Extrauterine environment affects the cortical responses to verbal stimulation in preterm infants

Using optical topography, changes in the cerebral oxygenation were compared in the parieto-temporal lobe of preterm and term infants of equal postconceptional age in response to verbal stimulation. Eight preterm infants of gestational age 23-34 weeks were studied at postconceptional term age (38-46 weeks). Ten term infants were studied at 2-11 days after birth. Twenty-four-channel near-infrared optical topography (NIOT) was used to measure changes in concentration of oxyhemoglobin ([oxyHb]), deoxyhemoglobin ([deoxyHb]) and total hemoglobin ([totalHb]) in the bilateral temporal cortices. Verbal stimulation was provided by a recording of a Japanese fairy tale. The latency in response to verbal stimulation was significantly shorter in the preterm infants than in the term infants. This time is thought to reflect brain development, particularly the development of the neuro-vascular coupling mechanisms in the cerebral cortex. The present results indicate that the number of days after birth is more closely related to development of auditory system and neuro-vascular coupling than is postconceptional age. Thus, this suggests that early extrauterine environment affects the cortical responses to verbal stimulation in preterm infants.