Is brain plasticity preserved during aging and in Alzheimer's disease?

Alzheimer's disease is a progressive neurodegenerative disorder believed to involve selective neuronal cell atrophy/loss in certain brain regions. The progress of the disease is accompanied by selective cognitive impairments and behavioral disturbances. The hypothesis has been put forward that by activation of selective brain areas throughout life one might protect or delay the degenerative process. This hypothesis, paraphrased as "a differential level of brain cell activity may account for cell selective loss" or "use it or lose it", further suggests that a certain level of neuronal plasticity persists during aging and even in Alzheimer's disease.