In the ‘Fragment’ Spinoza states his goal from the outset which is for us to acquire, “the knowledge of the union existing between our mind and the whole of nature.”
Please notice that he does not use the word ‘brain’.
He asks us to apply his ‘method’ to our own thinking process in order to clarify our thoughts and to select the power resident in our ability to form adequate ideas to recognize the truth of the reality which surrounds our daily lives. He would like us to harness our innate ability to think clearly in order to arrange our lives according to certain principles.