This post might get buried, but I feel it needs to be said.

N-methyl-D-aspartate (NMDA) receptor agonists cause excitoxity, resulting in neuronal death:

NMDA and Glutamate Evoke Excitotoxicity at Distinct Cellular Locations in Rat Cortical Neurons In Vitro / "We hypothesized that exogenous glutamate is toxic neu- rons under these circumstances by activating somatic receptors exclusively (Speliotes et al., 1994). In the present study, we provide experimental evidence that directly supports this hypothesis."

Asparatame binds to NMDA sites:

Effect of aspartame on N-methyl-D-aspartate-sensitive L-[3H]glutamate binding sites in rat brain synaptic membranes "These in vitro findings suggested that aspartame may act directly on the N-methyl-D-aspartate-sensitive glutamate recognition sites in the brain synaptic membranes."

There are many sources which indicate that aspartame also compromises the blood-brain barrier, which is not exactly a good thing (e.g. https://www.ncbi.nlm.nih.gov/...)

Make of this what you will, but our brains produce as much glutamate as we need. In case of head trauma such as stroke, it produces too much, which results in cell death and probably a lot of the disability following a stroke.

I don't think we need any extra NMDA agonists in our diet, but then again I'm just a layman in this area.