This work in humans is nicely supported by studies performed in mice by a Japanese team earlier this year (incidentally, published in the same journal). The mouse work showed that vitamin B deficiency caused cognitive impairment, which could be blocked with an antibody against homocysteic acid, another cysteine metabolite (Hasegawa et al., 2010).

References:
Hasegawa T, Mikoda N, Kitazawa M, Laferla FM. Treatment of Alzheimer's disease with anti-homocysteic acid antibody in 3xTg-AD male mice. PLoS One. 2010;5(1):e8593. Abstract

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