One can observe brain activity with magnetic resonance imaging

Functional Magnetic Resonance Imaging (fMRI) can make thought processes visible! Researchers use this method to see which areas of the brain are active – for example, while someone is sleeping, solving a task, or looking at pictures. How does this work, and what do researchers want to observe in the brain with this method?

When nerve cells are active, they need more oxygen. This indirectly influences the flow of oxygenated blood in their vicinity. Depending on oxygen saturation, blood has different magnetic properties, and functional magnetic resonance imaging makes use of this: oxygen-poor blood looks different on MRI images than oxygen-rich blood. This makes it possible to observe which areas of the brain are active.
A major advantage of this is that no surgery or other intervention is required. Test subjects can, for example, sleep, study, recall memories, look at pictures, or solve math problems during the measurement. This is a great opportunity for researchers who want to investigate these cognitive processes!
Romy Lorenz's Cognitive Neuroscience & Neurotechnology research group, for example, is interested in how the brain solves problems, plans, and makes decisions. The so-called frontoparietal network plays a key role in higher cognitive functions such as these. It is different in every person, as unique as a fingerprint! This makes it particularly challenging to investigate the role of its individual parts. Analyzing its different layers separately requires fMRI measurements with particularly strong magnetic fields.

fMRI or EEG – what’s the difference?

Of course, there are other ways to measure brain activity. One of them is electroencephalography (EEG): Electrodes attached to the scalp measure the electrical impulses that brain cells use to communicate. Each method has its pros and cons: In addition to being less expensive and much easier to transport, EEG can measure with a precision of milliseconds when an area of the brain is active; fMRI only achieves resolutions in the range of seconds. On the other hand, fMRI can observe with an accuracy of few millimeters where the brain is active; with EEG it is centimeters. Moreover, fMRI can look into the deepest regions of the brain, where EEG and many other methods only provide extremely imprecise images.
Sometimes the combination of different imaging techniques does the trick. Svenja Brodt's research group Brain States for Plasticity uses EEG and fMRI to investigate, among other things, how memories are permanently stored in the brain. New experiences first reach the hippocampus, an area deep in the brain. The hippocampus forwards them to the neocortex, the evolutionarily youngest part of the cerebral cortex. If the hippocampus reminds the neocortex often enough, the input will eventually be stored in long-term memory. This happens mostly during sleep. Surprisingly, Svenja Brodt was able to show that the neocortex can also learn independently of the hippocampus through repeated practice. This could be a silver lining for Alzheimer's patients, as the hippocampus is often affected in the early stages of the disease.

Piecing together the melodies of thought and perception

Robert Ohlendorf also combines fMRI with other methods, since fMRI alone is not precise enough for his purposes. His research group Molecular Signaling is interested in how exactly information is transmitted in the brain. Although we already know the neurotransmitters in the brain – serotonin, dopamine, and more – we do not yet know exactly what they do: It's like knowing all the notes in a song, but not their order or rhythm. This is why the team is building biological sensors: specially designed proteins that can be tracked using various imaging techniques. They show when and where in the brain the neurotransmitters are being used. The hope is that one day we will be able to piece together the melodies of perception, thought, and decision-making.