Methanol converts to formaldehyde, yes. However, the body recognizes that formaldehyde is very toxic.
Formaldehyde is thus very efficiently metabolized to formic acid in the body. It does not bioaccumulate. I don't know if it can cross the blood-brain barrier, but so can many other small molecules. You'll get a far bigger dose of formaldehyde by smoking a cigarette than ingesting a soda's worth of aspartame.
Formic acid is the same substance many insects use in their stings. It also does not bioaccumulate.
Want DP delivered to your inbox daily? Subscribe here: