How the world is created in the mind
According to a research group led by Christof Koch from the Allen Institute for Brain Science in Seattle, more than 90 percent of the nerve cells in the visual system of mice apparently work differently than the textbooks claim.
The visual cortex in the brain – also known as the visual cortex – plays a central role in our ability to see. It occupies large parts of the occipital lobe at the back of our head. The understanding that researchers have today of how it works is based on experiments that neurophysiologists David Hubel and Torsten Wiesel carried out around 60 years ago. In doing so, they discovered that some neurons are specialized for very specific characteristics - such as lines and edges that are aligned at a certain angle. Others, on the other hand, get excited at the sight of faces or special colors. Downstream brain regions then put together a picture of the world around us from a we alth of such information.
However, the results from that time are primarily based on activity measurements in a few individual nerve cells. Christof Koch and his colleagues therefore repeated the experiments on a larger scale and looked at the data from around 60,000 different neurons in the visual cortex of mice. They discovered that just ten percent of the cells behaved as one would expect based on the findings of Hubel and Wiesel. Two-thirds of the rest reacted in a much more specialized way – and one-third showed activity patterns that did not match any of the numerous visual impressions that the researchers presented to the rodents. It is still unclear what their task is. The researchers speculate that they may be calibrated to such specific characteristics that they only become active during later processing steps.
"The results of the earlier studies are not wrong, they only seem to apply to a very small proportion of the nerve cells in the cortex," says study leader Saskia de Vries. Apparently, the visual cortex of mice is much more complex than previously thought. However, it is not yet known whether this also applies to the visual cortex of other species, the researchers say. After all, a large part of the knowledge about the visual system is based on experiments with cats and primates, whose perception in the wild sometimes has to meet different requirements. Ultimately, the rodents could simply be a special case.
