I'm not taking psychology but I looked online and got this (look at 3rd paragraph if you want to jump right into it- I'm not sure if that's what you're asking about). This site specified Glutamic acid, Glutamine, and Glutamate:
Glutamic acid is an organic acid that is considered a "brain nutrient." It has been used with varying degrees of success in learning-disabled children, children with attention deficit syndrome (ADD), and others in whom "extra fuel" is thought to benefit. Glutamic acid is an amino acid, however, and it does have its drawbacks. Apparently, it does not easily pass the blood-brain barrier, a protective shield around the brain that keeps out toxic substances. To overcome this problem, glutamine comes into play.
Glutamine is a derivative of glutamic acid. Its chemical name is glutamic acid 5-amide. It is usually derived from sugarbeet juice. Some nutritionists believe glutamine, which is considerably more expensive than glutamic acid, can more easily pass through the blood brain barrier. Thus, glutamine is considered the nutrient of choice if this type of substance is required.
Glutamate is encountered mainly as an ingredient of monosodium glutamate, a substance used to enhance flavor. It is more commonly known as MSG or "Chinese Seasoning." Glutamate is derived from the reaction of glutamic acid with sodium. Unlike the situation with the previous two compounds, a percentage of the population is extremely sensitive to MSG. To those people MSG causes nausea, vomiting and dizziness. By law, ready-made foods purchased in supermarkets must be labeled if they contain MSG. "Chinese restaurant syndrome" results from the ingestion of MSG by individuals who are sensitive to it. In addition, this product contains 13 percent sodium and may be problematic for people with high blood pressure. Glutamate does not have any nutritional benefit.posted by Bobby
This is more physiology than psychology.
Since this is not my area of expertise, I searched Google under the key words "glutamate role" to get these possible sources:
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In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.posted by PsyDAG