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Causal manipulation of feed-forward and recurrent processing differentially affects measures of consciousness

Lookup NU author(s): Tommaso Viola



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© The Author(s) 2020.It has been theorized that cortical feed-forward and recurrent neural activity support unconscious and conscious cognitive processes, respectively. Here we causally tested this proposition by applying event-related transcranial magnetic stimulation (TMS) at early and late times relative to visual stimuli, together with a pulse designed to suppress conscious detection. Consistent with pre-registered hypotheses, early TMS affected residual, reportedly 'unseen' capacity. However, conscious perception also appeared critically dependent upon feed-forward processing to a greater extent than the later recurrent phase. Additional exploratory analyses suggested that these early effects dissociated from top-down criterion measures, which were most affected by later TMS. These findings are inconsistent with a simple dichotomy where feed-forward and recurrent processes correspond to unconscious and conscious mechanisms. Instead, different components of awareness may correspond to different phases of cortical dynamics in which initial processing is broadly perceptual whereas later recurrent processing might relate to decision to report.

Publication metadata

Author(s): Allen C, Viola T, Irvine E, Sedgmond J, Castle H, Gray R, Chambers CD

Publication type: Article

Publication status: Published

Journal: Neuroscience of Consciousness

Year: 2020

Volume: 2020

Issue: 1

Online publication date: 07/09/2020

Acceptance date: 07/05/2020

Date deposited: 03/03/2021

ISSN (electronic): 2057-2107

Publisher: Oxford University Press


DOI: 10.1093/NC/NIAA015


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