Preterm infants are at risk for poor neurodevelopmental outcomes, including deficits in learning and memory, disrupted sensory processing, attention deficit hyperactivity disorder, and autism spectrum disorder.1,2 Prematurity leads to a situation where critical in utero steps of brain development occur in an abnormal ex utero environment. This alters the quality and intensity of sensory stimuli that the premature infant experiences, and potentially affects normal maturation of sensory systems adversely. The identification of the impact of the NICU environment on the development of sensory systems may pave the way for the establishment of a comprehensive protocol of multisensory stimulation that can potentially ameliorate sensory deficits associated with prematurity.

The establishment of accurate sensory neural networks occurs during critical periods spanning the final months of gestation and the first month after birth, during which precise patterns of neuronal activity initiate processes of refinement that underlie the establishment of accurate sensory neural networks.3 For instance, even before birth, neighboring cells in the retina fire together (retinal waves) to sculpt the functional cytoarchitecture of the visual thalamus and cortex.3 In the auditory system, synchronous discharge of neighboring inner-hair cells is required to form clusters of primary auditory cortical neurons and establish tonotopic auditory sensory maps.4 There is also an extensive literature on the influence of peripheral sensory receptors on the development of somatosensory maps (see ref. 5 for review). Refinement of these processes continues through activity-dependent plasticity mechanisms during the perinatal period and early postnatal life. Consequently, exposure to inadequate and/or inappropriate visual, auditory, and somatosensory stimuli during these early development critical periods can result in long-lasting alterations in the connectivity and function of sensory cortices. For instance, disruption of visual experience can lead to amblyopia, strabismus, and alteration of the visual cortex orientation selectivity columns.3 Similarly, exposure to environmental noise can delay the establishment of tonotopic maps in the auditory cortex.6 In addition, there is strong evidence that abnormal somatosensory experience (i.e., painful procedures) can alter thalamocortical connectivity.7 Taking these factors together, one may conclude that premature infants can be particularly vulnerable since the NICU environment is very different than that inside the womb.

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