How does Hubert Selby use imagery in Requiem for a Dream: A Novel?

Imagery:

"The voice so filled with nostalgia that you could almost see the memories floating through the blue smoke, memories not only of music and joy and youth but perhaps of dreams."

"She would pick up her sketch pad and...nothing seemed to excite or inspire her so she went back to her fantasies and enjoyed the comfort and reassurance they gave her and they were more real than sitting on the couch looking at the pencils, the charcoal and the virgin sketch pad."