The fact that there are also mirror neurons among the human nerve cells is, according to some scientists, not sufficiently documented. Image: Wei-Chung Allen Lee et al .: PLoS Biology Vol. 2, e29
Read aloud More than ten years ago, researchers discovered in monkeys brain cells that become active during both their own and observed movements. The cells, which have since been called mirror neurons, are used by many scientists as an explanation for empathy, empathy and even language. But there are also skeptical voices that think these assumptions are exaggerated and unused - and even doubt that there are mirror neurons in the narrower sense at all. "One of the most important discoveries of the past decade", "Nobel Prize worthy" and "comparable to the discovery of DNA as a DNA": When it comes to mirror neurons, it seems for some researchers not enough superlatives to describe these very special brain cells. It refers to those cells that fire not only when, for example, a monkey performs a movement itself, but also when it observes this activity only in a conspecific. So they trigger a kind of echo in the brain, specifically in the brain area with which the animals plan actions.

Ever since an Italian research team discovered these unusual cells in rhesus monkeys about ten years ago, mirror neurons have made a career: Scientists have very quickly assumed that humans must possess such mirror cells - and that they are the basis for empathy, empathy, compassion and even language and Culture, as the magazine "bild der wissenschaft" reported in its November issue.

However, not all researchers are so convinced of the potential of mirror neurons. This includes, for example, the US developmental psychologist Alison Gopnik from California. Her most powerful argument: with one exception, the mirror cells in humans have not even been proven beyond doubt. Only one female patient implanted microelectrodes for the removal of electrical nerve impulses during brain surgery showed a single cell to have typical mirror activity: she fired both when the woman's finger was pricked and when she watched as her doctor the same thing happened.

Practically all other studies looking for the neurons, however, used imaging techniques such as magnetic resonance imaging - and they are unable to visualize individual neurons: "We get information about the average activity of hundreds of thousands of neurons, " explains Gopnik. In this way you can see areas that become active during certain movements and those that light up when you observe these movements. "The results so far only allow the conclusion that these two patterns of activity overlap to some extent, " the psychologist clarifies. display

To conclude that the cells are also responsible for compassion, language and morality, they logically also considers very daring - especially because there are no such abilities in the demonstrably equipped with mirror neurons monkey. "Macaques have neither language nor culture, and they are unable to empathize with their own kind. Careful experiments have shown that they are incapable of systematically mimicking the problem solving of a role model, "says Gopnik.

Other observations also speak against the involvement of the mirror cells in language ability. Many researchers postulate that speech understanding would depend on the activity of mirror neurons in the linguistic center of the brain, the Broca area. If that were true, says neuroscientist Greg Hickok in "bild der wissenschaft", breaking Broca's area in addition to the ability to speak would also impair speech understanding. However, this is not the case, as many patients with Broca damage showed who, although they can not speak sentences anymore, can easily understand them.

In general, Gopnik and other skeptics consider the idea that individual cells in the brain could work autonomously, as it were, unlikely. Their reasoning: All nerve cells in the central nervous system are embedded in a network of hundreds of thousands of other cells and work by forming different excitation patterns together with the others. For this reason, context and complex external functions greatly influence mental functions - which is reflected, among other things, in the fact that one does not feel sorry for every person whose suffering one sees.

Gopnik himself believes in a different explanation for the echo activity in the monkeys. The higher functions of the brain, they argue, are shaped by experience and learning. This means that a monkey who moves a hand is likely to see a picture of his moving hand in his mind's eye as well. This, in turn, would activate the brain cells responsible for the moving hand image - and of course they also respond to the observation of a moving hand in another animal.

Which explanation is correct or whether the truth lies between the two extremes must first be examined in further studies. Until then, Gopnik still thinks the mirror neurons are a myth and one that collapses as soon as you make experiments.

ddp / - Ilka Lehnen-Beyel

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