The 'proof of brain' is not a consensus algorithm, it is a system that the steem blockchain uses for reward content publication and curation. The consensus algorithm used in the steem blockchain is the Delegated Proof of Stake (DPOS), that I don't mention here but I'll write about it in the future. Basically in it, the first 19 witnesses are chosen randomly to validate a block and the other 2 blocks are validated by another witnesses not in the first 19 and the other one is validated in another way.