Neuron
Volume 92, Issue 5, 7 December 2016, Pages 1122-1134
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Article
Brain Mechanisms Underlying the Brief Maintenance of Seen and Unseen Sensory Information

https://doi.org/10.1016/j.neuron.2016.10.051Get rights and content
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Highlights

  • The link between working memory and visual awareness has recently been challenged

  • We study here the mechanism of unconscious maintenance with MEG and machine learning

  • Unseen stimuli can be partially maintained within high cortical assemblies

  • We show how to revise awareness theories to account for the maintenance of invisible stimuli

Summary

Recent evidence of unconscious working memory challenges the notion that only visible stimuli can be actively maintained over time. In the present study, we investigated the neural dynamics underlying the maintenance of variably visible stimuli using magnetoencephalography. Subjects had to detect and mentally maintain the orientation of a masked grating. We show that the stimulus is fully encoded in early brain activity independently of visibility reports. However, the presence and orientation of the target are actively maintained throughout the brief retention period, even when the stimulus is reported as unseen. Source and decoding analyses revealed that perceptual maintenance recruits a hierarchical network spanning the early visual, temporal, parietal, and frontal cortices. Importantly, the representations coded in the late processing stages of this network specifically predicted visibility reports. These unexpected results challenge several theories of consciousness and suggest that invisible information can be briefly maintained within the higher processing stages of visual perception.

Keywords

perception
magnetoencephalography
visual awareness
subliminal
decoding
machine learning
working memory
backward masking
temporal generalization
attention

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