Who are the "spirits" in 1 Peter 3:19?

[kyredneck]

I am looking for positions and data points regarding 1 Peter 3:19 and in particular who are the "spirits in prison" and what is Christ doing there.

The passage jibes neatly with the type of Joseph.

Joseph interpreted dreams while in prison before being elevated to the right hand of Pharoah and to ultimately feed the nations that came to him.

Christ preached to the prisoners before being elevated to sit at the right hand of God and feed the nations that come to Him.