Lars Muckli (University of Glasgow)
Predictive coding of auditory and contextual information in early visual cortex – evidence from layer specific fMRI brain reading
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Philippstr. 13, Haus 6
David Mumford (1991) proposed a role for reciprocal topographic cortical pathways in which higher areas send abstract predictions of the world to lower cortical areas. At lower cortical areas, top-down predictions are then compared to the incoming sensory stimulation. One question that arises within this framework is the following: Do descending predictions remain abstract, or do they translate into concrete level predictions, the ‘language’ of lower visual areas? We have exploited a strategy in which feedforward information is blocked or absent in parts of visual cortex: i.e. along the non-stimulated apparent motion path, behind a white square that we used to occlude natural visual scenes, or by blindfolding our subjects (Muckli & Petro 2013). By presenting visual illusions, contextual scene information, or by playing sounds, we were able to capture feedback signals to non-feedforwardly-stimulated areas of visual cortex. MVPA analysis of the feedback signals reveals that they are more abstract than the feedforward signal. Furthermore, using high resolution MRI, we found that feedback is sent to the outer cortical layers of V1. We also show that feedback to V1 is induced even by auditory information processing (Vetter, Smith & Muckli 2014). Auditory-induced feedback is especially strong in the periphery of V1, and contains abstract categorical information. I argue that these feedback signals function to provide abstract predictions, i.e. priors in a Bayesian framework, biasing future processing already at an early processing stage of V1.
References: Mumford (1991) On the computational architecture of the neocortex – the role of the thalamocortical loop. Biol Cybernetics Muckli & Petro (2013) Network interactions: non-geniculate input to V1. Curr Opin Neurobiol. Vetter, Smith & Muckli (2014) Decoding Sound and Imagery Content in Early Visual Cortex. Current Biology Clark (2013) Whatever Next? Predictive Brains, Situated Agents, and the Future of Cognitive Science. Behav Brain Sci