For Learning and Memory Dietary Supplement Magtein - Think Clearly Magnesium (Mg) plays an essential role in supporting cognitive function and brain health. Preliminary research suggests that Magtein (magnesium L-threonate) may provide more magnesium to the brain than other forms of magnesium. It is theorized that this is the reason why Magtein was shown in preclinical studies to support healthy memory and learning as well as healthy brain synapse density in regions of the brain associated with memory.