Paul was a close friend of mine, and we worked together on his research during his neurosurgery residency at Stanford. He was a hell of a human being, brilliant, dedicated, creative, refreshingly optimistic, and selfless. Before he was diagnosed, I'd planned to postdoc with him when he was considering starting a functional neurosurgery lab (actively manipulating the nervous system to achieve therapeutic benefit, with deep brain stimulation being the most successful example).

This piece he wrote shortly before he died is well worth your time. http://stanmed.stanford.edu/2015spring/before-i-go.html