“Keep your mind active.” We’re often told that this is a key to long term cognitive health: doing crossword puzzles or Sudoku or Wordle, reading, writing. But being a famous, award-winning critic and essayist hasn’t kept Prudence “Pru” Payne from one of the scourges of aging: dementia. The title character of Arizona Theatre Company‘s Pru Payne, at Herberger Theater Center through April 16, is an aesthetic conservative. The dour, caustic Pru insists that the critic’s role...