Translation:Reading is precisely what opens the mind.
I think that
ciò che is the relative pronoun meaning that which/what and the proprio is just for emphasis. So there are lots of translations of
proprio cio che. Mind you I put really first time which was not accepted. Google gives just what. M&R say that
ciò is for more elevated registers - the plebs use quello. What do you think?
Short answer to the question asked: no. In this sentence, proprio by itself means "exactly" or "precisely", while as peter2108 mentioned, ciò che is translated as "what". Madrelingua and prolific forum contributor CivisRomanus posted a nice explanation about ciò che vs. quello che just a few days ago. In bocca al lupo!
Timor mortis conturbat me.