A 76-year-old woman is brought to the emergency department by her neighbor after she noticed the woman wandering around the neighborhood. When she approached her, the woman seemed disoriented, emaciated, and could not remember why she had left her home. During the physical examination the physician learned that the woman has a history of chronic alcohol abuse and short-term memory loss. Considering this woman's history and physical examination, which of the following most likely accounts for her condition?