Just before Alex Godfrey’s grandmother died from dementia, she snapped back to lucidity and regaled him with stories of her youth. Could moments like this teach us more about the workings of the brain?

It was the red jelly that did it. It was Christmas 1999 in Rapid City, South Dakota, and Ward Porterfield, 83, was in a nursing home. He had been diagnosed with dementia three years earlier; he was confused and disoriented and eventually he no longer recognised his daughter, Kay. “When I went in,” she says of her later visits, “he didn’t know me at all.” That Christmas, he refused to eat. “Finally I just told them: ‘Bring him jello, he likes jello. Red jello.’ And he looked at me, really deeply, and said: ‘So. I suppose the jello’s gonna be my last meal. You’re gonna try to starve me, eh?’ That was like: ‘What’s going on here?’”

Her surprise wasn’t just at his coherence, but that the tone of this reply was undeniably her father’s dry humour. Later that night, nurses told Kay, when children visited to sing carols, tears streamed down Ward’s face. Kay becomes emotional recounting it. “Don’t cry,” a nurse told him. Ward looked at her. “If you were in my position, you’d cry too,” he said. “These are the last Christmas carols I’ll ever hear.”