adult also author brain brain's brains capacity cells center circuitry cleared closely colleagues damaged determining disease diseased disorders embryonic first forged functional functionally give grown healthy human hurdles implanted induced integrate known lab light many modulate national neurons new nov optogenetics parkinson's past plays pluripotent pnas potential previous previously proceedings processing professor question receive received receiving region related repair replace report reported reports represents rhythmic rise role sciences scientist scientists sclerosis send sending show shown signals slate spatial specialized specifically stem step stimulate study system talking team technology tissue tissues tool transplanted types using waisman way weick well-studied wisconsin zhang