Dataset Information

Dynamics of unconscious contextual effects in orientation processing.

ABSTRACT: Contextual effects abound in the real world; how we perceive an object depends on what surrounds it. A classic example of this is the tilt illusion (TI) whereby the presence of a surround shifts the perceived orientation of a target. Surprisingly, the magnitude and direction of this shift depend on the orientation difference between the target and surround: when their orientations are similar, the perceived difference is amplified and the target appears repelled in orientation from the surround (i.e., the TI). However, when their orientations are close to perpendicular, the difference is decreased and the target appears attracted in orientation toward the surround (i.e., the indirect TI). These misperceptions of orientation have revealed much about the underlying detectors involved in visual processing and how they interact with each other. What remains at stake are the levels of processing involved. To examine this, we designed a reverse-correlation technique whereby observers are blind to the orientation of the surround. We find that the TI and indirect TI occur reliably and over a similar time course, supporting the role of a single mechanism underlying orientation biases that operates in the early stages of visual processing before the conscious extraction of the surround orientation.

SUBMITTER: Mareschal I

PROVIDER: S-EPMC3358900 | biostudies-other | 2012 May

REPOSITORIES: biostudies-other

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Dynamics of unconscious contextual effects in orientation processing.

Mareschal Isabelle I Clifford Colin W G CW

Proceedings of the National Academy of Sciences of the United States of America 20120423 19

Contextual effects abound in the real world; how we perceive an object depends on what surrounds it. A classic example of this is the tilt illusion (TI) whereby the presence of a surround shifts the perceived orientation of a target. Surprisingly, the magnitude and direction of this shift depend on the orientation difference between the target and surround: when their orientations are similar, the perceived difference is amplified and the target appears repelled in orientation from the surround ...[more]

PMID: 22529393

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Project description:Semantic processing of visually presented words can be identified both on behavioral and neurophysiological evidence. One of the major discoveries of the last decades is the demonstration that these signatures of semantic processing, initially observed for consciously perceived words, can also be detected for masked words inaccessible to conscious reports. In this context, the distinction between conscious and unconscious verbal semantic processing constitutes a challenging scientific issue. A prominent view considered that while conscious representations are subject to executive control, unconscious ones would operate automatically in a modular way, independent from control and top-down influences. Recent findings challenged this view by revealing that endogenous attention and task-setting can have a strong influence on unconscious processing. However, one of the major arguments supporting the automaticity of unconscious semantic processing still stands, stemming from a seminal observation reported by Marcel in 1980 about polysemous words. In the present study we reexamined this evidence. We present a combination of behavioral and event-related-potentials (ERPs) results that refute this view by showing that the current conscious semantic context has a major and similar influence on the semantic processing of both visible and masked polysemous words. In a classical lexical decision task, a polysemous word was preceded by a word which defined the current semantic context. Crucially, this context was associated with only one of the two meanings of the polysemous word, and was followed by a word/pseudo-word target. Behavioral and electrophysiological evidence of semantic priming of target words by masked polysemous words was strongly dependent on the conscious context. Moreover, we describe a new type of influence related to the response-code used to answer for target words in the lexical decision task: unconscious semantic priming constrained by the conscious context was present both in behavior and ERPs exclusively when right-handed subjects were instructed to respond to words with their right hand. The strong and respective influences of conscious context and response-code on semantic processing of masked polysemous words demonstrate that unconscious verbal semantic representations are not automatic.

Project description:BackgroundThe unconscious processing of information is an important skill used by competitive athletes to handle the rapidly changing movements of opponents and equipment. Previous studies have shown that unconscious information processing among athletes is better than that among non-athletes in the sports-specific domain. However, it is not yet clear whether athletes also show superior unconscious information processing in the general cognitive domain.MethodsTwenty-five competitive table tennis players (athletes) and 26 aged-matched non-athletic college students (non-athlete controls) were recruited for this study. Participants first performed a masked priming task that used geometric shapes as primes and targets to examine unconscious information processing in the general cognitive domain. As a control, participants then completed a prime identification task to determine whether they could consciously detect the priming geometric forms. Reaction times and error rates were analyzed to examine whether motor expertise influenced unconscious information processing in the general domain. Nineteen athletes and 17 non-athletes from our present study, which used general stimuli, also participated in our previous study, which used sport-specific stimuli. The strength of the unconscious response priming effect was analyzed to examine whether the effect of motor expertise on unconscious processing could be transferred from a sports-specific domain to a general domain.ResultsSignal detection analyses indicated that neither athletes nor non-athletes could consciously perceive the priming stimuli. Two-way repeated-measures analyses of variance followed by simple main effects analyses of the masked priming performance, indicating that athletes responded faster and committed fewer errors when the priming stimulus was congruent with the target stimulus. These results suggested that athletes exhibited a significant unconscious response priming effect of geometric forms. By contrast, non-athletes did not respond faster or commit fewer errors for congruent vs. incongruent conditions. No significant difference was detected between athletes and non-athletes in error rates for congruent trials, but athletes committed significantly more errors than non-athletes on incongruent trials. The strength of the unconscious response priming effect that athletes exhibited was greater than that for non-athletes, both in the present study with general stimuli and in our previous study with sport-specific stimuli.ConclusionThe results indicated that motor expertise facilitated the unconscious processing of geometric forms, suggesting that the influence of motor expertise on unconscious information processing occurs not only for the sports-specific domain but also transfers to the general cognitive domain.

Project description:BACKGROUND:The intense loss processing that characterizes grieving may help people to adapt to the loss. However, empirical studies show that more conscious loss-related thinking and greater reactivity to reminders of the deceased correspond to poorer adaptation. These findings raise the possibility that loss processing that is unconscious rather than conscious and is self-generated rather than reactive may facilitate adaptation. Here, we used machine learning to detect a functional magnetic resonance imaging (fMRI) signature of self-generated unconscious loss processing that we hypothesized to correlate with lower grief severity. METHODS:A total of 29 subjects bereaved within the past 14 months participated. Participants performed a modified Stroop fMRI task using deceased-related words. A machine-learning regression, trained on Stroop fMRI data, learned a neural pattern for deceased-related selective attention (d-SA), the allocation of attention to the deceased. Expression of this pattern was tracked during a subsequent sustained attention fMRI task interspersed with deceased-related thought probes (SART-PROBES). d-SA pattern expression during SART-PROBES blocks without reported thoughts of loss indicated self-generated unconscious loss processing. Grief severity was measured with the Inventory for Complicated Grief. RESULTS:d-SA expression during SART-PROBES blocks without conscious deceased-related thinking correlated negatively with Inventory for Complicated Grief score (r25 = -.711, p < .001, 95% confidence interval = -0.89 to -0.42), accounting for 50% of variance. This relationship remained significant independent of demographic correlates of Inventory for Complicated Grief (B25 = -30, t = -2.64, p = .02, 95% confidence interval = -56.2 to -4.6). Unconscious d-SA pattern expression also correlated with activity in dorsolateral prefrontal cortex and temporal parietal junction during the SART-PROBES (voxel: p < .001, cluster: p < .05). CONCLUSIONS:Self-generated unconscious loss processing correlated with reduced grief severity. This activity, supported by a cognitive social neural architecture, may advance adaptation to the loss.

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Dynamics of unconscious contextual effects in orientation processing.

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Dynamics of unconscious contextual effects in orientation processing.

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