Obviously you want to avoid all excitotoxins (which literally excite your brain cells to death) including artificial sweeteners and MSG. But did you know the many hidden sources of MSG?
In general, if a food is processed you can assume it contains MSG (or one of its pseudo-ingredients). Eating a whole, fresh food diet is your best, if not only, guaranteed way to avoid this toxin.
This excellent article contains a chart with the many hidden sources of MSG.