The article offers information on the Ambient Glutamate is the brain's primary excitatory neurotransmitter. Topics discussed include during development, it acts as a regulatory signal that helps shape inhibitory cortical circuits; and mentions ambient glutamate gives rise to a tonic N-methyl-D-aspartate (NMDA) mediated current at the end of the first postnatal week in GABAergic interneurons (INs) in mice.