The human brain doesn’t work out of the box: it has to learn tasks; processing has to be developed. By “grey matter” we mean the 80 billion or so brain cells with which we’re born, but it’s the fatty white matter – or myelination – growing along the cells’ axonal projections, connecting different parts of the brain, that make it work faster and better. In this episode of the Neuromantics, we take a look at the surprising effects of that learning process on the neurophysiology of older people, as studied by Yuko Yotsumoto et al, in “White Matter in the Older Brain is More Plastic than in the Younger Brain” (2014). Both the young and the elderly can do new things. In Yotsumoto’s experiment, they learn to pick out letters against a variety of backgrounds (and both age groups get better at it). But MRIs show that the really marked changes in white-matter arrangement are confined to older participants. Why? Is that a good or bad thing? And how might these changes be related to more general cognitive decline, where, because the grey cells are dying off, white matter no longer has much to connect? Maintaining a connection with the world, as well as suffering its loss, is one of later life’s challenges, and nowhere is it more beautifully evoked than in Alice Munro’s short story about the strange plasticity of affection, “The Bear Came Over the Mountain”, first published in the New Yorker in 1999. Fiona has Alzheimer’s and goes into care. But it’s her unworldly and rather selfish husband, Grant, who finds himself changing, unlearning assumptions, and being driven by love to an act of uncommon kindness.