Visual Perception and Awareness

2010 ◽  
Vol 24 (2) ◽  
pp. 62-67 ◽  
Author(s):  
Gastone G. Celesia
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Visual Awareness ◽  
Perceptual Awareness ◽  
Visual Agnosia ◽  
Clinical Observations ◽  
Psychophysical Testing ◽  
Visual Cortices ◽  
Cortical Regions ◽  
Visual Percept

The study of visual processing and abnormalities due to lesions of cortical structures sheds light on visual awareness/consciousness and may help us to better understand consciousness. We report on clinical observations and psychophysical testing of achromatopsia/prosopagnosia, visual agnosia, and blindsight. Achromatopsia and prosopagnosia reveal that visual cortices have functionally specialized processing systems for color, face perception, and their awareness, and that furthermore these systems operate independently. Dysfunction is limited to some aspects of visual perception; someone with achromatopsia, although not conscious of color, is aware of the objects’ form, motion, and their relationship with sound and other sensory percepts. Perceptual awareness is modular, with neuronal correlates represented by multiple separate specialized structures or modules. Visual agnosia shows that awareness of a complete visual percept is absent, though the subject is aware of single visual features such as edges, motion, etc., an indication that visual agnosia is a disruption of the binding process that unifies all information into a whole percept. Blindsight is characterized by the subject’s ability to localize a visual target while denying actually seeing the target. Blindsight is mediated by residual islands of the visual cortex, which suggests that sensory modules responsible for awareness can function only when structurally intact. We conclude (1) that perceptual awareness (consciousness?) is modular, and (2) that perceptual integration is also modular, which suggests that integration among distinct cortical regions is a parallel process with multiple communication pathways. Any hypothesis about consciousness must include these observations about the presence of multiple parallel, but spatially and temporally different, mechanisms.

scholarly journals Semantic and spatial congruency mould audiovisual integration depending on perceptual awareness

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Patrycja Delong ◽  
Uta Noppeney
Keyword(s):  
Information Integration ◽  
Visual Processing ◽  
Visual Awareness ◽  
Audiovisual Integration ◽  
Backward Masking ◽  
Perceptual Awareness ◽  
Semantic Congruency ◽  
Multisensory Interactions ◽  
The Impact ◽  
Ventriloquist Effect

AbstractInformation integration is considered a hallmark of human consciousness. Recent research has challenged this tenet by showing multisensory interactions in the absence of awareness. This psychophysics study assessed the impact of spatial and semantic correspondences on audiovisual binding in the presence and absence of visual awareness by combining forward–backward masking with spatial ventriloquism. Observers were presented with object pictures and synchronous sounds that were spatially and/or semantically congruent or incongruent. On each trial observers located the sound, identified the picture and rated the picture’s visibility. We observed a robust ventriloquist effect for subjectively visible and invisible pictures indicating that pictures that evade our perceptual awareness influence where we perceive sounds. Critically, semantic congruency enhanced these visual biases on perceived sound location only when the picture entered observers’ awareness. Our results demonstrate that crossmodal influences operating from vision to audition and vice versa are interactively controlled by spatial and semantic congruency in the presence of awareness. However, when visual processing is disrupted by masking procedures audiovisual interactions no longer depend on semantic correspondences.

Visual perception is not visual awareness

2001 ◽  
Vol 24 (5) ◽  
pp. 985-985 ◽  
Author(s):  
Valerie Gray Hardcastle
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Visual Experience ◽  
Visual Awareness ◽  
Subliminal Processing

O'Regan & Noë mistakenly identify visual processing with visual experience. I outline some reasons why this is a mistake, taking my data and arguments mainly from the literature on subliminal processing.

Perceptual Awareness of Optic Flows Paced Optimally and Non-optimally to Walking Speed

Perception ◽  
2021 ◽  
Vol 50 (9) ◽  
pp. 797-818
Author(s):  
Paweł Motyka ◽  
Zuzanna Kozłowska ◽  
Piotr Litwin
Keyword(s):  
Visual Processing ◽  
Walking Speed ◽  
Visual Awareness ◽  
Threshold Level ◽  
Perceptual Awareness ◽  
Flow Speeds ◽  
Motion Speed ◽  
Optic Flows ◽  
Walking Speeds ◽  
Self Motion

Previous research suggests that visual processing depends strongly on locomotor activity and is tuned to optic flows consistent with self-motion speed. Here, we used a binocular rivalry paradigm to investigate whether perceptual access to optic flows depends on their optimality in relation to walking velocity. Participants walked at two different speeds on a treadmill while viewing discrepant visualizations of a virtual tunnel in each eye. We hypothesized that visualizations paced appropriately to the walking speeds will be perceived longer than non optimal (too fast/slow) ones. The presented optic flow speeds were predetermined individually in a task based on matching visual speed to both walking velocities. In addition, perceptual preference for optimal optic flows was expected to increase with proprioceptive ability to detect threshold-level changes in walking speed. Whereas faster (more familiar) optic flows showed enhanced access to awareness during faster compared with slower walking conditions, for slower visual flows, only a nonsignificant tendency for the analogous effect was observed. These effects were not dependent on individual proprioceptive sensitivity. Our findings concur with the emerging view that the velocity of one’s locomotion is used to calibrate visual perception of self-motion and extend the scope of reported action effects on visual awareness.

scholarly journals Distillation of Regional Activity Reveals Hidden Content of Neural Information in Visual Processing

2021 ◽  
Vol 15 ◽  
Author(s):  
Trung Quang Pham ◽  
Shota Nishiyama ◽  
Norihiro Sadato ◽  
Junichi Chikazoe
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Brain Activity ◽  
Activity Patterns ◽  
Mental States ◽  
Brain Regions ◽  
The Other ◽  
Visual Features ◽  
Visual Areas ◽  
Visual Cortices

Multivoxel pattern analysis (MVPA) has become a standard tool for decoding mental states from brain activity patterns. Recent studies have demonstrated that MVPA can be applied to decode activity patterns of a certain region from those of the other regions. By applying a similar region-to-region decoding technique, we examined whether the information represented in the visual areas can be explained by those represented in the other visual areas. We first predicted the brain activity patterns of an area on the visual pathway from the others, then subtracted the predicted patterns from their originals. Subsequently, the visual features were derived from these residuals. During the visual perception task, the elimination of the top-down signals enhanced the simple visual features represented in the early visual cortices. By contrast, the elimination of the bottom-up signals enhanced the complex visual features represented in the higher visual cortices. The directions of such modulation effects varied across visual perception/imagery tasks, indicating that the information flow across the visual cortices is dynamically altered, reflecting the contents of visual processing. These results demonstrated that the distillation approach is a useful tool to estimate the hidden content of information conveyed across brain regions.

scholarly journals Frontoparietal Networks Mediate the Behavioral Impact of Alpha Inhibition in Visual Cortex

2018 ◽  
Vol 29 (8) ◽  
pp. 3505-3513 ◽  
Author(s):  
Alex I Wiesman ◽  
Boman R Groff ◽  
Tony W Wilson
Keyword(s):  
Visual Processing ◽  
Regulatory Networks ◽  
Compensatory Mechanism ◽  
Interference Signal ◽  
Functional Inhibition ◽  
Neural Entrainment ◽  
Visual Cortices ◽  
Entrainment Effect ◽  
Cortical Regions ◽  
Behavioral Impact

Abstract Alpha oscillations are known to play a central role in the functional inhibition of visual cortices, but the mechanisms involved are poorly understood. One noninvasive method for modulating alpha activity experimentally is through the use of flickering visual stimuli that “entrain” visual cortices. Such alpha entrainment has been found to compromise visual perception and affect widespread cortical regions, but it remains unclear how the interference occurs and whether the widespread activity induced by alpha entrainment reflects a compensatory mechanism to mitigate the entrainment, or alternatively, a propagated interference signal that translates to impaired visual processing. Herein, we attempt to address these questions by integrating alpha entrainment into a modified Posner cueing paradigm, while measuring the underlying dynamics using magnetoencephalography. Our findings indicated that alpha entrainment is negatively related to task performance, such that as neural entrainment increases on the attended side (relative to the unattended side) accuracy decreases. Further, this attentional biasing is found to covary robustly with activity in the frontoparietal attention network. Critically, the observed negative entrainment effect on task accuracy was also fully mediated by activity in frontoparietal regions, signifying a propagation of the interfering alpha entrainment signal from bottom-up sensory to top-down regulatory networks.

Behavioural and EEG atypicalities during rest, visual perception, and cognitive control in autistic adults

2020 ◽  
Author(s):  
Amandine Lassalle ◽  
Michael X Cohen ◽  
Laura Dekkers ◽  
Elizabeth Milne ◽  
Rasa Gulbinaite ◽  
...  
Keyword(s):  
Visual Perception ◽  
Cognitive Control ◽  
Visual Processing ◽  
Autism Spectrum ◽  
Neural Dynamics ◽  
Simple Explanation ◽  
Control Task ◽  
Neural Structure ◽  
Eeg Power ◽  
Autistic Adults

Background: People with an Autism Spectrum Condition diagnosis (ASD) are hypothesized to show atypical neural dynamics, reflecting differences in neural structure and function. However, previous results regarding neural dynamics in autistic individuals have not converged on a single pattern of differences. It is possible that the differences are cognitive-set-specific, and we therefore measured EEG in autistic individuals and matched controls during three different cognitive states: resting, visual perception, and cognitive control.Methods: Young adults with and without an ASD (N=17 in each group) matched on age (range 20 to 30 years), sex, and estimated Intelligence Quotient (IQ) were recruited. We measured their behavior and their EEG during rest, a task requiring low-level visual perception of gratings of varying spatial frequency, and the “Simon task” to elicit activity in the executive control network. We computed EEG power and Inter-Site Phase Clustering (ISPC; a measure of connectivity) in various frequency bands.Results: During rest, there were no ASD vs. controls differences in EEG power, suggesting typical oscillation power at baseline. During visual processing, without pre-baseline normalization, we found decreased broadband EEG power in ASD vs. controls, but this was not the case during the cognitive control task. Furthermore, the behavioral results of the cognitive control task suggest that autistic adults were better able to ignore irrelevant stimuli.Conclusions: Together, our results defy a simple explanation of overall differences between ASD and controls, and instead suggest a more nuanced pattern of altered neural dynamics that depend on which neural networks are engaged.

Visual Processing without Awareness: Evidence from Unilateral Neglect

1992 ◽  
Vol 4 (4) ◽  
pp. 345-351 ◽  
Author(s):  
Anna Berti ◽  
Giacomo Rizzolatti
Keyword(s):  
Visual Processing ◽  
Visual Awareness ◽  
Visual Cognition ◽  
Congruent Condition ◽  
Experimental Conditions ◽  
Unilateral Neglect ◽  
Normal Field ◽  
The Third ◽  
Physically Identical ◽  
Physiological Theory

Can visual processing be carried out without visual awareness of the presented objects? In the present study we addressed this problem in patients with severe unilateral neglect. The patients were required to respond as fast as possible to target stimuli (pictures of animals and fruits) presented to the normal field by pressing one of the two keys according to the category of the targets. We then studied the influence of priming stimuli, again pictures of animals or fruits, presented to the neglected field on the responses to targets. By combining different pairs of primes and targets, three different experimental conditions were obtained. In the first condition, "Highly congruent," the target and prime stimuli belonged to the same category and were physically identical; in the second condition, "Congruent," the stimuli represented two elements of the same category but were physically dissimilar; in the third condition, "Noncongruent," the stimuli represented one exemplar from each of the two categories of stimuli. The results showed that the responses were facilitated not only in the Highly congruent condition, but also in the Congruent one. This finding suggests that patients with neglect are able to process stimuli presented to the neglected field to a categorical level of representation even when they deny the stimulus presence in the affected field. The implications of this finding for psychological and physiological theory of neglect and visual cognition are discussed.

scholarly journals Sustained Splits of Attention within versus across Visual Hemifields Produce Distinct Spatial Gain Profiles

2016 ◽  
Vol 28 (1) ◽  
pp. 111-124 ◽  
Author(s):  
Sabrina Walter ◽  
Christian Keitel ◽  
Matthias M. Müller
Keyword(s):  
Visual Attention ◽  
Visual Processing ◽  
Behavioral Performance ◽  
Lower Visual Field ◽  
Light Emitting ◽  
Visual Hemifield ◽  
Attention Tasks ◽  
Visual Cortices ◽  
Cortical Visual Processing ◽  
Visual Hemifields

Visual attention can be focused concurrently on two stimuli at noncontiguous locations while intermediate stimuli remain ignored. Nevertheless, behavioral performance in multifocal attention tasks falters when attended stimuli fall within one visual hemifield as opposed to when they are distributed across left and right hemifields. This “different-hemifield advantage” has been ascribed to largely independent processing capacities of each cerebral hemisphere in early visual cortices. Here, we investigated how this advantage influences the sustained division of spatial attention. We presented six isoeccentric light-emitting diodes (LEDs) in the lower visual field, each flickering at a different frequency. Participants attended to two LEDs that were spatially separated by an intermediate LED and responded to synchronous events at to-be-attended LEDs. Task-relevant pairs of LEDs were either located in the same hemifield (“within-hemifield” conditions) or separated by the vertical meridian (“across-hemifield” conditions). Flicker-driven brain oscillations, steady-state visual evoked potentials (SSVEPs), indexed the allocation of attention to individual LEDs. Both behavioral performance and SSVEPs indicated enhanced processing of attended LED pairs during “across-hemifield” relative to “within-hemifield” conditions. Moreover, SSVEPs demonstrated effective filtering of intermediate stimuli in “across-hemifield” condition only. Thus, despite identical physical distances between LEDs of attended pairs, the spatial profiles of gain effects differed profoundly between “across-hemifield” and “within-hemifield” conditions. These findings corroborate that early cortical visual processing stages rely on hemisphere-specific processing capacities and highlight their limiting role in the concurrent allocation of visual attention to multiple locations.

scholarly journals Camouflage, communication and thermoregulation: lessons from colour changing organisms

2008 ◽  
Vol 364 (1516) ◽  
pp. 463-470 ◽  
Author(s):  
Devi Stuart-Fox ◽  
Adnan Moussalli
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Comparative Studies ◽  
Visual Cues ◽  
Colour Change ◽  
Visual Environment ◽  
Multiple Predators ◽  
Physiological Colour Change ◽  
Colour Patterns ◽  
Insight Into

Organisms capable of rapid physiological colour change have become model taxa in the study of camouflage because they are able to respond dynamically to the changes in their visual environment. Here, we briefly review the ways in which studies of colour changing organisms have contributed to our understanding of camouflage and highlight some unique opportunities they present. First, from a proximate perspective, comparison of visual cues triggering camouflage responses and the visual perception mechanisms involved can provide insight into general visual processing rules. Second, colour changing animals can potentially tailor their camouflage response not only to different backgrounds but also to multiple predators with different visual capabilities. We present new data showing that such facultative crypsis may be widespread in at least one group, the dwarf chameleons. From an ultimate perspective, we argue that colour changing organisms are ideally suited to experimental and comparative studies of evolutionary interactions between the three primary functions of animal colour patterns: camouflage; communication; and thermoregulation.

scholarly journals Familiarity affects the same event-related brain potential components in note readers and non-note readers

2018 ◽  
Vol 1 ◽  
pp. 205920431877823 ◽  
Author(s):  
Linda Becker
Keyword(s):  
Visual Perception ◽  
Neural Plasticity ◽  
Visual Processing ◽  
Music Perception ◽  
Reaction Times ◽  
Future Research ◽  
Familiarity Effect ◽  
Professional Musicians ◽  
Brain Potential ◽  
Cognitive Domains

Musical expertise can lead to neural plasticity in specific cognitive domains (e.g., in auditory music perception). However, not much is known about whether the visual perception of simple musical symbols (e.g., notes) already differs between musicians and non-musicians. This was the aim of the present study. Therefore, the Familiarity Effect (FE) – an effect which occurs quite early during visual processing and which is based on prior knowledge or expertise – was investigated. The FE describes the phenomenon that it is easier to find an unfamiliar element (e.g., a mirrored eighth note) in familiar elements (e.g., normally oriented eighth notes) than to find a familiar element in a background of unfamiliar elements. It was examined whether the strength of the FE for eighth notes differs between note readers and non-note readers. Furthermore, it was investigated at which component of the event-related brain potential (ERP) the FE occurs. Stimuli that consisted of either eighth notes or vertically mirrored eighth notes were presented to the participants (28 note readers, 19 non-note readers). A target element was embedded in half of the trials. Reaction times, sensitivity, and three ERP components (the N1, N2p, and P3) were recorded. For both the note readers and the non-note readers, strong FEs were found in the behavioral data. However, no differences in the strength of the FE between groups were found. Furthermore, for both groups, the FE was found for the same ERP components (target-absent trials – N1 latency; target-present trials – N2p latency, N2p amplitude, P3 amplitude). It is concluded that the early visual perception of eighth note symbols does not differ between note readers and non-note readers. However, future research is needed to verify this for more complex musical stimuli and for professional musicians.

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