The study of postnatal and later development of the taste and olfactory systems using the human brain mapping approach: An update

Neophobia, sensory experience and child's schemata contribute to food choices

PURPOSE

The aim of the present review is to analyze dynamic interactions between nutrigenomics, environmental cues, and parental influence, which can all lead to children's neophobic reactions and its persistence in time.

METHODS

We reviewed studies available on electronic databases, conducted on children aged from birth to 18 years. We also considered official websites of Italian Institutions, providing advice on healthy eating during infancy.

RESULTS

Modern day societies are faced with an eating paradox, which has severe and ever-growing implications for health. In face of a wider availability of healthy foods, individuals instead often choose processed foods high in fat, salt and sugar content. Economic reasons surely influence consumers' access to foods. However, there is mounting evidence that food choices depend on the interplay between social learning and genetic predispositions (e.g., individual eating traits and food schemata). Neophobia, the behavioral avoidance of new foods, represents an interesting trait, which can significantly influence children's food refusal. Early sensory experiences and negative cognitive schemata, in the context of primary caregiver-child interactions, importantly contribute to the priming of children's food rejection.

CONCLUSIONS

As neophobia strongly affects consumption of healthy foods, it will be relevant to rule definitively out its role in the genesis of maladaptive food choices and weight status in longitudinal studies tracking to adulthood and, in meanwhile, implement early in life effective social learning strategies, to reduce long-term effects of neophobia on dietary patterns and weight status.

LEVEL OF EVIDENCE

Level II, controlled trials without randomization.

New insights into the ontogeny of human vegetable consumption: From developmental brain and cognitive changes to behavior

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There is research gap regarding how mental growth and brain maturation may impact on vegetable consumption.

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We have identified particular brain maturation and mental growth patterns that may affect child vegetable consumption.

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Both of these developmental patterns partially match with the Piagetian theory of development.

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We have identified a series of potential modulating factors.

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The 3–4 and 4−5 age ranges might potential sensitive periods for acquisition of brand knowledge of foods and health-related abstract concepts.

Relatively little is known about how mental development during childhood parallels brain maturation, and how these processes may have an impact on changes in eating behavior: in particular in vegetable consumption. This review aims to bridge this research gap by integrating both recent findings from the study on brain maturation with recent results from research on cognitive development. Developmental human neuroscientific research in the field of the sensory systems and on the relationship between children’s cognitive development and vegetable consumption serve as benchmarks. We have identified brain maturation and mental growth patterns that may affect child vegetable consumption and conclude that both of these developmental patterns partially match with the Piagetian theory of development. Additionally, we conclude that a series of potential modulating factors, such as learning-related experiences, may lead to fluctuations in the course of those particular developmental patterns, and thus vegetable consumption patterns. Therefore, we propose a theoretical predictive model of child vegetable consumption in which the nature of the relationship between its correlational and/or causal components should be studied in the future by adopting an integral research perspective of the three targeted study levels: brain, cognition and behavior.

[Experimental approaches to the investigation of behavioral disorders associated with prenatal alcohol exposure]

Fetal alcohol spectrum disorders (FASD) is an umbrella term which covers a wide range of deficits in prenatal and postnatal growth, anatomy and CNS functions produced by prenatal alcohol exposure. The most severe form of FASD is fetal alcohol syndrome (FAS) characterized by additional specific craniofacial and brain malformations. Despite a high prevalence and extensive clinical studies, the fundamental mechanisms of FASD are still poorly understood. Thereby, experimental models, which allow better control for both socio-environmental and genetic factors, are critical to our understanding of FASD. The review is focused on the effects of exposure to alcohol during the prenatal period in animal models. The authors outline that prenatally alcohol-induced changes in motor and executive functions, learning and memory, stress reactivity and affective state are remarkably parallel between animals and humans. Finally, the authors consider a potential impact of postnatal social and environmental factors on the outcome in experimental models of FASD.

Effects of infant formula composition on long-term metabolic health

Early nutrition may have long-lasting metabolic impacts in adulthood. Even though breast milk is the gold standard, most infants are at least partly formula-fed. Despite obvious improvements, infant formulas remain perfectible to reduce the gap between breastfed and formula-fed infants. Improvements such as reducing the protein content, modulating the lipid matrix and adding prebiotics, probiotics and synbiotics, are discussed regarding metabolic health. Numerous questions remain to be answered on how impacting the infant formula composition may modulate the host metabolism and exert long-term benefits. Interactions between early nutrition (composition of human milk and infant formula) and the gut microbiota profile, as well as mechanisms connecting gut microbiota to metabolic health, are highlighted. Gut microbiota stands as a key actor in the nutritional programming but additional well-designed longitudinal human studies are needed.

Promoting our understanding of neural plasticity by exploring developmental plasticity in early and adult life

Developmental plasticity (DP) is widely considered to be a property of early life stages, but evidence suggests it can be reactivated in mature brains. For example, recent developments on animal models suggest that experience in enriched environments (EE) can induce DP and enable adult recovery from amblyopia; even when the typical critical period for that recovery has closed. An interesting body of evidence suggests that extrapolation of the rejuvenatory power of that paradigm in mature human brains is feasible. These studies show that exposure to EE throughout life is associated with a delay, or even prevention, of age-related cognitive deficits. Consequently, it can be concluded that DP might underlie the neuroprotective effects against a neurocognitive breakdown that have been observed, and that EE exposure later in life might induce DP in a similar way to early EE exposure. Thus, the DP might exert its influence beyond the typical developing age ranges: childhood and adolescence. Although further research is still required, the observation of EE related neuroprotective effects are a breakthrough in the study of DP in humans and new advances in our understanding of neural plasticity have thus been reached.

Sensitive periods for hormonal programming of the brain

During sensitive periods, information from the external and internal environment that occurs during particular phases of development is relayed to the brain to program neural development. Hormones play a central role in this process. In this review, we first discuss sexual differentiation of the brain as an example of hormonal programming. Using sexual differentiation, we define sensitive periods, review cellular and molecular processes that can explain their restricted temporal window, and discuss challenges in determining the precise timing of the temporal window. We then briefly review programming effects of other hormonal systems and discuss how programming of these systems interact with sexual differentiation.

Studying the effects of smell and taste experience in the pediatric population using functional near infrared spectroscopy: a hypothesis

There are different postnatal sensitive periods throughout the development course of sensory functions. During sensitive periods, there is a biological display of an extreme neural sensitivity to the storage of experience-driven sensory information that is not present outside these developmental stages. This neural property is reflected in subjects' reported preferences for sensory stimuli, such as odors and tastes. The human brain mapping approach (HBA) has demonstrated that disease-free human postnatal and later development of any sensory function parallels morphological and functional development of the CNS and that this development correlates with signal changes that have been acquired by means of neuroimaging techniques. Whether experience with tastes and/or odors has a stronger effect on the perception of gustatory and/or olfactory stimuli the earlier subjects are exposed to certain odors and tastes is still unknown. It is also unknown, whether as well as how this effect is reflected in brain activation patterns and whether we are currently able to identify sensitive periods of gustatory and olfactory development from the imaging signals. To answer these research questions, repeated exposure to tastes and/or odors should be applied in children of different age ranges in order to induce different age-related degrees of olfactory/gustatory preferences as well as different aged-related patterns of oxyhemoglobin (OH) and deoxyhemoglobin (DOH) changes that should be measured by means of the functional near-infrared spectroscopy (fNIRS) technique.

Early influences on the development of food preferences

The ability to perceive flavors begins in utero with the development and early functioning of the gustatory and olfactory systems. Because both amniotic fluid and breast milk contain molecules derived from the mother's diet, learning about flavors in foods begins in the womb and during early infancy. This early experience serves as the foundation for the continuing development of food preferences across the lifespan, and is shaped by the interplay of biological, social, and environmental factors. Shortly after birth, young infants show characteristic taste preferences: sweet and umami elicit positive responses; bitter and sour elicit negative responses. These taste preferences may reflect a biological drive towards foods that are calorie- and protein-dense and an aversion to foods that are poisonous or toxic. Early likes and dislikes are influenced by these innate preferences, but are also modifiable. Repeated exposure to novel or disliked foods that occurs in a positive, supportive environment may promote the acceptance of and eventually a preference for those foods. Alternatively, children who are pressured to eat certain foods may show decreased preference for those foods later on. With increasing age, the influence of a number of factors, such as peers and food availability, continue to mold food preferences and eating behaviors.