and somatosensory cortices by functional near-infrared spectroscopy, and analyzed pain behaviors from videotaped recordings. Newborns integrated trigeminal/olfactory stimuli in trigeminal/olfactory and nociceptive processing areas beginning at 31 weeks postmenstrual age, and also exhibited pain behaviors. Pain scores were positively associated with the level of cortical activation. Oral glucose inhibited pain behaviors and cortical activation. There were developmental differences in cortical integration related to brain maturation and duration of the extra-uterine experience. In conclusion, VPT and FT infants showed trigeminal sensitivity after exposure to alien odors that induce pain, potentially affecting the wiring of the neuronal circuits of the newborn brain.

Investigation of the Pattern of the Hemodynamic Response as Measured by Functional Near-Infrared Spectroscopy (fNIRS) Studies in Newborns, Less Than a Month Old: A Systematic Review

“…One study investigated newborns with HIE alongside a control group (Chen et al, 2002 ); only the results from the control group are presented here. Similarly, some studies looked at both term and preterm newborns (Isobe et al, 2001 ; Ozawa et al, 2011a ; Naoi et al, 2013 ; Carlier-Torres et al, 2014 ; Frie et al, 2017 ; Arimitsu et al, 2018 ) or included subjects older than 30 days (Meek et al, 1998 ); the results presented here only include the responses from the term infants <30 days old.…”

“…Three studies used an olfactory stimulus in newborns. All studies monitored the frontal lobe with one study additionally monitoring the parietal lobe (Frie et al, 2017 ). All three studies found a positive response of Δ[HbO 2 ] with results of Δ[HHb] not being reported in two studies (Barton, 2000 ; Aoyama et al, 2010 ) and showing a negative response in one study (Frie et al, 2017 ).…”

Reducing toxic stress in the neonatal intensive care unit to improve infant outcomes

“…Bright light invokes physiologic dysregulation in NICU infants and can contribute to poor visual development (Watanabe et al, 2013). Finally, noxious smells from disinfectants, adhesives, lubricants, skin care products, and hand hygiene products induce pain responses in NICU infants (Frie, Bartocci, Lagercrantz, & Kuhn, 2017;Kuhn, Astruc, Messer, & Marlier, 2011;Lipchock, Reed, & Mennella, 2011).…”

Making of the mind

“…Smell is processed in the orbitofrontal cortex, which has been demonstrated with near‐infrared spectroscopy. Pleasant smells like vanilla and colostrum have been shown to evoke increased hemodynamic responses, unlike unpleasant smells like disinfectant or detergent …”