Enduring cognitive effects of early malnutrition: a theoretical reappraisal.

This article presents a reappraisal of the literature on the enduring cognitive effects of early malnutrition. In addition to summarizing the existing empirical literature, we present a theoretical framework for determining whether the processes likely to be most vulnerable to early malnutrition were adequately assessed. The two types of information used to make this determination are clinical and experimental behavioral data as well as reported neural changes. One point of clear consensus is that animals exposed to early malnutrition exhibit lasting changes in the realm of emotionality, motivation, and/or anxiety. Because these alterations profoundly affect all aspects of behavioral functioning, including cognition, it is suggested that future research focus on these changes, rather than control for them as many past studies have done. The functional integrity of specific cognitive processes is less clear. The only cognitive processes for which enduring cognitive changes were demonstrated in rehabilitated animals--outside of effects mediated by these affective changes--are cognitive flexibility and, possibly, susceptibility to proactive interference. However, the inference that these are the only processes affected does not appear to be warranted on the basis of the evidence that several cognitive processes likely to be affected have not been fully assessed. Examples include executive functions linked to the prefrontal cortex (for example, attention), transfer of learning, procedural learning and long-term memory. Future research focusing on these specific cognitive functions as well as on these unequivocal affective changes should allow a more definitive conclusion regarding the enduring functional consequences of early malnutrition.