In "In a Field of Stray Caterpillars," how does David use the layout of the hospital as a metaphor for the human mind?

David humorously talks about the innumerable branching and intersecting corridors as being "not too bright," using the multiple meanings of bright to refer both to the literal light levels and to a lack of intelligence (87). He talks about the "open junctions" leading to various places such as "Mood" and "Memory" (87). After he comments that one way to deal with being lost in this maze is to exit and come back in the main entrance to try again to find what you are searching for, he explicitly says that this is one way that mental health therapy works, meaning that ECT, for instance, allows Fellis to "exit" the maze of his own mind and then come back in, reoriented, from another direction.