The Brain: What's Going In There?
Analyzing Brain Images
Recent genetic studies and techologies have improved our ability to monitor brain activity and have enabled a greater understanding of how the addictive brain behaves. This efforts make it possible to develop more effective medications for treating addiction.
Scientists use Positron Emission Tomography to investigate the function of the living brain. Radioactive glucose is used to indentify the 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 areas are shown in red. Areas in yellow are less active than red,but are more active than areas in green. The least active areas are shown in blue and purple.
I am sure all of you have seen color-coded computer images on televison weather reports . In weather radar images, areas encountering heavy srorms appear in red and yellow, and areas experiencing milder weather disturbances appear in green or blue.
Are you ready now to look at some brain images with me? When you at different levels look at the image titled Set 1 you automatically notice the four images differ from one another. The brain images are all different sizes. How else are they different from one another? The images show variation in the amount and pattern of the different colors.
The pet images show a cross-section of the brain. The four images in the sets 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).
The four PET images in each set show the activity at four different levels of the brain. If a scientist examines only a single image, he or she could miss important information. Are you ready to start comparing the images with me?
How is the activity of the brain in the following Sets different from Set 1? Let's continue on to identify the image with the greatest change? Set 1
shows the activity of the brain in a resting place.
The PET images shown in Set 1 show brain activity in a resting brain.The images in Sets 2-5 show activity in the brains of humans who are doing different tasks. How is the activity of the brain in Set 2 different from Set 1? Identify the image that shows the greatest change? (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 it is on the right side.
When comparing the images in Set 1 to the images in Set 3 how is the activity of the brain different in Set 3? The main activation is in the back of the brain on both sides of the midline. Identify the image can you see the greatest change? (B)
When comparing the images in Set 1 to the images in Set 4, how is the activity of the brain in Set 4 different than Set 1? The main activation is at the front of the brain near the periphery on both sides of the midline. Identify the image you can see the greatest change? (C)
When comparing the images in Set 1 to the images in Set 5, how is the activity of the brain different? The main activation is in four areas, two on each side of the brain and two are farther forward. Identify the image that shows the greatest change? (D)
The brain is involved in regulating all human physiological,behavioral, and emotional functions. When most people think about breathing, they think about the lungs, but not the involvement of the brain. Am I right? Now, let's consider our heartbeat. Although, the heart is actually pumping the blood, the brain fulfills an important role in regulating the heartbeat.The involvement of the brain is more obvious for some of the tasks it performs than others.
How do scientists investigate what happens in the human brain? They investigate by watching a person's behavior, using various imaging techniques(such as PET scans, CT scans, or MRI)),and using animals(living or dead) for research. Most of us today have either had a CT scan or an MRI. We are not as familiar with PET scans.
PET scanning is a major neuroimaging technique used in drug abuse research. However, researchers also use other techniques when those techniques answer a scientific question.
Different areas of the brain process specific types of stimuli. Let's consider things that make us feel good, or are pleasurable. If you understand that brain functions are localized to specific brain areas, then you should deduct that things that make you feel pleasure will stimulate a specific brain region. Are you with me for it is important to me you see and understand what I am explaining to you.
The Reward System
The part of the brain that produces and regulates feelings of pleasure, scientists call reward. The brain region is called "The Reward System." The parts of the brain that make up the reward system are the ventral tegmental area, the nucleus accumbens, and part of the frontal region of the cerebral cortex. This brain region responds to life-sustaining activities such as eating and drinking, as well as species-sustaining sexual activity.
Drugs of abuse activate the brain's reward system, or pleasure circuit. Drugs alter the way the reward system functions. Drugs also act on other regions of the brain, but their action in the reward system makes the drug abuser feel pleasure and want to continue to take drugs. PET technology is not sensitive enough to visualize this reward system activation. The VTA and nuclueus accumbens are too small for PET images to detect significant activity changes. Scientists have relied on other technologies to learn that drugs of abuse do activate these brain regions.
If you understand that PET images reveal changes in brain activity and that drugs activate the reward system in the brain, you should be able to predict that the reward system should be more active after an individual takes drugs. These brain areas should appear red or yellow in PET scans taken after drug use, wheras they should be purple or blue in PET images taken before drug use.
References: The Brain: Understanding Neurobiology Through The Study of Addiction; Lesson 1 The Brain: What's Going In There? (NIDA 2004)
Compiled & Edited By: D. Shrira Dated: Dec. 26, 2006
Asst. Editor: Dee Black Updated: March 16, 2012