An Animal Model of Neonatal Intensive Care Unit Exposure to Light and Sound

SUMMARY: According to the World Health Organization, approximately 15 million children are born prematurely each year. Many of these infants end up spending days to weeks in a neonatal intensive care unit (NICU). Infants who are born prematurely are often exposed to noise and light levels that affect auditory and visual development.

Subsequently, these children can have long-term impairments in cognition, visuospatial processing, hearing, and language. We have developed a rodent model of NICU exposure to light and sound using the Mongolian gerbil (Meriones unguiculatus), which has a low frequency human-like audiogram and is altricial. To simulate preterm

infancy the eyes and ears will be opened prematurely, followed by exposure to the NICU-like sensory environment throughout the gerbil’s cortical critical period of auditory development. Here, natural eye-opening closes the critical period ~ P18, and early eye opening simulates the effect of preterm birth, by closing the critical

period precociously (Mowery et al., 2016). This motivated the core hypothesis that early eye opening induces precocious closure of auditory development through feed forward peripheral visual excitatory input onto cross modal synapses located in auditory cortex. Recent research has provided preliminary validation for the effect of

early light and noise exposure on long-term brain development (Gay et al., 2023). We will test this hypothesis with three aims. The first aim will track electrophysiological development of inhibition within the auditory cortex after NICU (early eye/ear opening) or noise only (early ear opening) exposed neonates, juveniles, and adults.

The second aim will track the development of physiological peripheral measures for auditory (auditory brainstem response) and visual (visual evoked potentials) function in NICU (early eye/ear opening) or noise only (early ear opening) exposed neonates as they develop into juveniles and then adults. Histological measurements of the

white and grey matter along the visual and auditory neuraxes will be generated and correlated with any impairments to peripheral physiology thresholds of each animal in AIM 2. The third aim will behaviorally test measures of auditory and visual based decision-making impairments in NICU (early eye/ear opening) or noise

only (early ear opening) exposed animals after they have become adults. Together, the findings from this project will introduce a new animal model of the NICU preterm infant, with which mitigative and treatment-based approaches to early light and sound exposure can be ethically carried out by the research community. We hope

to establish this animal model to create a bridge between clinical pediatric physician researchers and the animal research community to advance clinical treatments and care for the NICU-exposed preterm infant.