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Curr Biol. 2016 Feb 8;26(3):371-6. doi: 10.1016/j.cub.2015.12.038. Epub 2016 Jan 28.

Selective Activation of the Deep Layers of the Human Primary Visual Cortex by Top-Down Feedback.

Author information

1
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands. Electronic address: p.kok@donders.ru.nl.
2
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.
3
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN Nijmegen, the Netherlands.
4
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.

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.

KEYWORDS:

laminar fMRI; perceptual inference; predictive coding; shape perception

PMID:
26832438
DOI:
10.1016/j.cub.2015.12.038
[Indexed for MEDLINE]
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