I came across the following recently, and thought some here might
find it of interest.

P.S. capital letters below are as found...

Tom Billings

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West, ERIC D.; Ellis, Frey R.
  The Electroencephalogram in Veganism, Vegetarianism, Vitamin B12
  Deficiency, and in Controls.
Journal of Neurology, Neurosurgery + Psychiatry, 1966, v29 (n5):391-397.

Abstract:

THE EEGS IN 17 VEGANS (EXTREME VEGETARIANS WHO EXCLUDE MEAT,
DAIRY  PRODUCE, AND EGGS FROM THEIR DIET) WERE COMPARED WITH THOSE OF 18
CONTROLS, 10 VEGETARIANS, 11 PATIENTS WITH PERNICIOUS ANEMIA, AND 2 WITH FOLIC
ACID DEFICIENCY. THE EEG SCORING WAS CARRIED OUT BLIND. DIFFUSE
ABNORMALITIES  WERE FOUND IN THE VEGANS' EEGS OF A DEGREE THAT IS BETWEEN THAT OF THE VEGETARIANS
AND THE PERNICIOUS ANEMIA PATIENTS, BUT UNLIKE THE
ABNORMALITIES IN THE LATTER, THE ABNORMALITIES IN THE VEGANS' EEGS
WERE NOT AFFECTED BY HIGH DOSAGE VITAMIN B12 SUPPLEMENTS.