The frontal lobe has long been thought to be associated with ADD/ADHD. Many types of studies have been conducted to assess the functioning of the frontal lobe as it is related to symptoms of ADD/ADHD. The two main divisions of research assessing these functions are cognitive researchers, and brain imaging studies to asses activity. Cognitive researchers are those psychologists who study the specific capacities of our brains to perform certain processes or activities. They do not focus too much on brain structure per se, they tend to focus on how these systems work. Brain imaging studies have been used to illustrate the ways in which the brain is active in various circumstances, and have tested many scenarios to determine if the part of the brain they are viewing is responsible for the actions being seen in the person. These two techniques will be introduced separately and the evidence that each have accumulated points to the frontal lobe as having a central role in ADD/ADHD. More generally the frontal lobe is the area that dominates the front third of the brain. Through previous research this areas has been shown to be vital in the processes that regulate attention, impulsive acts, motor activity, and various other functions that may also impact ADD/ADHD suffers. Some of these other functions included in the frontal lobes are located in the section nearest the eyes, the pre-frontal lobes. These areas have been indicated as areas that control our ideas about rewards we receive for certain behaviors, and the motivation to get those rewards, or avoid them. The picture below is of a PET scan of an active brain, the image centers around the frontal lobe section of the brain. These types of images will come up later as important to the second section of frontal lobe research.
(photo courtesy of www.bic.uci.edu/Brain.jpg)
The first set of evidence comes from researches in the active mental processes, cognitive psychologists. Cognitive psychologists interested in ADD/ADHD have targeted tests at the brain's ability to processes certain types of materials. These researchers use tests to asses how certain areas are functioning. They target these tests at particular areas. In the case of ADD/ADHD they used tests that incorporate means to asses the structures involved in ADD/ADHD (such as the frontal lobe). As cognition is the study of the processes of information being taken in and analyzed in the brain, they have come to the conclusion that the areas in charge of processing information related to attention, impulsivity, and motor activity control have been associated with the frontal lobe of the brain. One of the more common tests to show this correlation is called the Stroop test. This test has been around since the very earliest stages of cognitive psychology. It is still relevant today, because it allows researchers to test the ability to pay attention to things. The test is basically aimed at tripping up the subject in the experiment. The test is conducted by showing a word that is a color, but the color is not the same as the word. (RED) When ADD/ADHD students take this test they are significantly different from normal controls, because they presumably cannot exert the mental energy needed to focus on the word instead of the color. This evidence points to the frontal lobe, but also the right frontal lobe which has also been identified as having control over understanding spatial connections and understanding spatial relationships. Other tests such as the Wisconsin Card Sorting Test have also been implemented to show cognitive deficits in ADD/ADHD. This test is similar to the Stroop test in assessing cognitive flexibility. It sets the experimenter across from the subject, and the experimenter and subject both have deck of cards. When the experimenter (dealer) places a card on the table, the subject has to match his/her cards with the experimenter. But there is always a catch. This particular matching task has three possible matching criteria. The subject can match with either similar shapes, colors, or number. The key is when the subject tries to match a card, the experimenter had decided which matching type is correct. The ADD/ADHD suffers fair particularly poor on these tasks at maintaining attention to the matching, and thus point to the frontal lobe as the part of the problem.
Brain imaging techniques have been introduced as a way into the brain, different from cognitive psychologists. These techniques are used to find regions affected by ADD/ADHD. They are also important, because they are the sources of evidence that these some brain areas are the problematic ones. Techniques used to figure out brain anatomy and brain functionality are called brain imaging techniques. Some of the names of these types of imaging are called EEG, MRI, fMRI, PET, SPECT (below a PET scanner is depicted) They have been used to accurately identify regions of the brain that can be associated with a particular function. There is evidence using these imaging techniques for the involvement of both the frontal, and pre-frontal lobe in ADD/ADHD. These areas have been located as having less visible activity when the imaging takes place
((courtesy of www.gemedicalsystems.com/rad/nm_pet/images/PET-CT_017769a1.jpg)
The a fore mentioned PET scan (brain imaging), is a system that measures how much energy is being used in each region of the brain. It does this by measuring the levels of glucose (sugar) that are being used (metabolized) by each section of the brain. So what really happens? The experimenters give the subject a harmless shot of radioactive glucose (sugar). This acts as a homing beacon for how to tell where the sugar is going. They then direct the subject to do a series of activities that will induce ADD/ADHD behavior. When the experimenters take these images from the ADD/ADHD activities, and subtract the images that they got earlier, they can show which areas became extra active, or less active in the test subject. From many studies like this, evidence has been collected by researchers that indicates right frontal lobes in ADD/ADHD have reduced levels of glucose utilization, meaning that this area is not as active as a normally activated brain. This indicates that this section of the brain (right frontal lobe) is less active, and from that behaviors that resemble ADD/ADHD could be connected with this area. To see an PET scan image click here.
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