How does the brain spatially allow pain receptors?

This is what happens in your head when you have a migraine

Around ten percent to one third of migraine sufferers experience an aura at the beginning of the migraine: They see things that are not there, have visual or speech impairments, paralysis or tingling, parts of the body become numb or dizzy - from about an hour before it Headache set in.

The optical effects are the most common: those affected perceive flickering, dots, lines or streaks. Sometimes they see double or blurred, or the field of vision is limited. These visual impairments are called scotomas. Some people even experience just an aura without the following headache. Here, the path from symptoms to diagnosis is often tedious guesswork.

How does this aura come about?

To really understand this, let's briefly go into detail: Our brain consists for the most part of nerve cells, the neurons. Stimuli are constantly firing through the brain, as so-called action potentials they chase from neuron to neuron at lightning speed. The mechanism for this: the Depolarization. For a few milliseconds the actually negative electrical potential of the nerve cell is reversed, it becomes positive. Then the neuron returns to its resting state, ready for the next stimulus. Usually.

At the beginning of an aura, however, this actually quite normal depolarization takes place in a changed manner - namely Extremely slow. Instead of racing through the brain, it moves slowly over the cerebral cortex at a speed of only three to six millimeters per minute.

Like dementors in the brain

What is special about this is that the cells do not immediately return to the resting state, but remain in their excited state for much longer - they can't react and are so to speak inaccessible to new signals. This so-called scattered polarization or "spreading depression" spreads over a relatively large area of ​​a few centimeters in the cerebral cortex. And reminds something of the Dementors in Harry Potter: If it comes near, it paralyzes everything, new stimuli do not come through.

As a result of the depolarization, the blood vessels in the brain widen and the blood circulation deteriorates. It is clear that such a Nervous thunderstorms followed by great silence and low blood pressure making us see things that don't exist or failing other functions. Symptoms differ depending on which areas of the cerebral cortex are affected.

Another factor: serotonin

The messenger substance serotonin regulates our emotions and has an inhibiting effect on aggression, fear and sadness - it has a balancing effect. If the serotonin content in the brain is too low, the cells are lighter and more excitable. This can mean that a "spreading depression" and thus an aura can arise more easily.