ANSWERS
Part 1 - Movement of Index Finger

1. What do these three patterns represent? (They are electroencephalograms that show the brain's electrical activity)
2. Did the "movement" EEG differ from the "No movement" recording? If so, how? (Yes. The movement had three extra activity spikes)
3. What was the signal strength of each of the first signal spikes? (+100)
4. At about what time did the last signature spike occur? (About .25 seconds)
5. Identify the strength and time of occurrence of all new spikes associated with the movement of an index finger. (+100 signal spike about 0.1 seconds after recording began, +100 signal spike about 0.05 seconds following first spike, -100 spike about 0.1 seconds after second spike)

Part 2 - Movement of Thumb and Index Finger

Now that you know how to isolate and identify a signal spike, determine the differences in signal characteristics between the index movement and the movement of the thumb and index finger (Recording #3). (+100 volt spike at .16 seconds disappears, -200 spike at .22 seconds appears, a series of three +200 spikes appear at about .3 seconds)

Part 3 - Destructive Inderstanding

When signals occur at the same time, their values can either reinforce or reduce each other. If the wave spikes are in sync and are both positive or both negative, they reinforce each other. This type of signal increase is called constructive interference. If, however, the in-sync signals have opposite values (one positive, the other negative),the spikes can cancel each other out. This type of interaction is called destructive interference. Check out the spike that occurs in the index finger movement at 0.1 seconds.

1. What is this signal's strength? (+100).
2. Was this spike present in the no movement EEG? (no)


3. Is this spike present in the movement of the thumb and index finger? (no)
4. What does this suggest about the signal generated to move the thumb alone? (The thumb signal produced destructive interference that cancelled the index finger movement)
5. Make a guess. What is the most likely value of a thumb signal spike that occurs at 0.1 seconds? (-1)
6. Explain (In order to cancel out the +1 signal, this spike had to be opposite and equal in value to the +1 signal)

EXTENSIONS
Part 1 - A Confusing Clasp

QUESTIONS

1. What happened when you tried to lift the finger identified by your partner? (often lifted the wrong finger)
2. Which fingers were least likely to be confused? (outside thumb and outside pinky)
3. Suppose you didn't invert your clasp. Would you still confuse the fingers? Why or why not? (Most likely not. You'd be able to trace the fingers to the hand to which they belonged.)

CURRICULUM LINKS

Mathematics:

Data Analysis, Wave Functions

Physical Science:

Properties of Materials

NATIONAL SCIENCE STANDARDS (Grades 5-8)

Science As Inquiry-Content Standard A

Students should develop abilities necessary to do scientific inquiry,

Students should develop an understanding about scientific inquiry

Physical Science -Content Standard B

Students should develop an understanding of properties and changes of properties  in matter

Life Science -Content Standard C

Students should develop an understanding of structure and function in living  systems

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