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Motor System Development Depends on Experience: A Microgravity Study of RatsAnimals move about their environment by sensing their surroundings and making adjustments according to need. All animals take the force of gravity into account when the brain and spinal cord undertake the planning and execution of movements. To what extent must animals learn to factor in the force of gravity when making neural calculations about movement? Are animals born knowing how to respond to gravity, or must the young nervous system learn to enter gravity into the equation? To study this issue, young rats were reared in two different gravitational environments (the one-G of Earth and the microgravity of low Earth orbit) that necessitated two different types of motor operations (movements) for optimal behavior. We inquired whether those portions of the young nervous system involved in movement, the motor system, can adapt to different gravitational levels and, if so, the cellular basis for this phenomenon. We studied two groups of rats that had been raised for 16 days in microgravity (eight or 14 days old at launch) and compared their walking and righting (ability to go from upside down to upright) and brain structure to those of control rats that developed on Earth. Flight rats were easily distinguished from the age-matched ground control rats in terms of both motor function and central nervous system structure. Mature surface righting predominated in control rats on the day of landing (R+O), while immature righting predominated in the flight rats on landing day and 30 days after landing. Some of these changes appear to be permanent. Several conclusions can be drawn from these studies: (1) Many aspects of motor behavior are preprogrammed into the young nervous system. In addition, several aspects of motor behavior are acquired as a function of the interaction of the developing organism and the rearing environment; (2) Widespread neuroanatomical differences between one-G- and microgravity-reared rats indicate that there is a structural basis for the adaptation to the rearing environment. These observations provide support for the idea that an animal's motor system adapts for optimal function within the environment experienced during a critical period in early postnatal life.
Document ID
Document Type
Walton, Kerry D. (New York Univ. New York, NY, United States)
Llinas, Rodolfo R. (New York Univ. New York, NY, United States)
Kalb, Robert (Children's Hospital of Philadelphia Philadelphia, PA, United States)
Hillman, Dean (New York Univ. New York, NY, United States)
DeFelipe, Javier (Cajal Inst. Madrid, Spain)
Garcia-Segura, Luis Miguel (Cajal Inst. Madrid, Spain)
Date Acquired
September 7, 2013
Publication Date
January 1, 2003
Publication Information
Publication: The Neurolab Spacelab Mission: Neuroscience Research in Space: Results from the STS-90, Neurolab Spacelab Mission
Subject Category
Aerospace Medicine
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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IDRelationTitle20030068190Analytic PrimaryThe Neurolab Spacelab Mission: Neuroscience Research in Space: Results from the STS-90, Neurolab Spacelab Mission