Human memory is important these days
A look into the living brain - New perspectives in brain research
Take a look inside the living brain - neuroimaging makes it possible. Scientists can use non-invasive examinations to learn about both the structure and the function of the brain. “The high resolution of the images meanwhile allows recordings with an accuracy of 1x1x1 millimeters. This means that researchers can already look at smaller changes in brain activity, ”says Prof. Dr. Christian Büchel from Neuroimage Nord in Hamburg, one of the German centers for neuroimaging. “The field of imaging processes has developed very quickly in recent years.” Even if these are the first attempts to look into the human brain, important findings are already being made.
An example: In patients who have symptoms of paralysis after a stroke, scientists have been able to prove that certain areas of the brain are already activated when the patients observe how someone else moves their leg, hand or mouth. Obviously, just looking at movement can speed up relearning of lost skills. According to initial studies, stroke patients were able to relearn unlearned movement patterns much more quickly during rehabilitation if they were able to observe them in others and not exclusively train themselves.
From structure to function
One of the first imaging techniques to measure activity in the brain was positron emission tomography (PET). In this method, the researchers use the fact that the metabolism of nerve cells is increased when a person carries out an activity. Prof. Dr. Büchel illustrates this with an example: “In the visual center there is a lot of work when we are looking at something. Then the nerve cells need more oxygen. Since the oxygen is transported via the blood, the blood flow increases in the brain region that is responsible for visual perception. ”So where the blood flow is high, the brain is particularly active.
How do the scientists now recognize whether a brain region has low, normal or increased blood flow? "With PET, this works via radioactive substances that are injected into the vein," explains Prof. Dr. Büchel. “In blood-rich areas there is a particularly large amount of radioactive substance that can be located with detectors.” Today, scientists can use PET to identify locations of neuronal activity in the brain.
The progress in imaging goes even further: about 20 years ago, magnetic resonance tomography (MRT) was developed, known as nuclear spin tomography, which does not require radioactivity. MRI works with a magnetic field to which the atoms in the body's cells react. Depending on the type of tissue, the number and composition of the atoms are different and different structures of the body can be shown in detail.
The next step was to record not only the structure but also the function. Here the scientists took advantage of the fact that the red blood pigment, hemoglobin, changes its magnetic properties when oxygen is transported. This means that where there is a lot of oxygen on the way, the MRT image now appears brighter, for example. Instead of an external contrast agent, the blood itself is used as a contrast agent to visualize active areas in the brain. Functional MRI, or fMRI for short, was born.
First successes in diagnosis
The use of functional imaging has advanced particularly in research into psychiatric, neurological and neurodegenerative diseases such as Alzheimer's disease. "First of all, we always examine what the healthy brain is doing with which activity," says Prof. Dr. Büchel. "For example, the prerequisite for research on Alzheimer's dementia is that we even understand how memory processes work and which areas of the brain are involved." specific disease. With a high-resolution device, even the smallest changes can be detected. For example, deviations in the networking of nerves provide important information about a possible Alzheimer's disease.
Another functional imaging success story is the diagnosis of cluster headache. With this severe form of headache, those affected suffer from one-sided extreme pain in the temple and eye area, which occurs in attacks. "Studies show that in cluster headache patients, individual structures in a certain brain region, the hypothalamus, are particularly active during a pain attack," explains Prof. Dr. Büchel. “In PET studies of cluster headache patients and people in whom a headache was caused experimentally, scientists were able to show that the cluster headache is caused by a malfunction of the hypothalamus. An examination of the brain structure with MRI was able to confirm this suspicion. ”The first patients already benefited from these results in the context of studies: The therapy method currently used is deep brain stimulation, which starts in the hypothalamus. The first successful treatment has already been achieved.
Interdisciplinarity is very important
Researching the functioning of the human brain down to the last detail is a scientific challenge that exceeds even the decoding of the human genome in terms of its dimensions. In order for this to succeed, the collaboration of researchers from different disciplines plays an important role: "If, for example, we want to look at the hippocampus for a memory study with a very high resolution, only an experienced MR physicist can set the machine to a correspondingly high resolution", emphasizes Prof. Dr. Büchel. “In addition, methodologists provide us with approaches on how data can be evaluated differently.” Initiatives such as those started by the BMBF are enormously helpful because they lead to the establishment of centers where interdisciplinary research and evaluation is carried out. "The funding measure of the BMBF was the initial spark to institutionalize the cooperation of different research groups and thereby make it successful", says Prof. Dr. Büchel. "I think the centers have made a significant contribution to the fact that imaging in Germany now operates at a very high international level."
What does the future of neuroimaging look like? Prof. Dr. sees potential Büchel especially in the cooperation with experts from the field of computational neuroscience, in which the behavior of nerve cells is simulated with the help of computer models. These models make it possible to depict the complexity of brain processes and thus to better understand them. Prof. Dr. Büchel's vision for the future of neuroimaging is not only to make changes in the metabolic activity in the brain visible, but also to be able to measure the actual electrical changes in the brain with the available magnetic resonance tomographs. “That would be a fantastic breakthrough, and not just for research. This would open up new opportunities for the diagnosis and treatment of diseases in the future. "
Neuroimaging is the observation of structures and processes in the human brain with the help of imaging processes. A distinction is made between two areas. In structural imaging, the scientists examine the anatomy of the brain in great detail. Functional imaging, on the other hand, is about the physiology of the human brain, that is, which processes take place in certain brain regions. Here, researchers create thousands of images of the brain within a short period of time. Individually, these don't say much about brain function. However, if you look at them over time, differences in activity can be recorded. This is because different brightness values can be seen in the images: a light structure in an fMRI examination, for example, is a sign of an increased need for oxygen due to increased metabolic activity in the corresponding brain region. Dark areas, on the other hand, mean that there is hardly any activity in one area of the brain.
Prof. Dr. Christian Büchel
Institute for Systems Neuroscience
Neurocenter University Medical Center Hamburg-Eppendorf
Tel .: 040 7410-54726
Fax: 040 7410-59955
Email: [email protected]
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