The fact that these questions can be researched today is thanks to advances in health research, as funded by the Federal Ministry of Education and Research (BMBF) Germany. In particular, the field of neuroimaging offers ever new approaches to better understand and diagnose disease patterns by looking at structures and activities in the brain.
Taking a look inside the living brain - neuroimaging makes it possible. In doing so, scientists can learn about both the structure and function of the brain with non-invasive examinations. "The high resolution of the images now allows imaging to 1x1x1 millimeter accuracy. This means researchers can now look at even small changes in brain activity," says Prof. Christian Büchel of Neuroimage Nord in Hamburg, one of Germany's centers for neuroimaging. "The field of imaging has developed very quickly in recent years." Even though these are still the first attempts to look inside the human brain, there are already important findings.
One example: in patients who have symptoms of paralysis after a stroke, scientists have been able to demonstrate that certain areas of the brain are already activated when the patients watch a counterpart move either leg, hand or mouth. Quite obviously, simply watching movements can accelerate the relearning of lost skills. According to initial studies, stroke patients were able to relearn lost movement patterns significantly faster during rehabilitation if they were able to observe them in others and did not exclusively train themselves.
One of the first imaging techniques to measure activity in the brain was positron emission tomography (PET). In this method, researchers take advantage of the fact that the metabolism of nerve cells is increased when a person is engaged in an activity. Prof. Dr. Büchel illustrates this with an example: "The visual center is particularly busy when we look at something. Then the nerve cells need more oxygen. Since oxygen is transported by the blood, blood flow increases in the brain region responsible for visual perception." So where blood flow is high, the brain is particularly active.
So how can scientists tell if a brain region has low, normal or increased blood flow? "In PET, this works via radioactive substances that are injected into the vein," explains Prof. Dr. Büchel. "There is a particularly large amount of radioactive substance in blood-rich areas, which can be located with detectors." So nowadays, scientists can use PET scanning to identify sites of neuronal activity in the brain.
But progress in imaging goes even further: about 20 years ago, magnetic resonance imaging (MRI) was developed, the so-called 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 vary, and different structures of the body can thus be depicted in detail.
In the next step, it was now necessary to capture 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, for example, the MRI image now appears brighter. Thus, instead of using an external contrast agent, the blood itself is used as a contrast agent to visualize active areas in the brain. Thus functional MRI, or fMRI for short, was born.
