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Stephen L. Macknik, Susana Martinez-Conde; The Role of feedback circuits in visibility, attention and awareness. Journal of Vision 2011;11(15):75. doi: https://doi.org/10.1167/11.15.75.
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© ARVO (1962-2015); The Authors (2016-present)
The mammalian visual system includes numerous brain areas that are profusely interconnected. With few exceptions, these connections are reciprocal. Feedback connections usually outnumber feedforward connections by about an order of magnitude, leading to widespread speculation that feedback connections play a critical role in visual awareness. However, evidence from physiological experiments that use illusions of invisibility as well as cognitive manipulation of the attentional spotlight suggest that feedback plays a modulatory role, rather than a driving role. In the primary visual cortex, attentional feedback has an exquisitely precise mechanistic pathway of action involving specific neuronal populations that reveal attention to be a form of surround-suppression. That is, focal attentional enhancement occurs as a function of suppressed neuronal activity in the surround, and therefore increased signal : noise is achieved in the focus because input from the surround otherwise serves as noise. Here we discuss theoretical constraints on the significance of feedback's anatomical numerical advantage and specificity, and we describe theoretical limits on feedback's potential physiological impact. These restrictions confine the potential role of feedback in visual awareness and rule out some extant models of visual awareness that require a fundamental role of feedback. These ideas further predict a mechanism for visual misdirection in magic tricks, based on the magician's successful manipulation of the spectator's focus of attention.
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