Menu

Heimel Group

Not seeing the trees for the wood

Researchers from the Netherlands Institute for Neuroscience have shown how it is possible that objects stand out less when they are surrounded by similar objects. This surround-suppression effect is caused by feedback from higher visual brain areas. The results of this research are important for a better understanding of the way in which the brain transforms incoming light into a cohesive image. The paper has been published in the scientific journal Current Biology.

The brain area responsible for processing vision is located at the back of the brain. The primary visual cortex, is the area where a visual stimulus first reaches the cortex. Nerve cells in this area are sensitive to perceiving objects within a very small field of vision. So when you look at a specific object, the nerve cells in the primary cortex are activated and you see this object. “But when this object is surrounded by similar objects, the cells are less active. So really what happens is that you don’t see the trees for the wood,” says Alexander Heimel, group leader at the Netherlands Institute.

Surround-suppression effect

“The theory had previously yielded the idea that this surround-suppression effect was the result of signals from higher visual brain areas. But until recently there was not much scientific evidence for this,” says principal researcher Joris Vangeneugden, aios at Maastricht University. In order to find out whether it really was a matter of higher visual brain areas signaling, the researchers measured mouse brain activity while the mouse was looking at images of different sizes. At the same time, the researchers managed to silence the higher visual areas for a couple of seconds. It turned out that the activity in the primary visual cortex increased for the larger images when these higher visual areas were paused. The suppression of the surroundings thus decreased. This shows that the higher areas do indeed provide some sort of feedback to the primary visual cortex. “They force the primary visual cortex to focus on the individual object, not on everything there is to see,” says Heimel.

Visual prothesis

Understanding this step is necessary to understand, eventually, how the brain transforms the light that enters via our eyes into a perception that makes us understand what we see. “An understanding of how our brain does this is essential for the development of prosthetics that will make blind people see again. Merely ensuring that light reaches the brain does not always suffice; what happens after that is even more important,” says Vangeneugden.

Share

Heimel Group

The microstructure of the cerebal cortex is remarkably similar and conserved across mammalian species. Width, lamination, neuronal cell types, connectivity, all show some species differences, but the overarching picture is one of similarity. That the same structure excels in interpreting speech, touch, vision and many other types of sensory information, suggests a circuit with amazingly adaptive information processing prowess. This has been known and appreciated for more than a century, but in the last few years the introduction of optical tools to observe and manipulate the thinking brain is promising to bring much better understanding of this marvelous structure. We are using electrophysiology, optogenetics, structural imaging, intrinsic signal imaging and calcium imaging to study the circuitry and function of mouse visual cortex and its interplay with other brain areas such as the thalamus and superior colliculus.

More background is available in a interview in Dutch with Malou van Hintum.

A recent list of all publications in English can be found at Google Scholar.

Also check out: News from the lab

Read more