A recent ball-catching experiment conducted in space by astronauts on board a space shuttle has led neuroscientists to conclude that the brain contains an internal model of gravity that is both powerful and persistent. At the same time, the experiment provided evidence that the brain can adapt to environments in which the force of downward acceleration is less pronounced than it is on earth.
The experiment's outcomes suggested that an individual's understanding of motion is hard-wired from an earth-centric perspective. In the experiment, the astronauts were asked to catch balls released from a spring-loaded cannon. Analyzing data gathered from infrared tracking cameras and electrodes placed on the astronauts' arms, McIntyre, the experiment's principal designer, noticed that the astronauts' anticipation of the ball's motion was slightly off. Though they were able to catch the ball, the astronauts expected the ball to move faster than it did. He theorized that this over-anticipation is due to the fact that the brain expects the force of the earth's gravity to act on the ball.
The experiment also demonstrates the brain's ability to adjust to conditions that run counter to its pre-set wiring. While the astronauts did not adapt to the conditions in space for some time, by day 15 of the experiment, the amplitude of the premature arm movements decreased and a new well-timed arm movement immediately preceded the catch. Upon returning to earth, the astronauts again mis-anticipated the ball's motion, though this time the ball moved faster than anticipated. However, the astronauts were able to adjust back to the earth's gravitational effect on the balls much more quickly than they had been able to adapt to the conditions in space.
Many scientists view the findings as a first step in research that could have serious practical benefits. The ability of astronauts to safely explore space and investigate other planets is dependent on understanding the differences between our physical reactions on earth and elsewhere. On another level, understanding timing processes in the body might lead to the development of treatments for coordination problems experienced by individuals with certain types of brain damage.