Trace elements are naturally present in ground surfaces and water around the world. Since its concentrations have been found to be very low in comparison with the rest of the chemical inorganic elements of the periodic table, its relevance to health and biological functions in man was disregarded for many years. Previous work from our laboratory show that phenotypic expression of the HSR (Hand Skill Relative) gene was altered in school children in La Rioja province, Argentina, living in a region with mines and mineral deposits, including trace elements which were present in higher concentrations but not at toxic levels compared to plain geographical regions of other provinces. The HSR gene is related to handedness, writing ability and brain asymmetry in humans and subjected to epigenetic modulation. This finding suggested that trace elements as environmental factors might be related to modulation of cognitive functions in humans. After developing an animal model in the rat, the chronic administration of ZnTe at the same concentrations observed in ground and waters of La Rioja environment, induced similar cognitive-like changes in the animals, supporting the hypothesis that trace elements might have some role in brain functions. Administration of trace elements in rats induced demethylation of cytosine bases of DNA extracted from hippocampal structure, while at the same time methylated DNA cytosine from prefrontal cortex was not affected. These changes in the methylated cytosine/non-methylated ratio of DNA was also observed in blood samples of children where the phenotypic expression of HSR was modified, suggesting a common metabolic action of trace elements on cognitive functions in mammalian species. This evidence opened the possibility that trace elements, despite their very low concentrations in ground and waters in the environment, might be exerting biologic modulation actions never suspected until now.