Even though we have the impression that we see the world around us as it really is, our perception is strongly influenced by our expectations. Our knowledge of the world helps us recognise objects and people quickly and accurately, even when the image we receive is noisy or unclear, such as cyclists in the park at dusk, or football players on a television set with poor reception.
Until now, knowledge of the way the brain combines prior expectations with information from the outside world has been lacking. A recent study at the Radboud University, at the Donders Institute for Brain, Cognition, and Behaviour in Nijmegen, sheds light on this process.
During the study, participants were presented with both expected and unexpected images, while their brain activity was recorded with an MRI scanner. When participants viewed expected images, regions of the brain known to be involved in visual processing were less active than when they viewed unexpected images. Surprisingly though, at the same time, these regions contained a clearer representation of the expected images than of the unexpected ones. This latter finding was established through use of a so-called brain-decoder; a computer algorithm that tried to decode which image a participant saw from their brain activity. It turned out that the brain-decoder was more successful at decoding expected than unexpected images, an indication that the activity in these brain regions contained a clearer representation for expected images.
Therefore, expectations lead to less but more efficient processing in the human brain.
- Peter Kok, Janneke F.M. Jehee, Floris P. de Lange. Less Is More: Expectation Sharpens Representations in the Primary Visual Cortex. Neuron, 2012; 75 (2): 265 DOI: 10.1016/j.neuron.2012.04.034
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