1 Department of Neural Sciences, Lewis Katz School of Medicine, Temple University, 3500 North Broad Street, Philadelphia, PA 19140, United States of America. Electronic address: george.smith@temple.edu.
2 Reeve-Irvine Research Center, 837 Health Sciences Dr., University of California Irvine School of Medicine, Irvine, CA 92697, USA.
3 King's College London, Regeneration Group, The Wolfson Centre for Age-Related Diseases, Guy's Campus, London Bridge, London SE1 1UL, UK.