How expectation shapes perception: from cortical layers to brain-wide networks Peter Kok (Wellcome Centre for Human Neuroimaging, University College London, London, United Kingdom) PL7
The way we perceive the world is strongly influenced by our expectations about what we are likely to see at any given moment. However, the neural mechanisms by which the brain achieves this remarkable feat have yet to be established. In order to understand the neural mechanisms underlying the interplay between sensory inputs and prior expectations, we need to investigate the way these signals flow through the cortical layers. Until recently, it was not possible to do this in non-invasive studies of humans, because the typical voxel size in fMRI is bigger than the full thickness of the cortex (2-2.5mm). I will discuss recent work in which we met this challenge by using fMRI at ultra-high field (7T) to obtain BOLD signals at very high resolution, and using a novel spatial regression analysis to disambiguate signals from the different cortical layers. This approach has allowed us to reveal the neural circuitry underlying effects of expectation on sensory processing. I will also discuss the role of the hippocampus as a potential generator of top-down expectation effects in visual cortex. Together, this work demonstrates that expectations play a fundamental role in sensory processing, and ultimately in the way we perceive the world.