PowerPoints are a pain when it comes to using title/headline case for AE. (BE doesn't tend to use title/headling case as often as AE.)

If the top lines are actually written as headlines (short, few extraneous words), I use title/headline case for AE. If they are long, wordy or multi-sentence affairs, title/headline case looks terrible. Even worse is the judgement of what to do when they're a mixture of the two above. So, it's hard to say what you should do. (If it's BE, I'd just leave it in sentence case.)

By the way, according to Chicago Manual of Style, the rules for title/headline case are a bit more complicated that what you write.

Capitalized: First and last words always; all nouns, verbs, adverbs, adjectives, pronouns...
Not capitalized: Articles, prepositions (in the most recent version of CMS, regardless of length).

Two hyphenated words, etc., are both capitalized if both are complete words. In the first is merely a prefix that can't stand on its own, only the prefix is capitalized (e.g., Non-standard). (The last rule is an odd one, but I follow it for consistency.)

The list may not be entirely complete -- I wrote from memory. Other style guides have slight variations.

By the way.