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| Content Standard A: Scientists rely on technology to enhance the gathering and manipulation of data. Content Standard C: Organisms have behavioral responses to internal changes and to external stimuli. |
The
following procedures describe how to conduct the Web version of this
activity, which is the preferred method of instruction. Instructions for conducting
the alternative print version follow.
1. Before starting the computer-based activity, inform students that they will be analyzing positron emission tomography (PET) images. Scientists use PET to investigate the function of the living human brain. The PET images that the students will examine use radioactive glucose to identify parts of the brain that are active. Active brain areas use more glucose than less active areas and thus more of the labeled glucose is taken up into the active areas. PET images are color-coded by a computer. The most active brain areas are shown in red. Areas in yellow are less active than areas in red, but are more active than areas in green. The least active areas are shown in blue or purple.
PET images are color-coded by computer to show activity in the brain. Students will see a color scale on the screen with the PET images for reference.
Students may have seen color-coded computer images on television weather reports. In weather radar images, areas encountering heavy storms appear in red and yellow, and areas experiencing milder weather disturbances appear in green or blue.
2. Divide the class into groups of three students. Arrange for each group to work at a computer to complete the Web site activity, Analyzing Brain Images. Give each group a copy of Master 1.2, Interpreting PET Images.
Open the Web site in your browser (see Using the Web Site). From the main page, click on Student Activities and then select The Brain: What's Going On in There? Click on Analyzing Brain Images.
3. Instruct students to work with their group members to analyze the PET images and to answer the questions on Master 1.2. When students reach question #5, display a transparency of Master 1.3, PET Image Tasks, to provide the needed information.
4. After the groups complete the activity and write their answers to the questions on Master 1.2, discuss the answers to the questions as a class.
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Question 1. When you look at the images that make up Set #1, how do the four images differ from each other?
The brain images are different sizes. The images show variation in the amount and pattern of the different colors.
Question 2. Why are four images shown in each set of PET images? Why would scientists need to examine more than one PET image taken of a subject's brain?
The four PET images in each set show the activity at different levels of the brain. If scientists examine only a single image, they could miss important information.
Question 3. When comparing the images in Set #1 to the images in Sets #2, 3, 4, 5, and 6, how is the activity of the brain in each of these sets different from Set #1?
| Set number | Identify the image that
shows the greatest change (a, b, c, or d) |
Describe the change in brain activity |
|---|---|---|
|
2 |
b |
There is more red on the right side of the brain, mainly near the center in terms of front-to-back direction. There is also red on the left side, but it is not as strong as on the right side. |
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3 |
b |
The main activation is in the back of the brain on both sides of the midline. |
|
4 |
c |
The main activation is at the front of the brain near the periphery on both sides of the midline. |
|
5 |
d |
The main activation is in four areas, two on each side of the brain. Two are very near the back of the brain, and two are farther forward. |
|
6 |
a |
The main areas of activation are a spot on the left side of the brain and a smaller spot near the front of the brain on the midline. |
Question 4. The PET images shown in Set #1 show brain activity in a resting brain. The images in Sets #2 through 6 show activity in the brains of humans who are doing different tasks. When you look at the PET scans and the chart in question #3, what generalizations can you make about the activity of the brain when different tasks are performed?
The key points of this exercise are that different brain areas are activated during different tasks and different brain functions are localized to different brain areas.
Question 5. Compare the tasks that the subject performed during each of the PET scans (as shown on the overhead transparency) with the individual's brain activity. Use the information from the overhead and from the PET images to complete the following chart.
| Set number | Name of the brain region that is more active in the PET image | This part of the brain is involved in processing information related to |
|---|---|---|
|
2 |
auditory cortex |
hearing |
|
3 |
primary visual cortex |
vision, sight |
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4 |
frontal cortex |
thinking |
|
5 |
hippocampus |
memory |
|
6 |
motor cortex |
movement |
5. Instruct students to watch the Web site video How PET Works.
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Open the Web site in your browser (see Using the Web Site). From the main page, click on Student Activities, then select The Brain: What's Going On in There? This will open the page, How Is PET Done?
This video expands students' understanding of PET. A scientist explains how PET imaging is done.
After students have completed the activity, you may wish to challenge them by asking them to propose an explanation for why functions are localized to specific brain areas. Why would this be beneficial from an evolutionary standpoint? (See Background Information.)
The
following procedure provides instruction for completing Activity 2 without
the use of the computer. Use this version if your students do not have access
to computers equipped with an Internet connection.
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| Content Standard A: Scientists rely on technology to enhance the gathering and manipulation of data. Content Standard C: Organisms have behavioral responses to internal changes and to external stimuli. |
1. Tell students that one of the ways that scientists investigate the function of the living human brain is by using positron emission tomography (PET). The PET images that the students will examine use radioactive glucose to identify parts of the brain that are active. Active brain areas use more glucose than less active areas and thus more of the labeled glucose is taken up into the active areas. PET scans are color-coded. The scale bar shown on Master 1.1, Positron Emission Tomography (PET) Images, with the PET images provides a reference. The most active brain areas are shown in red. Areas in yellow are less active than areas in red, but are more active than areas in green. The least active areas are shown in blue or purple.
PET images are color-coded by computer to show activity in the brain. This is similar to color-coded images students may have seen on television weather reports. In weather radar images, areas encountering heavy storms appear in red and yellow, and areas experiencing milder weather disturbances appear in green or blue.
2. Divide the class into groups of three students. Give each group a copy of Master 1.1, Positron Emission Tomography (PET) Images, and a copy of Master 1.2, Analyzing Positron Emission Tomography (PET) Images.
3. Help students understand how the PET images correlate to the orientation of the brain in the body.
The PET images show a cross-section of the brain. The four images in each set show four different levels of the brain. In these images, the front of the brain is toward the top (the subject's face is toward the top of the image). Have the students examine the PET scans and identify the regions that become active in response to each stimulus.
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4. Instruct students to work with their group members to answer the questions on Master 1.2. When students reach question #5, display a transparency of Master 1.3, PET Image Tasks, to provide the needed information.
5. Discuss the answers to the questions on Master 1.2 as a class.
Answers for the questions on Master 1.2 are listed in the procedure for the Web version of the Teacher's Guide for Activity 2.
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Note to teachers: This activity is intended for classes that want more information about the anatomy of the brain. Learning the names and functions of brain lobes and regions is not a major focus and could distract some students from the main concept that brain functions are localized to specific brain areas. Understanding the main concept is critical for understanding how neurons communicate and how drugs of abuse affect neuronal function. These topics are covered in Lessons 2 and 3.
1.
Have students continue in their groups to conduct the segment of the Web site
titled, What Does This Part of the Brain Do?
Open the Web site in your browser (see Using the Web Site). From the main page, click on Web Portion of Student Activities, then select Lesson 1—The Brain: What's Going On in There? Click on What Does This Part of the Brain Do?
Remember, the names of the parts of the brain are not the important concepts
that students need to learn. Rather, this is a way for students to relate
what they have learned about localization of brain function to other activities
and thus reinforce the concept that different brain regions control different
functions. |
1.
Display a transparency of Master 1.4, Major Regions of the Brain, that
shows major brain regions and Master 1.5, Areas of the Cerebral Cortex
and Their Function, that shows the lobes of the cerebral cortex and their
general functions.
2. Ask students to take out their completed worksheet on Master 1.2.
Review the tasks that the students performed in Step 1 of Activity 1 and ask students to identify the part of the brain that was active in each case.
From the information in question #5 on Master 1.2, students should be able to identify the brain area involved in some of the tasks performed in Step 1 in Activity 1, but others were not covered in that question. Also, for some of the activities listed, more than one function is involved. For example, reciting the Pledge of Allegiance requires both memory and speech. Be aware that this chart is very simplified. Virtually all mental functions involve more than one brain area.
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