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Putting Vision Into Context

The Thalamus not only relays visual signals from the eye to the visual cortex as previously thought, but also conveys additional, contextual information. Integrating these different signals is essential to understand and interpret what we see in the world around us. Prof. Sonja Hofer and her research team at the Biozentrum, University Basel, investigate how the brain processes visual stimuli and how contextual information shapes our visual perception. Their latest findings are reported in “Nature Neuroscience”.

23 December 2015

As soon as we open our eyes in the morning, our brain is flooded with images. Information about these images is sent from the eyes to a brain region called the thalamus, and from there on to the visual cortex. The visual cortex, which comprises the largest part of the human brain, is responsible for analyzing visual information and allows us to see. In contrast, the thalamus has until now been considered mostly as a relay for visual information. The research team led by Prof. Sonja Hofer at the Biozentrum, University of Basel, has discovered in mice that a special part of the thalamus — called the Pulvinar — supplies the visual cortex with additional, non-visual information.

Optical illusion
This optical illusion shows how strongly the context of a visual scene influences what we see, and how this context can sometimes mislead us. The three people in the picture are exactly the same size. However, our brain judges the size of an object based on its perceived distance. The person at the back seems to be further away and therefore appears larger. © Sonja Hofer

Contextual information is essential for visual perception

What we see is not only based on the signals that our eyes send to our brain, but is influenced strongly by the context the visual stimulus is presented in, on our previous knowledge, and expectations. Optical illusions, as the one shown here, illustrate how important such non-visual, contextual information is for our perception. The visual cortex receives this additional information from other brain areas and uses it to allow us to understand and interpret the visual world. Prof. Hofer and her team measured the specific signals transmitted to visual cortex from the Thalamus, and found that the Pulvinar not only conveyed visual signals but is also one of the brain areas that provide additional information about the context of visual stimuli.

Movements in the environment can be detected effectively

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