Early-onset binocularity in preterm infants reveals experience-dependent visual development in humans

Abstract

Although there is a great deal of knowledge regarding the phylo- and ontogenetic plasticity of the neocortex, the precise nature of environmental impact on the newborn human brain is still one of the most controversial issues of neuroscience. The leading model–system of experience-dependent brain development is binocular vision, also called stereopsis. Here, we show that extra postnatal visual experience in preterm human neonates leads to a change in the developmental timing of binocular vision. The onset age of binocular function, as measured by the visual evoked response to dynamic random dot correlograms (DRDC-VEP), appears to be at around the same time after birth in preterm (4.07 mo) and full-term (3.78 mo) infants. To assess the integrity of the visual pathway in the studied infants, we also measured the latency of the visual-evoked response to pattern reversal stimuli (PR-VEP). PR-VEP latency is not affected by premature birth, demonstrating that the maturation of the visual pathway follows a preprogrammed developmental course. Despite the immaturity of the visual pathway, clearly demonstrated by the PR-VEP latencies, our DRCD-VEP data show that the visual cortex is remarkably ready to accept environmental stimulation right after birth. This early plasticity makes full use of the available extra stimulation time in preterm human infants and results in an early onset of cortical binocularity. According to our data, the developmental processes preceding the onset of binocular function are not preprogrammed, and the mechanisms turning on stereopsis are extremely experience-dependent in humans.

The Infancy of the Human Brain

“…In a series of experiments, Peñ a and colleagues showed that the loss of sensitivity to suprasegmental and segmental features of a foreign language that normally occurs during the first year of life was not dependent on the duration of exposure to broadcast speech (Peñ a et al, 2010(Peñ a et al, , 2012. In contrast, sensitivity to the phonotactic rules of the native language varies with the duration of postnatal experience (Gonzalez-Gomez and Nazzi, 2012), as do a number of visual functions including binocular perception (Jandó et al, 2012) and gaze following (Peñ a et al, 2014). These variations should not be viewed as inconsistent but as pertinent dissociations shedding light on how these computations are realized in vivo.…”

Accelerated establishment of mature signaling patterns following stimulation of developing neuronal networks: “learning” versus “plasticity”

“…The pivotal argument against such a reductionist approach to model anything beyond “simple” plasticity in cultured neuronal networks is the lack of input/interaction of such networks with the environment. However, both plasticity and learning are impacted by environmental stimulation (Callaway and Borrell, 2011; Froemke and Jones, 2011; Henderson et al, 2012; Jando et al, 2012; Young et al, 2012). To address this issue, we compared the overall pattern of developmental signaling in ex vivo neuronal networks in the absence and presence of a model of the onset of sensory input.…”

A neural window on the emergence of cognition

“…In other words, the developmental trajectory of preterm infants was not accelerated by their earlier exposure to speech and face‐to‐face exchange with their parents, suggesting that the external world does not influence the phonetic repertoire during the first weeks of life and thus that learning needs a more mature circuitry reached a few weeks later to stabilize and memorize the external world . Note that other capacities such as binocular perception, gaze following, or sensitivity to the phonotactic rules of the native language are advanced in healthy preterm infants relative to full‐term infants, suggesting a different sensitivity to external stimulation between domains but also within a given processing pathway, owing to different tempos of maturation . These results underscore that, in order to evaluate neonatal care and preterm infant outcomes, it is necessary to precisely evaluate development in terms of cognitive systems and brain networks and not confine studies to general capacities as reflected by IQ.…”