After earning his doctoral degree in Pathology from the University of London, Faculty of Medicine, Dr. Spencer joined the Albert Einstein College of Medicine, New York, where he rose to the rank of Tenured Professor of Neuroscience, Neurology and Pathology, and Director, Institute of Neurotoxicology. He joined Oregon Health Sciences University in 1988 to found the Center for Research on Occupational and Environmental Toxicology.

Dr. Spencer is 2005 Honorary Member of the Indian Academy of Neurosciences; recipient of the 2003 Distinguished Service Award, African Society of Toxicological Sciences; the 2002 Distinguished Scientist Award in Neurotoxicology, American Society of Toxicology; the 1998 Alzheimer's Association Brumback Award for Outstanding Achievement in Research; the 1997 Snider Foundation Award for Lifetime Contributions to Toxicology, and the 1997 Silvio O. Conte prize for basic and applied neuroscience contributions relevant to environmental health. Other honors include: Joseph P. Kennedy, Jr., Fellow in the Neurosciences; Weil Awardee and Moore Awardee of the American Association of Neuropathologists; Member, American Neurological Association, and Fellow, Royal College of Pathologists, U.K. National and international named visiting professorships and lectureships include: Alice B. Hamilton Lecturer, George H. Germann Memorial Lecturer, Sibte Hasan Zaidi Orator, Ellerman Lecturer, Hanninen Lecturer, Kugelberg Lecturer, Grass Traveling Neuroscience Lecturer, Sterling Visiting Professor, Sitlington Lecturer in Toxicology, and Tarbox Distinguished Neurosciences Lecturer.

Dr. Spencer has authored more than 350 scientific papers and seven books, including the standard text Experimental and Clinical Neurotoxicology, the second edition which was published in 2000. The entire first edition of the book is available online.

Dr. Spencer is a member of the advisory or editorial boards of seven professional journals. Past national appointments include Member, Science Advisory Board, National Center for Toxicological Research, U.S. Food and Drug Administration; Member, U.S. Environmental Protection Agency Advisory Panel; Member, National Advisory Council, National Foundation for Brain Research; Member, Science Advisory Committee, National Institute of Aging Marianas Dementia Research Grant, and Member, Parkinson's Epidemiology Research Committee; Chair, New Developments in Neuroscience, Biological Applications Program, Office of Technology Assessment, U.S. Congress; Member, Board of Toxicology and Environmental Health Hazards, Committee on Neurotoxicology and Risk Assessment, Committee on Toxicology, and Committee on Safe Drinking Water, National Academy of Sciences, National Research Council. Current appointments (1998-) include Member, Subcommittee on Chronic Reference Doses for Selected Chemical Warfare Agents, Committee on Toxicology, National Academy of Sciences, National Research Council and Member, Expert Panel Advising Arkansas Department of Health on Department of Defense Program on Chemical Demilitarization at Pine Bluff Arsenal.

International appointments have included Temporary Advisor, Pan American Health Organization and World Health Organization; Secretary, Third World Medical Research Foundation; Chair, International Network for the Improvement of Lathyrus sativus and the Eradication of Lathyrism; Member, Cassava Biotechnology Network; Vice-Chair, International Advisory Committee, Society of Toxicology for Developing Countries, and Program Organizer and Chair, Environmental Neurology, World Congress of Neurology.