OK, I found the article. Here is a short summary.

Scores between 1 (normal) and 8 (most abnormal) were given to EEGs of
vegans, vegetarians, controls, B12 deficient people. In addition,
different measeures were performed, like: neuroticitsm, extroversion,
serum B12, obesity index...

A FEW RESULTS (means):

              | EEGs | serum B12 | neuroticism | extroversion |
---------------------------------------------------------------
Controls      | 2.92 |  326.5    |   12.26     |    26.06     |
Vegetarians   | 2.75 |  194.2    |   18.60     |    23.20     |
Vegans        | 4.03 |  240.0    |   17.78     |    24.46     |
B12 deficient | 5.91 |   57.1    |     ?       |      ?       |
---------------------------------------------------------------

FACTS:
 -There is no significant difference of neuroticism and extroversion
scores between the various groups.
 -Vegetarians have low B12 but normal EEGs.
 -EEG scores are improved (but not restored to normal) after B12 treatment
on B12 deficient (non vegan) people, but not on vegans.
 -There is no correlation between serum B12 and EEG scores among vegans
 -EEG scores correlate positively with length of time as vegan.
 -EEG scores are not significantly correlated with neuroticism or
extroversion.

POSSIBLE EXPLANATIONS (of abnormal EEGs among vegans):
 1. Low B12: probably not the sole explanation, since vegetarians also
have low B12 but normal EEGs.

 2. Undefined deficiency: possible, but if this were so, it would be
expected that a minimal cerebral deficit might be reflected in raised
neuroticism scores, which was not found.

 3. The changes represent a metabolic readjustment to th vegan diet.


Best wishes,

Jean-Louis
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