FFvsFB-UHF-fMRI · The role of layer-specific population receptive field properties in visual recurrent processing

The role of layer-specific population receptive field properties in visual recurrent processing

The brain is constantly presented with large amounts of ambiguous information: a given pattern of sensory signals can arise from many different real-world conditions. Yet, despite this ambiguity, the brain rapidly parses incoming signals into coherent and stable percepts. How does the brain resolve the inherent uncertainty of the world around? A prominent theory proposes that sensory information is combined with expectations originating from a mental model of the environment, which is built and refined through experience. Vision can thus be understood as an inference process, where higher-order cognition guides the interpretation of sensory input. For instance, a Mooney face – a two-tone, minimally informative depiction of a face – is often unrecognizable until exposure to the original undistorted image enables identification. This ability to resolve sensory ambiguity using prior knowledge highlights the crucial role of feedback in shaping visual perception. Every feedforward sensory pathway is paralleled by a reciprocal feedback projection, yet the distinct roles and mechanisms of feedforward and feedback processing remain poorly understood. A key organizing principle of the visual system is retinotopy, in which visual space is topographically mapped from the retina onto the cortex. Receptive fields (RFs) serve as the fundamental unit of this organization, traditionally viewed as fixed spatial filters. However, evidence from animal studies suggests that RFs are dynamic and modulated by feedback, making them a strong candidate for integrating feedforward sensory input with top-down expectations. This project investigated RFs as a mechanism for feedforward-feedback integration, focusing on how spatial context and prior knowledge influence early visual processing. Using ultra-high field (UHF) fMRI with population receptive field (pRF) mapping, this work examined cortical layer-specific processing in the human brain. Complementary psychophysical experiments explored two expectation-related modulations: spatial context, studied via visual crowding, and prior knowledge, examined using Mooney images. By elucidating how feedforward and feedback signals are integrated in the brain, this work advances basic research in cognitive neuroscience while also informing applications in technology and healthcare. Potential impacts include improvements in biologically inspired neural network architectures, better diagnostic tools for conditions involving abnormal recurrent processing (such as schizophrenia or autism spectrum disorder), and novel strategies for vision rehabilitation.

Data: CORDIS, © European Union