Twirls, Whirls, Spins, & Turns: The Science & Reflexes of Dizziness

The body’s key balancing and equilibrium center lies within the ear and is known as the vestibular system. It is a collection of inner ear structures close to—but independent from—those that amplify and transmit sounds to the brain. Rather than sound, the inner ear’s vestibular system conveys information about motion and position. This system tells us, even when our eyes are closed, if we are standing tall or balancing on our head, leaning forward or leaning backwards, leaping up or falling down.

Sensation of motion primarily comes from a series of fluid-filled tubes within the vestibular system called the semicircular canals. These small, enclosed loops embedded within both sides of the skull help us sense the direction, angle, and speed we are moving whether we’re going up, down, forward, backwards, or turning in circles. The semicircular canals detect motion using the fluid inside the canals and microscopic hair-like nerve endings that line the inner surface of the canals. When we are sitting still, the fluid and hairs are basically at rest. When we begin a motion like a turn, the liquid begins to sway inside the loops and triggers the hairs to send nerve signals to regions of the brain that recognize and interpret the initial motion. As we continue to turn, as in a series of rapids spins, the fluid picks up speed (angular momentum) within the canals and, because of inertia, continues to move and send signals to the brain even after we have come to an abrupt stop.

That’s when the sensation of feeling dizzy begins. It’s explained by a clash of conflicting information coming into your brain from your eyes, inner ear, and specialized nerve endings in your muscles and skin. Your eyes and limbs are telling it one thing (I’ve stopped spinning or turning), while the fluid in the semicircular canals is telling the brain something different (I’m still going around). It’s the same reaction that occurs when someone gets sea sick or motion sickness. In these examples, the eyes are fixed on a relatively immobile spot like the deck of a boat or the inside of a car. So the eyes are not sensing the shifts of motion that the inner ear is detecting every time the boat hits a swell or the car leans into a curve. Your brain finds these mixed signals disorienting, and soon the message becomes very clear that you’ll have to settle the sensory dispute or risk an upset stomach.

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts:

  • Spins and turns
  • Inner ear
  • Vestibular system
  • Semicircular canals
  • Vestibular nystagmus
  • Angular momentum
  • Acceleration
  • Inertia

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • Four people
  • An office chair that spins smoothly and doesn’t tilt back when spinning
  • A room with plenty of clearance to spin the chair
  • Stop watch or a video camera with a time stamp that shows seconds
  • A tripod, if you use a video camera
  • Soft ear plugs for each volunteer
  • Notebook or paper
  • Pen or pencil

Experimental Procedure

General Instructions

  1. Decide who will be spun in the chair first. One other person should be designated as the “observer.” The observer will be in charge of the stop watch or video camera, if you are using one. Two other people will act as the “spinners” of the chair. These roles can be switched as each person takes their turn being spun in the chair.
  2. Make sure no furniture or obstacles are near or around the chair.
  3. For each test, have the volunteer sit down in the chair, insert the ear plugs, put their hands in their laps, and close their eyes. They should keep their eyes closed during each test and not open them until the observer says so. Ear plugs should also be worn during the test unless the volunteer is told to take them off.
  4. Ask the volunteer to make two fists with their thumbs straight up and keep their hands in this position on their thighs during each test. Using their thumbs, they should indicate the direction they feel they are moving while they are spinning with their eyes closed. Immediately after they stop spinning, while their eyes remain closed the volunteer should use their thumbs to again indicate if they feel they are moving to the right, left, or not at all (thumbs straight up).
  5. At the end of each spin test, ask the volunteer to remain seated, open their eyes, and look directly into the camera or at the designated observer.
  6. The observer should note or film any eye movements, time how long they last, and record which direction the eyes are moving, if they are moving at all.
  7. Each spin test should be done three times by each volunteer.
  8. If a volunteer feels very dizzy after a test, let him/her sit in a non-moving chair for a few minutes before trying the next test. If a volunteer begins to feel sick at any time, he/she should stop all tests.

Test 1: Spin with gradual stop

  1. Have the first volunteer sit in the chair and keep their eyes closed during the test. They should also put in the ear plugs so they don’t receive any auditory cues.
  2. The two spinners should start spinning the chair at medium/fast speed counterclockwise. Make sure the volunteer does not fall out of the chair by gently touching just the back of the chair to spin it and by keeping the pushes smooth and consistent, not jerky.
  3. Note and record the position of the volunteer’s thumbs during and right after the test.
  4. After about 5 to 10 medium to fast spins, let the chair slow down a bit and help it slow down further by catching the chair lightly so it comes to a gradual stop.
  5. When the chair stops, ask the volunteer to open their eyes and record or film any eye movements.
  6. Ask the volunteer to describe how dizzy they feel. Have them rank their dizziness using a numerical system such as 1–5, with 1 = slightly dizzy and 5 = extremely dizzy.
  7. Have the volunteer repeat this test two more times, and record the results.
  8. Repeat the procedure with the remaining three volunteers.

Test 2: Spin with quick stop

  1. Have the first volunteer sit in the chair and close their eyes. They should have the ear plugs in their ears.
  2. Start spinning the chair at a medium/fast speed as in the first test.
  3. Note and record the position of the volunteer’s thumbs during and right after the test.
  4. After about five to ten spins, the two spinners should catch the chair and stop it quickly. They should “spot” the volunteer so that he/she doesn’t tip forward or fall out of the chair when it stops.
  5. Immediately after the stop, notice and record the observations of eye movements and dizziness as in the first test.
  6. Have the volunteer repeat this test two more times, and record the results.
  7. Repeat the procedure with the remaining three volunteers.

Test 3: Spin with quick stop; eyes open and ears not plugged

  1. Have the first volunteer sit in the chair, not wear any ear plugs, and keep their eyes open during this test.
  2. Repeat the spinning test, with a quick stop as in Test 2.
  3. Note and record the position of the volunteer’s thumbs during and right after the test.
  4. Immediately after the stop, notice and record the observations of eye movements and dizziness as in the first and second tests.
  5. Have the volunteer repeat this test two more times, and record the results.
  6. Repeat the procedure with the remaining three volunteers.

Analyzing Your Data

  1. Prepare a separate data table for each test. See the data table for a guideline. In each table, record the thumb signals, eye movement times, eye movement directions, and dizziness ratings for all volunteers.
    Test Number: ___Volunteer 1Volunteer 2Volunteer 3Volunteer 4
    Thumb Direction (During)
    Thumb Direction (After)
    Eye Movement Time (sec)
    Eye Direction
    Dizziness Rating (1-5)
  2. Total the three eye movement times of each volunteer, and calculate the average eye movement times for each volunteer for all tests.
  3. Calculate the average “dizziness ratings” for each volunteer in each test.
  4. Prepare a bar chart showing the average results of each volunteer next to each other for Test 1, 2, and 3.
  5. What differences do you see between Test 1, 2, and 3 in average eye movement times for each volunteer? Do all the volunteers have similar results or are there some differences?
  6. What differences do you see between Test 1, 2, and 3 in average dizziness ratings for each volunteer? Are the results the same for all volunteers?
  7. How do the directions the eyes move compare between Test 1, 2, and 3 for each volunteer? Are the results the same for all volunteers?
  8. How do the thumb signals compare between Test 1, 2, and 3 for each volunteer? Are the results the same for all volunteers?
  9. What effect, if any, did having their eyes open and ears unplugged have on the volunteers’ eye movements and dizziness ratings at the end of test 3?
  10. For help with data analysis and setting up tables, see Data Analysis & Graphs.
  11. For a guide on how to summarize your results and write conclusions based on your data, see Conclusions.

Variations

  • Does experience matter? Try these tests with a volunteer who is experienced with spinning motions like an ice skater, gymnast, diver, or dancer. Compare their results with another athlete who doesn’t practice spinning or turning on a regular basis in their sport (soccer, track, football, baseball, etc). Research the ability of the vestibular system to adapt to repeated spinning in sports. Find out if the vestibular system adapts in other situations like sailors getting used to ocean travel or astronauts adjusting to floating in the microgravity conditions of space travel.
  • Effect on balance. Repeat these experiments and ask the volunteers to stand up and walk straight ahead right after each test. Measure the distance they walk and note the direction(s) they travel. Be sure to have someone spot them as they walk. Try doing this test with and without a long piece of tape on the floor for the volunteers to look at as they try to walk. Research how visual cues after spinning may influence dizziness and sense of balance.
  • Dizzy to the Extreme. For volunteers who don’t get too dizzy on the original tests, you can ask them to try changing their head position while spinning in the chair for Test 1 (gradual stop). Have them put their head down for one test and back for another. They should grip the handles of the chair, keep their eyes closed, and wear ear plugs during both tests. Be sure to have spotters close to the volunteers when the chair stops. Record your observations and compare them with the results from your original tests. Research the function and orientation of the semicircular canals to help explain the results from these tests.

if you like this project you can work as a neurologist.