imagination vs mental picture

imagination

noun
  • Particularly, construction of false images; fantasizing. 

  • Creativity; resourcefulness. 

  • The image-making power of the mind; the act of mentally creating or reproducing an object not previously perceived; the ability to create such images. 

  • A mental image formed by the action of the imagination as a faculty; something imagined. 

mental picture

How often have the words imagination and mental picture occurred in a corpus of books? (source: Google Ngram Viewer )