GABA is the primary inhibitory neurotransmitter in the brain. It is an inhibitory neurotransmitter that is very widely distributed in the neurons of the cortex. GABA contributes to motor control, vision, and many other cortical functions. Two of the most common neurochemicals are glutamate and GABA and both are a neurotransmitter. Neurons that use GABA and glutamate as neurotransmitters are used by more than 80% of the neurons in the brain and constitute the most important inhibition and excitation systems, respectively, of the substantia nigra pars.