American movie : a guy running in a rat maze

I was young late seventies. The movie, where reality is mixed with dreams and dreams become reality, is about a guy who is falling slowly into madness, as my child mind understood it.

Two scenes I remember the most are :

1 – an analogy with a rat’s running through a maze as in a scientific experiment and the guy’s running in the same maze, opening doors and falling in another corridor with many other doors.

2 – and a scene near the end I think : all along the movie the guy fantasizes about a woman in red, lying down on a board in front of his motel/house. This is a giant board, advertising for something I don’t remember. And then, at the end, in one of his fantasies, he is very small and climbs the woman (who is alive) between her breasts.

The movie is in color and was made, I guess in the sixties or seventies.I’d really like to watch it with my now old eyes.