The Brain in Health and Disease

Activities

Activity 1—The Action Potential Wave

Ever been to a stadium where the crowd does the "wave"? No one moves from their seat, but the wave travels from one end of the stadium to the other. You can use this idea to help students understand how a signal can travel down a neuron without molecules actually moving down the axon. This could be done before or after a lecture on action potentials.

The Action Potential

Depending on the size of your class, divide the students into two groups. Have each group line up shoulder to shoulder, with a 2-3 foot gap between the two groups. Explain to the students that they are going to do the wave, but that if there is no one within 3 inches of them doing the wave, then they can not raise their arms. Have the first person in group 1 start the wave at a signal from you. The second group will not be able to continue the wave, because they will be too far from the last person in the first group.

Discussion: Why did the first person in the group start the wave off? Why did the wave only travel in one direction? Was anything physically passed down the "neuron"? How could the wave get passed to the second group if there is a gap?

Teacher's verbal signal—a stimulus that starts an action potential in a sensory neuron. If you say the "start" signal too quietly, the group will not begin the wave. The verbal signal has to reach a "threshold" level for the group to begin the wave. The signal can be given repetitively to start new wave action potentials in the student neuron. If the teacher gives the signal too rapidly, the first student in line will not be ready to start the wave again.

Students—Each student represents a section of the axon. When the threshold has been reached (a stimulus or an action potential has occurred next to them) the sodium gates open (arms go up—depolarization), then sodium gates close (arms go down—repolarization). A student's arms cannot start going back up when they are only half way down—representing the refractory period.

Synaptic Transmission

In order for this next step to go well, you should discuss this response with the two students involved before the demonstration. The last student in the line represents the axon terminal. Give this student either a piece of candy or a rock. When the wave gets to that student they toss or pass this "neurotransmitter" to the first person in the "neuron" across the gap. When the student in the second row receives the candy or rock, they will either be excited and throw their hands up in the air, starting a second wave, or they will be sad, and their arms will stay down.

Discussion: How does the signal change as it goes across the gap? How do different "neurotransmitters" affect the post-synaptic neuron? What if one piece of candy was not enough to excite the receiver? (Be sure to note that neurons only release one kind of neurotransmitter, but that post-synaptic neurons will have receptors for both types of neurotransmitters. Also discuss that neurotransmitters are not taken up by the post-synaptic neuron, but are released from the receptor, destroyed by enzymes in the synapse, or reabsorbed by the pre-synaptic neuron.)

Saltatory Transmission

To represent an action potential down a myelinated axon, have students line up as before, but leave spaces between some of the students in the "axon". Students at the gaps will be connected to each other by a short piece of rope. When the student at the beginning of the space raises their hands, they will also raise the rope, which will be the signal for the student at the other end of the space to raise their hands for the wave. To compare the speed of the signal, have students create two parallel lines of equal length. One line of students might have only 4 students, because some will be replaced with sections of rope. The other line might have 10 students. Give both the start signal and observe which "neuron's" signal reaches the end first.

Discussion: Why does transmission of the signal happen faster down the myelinated neuron? If the arms going up represents sodium channels opening, then how is the signal moving through the rope sections?

Activity 2—MRI Model of the Brain

Students will construct and label a three dimensional model of the brain using layers of sagittal sections from MRI images of a normal brain. These images are available from The Whole Brain Atlas website: http://www.med.harvard.edu/AANLIB/home.html .

Teacher Preparation:

At the Whole Brain Atlas website, open Normal Anatomy in 3-D with MRI/PET (Javascript). Copy sagittal images 34, 38, 42, 46, 50, 54, 58, 62, 66, 68, and 69, into a Word document with all margins set at 0.5" and in landscape orientation. Enlarge each picture to 8" in order to bring the model closer to life size. Since this MRI was made through the brain from the left side through to the right, the images past the midline will need to be reversed to be seen from the right outside of the model. To do this, copy sagittal image 70 into MS Paint and under Image, select Flip/Rotate and flip the image horizontally. Then copy the reversed image to the word document and enlarge. Do the same for images 72, 76, 80, 84, 88, and 92. You may want to number the images to help students keep them in order. You may also want to trim away everything on the images except the brain, so that more than one image can be copied to a page, and to reduce the amount of black area on each image. Make a copy of the set for each student.

Materials:

Brain image copies. Foam board or cardboard, glue sticks, scissors, straight pins

Student Instructions:

Cut out the MRI images of the brain and glue them to cardboard or foamboard pieces, trimmed to fit. On each layer, label the following parts of the brain that are visible: cortex, cerebellum, medulla, pons, hippocampus, corpus callosum, pituitary gland, hypothalamus, ventricles, occipital lobe, frontal lobe, temporal lobe, parietal lobe, and spinal cord. Use straight pins to put the sections of the brain together in order.

Activity 3—An Introduction to the Origins of the Left and Right Brain

Teacher Notes:

Distribute copies of the following article and the reading guide to students to complete for homework. Have them work in groups the next day to compare answers. Each group should come up with 2 questions they still have about the topic of hemispheric lateralization of the brain to discuss with the class. Lead a discussion on how the experiments described in the article might have been carried out, reviewing the parts of the scientific method as needed.

Reading Guide:

"Origins of the Left and Right Brain"—Peter F. MacNeilage, Lesley J. Rogers, and Giorgio Vallortigara. Scientific American, July 2009

Directions: Read the article and answer the following questions in complete sentences on a separate sheet of paper.

1. What does the left side of the brain control?
2. What does the right side of the brain control?
3. What did scientists believe about the brain 40 years ago?
4. What was once believed about the connection between right handedness and language?
5. The hypothesis of this paper about the evolution of left brain specialization is….
6. The hypothesis of this paper about the evolution of right brain specialization is….
7. What are the areas of control of the two hemispheres

The Left Hemisphere

8. What kind of evidence was collected to test the hypotheses?
9. Describe the brain specialization evidence for:
1. Fishes, reptiles, and toads
2. Chickens, pigeons, quails and stilts
3. New Zealand wry-billed plover
4. Humpback whales

Origins of Right-Handedness

10. What evidence is more supportive of the idea that human right-handedness evolved from some earlier ancestor?
11. How did William D. Hopkins test for handedness in apes and what were the results?
12. What would have been an evolutionary advantage for right handedness in human ancestors?

Communication and the Left Brain

13. What do the authors hypothesize about the specialization of the left hemisphere for language?
14. What are some other examples of left brain specialization for language in animals?
15. Describe exceptions to the idea that the right hemisphere controls under emotional circumstances?
16. What are some examples of left brain control of nonvocal communication?

Evolution of Speech

17. What is a syllable?
18. How would syllables lead to language?

Did the Syllable evolve from Chewing? (p65)

19. How does the evolution of syllabic utterances relate the left brain specialization?

The Right Hemisphere

20. What is the animal evidence that the right hemisphere specialized in detecting and responding to unexpected stimuli?
21. How has evidence for human hemispheric specialization been collected?
22. Which eye is most likely to be used to watch for predators or competitors?
23. What negative emotional behaviors in humans are the result of right-hemisphere activity?

Responding to Surprise (p66)

24. What happens when the toad is presented with a predator from different directions?

Recognizing Others

25. The right hemisphere is also involved in reacting to others of its own species in the environment, which led to the role of the right hemisphere in ____________.
26. Some animals that exhibit the ability for individual recognition are ________.
27. What is prosopagnosia and what is the most common cause?

Photogenic Left

28. What might portraits reveal about right hemisphere control of facial emotion?

Global and Local

29. Which hemisphere is more global, which more local in analyzing spatial aspects of the environment?
30. Describe why chicks with vision only in the right eye focused only on a few specific features.

Division of Labor in the Hemispheres (p63)

31. Describe why the brain damaged patients in the experiment drew the H as they did.

Why do Hemispheres Specialize?

32. When an animal receives stimuli of different types from its environment, it must process the information in order to make an appropriate response. What would be the selective advantage of hemispheric specialization?
33. How did Rogers create chicks without hemispheric specialization for visual processing?
34. How did this affect the chicks' behavior?
35. How do these result support the idea that hemispheric specialization is an evolutionary advantage?

Social "Symmetry Breaking"

36. Why would it be more likely to see the same types of hemispheric specialization in a variety of animal species rather than a 50-50 distribution?
37. What might be an evolutionary disadvantage to hemispheric specialization?
38. Why might these disadvantages have not kept brain specialization from evolving in populations?

Activity 4—Dissection of an Experiment

A Lab Dissection of "Complementary right and left hemifield use for predatory and agonistic behavior in toads" by G. Vallortigara, L.J. Rogers, A. Bisazza, G. Lippolis, and A. Robins

Teacher Notes:

After students have read the article in Scientific American, distribute copies of the original paper described in the article: Vallortigara, G., L.J. Rogers, A. Bisazza, G. Lippolis, and A. Robins. "Complementary right and left hemifield use for predatory and agonistic behavior in toads." Neuroreport 9 (14) (1998): 3341-3344. Go over the vocabulary words students will need to know in order to understand the paper. They should be able to predict what many of the words mean. Have students work with a lab partner to "dissect" the paper and find out how the researchers designed their experiment and collected data. Live toads can be ordered from Carolina Biological Supply (http://www.carolina.com/home.do) for $ 17.95 for three live toads. They are only available from March through September, so this unit must be taught within that time frame. Crickets and worms can be purchased from local pet stores or bait shops.

Student Directions:

Read the original paper from Neuroreport about one of the experiments done with toads described in the article from Scientific American. As you go through the paper, you will "dissect" it to find the parts of the scientific method that the researchers used.

• Vocabulary:
• Lateralization
• Hemifield
• Agonistic
• Conspecifics
• Complementary specializations
• Response competition
• Medial organs
• Lateral
• Anurans
• De novo
• Avian
• Modes of analysis
• Monocular

"The Introduction"

1. Describe the problem being addressed in this experiment.
2. Why would the answer to this problem be important to know?
3. What was already known that may relate to this problem?
4. What methods were used to find the answer to this problem?
5. Summarize the types of information included in the "Introduction"

"Materials and Methods"

Predatory behavior

6. List the materials used in the Predatory behavior experiment with B.bufo and B.viridis.
7. List the constants in this experiment
8. What were the dependent variables? How were they measured?
9. Describe the experimental groups.
10. Was there a control group?
11. Describe the testing apparatus or draw what you think it looked like.
12. Why was the outer cylinder white, and not clear like the inner cylinder?
13. Describe the procedure in your own words. Use diagrams if helpful.
14. What were the independent variables?
15. Why do you think the toads were isolated before the experiment began?
16. Why were they all males?
17. List the materials used in the predatory behavior experiment with B. marinus.
18. List the constants in this experiment.
19. What were the dependent variables? How were they measured?
20. Describe the experimental groups.
21. Describe the procedure in your own words. Use diagrams if helpful.
22. Why do you think crickets were chosen as the prey? Why were they all about the same size?
23. Why was the data from this experiment not combined with the data from the first experiment?

Agonistic behavior

24. List the materials used in the agonistic behavior experiment.
25. How did the scientists distinguish agonistic behavior form predatory behavior?
26. Describe the procedure in your own words.
27. How was the data collected?
28. How was the agonistic behavior of B. bufo different from that of B. marinus?
29. Was any data reported in the "Materials and Methods" section?

"Results"

Predatory behavior

30. Compare the number of strikes to the right and left visual fields.
31. Compare the rotation direction to the visual field interaction.
32. Compare the strike direction when the rotation was clockwise.
33. Compare the strike direction when the rotation was counterclockwise.

Agonistic behavior

34. Describe the results of the agonistic behavior experiment.
35. How are statistical tests helpful in analyzing data such as this?
36. How were the results processed and presented in this section of the report?

"Discussion"

37. How are toads' eyes different from birds and lizards? Why are the authors careful to avoid referring to left eye/right hemisphere and right eye/left hemisphere when discussing the toad data? (A diagram might aid your explanation.)
38. How can the experimental results be summarized?
39. What are two explanations proposed by the authors for the apparent lateralization seen in the experiments?

"Conclusion"

1. What is the conclusion of the authors about the data?
2. What two explanations do they suggest might account for the results?