Magnesium supplement to help Memory?

Based on a study done last year looks like they found that more magnesium in the brain helps with short term and long term memory.

"Magnesium is essential for the proper functioning of many tissues in the body, including the brain and, in an earlier study, we demonstrated that magnesium promoted synaptic plasticity in cultured brain cells," - Professor Guosong Liu, Director of the Center for Learning and Memory at Tsinghua University in Beijing

Here is the original article:
Magnesium Supplement Helps Boost Brainpower
http://www.sciencedaily.com/releases/2010/01/100127121524.htm

Here is the original study published:
Enhancement of Learning and Memory by Elevating Brain Magnesium
http://download.cell.com/neuron/pdf/PIIS0896627309010447.pdf?intermediate=true

Anyone believe in this stuff, looks like only the specific magnesium l-threonate helps with increasing magnesium levels in the brain? I am a bit skeptical but looks promising. Anyone have any idea on how magnesium affect the brain? Or even where we can find this stuff? Only thing I found was a few forum topics and these guys mlt500.com