By Irene Wong
news staff writer

WALTHAM – Gravity is one of the few things in life you count on to remain constant. But how would your body respond if it didn't? This is just one of many issues explored be researchers of the Ashton Graybiel Spatial Orientation Laboratory at Brandeis University in Waltham.

"We're interested in just about any kind of unusual force environment and how that relates to normal conditions," said associate lab director Paul DiZio, who has been working for Brandeis since 1978. DiZio said the lab is mainly interested in human movement control and orientation. By orientation he is referring to such questions as how you know what's up and down or when you're moving and standing still – and your brain's role in such decisions. How do you know these conditions exist and how do you control them?

Variable gravity is used to test how our bodies function in different environments. "You would think our brain would be very hard–wired to expect a certain kind of gravity and have hardwired reactions. And that when you go into different gravity levels just be totally fouled up and not be able to readjust very quickly. Turns out you adjust very rapidly," said DiZio.

For example, a simple activity such as reaching for a target becomes challenging when normal gravity is not present. However, a study showed that within an average of 10–20 attempts, the brain, eyes and sense of touch can reprogram the arm muscles for the job. Although the human body can readjust to new gravity levels, DiZio said there can be some negative effects from zero gravity, such as astronauts losing muscle and bone mass after spending an extended duration in space.

The exact source of those problems is hard to pinpoint, but he said searching for a reason behind problems in zero gravity helps the lab to understand how we are adjusted to normal gravity. "We're basically interested in what the normal human capacities for movement and orientation are. In order to study how things work under normal conditions, sometimes you have to use extraordinary conditions," said DiZio.

Many of these "extraordinary conditions" are simulated in a rotating room, one of two such rooms in the country. As the room rotates, natural gravity and centrifugal force (artificial gravity) are combined to alter the gravity in the room. According to DiZio, the gravity level can range between one to 4.5, with one being gravity as we know it an 4.5 simulating extra forces present in the takeoff and re–entry of a space shuttle. The center of the room has no centrifugal force so researchers can use a combination of rotation speed and gravity to determine how people are affected.

Any differences that we get between (the center and the wall) we know is due to gravity level because the rotation speed is the same. But anything that happens right at the center we know is not an effect of gravity – it's an effect just of rotation," said DiZio.

Experiments take place in the lab daily and DiZio said researchers are learning more about how people can adapt to different speeds and gravity levels. "We're starting to understand why the errors occur and why we can adjust. That will help us define what kind of environments we can live in," he said.

The Ashton Graybiel Spatial Orientation lab opened in 1982 and was named after Dr. Graybiel, who was one of the founders of aerospace medicine. Construction of the rotating room was finished in 1988–89. The other rotating room is located in a U.S. Navy lab in Pensacola, Fla., but that facility is not as modern.

"The rotating room is pretty much of a unique facility and then the rotating room in combination with everything else we have is really among the few of the best facilities around the world for studying movement and orientations said DiZio. Other labs maybe larger, but their work involves more applied situations whereas the Graybiel lab is directed more at understanding how people respond. The two different styles complement each other, said DiZio. "You can simulate every situation you want exactly and then you can predict it. Or you can try to understand how people work and then you can predict what's going to happen without even ever doing it," he said.

In terms of long-term goals, the researchers hope to apply their findings to a large scale, possibly through the design of simulators to prepare astronauts for artificial gravity environments. "In terms of helping astronauts prepare, it's really just to help define the size versus the speed tradeoff for the space station, to try to understand ways of pre-exposing them in order to be able to tolerate the changes better," he said.

The overall goal of the researchers is to learn how the brain adsorbs all the sensory information it encounters and then re-orients itself.

This article was published in the News Tribune of Waltham.