Luca Vizioli, University of Glasgow
Title: Supra-Granular Layers of Human V1 Receives Contextual Feedback
Abstract: Neuronal cortical circuitry comprises feedforward-, lateral and feedback-projections, each of which terminates in distinct cortical layers (Larkum, 2013; Markov, 2014; Sillito, 2006). In sensory systems, feedforward processing transmits signals from the external world into the cortex; while - as suggested by our group and others - feedback pathways signal the brain's inference of the world (Bastos, 2012; Bullier, 2001; Clark, 2013;Gilbert, 2007; Meyer, 2012; Muckli, 2013; Mumford, 1992; Park, 2013). However, the merging of feedforward, lateral and feedback inputs within each cortical area impedes the investigation of feedback, and to date no technique could measure the functional responses of feedback in distinct layers of healthy human cortex. Here we show, by masking sensory feedforward input to a cortical compartment and studying the remaining internal processing, that superficial (supragranular) layers of V1 receive feedback signalling the brains inference of visual scenes. Specifically, using high resolution functional brain imaging (0.8 mm3) and information reading techniques, we demonstrate that during normal visual stimulation, natural scene information peaks in mid--layers of V1. Conversely, contextual feedback arrives predominantly to outer layers of V1. Our results reveal the layered cortical organization of external versus internal visual processing streams during perception, in healthy human subjects. Our data provides critical empirical support for theoretical models of brain function and reveals the potential of high- resolution fMRI to access internal brain processing in sub--millimetre human cortex.
Please join Dr. Morgan Barense in welcoming Dr. Meike Ramon and Dr. Luca Vizioli, visiting scientists from the University of Glasgow, who will be speaking on May 6 and May 12, respectively.
All are welcome to attend. For further information, please contact Dr. Morgan Barense at firstname.lastname@example.org.