I did a PubMed search using the keywords: aspartame toxicity
It came up with only 5 pages of references, which is a fairly small number of articles for anything that general. As I skimmed through, most of them are letters, not actual research articles, others are testing aspartame for interactions in other models of toxicity (I didn't read them, just from skimming it was clear it wasn't what you're looking for). The only relevant paper I came across is a review written by the folks working for NutraSweet that concludes it's safe (yes, there is a clear potential for conflict of interest there). I didn't come across anything that refutes that claim though, other than that if you administer it intraperitoneally to rats instead of orally, their wheel-running is decreased, but that really doesn't mean much unless you're planning to inject yourself with the stuff.
Holder MD, Yirmiya R. Behavioral assessment of the toxicity of aspartame. 1989 Pharmacol Biochem Behav. 32:17-26.
If there was any merit to those claims, I'd have expected to find at least a few legitimate articles claiming toxic effects.
Just to add:
Since in that book review, Blaylock was claiming to be a neurosurgeon with journal publications, I thought I'd check out his claims. These are the hits for his name on PubMed (I can only assume it's the same person since none of these are recent enough to get the full articles to check his full name).
Considering the concentration of dates and how many have the same senior authors, and that these are all case reports, not actual experimental studies, I'd have to guess they were all written during a residency. Note that NONE of them are related to excitotoxins or in any way indicate that he has any degree of expertise in that area.
1: Blaylock RL.
Hydrosyringomyelia of the conus medullaris associated with a thoracic
meningioma: case report.
J Neurosurg. 1981 Jun;54(6):833-5. No abstract available.
PMID: 7241193 [PubMed - indexed for MEDLINE]
2: Blaylock RL, Kempe LG.
Hydrocephalus associated with subarachnoid haemorrhage.
Neurochirurgia (Stuttg). 1978 Jan;21(1):20-8.
PMID: 628501 [PubMed - indexed for MEDLINE]
3: Blaylock RL, Kempe LG.
Pituitary adenomas--a re-appraisal of their pathology and treatment.
Neurochirurgia (Stuttg). 1977 May;20(3):63-78. Review. No abstract available.
PMID: 196229 [PubMed - indexed for MEDLINE]
4: Blaylock RL, Kempe LG.
Chondrosarcoma of the cervical spine. Case report.
J Neurosurg. 1976 Apr;44(4):500-3.
PMID: 1255239 [PubMed - indexed for MEDLINE]
5: Blaylock RL.
American medicine: Bicentennial celebration.
J S C Med Assoc. 1976 Jan;72(1):18. No abstract available.
PMID: 1107664 [PubMed - indexed for MEDLINE]
6: Blaylock RL, Kempe LG.
Review and new proposals for immunotherapy of brain tumors.
Neurochirurgia (Stuttg). 1976 Jan;19(1):10-21.
PMID: 765879 [PubMed - indexed for MEDLINE]
7: Blaylock RL, Ducker TB, Rittenbury MS, Perot PL Jr.
Intraventricular monitoring of the craniocerebral trauma patient.
J S C Med Assoc. 1974 Nov;70(11):348-55. No abstract available.
PMID: 4530127 [PubMed - indexed for MEDLINE]
8: Ducker TB, Blaylock RL, Perot PL Jr.
Emergency care of patients with cerebral injuries.
Postgrad Med. 1974 Jan;55(1):102-10 passim. No abstract available.
PMID: 4809671 [PubMed - indexed for MEDLINE]