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Mark J. Shelhamer, Sc.D.
Associate Professor of Otolaryngology - Head and Neck Surgery
Research Interests: vestibular, oculomotor, sensorimotor, nonlinear dynamics, complex systems, integrative physiology, human spaceflight
Dr. Shelhamer started at Johns Hopkins as a postdoctoral fellow in 1990. He has bachelor’s and master’s degrees in electrical engineering from Drexel University and a doctoral degree in Biomedical Engineering from MIT. At MIT, he worked on sensorimotor physiology and modeling, including the study of astronaut adaptation to space flight. He then came to Johns Hopkins where he continued the study of sensorimotor adaptation with an emphasis on the vestibular and oculomotor systems. He has applied nonlinear dynamical analysis to the control of eye movements, including investigations of the functional implications of fractal activity in physiological behavior. In parallel with these activities, he has had support from NASA to study sensorimotor adaptation to space flight, amassing a fair amount of parabolic flight (“weightless”) experience in the process. He also serves as an advisor to the commercial spaceflight industry on the research potential of suborbital space flight. Dr. Shelhamer is the author of Nonlinear Dynamics in Physiology: A State-Space Approach, has published over 70 scientific papers and has had research support from NIH, NSF, NASA, NSBRI, and the Whitaker Foundation. From 2013 to 2016 he was on leave from his academic position to serve as NASA’s Chief Scientist for human research at the Johnson Space Center.
- Associate Professor of Otolaryngology - Head and Neck Surgery
- Associate Professor of Biomedical Engineering
Research & Publications
The main thrust of Dr. Shelhamer’s work is in the area of vestibular and oculomotor adaptation. This includes studies of the error signals that drive adaptation, ways to improve adaptation, and context-specific adaptation. This line of investigation uses a dynamic-systems approach, leading to the study of the statistical properties (fractal correlations) of sequences of responses. This began with the finding that sequences of consecutive predictive saccades are highly correlated, reflecting the need to store past performance to program a movement with the proper parameters (timing, amplitude). The correlations exhibit power-law decay, which is a form of fractal scaling and suggests a process that optimally balances flexibility and stability. The most recent results of this work demonstrate that the strength and extent of the inter-trial correlations are directly related to the ability to adaptively alter saccade gain. This has been extended to adaptive control of the VOR. These results are among the first that demonstrate the potential to forecast an individual’s predictive ability, which might be used to tailor adaptation and training paradigms. This work is now being expanded more broadly, based on multi-system adaptation of humans to environmental perturbations such as extended space flight. The challenges of understanding, assessing, and promoting adaptation to space flight are similar to those involved with compensation from injury or disease, and both aspects can be studied in normal subjects exposed to controlled sensorimotor perturbations: this is the guiding hypothesis of ongoing research. The overall theme of this work is resilience: the ability to reorganize physiological processes to recover from injury, pathology, and environmental perturbation.
Technology Expertise Keywordssensorimotor assessment, ambulatory monitoring
Shelhamer M. Nonlinear Dynamics in Physiology: A State-Space Approach. Singapore: World Scientific, 2007.
Shelhamer M, Joiner W. Saccades exhibit abrupt transition between reactive and predictive, predictive saccade sequences have long-term correlations. J Neurophysiol, 2003, 90:2763-2769.
Shelhamer M. Sequences of predictive saccades are correlated over a span of ~2 s and produce a fractal time series. J Neurophysiol, 2005, 93:2002-2011.
Shelhamer M. Sequences of predictive eye movements form a fractional Brownian series - implications for self-organized criticality in the oculomotor system. Biol Cybern, 2005, 93:43-53.
Wong AL, Shelhamer M. Sensorimotor adaptation error signals are derived from realistic predictions of movement outcomes. J Neurophysiol, 2011, 105:1130-1140.
Wong AL, Shelhamer M. Exploring the fundamental dynamics of error-based motor learning using a stationary predictive-saccade task. PLoS ONE, 2011, 6:e25225.
Wong AL, Shelhamer M. Similarities in error processing establish a link between saccade prediction at baseline and adaptation performance. J Neurophysiol, 2014, 111:2084-2093.
Shelhamer M. Trends in sensorimotor research and countermeasures for exploration-class space flights. Front Syst Neurosci, 2015, 9:115.
Shelhamer M. A call for research to assess and promote functional resilience in astronaut crews. J App Physiol, 2016, 120:471-472.
Activities & Honors
- NSF Graduate Fellowship, 1982 - 1985
- NASA Group Achievement Award, for Life Sciences Experiments on Spacelab-1, 1984 - 1984
- Whitaker Health Sciences Fund Fellowship, 1986 - 1988
- Award for outstanding contributions to the MIT Man-Vehicle Laboratory, 1989 - 1989
- Senior Member, IEEE, 2007 - 2007
- Best paper award, Eye Tracking Research and Applications meeting, 2008 - 2008
- NASA JSC “On the Spot” Award, for reducing ISS crew time requirements, 2015 - 2015
- Institute of Electrical and Electronics Engineers (IEEE)
- IEEE Engineering in Medicine and Biology Society
- IEEE Acoustics, Speech, and Signal Processing Society
- Society for Neuroscience
- Society for Chaos Theory in Psychology and Life Sciences
- NASA Grant review panel, NASA Neurolab, 1994
- NIH Special Emphasis Panel, 1997 - 2000
- NASA Neurobiology grant review panel, 2000 - 2002
- NIH Communication Disorders Review Committee, ad hoc reviewer, 2000 - 2000
- NSF grant review panel (2003), ad hoc reviewer
- NIH/NIBIB site visit panel for USC project grant, 2003 - 2008
- DoD/AIBS ad hoc reviewer
- NIH Special Emphasis Panel: Clinical Neurophysiology, Devices, Auditory Devices and Neuroprosthesis Small Business, 2009 - 2012
- NSBRI fellowship review panel, 2011 - 2012
Videos & Media
Lectures and Presentations
Fractal Correlations and Motor Control
Invited lecture, Brain Science Institute working group on computational neuroscience (04/01/2013)
Johns Hopkins University School of Medicine
What Happens to the Human Body in Space – And What To Do About It
Invited Lecture, Astrobiology Lecture Series, Space Telescope Science Institute (12/01/2013)
NASA’s Approach to Critical Risks for Extended Human Space Flight
Invited lecture, Future In-Space Operations webinar series (04/01/2014)
NASA Goddard Space Flight Center
Predicting Sensorimotor Adaptation Ability through Fractal Time Series Analysis
Invited lecture (04/01/2014)
University of Houston
From the Bench to Exploration Medicine: NASA Translational Research Roadmap (TRR) Synergies Within Space and Synthetic Biology, Astrobiology, and the Human Research Program
Invited lecture, session chair, discussion leader, American Society for Gravitational and Space Research annual meeting (10/01/2014)
Can Humans Survive 1000 Days in Space?
Invited lecture, panel member, International Space Station Research and Development Conference (07/01/2015)
Good Health: The Impact of Space Science on Precision Medicine
Invited lecture, panel member (07/01/2015)
Complexity and Human Spaceflight: Ideas for Resilient Systems Development
Invited lecture (09/01/2015)
Santa Fe Institute
Microgravity Platforms other than ISS
Invited lecture, panel member, American Society for Gravitational and Space Research annual meeting (11/01/2015)
Recent News Articles and Media Coverage
What Happens to the Human Body in Space -- And What To Do About It. Institute for Planets and Life seminar series - December 06, 2013
A Match Made in the Heavens. MIT Review. https://www.technologyreview.com/s/529711/a-match-made-in-the-heavens/
A Rising Star at NASA. Johns Hopkins. http://www.hopkinsmedicine.org/news/publications/headway/headway_summer_2013/a_rising_star_at_nasa_
The Biggest Health Risks to Humans in Space. Gizmodo.