CAPE CANAVERAL, SEPT. 13 -- Japan's first professional astronaut, his head plastered with electrodes and secured in a vise, squinted at flashing lights aboard Endeavour today to help unravel the mysteries of motion sickness.

A shuttle crewmate, American Mae Jemison, relied on the power of positive thinking, or biofeedback, to avoid nausea and other symptoms of motion sickness.

Mamoru Mohri spent day two of the laboratory research mission, a joint venture between the United States and Japan, staring at flickering lights from all directions. The nuclear scientist was propped first right-side up in a restraining chair, to the side and then upside down as he kept his eyes fixed on lights attached to two perpendicular bars.

White electrodes stuck on Mohri's face and neck measured eye movement and neck muscle tension. Data were transmitted to Japanese researchers at NASA's Marshall Space Flight Center in Huntsville, Ala.

Officials refused, citing privacy rules, to say whether the test made Mohri sick or whether anyone else aboard Endeavour had motion sickness.

Space agencies around the world are eager to learn more about the motion sickness that strikes most astronauts during their first few days in space. The illness affects flight planning; critical activities like spacewalks, for example, are never scheduled early in a mission.

Medicine helps control space motion sickness, but often has side effects like drowsiness. That's why Jemison is trying to control it with biofeedback, which has no side effects. Shuttle astronauts have tried biofeedback before in space, but the results were inconclusive, a psychologist said. The process involves using relaxation and mental exercises to control such body functions as heart rate, sweating and skin temperature.

Jemison, a physician, is the only one among Endeavour's seven-member crew who is trained in biofeedback. "I do know it works on the ground so we'll see how it works in space," Jemison, the first black woman in space, said before the flight.