Before-life is pre-existence
One does not need a brain for that. It is soul memory, woven into the soul. The pre-existence is remembered at first but as the baby matures into a child, the memories fade.
William Wordsworth knew. "ODE
INTIMATIONS OF IMMORTALITY FROM RECOLLECTIONS OF EARLY CHILDHOOD" http://www.bartleby.com/145/ww331.html
I know a young man who as a young child remembered. I heard him speak of Nabiya (Nabiya is the one who shepherds us through reincarnation). He also spoke of "his other mother." "You know, my mother before Nabiya made me come back." He was all of 4 when he said that.