Monday, April 28, 2008

Development, nutrition, and learning

Compensatory Growth Impairs Adult Cognitive Performance (Fisher et al)

In this study, zebra finch birds were used to explore the consequences of poor nutrition early in life on cognitive performance later in life. The researchers found that the zebra finches that exhibited the most growth following the end of the period of poor nutrition showed the slowest performance on the learning task. What's interesting is that all birds tested for speed on a learning task as adults were of the same size, even though one group of birds had been subjected to nutritional deprivation. So, the researchers were able to compare the adult size of the bird with their size at the end of the period of poor nutrition to quantify the compensatory growth their bodies produced when a healthier diet became available. Similar studies are cited in the research that involved comparing the cognitive performance of human babies born at low birth weight, some of whom received a nutritionally-enriched diet and others of whom did not; the results were similar to those found in the zebra finch bird study. This study provides further support for the well-accepted idea that phenotypes are influenced by environmental variables such as nutrition, and that cognitive phenotypes are not an exception. However, this study adds significant detail on phenotype variability resulting from changes in the environment that take place during critical periods of development, particularly relative to the development of the brain. Although the "big picture" suggestion is certainly not to withhold better nutrition if and when it is available, it is interesting to note that the overall benefit of compensatory growth can cause some specific deficiencies later in life, particularly with regard to cognitive systems. Further research should investigate the consequences of varied timing of nutritional deficits and their impact on learning later in life, but for now it seems clear that we should make every effort to ensure that nutritious food is available from the beginning and throughout a child's life.

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