News

31.10.2013 17:00

The Visual Brain Colors Black and White Images

Scientists at the University of Tübingen explore how prior knowledge influences our visual senses

The brain colors black and white images. Copyright: Mareike Kardinal/Bernstein Coordination Site (BCOS)

The brain colors black and white images. Copyright: Mareike Kardinal/Bernstein Coordination Site (BCOS)

The perception and processing of color has fascinated neuroscientists for a long time, as our brain influences our perception of it to such a degree that colors could be called an illusion. One mystery was: What happens in the brain when we look at black-and-white photographs? Do our brains fill in the colors?

 

Neuroscientists Michael Bannert and Andreas Bartels of the Bernstein Center and the Werner Reichardt Centre for Integrative Neuroscience in Tübingen addressed these questions. In their work, published in the leading scientific journal Current Biology, they showed study participants black-and-white photos of bananas, broccoli, strawberries, and of other objects associated with a typical color (yellow, red and green in the examples above). While doing so, they recorded their subjects’ brain activity using functional imaging. The true purpose of the study was unknown to the subjects, and to distract their attention they were shown slowly rotating objects and told to report the direction in which they were moving.

 

After recording brain responses to the black and white objects, the scientists presented real colors to their subjects, in the shape of yellow, green, red and blue rings. This allowed them to record the activity of the brain as it responded to different, real colors.

 

It turned out that the mere sight of black-and-white photos automatically elicited brain activity patterns that specifically encoded colors. These activity patterns corresponded to those that were elicited when the observers viewed real color stimuli. These patterns encoded the typical color of the respective object seen, even though it was presented in black and white. The typical colors of the presented objects could therefore be determined from the brain’s activity, even though they were shown without color.

 

“It was particularly interesting that the colors of the objects were only encoded in the primary visual cortex,” says Michael Bannert. The primary visual cortex is one of the first places a visual signal arrives in the brain. Scientists had assumed it simply passed on information about the physical properties of things seen, but was not able to recognize objects or to store color knowledge associated with objects. “This result shows that higher-level prior knowledge – in this case of object-colors – is projected onto the earliest stages of visual processing,” according to Andreas Bartels.

 

This study represents a significant contribution to answering the question of how prior knowledge contributes to perception on a neuronal basis. The projection of prior knowledge onto the earliest processing stages of the visual brain may facilitate the recognition of objects in difficult and noisy environments, such as in fog, and be relevant for colors in changing light conditions over the course of the day, when the weather is overcast, when we are indoors and so on. On the other hand, if prior knowledge or expectations have too much influence on early visual processing stages, this may account for hallucinations and the pathological perception of illusions.

Original Publication:

Michael Bannert and Andreas Bartels: Decoding the yellow of a gray banana. Current Biology, October 31 2013.

Contact:

Dr. Andreas Bartels
University of Tübingen
Werner Reichardt Centre for Integrative Neuroscience (CIN)
Vision and Cognition Junior Research Group
Phone: +49 7071 29-89168

andreas.bartels[at]cin.uni-tuebingen.de
http://www.cin.uni-tuebingen.de/research/bartels.php

 

 

Eberhard Karls Universität Tübingen
Public Relations Department
Dr. Karl Guido Rijkhoek
Director

 

Janna Eberhardt
Research Reporter
Phone +49 7071 29-76753
Fax +49 7071 29-5566
janna.eberhardt[at]uni-tuebingen.de
www.uni-tuebingen.de/aktuell

 

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The University of Tübingen

Innovative. Interdisciplinary. International. Since 1477. These have always been the University of Tübingen’s guiding principles in research and teaching. With its long tradition, Tübingen is one of Germany’s most respected universities. Tübingen’s Neuroscience Excellence Cluster, Empirical Education Research Graduate School and institutional strategy are backed by the German government’s Excellence Initiative, making Tübingen one of eleven German universities with the title of excellence. Tübingen is also home to five Collaborative Research Centers, participates in six Transregional Collaborative Research Centers, and hosts six Graduate Schools.

 

Our core research areas include: integrative neuroscience, clinical imaging, translational immunology and cancer research, microbiology and infection research, biochemistry and pharmaceuticals research, the molecular biology of plants, geo-environment research, astro- and elementary particle physics, quantum physics and nanotechnology, archeology and prehistory, history, religion and culture, language and cognition, media and education research.

 

The excellence of our research provides optimal conditions for students and academics from all over the world. Nearly 28,000 students are currently enrolled at the University of Tübingen. As a comprehensive research University, we offer more than 250 subjects. Our courses combine teaching and research, promoting a deeper understanding of the material while encouraging students to share their own knowledge and ideas. This philosophy gives Tübingen students strength and confidence in their fields and a solid foundation for interdisciplinary research.

The Werner Reichardt Centre for Integrative Neuroscience (CIN)

The Werner Reichardt Centre for Integrative Neuroscience (CIN) is an interdisciplinary institution at the University of Tübingen funded by the DFG’s German Excellence Initiative program. Its aim is to deepen our understanding of how the brain generates functions and how brain diseases impair them, guided by the conviction that any progress in understanding can only be achieved through an integrative approach spanning multiple levels of organization.

The Bernstein Center Tübingen

The Bernstein Center Tübingen is part of the National Bernstein Network Computational Neuroscience in Germany. With this funding initiative, the German Federal Ministry of Education and Research (BMBF) has supported the new discipline of Computational Neuroscience since 2004 with over 170 million euros. The network is named after the German physiologist Julius Bernstein (1835-1017).