1. Division of Physical Medicine and Rehabilitation, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio.
2. Division of Biostatistics and Epidemiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio.
3. Division of Developmental and Behavioral Pediatrics and Psychology, Department of Pediatrics, Case Western Reserve University and Rainbow Babies and Children's Hospital, University Hospitals Case Medical Center, Rainbow Child Development Center, Cleveland, Ohio.
4. Department of Psychology, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.