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Psychology

Visual Functions Generating Conscious Seeing

Profile image of Victor LammeVictor Lamme

Frontiers in Psychology

https://doi.org/10.3389/FPSYG.2020.00083
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10 pages

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Abstract

Visual functions are reviewed that coincide with conscious as opposed to unconscious vision. Four stages of vision are identified, going from the fully invisible, to subjectively invisible, unattended, and clearly visible. It is proposed that feature extraction, categorization, and some aspects of visual inference occur during full and subjective invisibility. Functions related to perceptual organization, such as grouping and figure-ground segregation, occur during inattention as well as full visibility. It is argued that perceptual organization is the function that is central to understanding the transition from unconscious to conscious seeing. It is discussed what this implies for theories of consciousness such as Recurrent Processing Theory,

FAQs

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AI

What distinguishes fully unconscious vision from subjectively unconscious vision?add

The study identifies that fully unconscious vision occurs when stimuli are below objective visibility thresholds, while subjectively unconscious vision occurs when stimuli surpass these thresholds but are still reported as unseen.

How does attention influence perceptual organization in visual processing?add

Attention enhances the strength of visual representations, but does not affect the execution of perceptual organization functions, which are completed during stage 3 of visual processing.

What is the role of metacognition in understanding conscious vision?add

Metacognition influences decision-making and awareness in visual tasks, particularly in distinguishing between phases of subjective and objective visibility, yet does not alter the fundamental visual processing stages.

How do visual operations differ in stages of unconscious and conscious perception?add

Visual operations like feature extraction and categorization are independent of consciousness, while perceptual organization and grouping require conscious awareness and operate at a higher level.

What are the proposed neural correlates of conscious vision?add

The research suggests that neural functions supporting conscious perception include those related to perceptual organization and integration, which are absent during fully unconscious processing stages.

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    Marty Woldorff

    Scientific Reports, 2022

    We investigated whether prestimulus alpha-band oscillatory activity and stimulus-elicited recurrent processing interact to facilitate conscious visual perception. Participants tried to perceive a visual stimulus that was perceptually masked through object substitution masking (OSM). We showed that attenuated prestimulus alpha power was associated with greater negative-polarity stimulus-evoked ERP activity that resembled the visual awareness negativity (VAN), previously argued to reflect recurrent processing related to conscious perception. This effect, however, was not associated with better perception. Instead, when prestimulus alpha power was elevated, a preferred prestimulus alpha phase was associated with a greater VAN-like negativity, which was then associated with better cue perception. Cue perception was worse when prestimulus alpha power was elevated but the stimulus occurred at a nonoptimal prestimulus alpha phase and the VAN-like negativity was low. Our findings suggest that prestimulus alpha activity at a specific phase enables temporally selective recurrent processing that facilitates conscious perception in OSM. Conscious perception entails subjectively experiencing external inputs in an accessible and reportable way. Although ubiquitous in our everyday experiences, conscious perception of visual stimuli does not always occur. This has led scientists, clinicians, and philosophers alike to debate what complex, interactive, and covarying mechanisms actually engender conscious visual perception 1,2,4. In visual processing, there is an initial feedforward sweep of neuronal activity through lower-level visual areas toward higher-order ones 5. After this feedforward sweep reaches a given visual area, activation propagates back to the lower-level visual areas via feedback connections (i.e., recurrent processing) 6,7. Such feedback connections have been suggested to transmit predictions regarding incoming sensory signals, whereas feedforward connections may transmit residual errors in these predictions that are then used to update the feedforward activation 8. At least two prominent theories argue that stimulus-elicited recurrent processing at more local-level 9,10,12 or more global-level interactions (e.g., involving parietofrontal areas) 13-15 is necessary for conscious perception. Indeed, past research has shown that conscious perception is disrupted when stimulus-elicited recurrent processing is impaired 12,16-20. In addition to recurrent processing, however, the neurocognitive state of the brain prior to stimulus presentation may also play an important role in conscious perception. Past research has shown that detection accuracy for difficult-to-detect stimuli was better when prestimulus oscillatory brain activity in the alpha-band (8-12 Hz) was attenuated over posterior cortical brain regions 21-30 , although this effect has not always been observed in stimulus discrimination-oriented tasks 31-34. Stimulus detection accuracy has also been associated with the stimulus having occurred at a preferred prestimulus alpha phase 22,35-37 , particularly when prestimulus alpha power was elevated 27,28,38. In general, alpha is thought to reflect inhibitory mechanisms that vary between states of cortical inhibition and excitation. Alpha power across multiple oscillatory periods inversely scales with cortical excitability, and the phase of the oscillatory period reflects rhythmic fluctuations between maximal excitability and maximal

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