Redefining the Role of Limbic Areas in Cortical Processing. Issue 2 (February 2016) - Chanes, Lorena
Abstract : There is increasing evidence that the brain actively constructs action and perception using past experience. In this paper, we propose that the direction of information flow along gradients of laminar differentiation provides important insight on the role of limbic cortices in cortical processing. Cortical limbic areas, with a simple laminar structure (e.g., no or rudimentary layer IV), send 'feedback' projections to lower level better laminated areas. We propose that this 'feedback' functions as predictions that drive processing throughout the cerebral cortex. This hypothesis has the potential to provide a unifying framework for an increasing number of proposals that use predictive coding to explain a myriad of neural processes and disorders, and has important implications for hypotheses about consciousness. Trends: The brain functions as a generative model of the world that, following the principles of Bayesian probability, explains sensory input based on past experience. The structural model of corticocortical connections allows us to hypothesize that predictions flow from less to better laminated areas and prediction errors flow in opposite direction. Limbic cortices, with their simple laminar structure, issue predictions from the top of the hierarchy within every sensory system. The lowest levels correspond to primary sensory cortices, with a well-developed laminar structure. Owing to their position in cortical hierarchies and their connectivity, limbic cortices are well suited to integrate a neural 'workspace' for a unified conscious experience. This model motivates novel hypotheses about the organization of intrinsic networks and has the potential to integrate a range of neural processes and disorders.