Nutrition and the development of cognitive functions: interpretation of behavioral studies in animals and human infants.

A rapidly accumulating body of evidence on the neural basis of cognition suggests that cognition is not a unitary function but rather depends on the functions of multiple and dissociable neural systems. The nonlinear interactions in the differing trajectories of these systems during development result in changing patterns of cognitive functions over time; they may also lead to paradoxical outcomes, for which enhancement of one function through dietary intervention may be at the expense of another. This emerging understanding has important implications for the design and interpretation of studies on the cognitive effects of specific nutrients during development. It is important that researchers move away from global tests of development and strive rather to ensure that their choice of behavioral task is based on specific hypotheses of the systems expected to be altered by a dietary manipulation and on an understanding of which behavioral tests are valid, sensitive, and reliable indicators of this disruption. Furthermore, to understand whether accelerated or delayed development related to a particular cognitive function is beneficial or problematic, it is important to study the entire behavioral profile over different time points, rather than relying on one outcome measured at one time point. It is also necessary to control for sensory or motivational differences that will affect performance on the behavioral tasks. Implementation of these methodologic recommendations may contribute to a deeper understanding of the mechanisms involved in the nutrition-associated changes in cognitive functions and thereby aid in the development of an appropriate population-based dietary policy.