The researcher said that before the body begins to freeze, cold can cause changes in brain chemistry which lead to hallucinations.

VOA: special.2010.02.24

But my brain is so cold I can't remember if I did.

BBC: Chick Young's view

If a subject is presented with a sentence like, "When she came in from the cold her cheeks were like roses, " many sections of the brain become involved, including those responsible for visual processing.

WSJ: Book Review: Surfaces and Essences