scholarly journals Perceptual load modulates contour integration in conscious and unconscious states

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7550 ◽  
Author(s):  
Kaiwen Cheng ◽  
Keyu Yang ◽  
Long Qin ◽  
Yixuan Zhuo ◽  
Hongmei Yan
Keyword(s):  
Perceptual Load ◽  
Contour Integration ◽  
Contour Detection ◽  
Cognitive Factors ◽  
Orientation Discrimination ◽  
Conscious Awareness ◽  
Sensory Features ◽  
High Level ◽  
Conscious Attention ◽  
Closure Effect

Previous research has documented that contour detection and integration may either be affected by local features such as the distances between elements or by high-level cognitive factors such as attention in our visual system. Less is known about how low and high level factors interact to influence contour integration. In this paper, we investigated how attention modulates contour integration through saliency (different element spacing) and topological propert ies (circle or S-shaped) when the state of conscious awareness is manipulated. A modified inattentional blindness (IB) combined with the Posner cuing paradigm was adopted in our three-phased experiment (unconscious-training-conscious). Attention was manipulated with high or low perceptual load for a foveal go/no-go task. Cuing effects were utilized to assess the covert processing of contours prior to a peripheral orientation discrimination task. We found that (1) salient circles and S-contours induced different cuing effects under low perceptual load but not with high load; (2) no consistent pattern of cuing effects was found for non-salient contours in all the conditions; (3) a positive cuing effect was observed for salient circles either consciously or unconsciously while a negative cuing effect occurred for salient S-contours only consciously. These results suggest that conscious awareness plays a pivotal role in coordinating a closure effect with the level of perceptual load. Only salient circles can be successfully integrated in an unconscious state under low perceptual load although both salient circles and S-contours can be done consciously. Our findings support a bi-directional mechanism that low-level sensory features interact with high-level cognitive factors in contour integration.

scholarly journals How long range is contour integration in human color vision?

2003 ◽  
Vol 20 (1) ◽  
pp. 51-64 ◽  
Author(s):  
WILLIAM H.A. BEAUDOT ◽  
KATHY T. MULLEN
Keyword(s):  
Color Vision ◽  
Long Range ◽  
Short Range ◽  
Contour Integration ◽  
Contour Detection ◽  
Critical Element ◽  
Element Size ◽  
Human Color Vision ◽  
The Mean ◽  
Gabor Elements

We quantified and compared the effect of element spacing on contour integration between the achromatic (Ach), red–green (RG), and blue–yellow (BY) mechanisms. The task requires the linking of orientation across space to detect a contour in a stimulus composed of randomly oriented Gabor elements (1.5 cpd, σ = 0.17 deg), measured using a temporal 2AFC method. A contour of ten elements was pasted into a 10 × 10 cells array, and background elements were randomly positioned within the available cells. The effect of element spacing was investigated by varying the mean interelement distance between two and six times the period of the Gabor elements (λ = 0.66 deg) while the total number of elements was fixed. Contour detection was measured as a function of its curvature for jagged contours and for closed contours. At all curvatures, we found that performance for chromatic mechanisms declines more steeply with the increase in element separation than does performance for the achromatic mechanism. Averaged critical element separations were 4.6 ± 0.7, 3.6 ± 0.4, and 2.9 ± 0.2 deg for Ach, BY, and RG mechanisms, respectively. These results suggest that contour integration by the chromatic mechanisms relies more on short-range interactions in comparison to the achromatic mechanism. In a further experiment, we looked at the combined effect of element size and element separation in contour integration for the Ach mechanism.

scholarly journals Reduced influence of perceptual context in schizophrenia: behavioral and neurophysiological evidence

2019 ◽  
pp. 1-9 ◽  
Author(s):  
Victor J. Pokorny ◽  
Timothy J. Lano ◽  
Michael-Paul Schallmo ◽  
Cheryl A. Olman ◽  
Scott R. Sponheim
Keyword(s):  
Event Related Potentials ◽  
Contour Integration ◽  
Contour Detection ◽  
Group Differences ◽  
Neural Responses ◽  
Contour Perception ◽  
Accurate Perception ◽  
Visual Contour ◽  
Related Potentials ◽  
Intermediate Performance

Abstract Background Accurate perception of visual contours is essential for seeing and differentiating objects in the environment. Both the ability to detect visual contours and the influence of perceptual context created by surrounding stimuli are diminished in people with schizophrenia (SCZ). The central aim of the present study was to better understand the biological underpinnings of impaired contour integration and weakened effects of perceptual context. Additionally, we sought to determine whether visual perceptual abnormalities reflect genetic factors in SCZ and are present in other severe mental disorders. Methods We examined behavioral data and event-related potentials (ERPs) collected during the perception of simple linear contours embedded in similar background stimuli in 27 patients with SCZ, 23 patients with bipolar disorder (BP), 23 first-degree relatives of SCZ, and 37 controls. Results SCZ exhibited impaired visual contour detection while BP exhibited intermediate performance. The orientation of neighboring stimuli (i.e. flankers) relative to the contour modulated perception across all groups, but SCZ exhibited weakened suppression by the perceptual context created by flankers. Late visual (occipital P2) and cognitive (centroparietal P3) neural responses showed group differences and flanker orientation effects, unlike earlier ERPs (occipital P1 and N1). Moreover, behavioral effects of flanker context on contour perception were correlated with modulation in P2 & P3 amplitudes. Conclusion In addition to replicating and extending findings of abnormal contour integration and visual context modulation in SCZ, we provide novel evidence that the abnormal use of perceptual context is associated with higher-order sensory and cognitive processes.

scholarly journals The observant mind: self-awareness of attentional status

2010 ◽  
Vol 277 (1699) ◽  
pp. 3421-3426 ◽  
Author(s):  
Noriko Yamagishi ◽  
Stephen J. Anderson ◽  
Mitsuo Kawato
Keyword(s):  
Threshold Model ◽  
Discrimination Performance ◽  
Attentional Focus ◽  
Orientation Discrimination ◽  
Self Awareness ◽  
Neural Basis ◽  
Attentional Processes ◽  
Delay Times ◽  
Linear Rise ◽  
High Level

Visual perception is dependent not only on low-level sensory input but also on high-level cognitive factors such as attention. In this paper, we sought to determine whether attentional processes can be internally monitored for the purpose of enhancing behavioural performance. To do so, we developed a novel paradigm involving an orientation discrimination task in which observers had the freedom to delay target presentation—by any amount required—until they judged their attentional focus to be complete. Our results show that discrimination performance is significantly improved when individuals self-monitor their level of visual attention and respond only when they perceive it to be maximal. Although target delay times varied widely from trial-to-trial (range 860 ms–12.84 s), we show that their distribution is Gaussian when plotted on a reciprocal latency scale. We further show that the neural basis of the delay times for judging attentional status is well explained by a linear rise-to-threshold model. We conclude that attentional mechanisms can be self-monitored for the purpose of enhancing human decision-making processes, and that the neural basis of such processes can be understood in terms of a simple, yet broadly applicable, linear rise-to-threshold model.

Global Contour Saliency and Local Colinear Interactions

2002 ◽  
Vol 88 (5) ◽  
pp. 2846-2856 ◽  
Author(s):  
Wu Li ◽  
Charles D. Gilbert
Keyword(s):  
Limited Range ◽  
Average Density ◽  
Contour Integration ◽  
Contour Detection ◽  
Intermediate Step ◽  
Line Segments ◽  
Critical Range ◽  
Horizontal Connections ◽  
Line Elements ◽  
Contextual Interactions

Our visual system can link components of contours and segregate contours from complex backgrounds based on geometric grouping rules. This is an important intermediate step in object recognition. The substrate for contour integration may be based on contextual interactions and intrinsic horizontal connections seen in primary visual cortex (V1). We examined the perceptual rules governing contour saliency to determine whether the spatial extents of contextual interactions and horizontal connections match those mediating saliency. To quantify these rules, we used stimuli composed of randomly oriented nonoverlapping line segments. Salient contours within this complex background were formed by colinear alignment of nearby segments. Contour detectability was measured using a 2-interval-forced-choice design. Contour detectability deteriorated with increasing spacing between contour elements and improved as the number of colinear line elements was increased. At short contour spacing, the detectability reached a plateau with alignment of a few line segments that together formed a contour subtending several visual degrees. At intermediate spacing, saliency built up progressively with a greater number of colinear lines, extending up to 30°. When contour spacing was beyond a critical range (about 2°), however, the detectability dropped to chance levels, regardless of the number of colinear lines. Contour detectability was found to be a function not only of the relative spacing of contour elements with respect to the noise elements but also of the average density of the overall pattern. Furthermore, training significantly improved contour detection, increasing the critical spacing of line elements beyond which contours were no longer detectable. Our data suggest that global contour integration is based on mechanisms of limited spatial extent, comparable to the interactions observed in V1. These interactions can cascade over larger distances provided the spacing of stimulus elements is kept within a limited range.

scholarly journals Visual Learning Alters the Spontaneous Activity of the Resting Human Brain: An fNIRS Study

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Haijing Niu ◽  
Hao Li ◽  
Li Sun ◽  
Yongming Su ◽  
Jing Huang ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Functional Connectivity ◽  
Perceptual Learning ◽  
Near Infrared ◽  
Visual Learning ◽  
Orientation Discrimination ◽  
Right Visual Field ◽  
Resting State Functional Connectivity ◽  
Functional Near Infrared Spectroscopy ◽  
High Level

Resting-state functional connectivity (RSFC) has been widely used to investigate spontaneous brain activity that exhibits correlated fluctuations. RSFC has been found to be changed along the developmental course and after learning. Here, we investigated whether and how visual learning modified the resting oxygenated hemoglobin (HbO) functional brain connectivity by using functional near-infrared spectroscopy (fNIRS). We demonstrate that after five days of training on an orientation discrimination task constrained to the right visual field, resting HbO functional connectivity and directed mutual interaction between high-level visual cortex and frontal/central areas involved in the top-down control were significantly modified. Moreover, these changes, which correlated with the degree of perceptual learning, were not limited to the trained left visual cortex. We conclude that the resting oxygenated hemoglobin functional connectivity could be used as a predictor of visual learning, supporting the involvement of high-level visual cortex and the involvement of frontal/central cortex during visual perceptual learning.

scholarly journals Perceptual integration of head and eye cues to gaze direction in schizophrenia

2018 ◽  
Vol 5 (12) ◽  
pp. 180885 ◽  
Author(s):  
Colin J. Palmer ◽  
Nathan Caruana ◽  
Colin W. G. Clifford ◽  
Kiley J. Seymour
Keyword(s):  
Computational Modelling ◽  
Contour Detection ◽  
Gaze Direction ◽  
Head Orientation ◽  
Head Region ◽  
Facial Cues ◽  
Sensory Features ◽  
The Face ◽  
Integrative Processing ◽  
Eye Region

The perceptual mechanisms that underlie social experience in schizophrenia are increasingly becoming a target of empirical research. In the context of low-level vision, there is evidence for a reduction in the integration of sensory features in schizophrenia (e.g. increased thresholds for contour detection and motion coherence). In the context of higher-level vision, comparable differences in the integration of sensory features of the face could in theory impair the recognition of important social cues. Here we examine how the sense of where other people are looking relies upon the integration of eye-region cues and head-region cues. Adults with schizophrenia viewed face images designed to elicit the ‘Wollaston illusion’, a perceptual phenomenon in which the perceived gaze direction associated with a given pair of eyes is modulated by the surrounding sensory context. We performed computational modelling of these psychophysical data to quantify individual differences in the use of facial cues to gaze direction. We find that adults with schizophrenia exhibit a robust perceptual effect whereby their sense of other people's direction of gaze is strongly biased by sensory cues relating to head orientation in addition to eye region information. These results indicate that the visual integration of facial cues to gaze direction in schizophrenia is intact, helping to constrain theories of reduced integrative processing in higher-level and lower-level vision. In addition, robust gaze processing was evident in the tested participants despite reduced performance on a theory of mind task designed to assess higher-level social cognition.

A “Global Closure” Effect in Contour Integration

2009 ◽  
pp. 259-266
Author(s):  
Kazuhiro Sakamoto ◽  
Hidekazu Nakajima ◽  
Takeshi Suzuki ◽  
Masafumi Yano
Keyword(s):  
Contour Integration ◽  
Closure Effect

scholarly journals Reduced Influence of Perceptual Context in Schizophrenia: Behavioral and Neurophysiological Evidence

2019 ◽  
Author(s):  
Victor J. Pokorny ◽  
Timothy J. Lano ◽  
Michael-Paul Schallmo ◽  
Cheryl A. Olman ◽  
Scott R. Sponheim
Keyword(s):  
Bipolar Disorder ◽  
Event Related Potentials ◽  
Contour Integration ◽  
Contour Detection ◽  
Group Differences ◽  
Neural Responses ◽  
Contour Perception ◽  
Accurate Perception ◽  
Visual Contour ◽  
Related Potentials

AbstractBackgroundAccurate perception of visual contours is essential for seeing and differentiating objects in the environment. Both the ability to detect visual contours and the influence of perceptual context created by surrounding stimuli are diminished in people with schizophrenia. The central aim of the present study was to better understand the biological underpinnings of impaired contour integration and weakened effects of perceptual context. Additionally, we sought to determine whether visual perceptual abnormalities reflect genetic factors in schizophrenia and are present in other severe mental disorders.MethodsWe examined behavioral data and event-related potentials (ERPs) collected during the perception of simple linear contours embedded in similar background stimuli in 27 patients with schizophrenia (SCZ), 23 patients with bipolar disorder, 23 first-degree relatives of SCZ and 37 controls.ResultsSCZ exhibited impaired visual contour detection while patients with bipolar disorder exhibited intermediate performance. The orientation of neighboring stimuli (i.e., flankers) relative to the contour modulated perception across all groups, but SCZ exhibited weakened suppression by the perceptual context created by flankers. Late visual (occipital P2) and cognitive (centroparietal P3) neural responses showed group differences and flanker orientation effects, unlike earlier ERPs (occipital P1 and N1). Moreover, behavioral effects of flanker context on contour perception were correlated with modulation in P2/P3 amplitudes.ConclusionIn addition to replicating and extending findings of abnormal contour integration and visual context modulation in SCZ, we provide novel evidence that abnormal use of perceptual context is associated with higher-order sensory and cognitive processes.

scholarly journals Attitude Moralization: Probably Not Intuitive or Rooted in Perceptions of Harm

2017 ◽  
Vol 27 (1) ◽  
pp. 9-13 ◽  
Author(s):  
Linda J. Skitka ◽  
Daniel C. Wisneski ◽  
Mark J. Brandt
Keyword(s):  
Field Study ◽  
Cognitive Factors ◽  
Conscious Awareness ◽  
Attitude Object ◽  
Moral Conviction

People vary in the extent to which they imbue attitudes with moral conviction, and this variation is consequential. Yet we know relatively little about what makes people’s feelings about a given attitude object transform from a relatively nonmoral preference to a moral conviction. In this article, we review evidence from two experiments and a field study that sheds some light on the processes that lead to attitude moralization. This research explored the roles of incidental and integral affect, cognitive factors such as recognition of harm, and whether attitude-moralization processes can occur outside conscious awareness or require some level of conscious deliberation. The findings present some challenges to contemporary theories that emphasize the roles of intuition and harm and indicate that more research designed to better understand moralization processes is needed.

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