title: Selective Activation of the Deep Layers of the Human Primary Visual Cortex by Top-Down Feedback.
abstract: In addition to bottom-up input, the visual cortex receives large amounts of feedback from other cortical areas [1-3]. One compelling example of feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while top-down feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5, 6]. Therefore, the feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7-14]. We found that, whereas bottom-up stimulation activated all cortical layers, feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of top-down signals during perceptual processing.
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands. Electronic address: p.kok@donders.ru.nl.
authors.forename: Peter
authors.initials: P
authors.lastname: Kok
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands; Erwin L. Hahn Institute for Magnetic Resonance Imaging, UNESCO-Weltkulturerbe Zollverein, Leitstand Kokerei Zollverein, Kokereiallee 7, 45141 Essen, Germany.
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Bains
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: van Mourik
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands; Erwin L. Hahn Institute for Magnetic Resonance Imaging, UNESCO-Weltkulturerbe Zollverein, Leitstand Kokerei Zollverein, Kokereiallee 7, 45141 Essen, Germany; MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, 7500 AE Enschede, the Netherlands.
authors.forename: David G
authors.initials: DG
authors.lastname: Norris
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands.
authors.forename: Floris P
authors.initials: FP
authors.lastname: de Lange
mesh_terms: D000328:Adult; D005246:Feedback; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: laminar fMRI; perceptual inference; predictive coding; shape perception