EXAMINING THE EFFECTS OF SPACE FLIGHT ON THE HUMAN SENSORY AND BALANCE SYSTEM

CASE STUDY 6
VESTIBULAR EXPERIMENTS IN SPACELAB

Principal Investigator
Laurence R. Young, Sc.D.
Massachusetts Institute of Technology
Cambridge, Massachusetts

INTRODUCTION

Have you ever watched a scene on television where a person steps off a curb, a rushing vehicle blares its horn, and the person leaps back to safety in the nick of time as a car or truck thunders past? Have you ever experienced forgetting a certain word that you really want to use to describe something but you just can't think of it, and then the word comes to you in the middle of the night or some other time when it doesn't do you any good anymore?! But at least you finally remembered it! Also, how is it possible for an owl to dive, almost silently, out of the night sky and entrap a scurrying mouse in its clutches? Both organisms are on the move, yet the owl's timing is precise, and it neither crashes into the ground nor comes up empty-handed. Think about how elegant it is just for all of us to be able to walk, and to walk at varying speeds and over various obstacles. You may have never considered walking as elegant but that's because we take it for granted that our legs are going to get us places. Look at a nervous system that is not performing normally because it has been altered by drugs, or by disease, or by trauma to the inner ear, for example, and we get a glimpse of the awesome complexity that underlies the smooth physical and mental coordination we normally take for granted.

The examples that we just considered are just four small examples of the routine, everyday functioning of the human nervous system. Even a thousand examples would not be enough to describe its capabilities. Its presence in the body makes of each of us, in effect, a vast switchboard of humming, flashing, blinking signals, constantly sending and receiving messages - some urgent, some not - all concerned with the conduct of the body's affairs.

From the moment we are born to the moment we die, this communications network controls our every thought, our every emotion, every impression we get, and every single movement we make. Without it we could not plan, feel, move around, nor distinguish between pleasure and pain; we could be deprived of such amenities of life as the enjoyment of food, or music, or the color of a painting, or dancing and moving, or the pressure of a friendly handshake. In this chapter, we are going to examine how our brain and overall nervous system work together to provide us with the direction, guidance, and impulses necessary to move about and function day to day. In particular, we will discuss the influence of gravity on the sensory and balance centers within our brains and we will examine a space flight investigation that was designed to learn more about the major effects on our senses and our perceptions that result from the removal of gravity. This is our last chapter, so let's get started!