WE HAVE PREVIOUSLY SHOWN AN UPWARD SHIFT OF THE BRAIN AND CROWDING OF ELOQUENT BRAIN TISSUE AT THE VERTEX IN ASTRONAUTS FOLLOWING LONG-DURATION MISSIONS ABOARD THE INTERNATIONAL SPACE STATION (ISS) AND THAT LONG-DURATION BUT NOT SHORT-DURATION SPACEFLIGHT RESULTED IN A SIGNIFICANT INCREASE IN TOTAL VENTRICULAR VOLUME (%DVV 10.7% VS 0% P<0.001). MORE RECENTLY WE FOUND AN ASSOCIATION BETWEEN THE STRUCTURAL BRAIN CHANGES AND ALTERED COGNITIVE AND MOTOR PERFORMANCE. IN A SMALL GROUP OF ASTRONAUTS WE FOUND THAT %DVV CORRELATED SIGNIFICANTLY WITH WORSENING POSTURAL CONTROL (R0.74 P<0.05 N8) A DECREMENT IN ACCURACY FOR A LEARNING-RELATED CODE SUBSTITUTION TEST (R -0.60 P<0.05 N12) BUT FASTER REACTION TIMES FOR CONTINUOUS PERFORMANCE TESTING (R -0.62 P<0.05 N12). FURTHERMORE WE IDENTIFIED LOCAL BRAIN STRUCTURAL CHANGES POST-FLIGHT WHICH CORRELATED WITH CHANGES IN POSTURAL CONTROL (LEFT CAUDATE) COMPLETION TIME OF A COMPLEX MOTOR TASK (RIGHT PRIMARY MOTOR AREA/MID CINGULATE) AND ALTERED REACTION TIMES (BILATERAL OPTIC RADIATIONS AND SPLENIUM OF THE CORPUS CALLOSUM). WE ALSO FOUND THAT ASTRONAUTS WHO DEVELOPED SPACEFLIGHT ASSOCIATED NEURO-OCULAR SYNDROME (SANS) DEMONSTRATED A SIGNIFICANTLY SMALLER CHANGE IN %DVV THAN THOSE WITHOUT SANS (12.8% VS 6.5% P0.02 N8 VS N4). WE HYPOTHESIZE THAT THESE CHANGES IN BRAIN STRUCTURE CONTRIBUTE TO ALTERED COGNITIVE AND MOTOR PERFORMANCE IN ASTRONAUTS POST-FLIGHT. LIMITATIONS DUE TO THE RETROSPECTIVE NATURE OF OUR STUDY INCLUDED THE LACK OF LONG-TERM FOLLOW-UP IMAGING AND CLINICAL ASSESSMENTS TO DETERMINE WHETHER OR NOT THE BEHAVIORAL AND STRUCTURAL BRAIN CHANGES WERE REVERSIBLE. ANOTHER LIMITATION WAS THE SMALL NUMBER OF FEMALE ASTRONAUTS. HERE WE PROPOSE TO INVESTIGATE GENDER DIFFERENCES AND THE REVERSIBILITY OF POST-FLIGHT STRUCTURAL BRAIN CHANGES IN ASTRONAUTS AFTER SOME TIME BACK IN THE 1 GRAVITY ENVIRONMENT OF EARTH AND TO ASSESS FOR ANY ASSOCIATION WITH ALTERED COGNITIVE/BEHAVIORAL PERFORMANCE.

The Medical University Of South Carolina

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