What is the theme in I felt a Funeral, in my Brain by Emily Dickinson?

Madness and sanity is the main theme of the story. "I felt a Funeral, in my Brain" is a poem that, in part, presents the impending mental collapse of its speaker, a collapse thatDickinson likens to the rituals of a funeral to ultimately explore the figurative "death" of the speaker's sanity. The word felt in the poem's opening line suggests that the first throbbings of the collapse could be physically perceived; this merging of physical sensation and mental perception is sustained throughout the poem. By comparing the speaker's mental breakdown to a funeral,Dickinson suggests the horror and finality of such an event.