A chronic alcoholic develops severe memory loss with marked confabulation. Deficiency of which of the following vitamins would be most likely to contribute to the neurologic damage underlying these symptoms?

Wernicke-Korsakoff syndrome refers to the constellation of neurologic symptoms caused by thiamine deficiency. Among these, a severe memory deficit, which the patient may attempt to cover by making up bizarre explanations (confabulation), is prominent. Anatomical damage to the mamillary bodies and periventricular structures has been postulated as the cause. Thiamine deficiency can also damage peripheral nerves ("dry" beriberi) and the hea ("wet" beriberi). Folic acid deficiency produces megaloblastic anemia without neurologic symptoms. Niacin deficiency produces pellagra, characterized by depigmenting dermatitis, chronic diarrhea, and anemia. Riboflavin deficiency produces ariboflavinosis, characterized by glossitis, corneal opacities, dermatitis, and erythroid hyperplasia.