Activation of olfactory cortex in newborn infants after odor stimulation: A functional near-infrared spectroscopy study

In mammals, perception of smells during the first hours of lift: is an esse ntial prerequisite for adaptation of the newborn to the new extrauterine wo rld. Functional magnetic resonance studies have shown that olfactory impres sion is processed in the lateral and anterior orbito-frontal gyri of the fr ontal lobe. Near-infrared spectroscopy (NIRS) can detect changes in oxygena ted [Hb O-2], and deoxygenated [Hb H] Hb during cortical activation. The ai m of this study was to assess by NIRS olfactory cortex activity in newborn infants receiving olfactory stimuli. Twelve males and 11 females were studi ed when awake at 6 h to 8 d after birth. NIRS monitoring was carried out us ing two optodes placed above the left anterior orbito-frontal gyri. Each ne wborn was exposed for 30 s to two different smell stimuli-mother's colostru m and vanilla-and to a negative control, distilled water. Changes in Hb con centration were measured over the orbitofrontal region. During exposure to vanilla,[Hb O-2] increased significantly over the left orbito-frontal area in all babies. The magnitude of the [Hb O-2] increase over the illuminated region during colostrum exposure was inversely related to postnatal age. We conclude that monitoring Hb changes by NIRS can be valuable in assessing o lfactory responsiveness in infants.