Materials Included In Kit

Additional Materials Required

Safety Precautions

The “sensations” created in this activity should be created using gentle taps and pokes rather than with hard taps. Caution students about safety when tapping on the face and hands.

Disposal

All materials can be reused numerous times.

Teacher Tips

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. All materials are reusable. The activity can be reasonably completed in one class period.

• Remind students that gentle tapping of the nose creates a better sensation than hard tapping. Each student will want to participate as “the subject” and sensations will vary widely from student to student.
• Preparing the wire hanger “forks” yourself (Part II, step 3) ensures a consistent size.
• The secret to the phantom hand test is the concentration on the photograph as opposed to the actual hand. Also make sure the hand of the subject is palm up.

Further Extensions

• Another option in the phantom hand procedure is to have the “tester” stab the photo with a pencil after several minutes of tapping and observe the response of the test subject.
• To make this activity more personal, use a digital camera to take and print color photos of each student’s hand or ask the school’s photography students to assist you.

Discussion

In Part I, the Nose Length procedure, the test subject may feel the sensation that his nose is stretched a couple of feet in front of him. As the test subject performs the Phantom Hand procedure, she may sense her hand actually shifting toward the photograph. After a few minutes, the test subject may actually feel the hanger’s touch on the photograph. It is theorized that the awareness of body parts is not hardwired into the brain, but is learned from sensory experience. In other words, we may learn that our arms (or other body parts) are part of our bodies because whenever they are touched, the tactile sensations exactly correlate in time and place with our muscle and joint positions associated with the experience. Repeated agreement of these feelings ultimately convinces the brain that our body parts belong to us.

In these activities, it is shown that what is learned can ultimately be “unlearned” when senses strongly disagree with one another. Tactile and/or visual cues were in discord, making the test subject feel something that was not really true. These activities provide great insight on how the brain can rewire itself to recover from damage. Similar techniques are currently being used by neuroscientists to help patients reclaim sensory awareness that may have been lost through injury.

References

Discover. Phantom Sensations, May 2002, p 88.

Introduction

Can pain and other sensations be felt by a body part even when it is missing? If so, how can this happen?

Concepts

• Response to stimuli

• Phantom sensations

Background

The brain has a remarkable ability to rewire itself. For instance, stroke patients can eventually regain speech by training non-speech centers of the brain to process language. The brain’s ability to rewire itself may not always be beneficial. Evidence suggests that the rerouting of nerve fibers is also responsible for pathological conditions such as pain in the phantom limbs of amputees.

It was once thought that the rewiring of the brain took several weeks, allowing time for nerve cells to grow fibers and make new connections. However, it has been found that rewiring can occur much more quickly. Can your brain be rewired to feel things that are not really there? Perform the following activities and find out.

Materials

Safety Precautions

Although this activity is considered nonhazardous, follow all laboratory safety guidelines. Use gentle taps and pokes to create the sensations.

Procedure

Part I. Nose Length

1. Form a team of three individuals and take turns being the test subject.
2. The test subject sits or stands directly behind a partner.
3. The test subject must close his or her eyes and keep them closed throughout the entire procedure.
4. The test subject should reach around the partner in front of them with one arm and touch the end of the partner’s nose with their index finger (see Figure 1).

5. The third person in the team touches the tip of the test subject’s nose and begins a gently, rhythmic tapping.
6. When the test subject feels his nose being tapped, he should begin tapping the tip of the nose of the partner in front of him with the same soft tapping rhythm.
7. All team members should keep tapping for two minutes while the test subject’s eyes are closed or covered.
8. Stop tapping and the test subject will describe, in writing on a separate sheet of paper, the sensations he experienced.
9. Switch roles so that all three partners serve as the test subject.
10. Make sure each partner has written a brief description of what he or she felt.

Part II. Phantom Hand

1. This activity should be done with a partner.
2. Take turns being the subject and the tester so that the “sensations” can be experienced by each person.
3. Bend a wire hanger into a two-pronged fork (see Figure 2). The fork of the bent hanger must fit over the top of the book cover separating the subject’s hand and the photo.

4. Place a hand photo on the front inside cover of a textbook. Use the cover as a divider to shield the view of the real hand.
5. The subject should place her hand, palm up, on the table or desktop and stand in such a way that she can only see the photo of the hand when the tester has the book cover upright (see Figure 3).

6. The subject must look only at the hand photograph throughout the testing session and not at her own hand.
7. The tester should tap the two ends of the bent hanger on the photo and the subject’s hand at precisely the same moments. The tapping should be random and unpredictable, like Morse code.
8. Continue to tap on the photo and the subject’s hand simultaneously for a few minutes while the subject concentrates on looking at the photo.
9. The tester should continue the tapping and then without warning stop tapping on the subject’s hand and only tap on the photo. This tapping should be with the same rhythm as before so the test subject does not notice any difference. Does the subject still “feel” the taps even though the hanger no longer touches the hand? The test subject should then describe in writing the sensations and feelings experienced.
10. Reverse roles and repeat the entire procedure with the tester becoming the subject.

Post-Lab Questions(Write answers on a separate sheet of paper.)

1. Based on what you experienced in Parts I and II, can the brain be fooled into sensing things that are not really there? Explain.
2. Now that you are finished with the activity, was your brain permanently rewired? How do you know?
3. Give an example of a phantom sensation you have experienced or detected through one of the five senses in the past.