Visibility, visual awareness, and visual masking of simple unattended targets are confined to areas in the occipital cortex beyond human V1/V2

<p>Multisensory integration describes the cognitive processes by which information from various perceptual domains is combined to create coherent percepts. For consciously aware perception, multisensory integration can be inferred when information in one perceptual domain influences subjective experience in another. Yet the relationship between integration and awareness is not well understood. One current question is whether multisensory integration can occur in the absence of perceptual awareness. Because there is subjective experience for unconscious perception, researchers have had to develop novel tasks to infer integration indirectly. For instance, Palmer and Ramsey (2012) presented auditory recordings of spoken syllables alongside videos of faces speaking either the same or different syllables, while masking the videos to prevent visual awareness. The conjunction of matching voices and faces predicted the location of a subsequent Gabor grating (target) on each trial. Participants indicated the location/orientation of the target more accurately when it appeared in the cued location (80% chance), thus the authors inferred that auditory and visual speech events were integrated in the absence of visual awareness. In this thesis, I investigated whether these findings generalise to the integration of auditory and visual expressions of emotion. In Experiment 1, I presented spatially informative cues in which congruent facial and vocal emotional expressions predicted the target location, with and without visual masking. I found no evidence of spatial cueing in either awareness condition. To investigate the lack of spatial cueing, in Experiment 2, I repeated the task with aware participants only, and had half of those participants explicitly report the emotional prosody. A significant spatial-cueing effect was found only when participants reported emotional prosody, suggesting that audiovisual congruence can cue spatial attention during aware perception. It remains unclear whether audiovisual congruence can cue spatial attention without awareness, and whether such effects genuinely imply multisensory integration.</p>

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P1-15 Face-sensitive neural responses in the occipital cortex without visual awareness

Clinical Neurophysiology ◽

10.1016/s1388-2457(10)60428-2 ◽

2010 ◽

Vol 121 ◽

pp. S104

Author(s):

T. Mistudo ◽

Y. Kamio ◽

Y. Goto ◽

T. Nakashima ◽

S. Tobimatsu

Keyword(s):

Visual Awareness ◽

Occipital Cortex ◽

Neural Responses

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Connectivity and signal intensity in the parieto-occipital cortex predicts top-down attentional effect in visual masking: An fMRI study based on individual differences

NeuroImage ◽

10.1016/j.neuroimage.2008.11.028 ◽

2009 ◽

Vol 45 (2) ◽

pp. 587-597 ◽

Cited By ~ 11

Author(s):

Hiroyuki Tsubomi ◽

Takashi Ikeda ◽

Takashi Hanakawa ◽

Nobuyuki Hirose ◽

Hidenao Fukuyama ◽

...

Keyword(s):

Individual Differences ◽

Signal Intensity ◽

Visual Masking ◽

Occipital Cortex ◽

Top Down ◽

Fmri Study ◽

Attentional Effect

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GABAA Agonist Reduces Visual Awareness: A Masking–EEG Experiment

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_00197 ◽

2012 ◽

Vol 24 (4) ◽

pp. 965-974 ◽

Cited By ~ 18

Author(s):

Anouk M. van Loon ◽

H. Steven Scholte ◽

Simon van Gaal ◽

Björn J. J. van der Hoort ◽

Victor A. F. Lamme

Keyword(s):

Receptor Antagonist ◽

Detection Rate ◽

Visual Masking ◽

Visual Awareness ◽

Pharmacological Intervention ◽

Common Mechanism ◽

Backward Masking ◽

Neural Event ◽

Visual Consciousness ◽

Human Participants

Consciousness can be manipulated in many ways. Here, we seek to understand whether two such ways, visual masking and pharmacological intervention, share a common pathway in manipulating visual consciousness. We recorded EEG from human participants who performed a backward-masking task in which they had to detect a masked figure form its background (masking strength was varied across trials). In a within-subject design, participants received dextromethorphan (a N-methyl-d-aspartate receptor antagonist), lorazepam (LZP; a GABAA receptor agonist), scopolamine (a muscarine receptor antagonist), or placebo. The behavioral results show that detection rate decreased with increasing masking strength and that of all the drugs, only LZP induced a further decrease in detection rate. Figure-related ERP signals showed three neural events of interest: (1) an early posterior occipital and temporal generator (94–121 msec) that was not influenced by any pharmacological manipulation nor by masking, (2) a later bilateral perioccipital generator (156–211 msec) that was reduced by masking as well as LZP (but not by any other drugs), and (3) a late bilateral occipital temporal generator (293–387 msec) that was mainly affected by masking. Crucially, only the intermediate neural event correlated with detection performance. In combination with previous findings, these results suggest that LZP and masking both reduce visual awareness by means of modulating late activity in the visual cortex but leave early activation intact. These findings provide the first evidence for a common mechanism for these two distinct ways of manipulating consciousness.

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Visual awareness of objects correlates with activity of right occipital cortex

Neuroreport ◽

10.1097/00001756-199612200-00037 ◽

1996 ◽

Vol 8 (1) ◽

pp. 183-186 ◽

Cited By ~ 57

Author(s):

Simo Vanni ◽

Antti Revonsuo ◽

Jukka Saarinen ◽

Riita Hari

Keyword(s):

Visual Awareness ◽

Occipital Cortex

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Dichoptic Visual Masking Reveals that Early Binocular Neurons Exhibit Weak Interocular Suppression: Implications for Binocular Vision and Visual Awareness

Journal of Cognitive Neuroscience ◽

10.1162/0898929041502788 ◽

2004 ◽

Vol 16 (6) ◽

pp. 1049-1059 ◽

Cited By ~ 48

Author(s):

Stephen L. Macknik ◽

Susana Martinez-Conde

Keyword(s):

Visual Masking ◽

Visual Awareness ◽

Cortical Circuits ◽

Physiological Mechanisms ◽

Interocular Suppression ◽

V1 Neurons ◽

Proposed Model ◽

Timing Effects ◽

Multiple Levels ◽

The Brain

Visual masking effects are illusions in which a target is rendered invisible by a mask, which can either overlap or not overlap the target spatially and/or temporally. These illusions provide a powerful tool to study visibility and consciousness, object grouping, brightness perception, and much more. As such, the physiological mechanisms underlying the perception of masking are critically important to our understanding of visibility. Several models that require cortical circuits have been proposed previously to explain the mysterious spatial and timing effects associated with visual masking. Here we describe single-unit physiological experiments from the awake monkey that show that visual masking occurs in at least two separate and independent circuits, one that is binocular and one that is monocular (possibly even subcortical), without feedback from higher-level visual brain areas. These and other results together fail to support models of masking that require circuits found only in the cortex, but support our proposed model that suggests that simple ubiquitous lateral inhibition may itself be the fundamental mechanism that explains visual masking across multiple levels in the brain. We also show that area V1 neurons are dichoptic in terms of excitation, but monoptic in terms of inhibition. That is, responses within area V1 binocular neurons reveal that excitation to monocular targets is inhibited strongly only by masks presented to the same eye, and not by masks presented to the opposite eye. These results lead us to redefine the model for the first stage of binocular processing in the visual system, and may be crucial to interpreting the effects of other similar binocular and dichoptic stimulation paradigms, such as the binocular rivalry family of illusions.

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The Finger in Flight: Real-Time Motor Control by Visually Masked Color Stimuli

Psychological Science ◽

10.1111/1467-9280.00421 ◽

2002 ◽

Vol 13 (2) ◽

pp. 112-118 ◽

Cited By ~ 111

Author(s):

Thomas Schmidt

Keyword(s):

Visual Masking ◽

Visual Awareness ◽

Dorsal Stream ◽

Color Information ◽

Brain Areas ◽

Pointing Movements ◽

Time Motor ◽

Motor Effects ◽

Forced Choice Tasks ◽

Choice Tasks

Current theories of dual visual systems suggest that color is processed in a ventral cortical stream that eventually gives rise to visual awareness but is only indirectly involved in visuomotor control mediated by the dorsal stream. If the dorsal stream is indeed less sensitive to color than the ventral stream, color stimuli blocked from awareness by visual masking should also be blocked from guiding fast motor responses. In this study, pointing movements to one of two isoluminant color targets were preceded by consistent or inconsistent color primes. Trajectories were strongly affected by priming, with kinematics implying a continuous flow of color information into executive brain areas while the finger was already moving. Motor effects were more sensitive to color of the primes than were deliberate attempts to identify the primes in forced-choice tasks based on visual awareness. Priming was observed even when masking was complete.

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