Aphantasia

The inability to form mental images of objects that are not present.

A representation of how people with differing visualization abilities might picture an apple in their mind. The first image (leftmost, numbered 1) is bright and photographic, levels 2 through 4 show increasingly simpler and more faded images, and the last (rightmost, numbered 5)—representing complete aphantasia—shows no image at all. From a- (prefix meaning ‘opposite of; without’) +‎ phantasia, from Ancient Greek ἀ- (a-, prefix forming words having senses opposite to the stems or words to which the prefix is attached) + φᾰντᾰσῐ́ᾱ (phăntăsĭ́ā, “appearance, look; image; impression, perception”).