How does Ned Vizzini use imagery in It's Kind of a Funny Story?

Imagery:

Tentacles is my term -- the Tentacles are the evil tasks that invade my life.

And I did that for the next five years -- whenever I was in class, I didn't doodle, I drew maps. Hundreds of them. When I finished, I crumpled them; it was making them that was important. I did cities on the ocean, cities with two rivers meeting in the middle, cities with one big river that bent, cities with bridges, crazy interchanges, circles and boulevards. I made cities. That made me happy. That was my Anchor.