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Published November 15, 2017 | Supplemental Material + Accepted Version + Submitted
Journal Article Open

Intracranial markers of conscious face perception in humans


Investigations of the neural basis of consciousness have greatly benefited from protocols that involve the presentation of stimuli at perceptual threshold, enabling the assessment of the patterns of brain activity that correlate with conscious perception, independently of any changes in sensory input. However, the comparison between perceived and unperceived trials would be expected to reveal not only the core neural substrate of a particular conscious perception, but also aspects of brain activity that facilitate, hinder or tend to follow conscious perception. We take a step towards the resolution of these confounds by combining an analysis of neural responses observed during the presentation of faces partially masked by Continuous Flash Suppression, and those responses observed during the unmasked presentation of faces and other images in the same subjects. We employed multidimensional classifiers to decode physical properties of stimuli or perceptual states from spectrotemporal representations of electrocorticographic signals (1071 channels in 5 subjects). Neural activity in certain face responsive areas located in both the fusiform gyrus and in the lateral-temporal/inferior-parietal cortex discriminated seen vs. unseen faces in the masked paradigm and upright faces vs. other categories in the unmasked paradigm. However, only the former discriminated upright vs. inverted faces in the unmasked paradigm. Our results suggest a prominent role for the fusiform gyrus in the configural perception of faces, and possibly other objects that are holistically processed. More generally, we advocate comparative analysis of neural recordings obtained during different, but related, experimental protocols as a promising direction towards elucidating the functional specificities of the patterns of neural activation that accompany our conscious experiences.

Additional Information

© 2017 Elsevier Inc. Received 2 February 2017, Revised 15 August 2017, Accepted 24 August 2017, Available online 4 September 2017. We thank all subjects for their participation in the study, the medical team at University of Iowa Hospital for their assistance, Haiming Chen for his technical assistance. We thank Andrew Haun for generating Fig. 1. NT is supported by Australian Research Council (ARC) Future Fellowship (FT120100619) and Discovery Project (DP130100194). NT and FB were supported by Japan Science and Technology Agency (JST) PRESTO fellowship 3630 to NT. CKK, HK, HO, and MAH were supported by NIH grants R01 DC004290 and UL1RR024979. Author contributions: Conceived the idea of the study: FB NT. Conceived and designed the experiments: HK CKK MAH RA NT. Performed neurosurgery: HK MAH. Collected the data: HK CKK NT. Conducted preliminary analyses including anatomical localization of electrodes: HK HO NT. Analyzed the data: FB JvK NT. Wrote the manuscript: FB NT. Commented critically on the manuscript: FB JvK HK CKK HO MAH RA NT. Competing interests: NT collaborates with Dr Ryota Kanai, CEO of a venture company, called Araya Brain Imaging (araya.org) based in Tokyo, Japan. In October 2015, Araya received a grant from Japan Science and Technology (JST; approximately 3 million yen for 5 years), which aims to potentially commercial projects related to artificial consciousness. NT is part of this grant and he is supposed to host several students/research assistants/postdocs hired at Araya until March 2020. However, his institute (Monash University) does not receive any research income directly from JST. NT does not hold stocks or shares of Araya. NT is not and will not be paid by Araya. As the collaboration has barely started, no patent application has been submitted. Some of NT's travels are covered by the JST through Araya. Please note that the research reported here is unrelated with the grant from JST, which just started on November 2015.

Attached Files

Accepted Version - nihms907466.pdf

Submitted - 037234.full.pdf

Supplemental Material - mmc1.pdf


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