Sentence:  Psychical blindness is a condition in which there <WSD>is</WSD> a total absence of visual memory-images , a condition in which , for example , one is unable to remember something just seen or to conjure up a memory-picture of the visible appearance of a well-known friend in his absence . 
Meaning of the word marked with <WSD> tags:  happen, occur, take place; this was during the visit to my parents' house"