Huffington Post – Magnesium is vital for the function of GABA receptors, which exist across all areas of the brain and nervous system. GABA is a calming neurotransmitter that the brain requires to switch off; without it, we remain tense, our thoughts race and we lie in bed staring at the ceiling. Whether the brain is in ‘on’ of ‘off’ mode is a very complex area, and can also be affected by chemicals like noradrenaline, serotonin and histamine. However, on a more simple level, the most crucial balance is that of GABA vs glutamate. Whereas GABA calms, glutamate fires the brain into higher states of activity; you use the latter when solving sudoku puzzles, but you need GABA to prevail in order to go to sleep.