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Sensory Motor and Performance Team

A question to consider as you read . . .

Vocabulary that will help you understand this section

• central nervous system
• dynamics
• kinematics
• stimuli

During space flight the lack of a gravitational reference as experienced on Earth causes an alteration in the perception of objects and motions in crewmembers. These changes in perception and motor functions can lead to deterioration in crewmember 's work performance. To build a more thorough picture of the neurological systems associated with perception and motor performance, the Sensory Motor and Performance Team will document human adaptation to the microgravity environment through three unique studies. These studies will be combined with individual investigators concentrating on specific elements of the experiments.

Dr. Berthoz's Study

Dr. Berthoz's study will focus on the central nervous system's ability to accept visual stimuli, interpret those stimuli, and make the appropriate motor response in space flight. This performance chain will be demonstrated through the activity of catching a ball. Two internal systems--kinematics and dynamics, which make the performance of catching the ball possible--can be analyzed. First, the central system must take into account the kinematic relationship between a visually perceived location in space and the limb configuration necessary to place the hand at the appropriate place. Second, the central nervous system must model the dynamic properties of the falling ball to properly account for gravitational acceleration or the absence of gravity resulting in constant velocity in the prediction of the ball's trajectory. Data on the muscle activity and movement of the arm used by the subject to catch the ball will be collected to support this portion of the study.

Dr. Bock's Study

In another study, Dr. Bock will concentrate on the deficiencies of motor performance during adaptation to space flight. Crewmembers will be required to point at dots as they appear on a screen, grasp at dots as they change in size, track moving dots, and press a button in an input device whenever the dot changes to a ring. By allowing the crewmembers to observe hand activity during certain portions of the testing and covering up hand activity during other portions of the testing, the contributions of visual feedback during motor performance skills early, midway, and late in the mission will enable investigators to evaluate motor deficit compensation during space flight.

Dr. Oman's Study

Dr. Oman will focus on determining how microgravity alters the perception of objects and self-orientation. On Earth gravity provides a constant cue of which direction is up, therefore influencing how objects are recognized. This orientation reference is missing in microgravity, and the body becomes dependent on visual stimuli. Donning helmets that generate virtual reality scenes, subjects will participate in three types of tests. The first test will examine the principles of why crewmembers sometimes become confused about the reference for the spatial floor and ceiling in the absence of microgravity. The second test will examine how visual stimulation of objects moving past the subject gives the subject the sensation that the objects are in motion. The third test will examine how recognition of objects in different orientations of different shading patterns is influenced by the subject's frame of reference.

Investigations of the Sensory Motor and Performance Team are expected to provide relevant information to the Earth-based medical community seeking new understanding, testing, and treatment of neurological diseases such as Parkinson's disease, basal ganglia disorders, and cerebella deficiency.