93 research outputs found
Disentangling neural processing of masked and masking stimulus by means of event-related contralateral – ipsilateral differences of EEG potentials
In spite of the excellent temporal resolution of event-related EEG potentials
(ERPs), the overlapping potentials evoked by masked and masking stimuli are hard
to disentangle. However, when both masked and masking stimuli consist of pairs
of relevant and irrelevant stimuli, one left and one right from fixation, with
the side of the relevant element varying between pairs, effects of masked and
masking stimuli can be distinguished by means of the contralateral preponderance
of the potentials evoked by the relevant elements, because the relevant elements
may independently change sides in masked and masking stimuli. Based on a
reanalysis of data from which only selected contralateral-ipsilateral effects
had been previously published, the present contribution will provide a more
complete picture of the ERP effects in a masked-priming task. Indeed, effects
evoked by masked primes and masking targets heavily overlapped in conventional
ERPs and could be disentangled to a certain degree by contralateral-ipsilateral
differences. Their major component, the N2pc, is interpreted as indicating
preferential processing of stimuli matching the target template, which process
can neither be identified with conscious perception nor with shifts of spatial
attention. The measurements showed that the triggering of response preparation
by the masked stimuli did not depend on their discriminability, and their
priming effects on the processing of the following target stimuli were
qualitatively different for stimulus identification and for response
preparation. These results provide another piece of evidence for the
independence of motor-related and perception-related effects of masked
stimuli
Effects of stimulus duration on audio-visual synchrony perception
The integration of visual and auditory inputs in the human brain occurs only if the components are perceived in temporal proximity, that is, when the intermodal time difference falls within the so-called subjective synchrony range. We used the midpoint of this range to estimate the point of subjective simultaneity (PSS). We measured the PSS for audio-visual (AV) stimuli in a synchrony judgment task, in which subjects had to judge a given AV stimulus using three response categories (audio first, synchronous, video first). The relevant stimulus manipulation was the duration of the auditory and visual components. Results for unimodal auditory and visual stimuli have shown that the perceived onset shifts to relatively later positions with increasing stimulus duration. These unimodal shifts should be reflected in changing PSS values, when AV stimuli with different durations of the auditory and visual components are used. The results for 17 subjects showed indeed a significant shift of the PSS for different duration combinations of the stimulus components. Because the shifts were approximately equal for duration changes in either of the components, no net shift of the PSS was observed as long as the durations of the two components were equal. This result indicates the need to appropriately account for unimodal timing effects when quantifying intermodal synchrony perceptio
Dos and don’ts in response priming research
Response priming is a well-understood but sparsely employed paradigm in cognitive
science. The method is powerful and well-suited for exploring early visuomotor
processing in a wide range of tasks and research fields. Moreover, response
priming can be dissociated from visual awareness, possibly because it is based
on the first sweep of feedforward processing of primes and targets. This makes
it a theoretically interesting device for separating conscious and unconscious
vision. We discuss the major opportunities of the paradigm and give specific
recommendations (e.g., tracing the time-course of priming in parametric
experiments). Also, we point out typical confounds, design flaws, and data
processing artifacts
Evaluation of 3D-Jury on CASP7 models
<p>Abstract</p> <p>Background</p> <p>3D-Jury, the structure prediction consensus method publicly available in the Meta Server <url>http://meta.bioinfo.pl/</url>, was evaluated using models gathered in the 7<sup><it>th </it></sup>round of the Critical Assessment of Techniques for Protein Structure Prediction (CASP7). 3D-Jury is an automated expert process that generates protein structure meta-predictions from sets of models obtained from partner servers.</p> <p>Results</p> <p>The performance of 3D-Jury was analysed for three aspects. First, we examined the correlation between the 3D-Jury score and a model quality measure: the number of correctly predicted residues. The 3D-Jury score was shown to correlate significantly with the number of correctly predicted residues, the correlation is good enough to be used for prediction. 3D-Jury was also found to improve upon the competing servers' choice of the best structure model in most cases. The value of the 3D-Jury score as a generic reliability measure was also examined. We found that the 3D-Jury score separates bad models from good models better than the reliability score of the original server in 27 cases and falls short of it in only 5 cases out of a total of 38. We report the release of a new Meta Server feature: instant 3D-Jury scoring of uploaded user models.</p> <p>Conclusion</p> <p>The 3D-Jury score continues to be a good indicator of structural model quality. It also provides a generic reliability score, especially important for models that were not assigned such by the original server. Individual structure modellers can also benefit from the 3D-Jury scoring system by testing their models in the new instant scoring feature <url>http://meta.bioinfo.pl/compare_your_model_example.pl</url> available in the Meta Server.</p
A modal theorem-preserving translation of a class of three-valued logics of incomplete information
International audienceThere are several three-valued logical systems that form a scattered landscape, even if all reasonable connectives in three-valued logics can be derived from a few of them. Most papers on this subject neglect the issue of the relevance of such logics in relation with the intended meaning of the third truth-value. Here, we focus on the case where the third truth-value means unknown, as suggested by Kleene. Under such an understanding, we show that any truth-qualified formula in a large range of three-valued logics can be translated into KD as a modal formula of depth 1, with modalities in front of literals only, while preserving all tautologies and inference rules of the original three-valued logic. This simple information logic is a two-tiered classical propositional logic with simple semantics in terms of epistemic states understood as subsets of classical interpretations. We study in particular the translations of Kleene, Gödel, ᴌukasiewicz and Nelson logics. We show that Priest’s logic of paradox, closely connected to Kleene’s, can also be translated into our modal setting, simply by exchanging the modalities possible and necessary. Our work enables the precise expressive power of three-valued logics to be laid bare for the purpose of uncertainty management
Effects of auditory stimulus intensity on response force in simple, go/no-go, and choice RT tasks
Neuro-cognitive mechanisms of conscious and unconscious visual perception: From a plethora of phenomena to general principles
Psychological and neuroscience approaches have promoted much progress in
elucidating the cognitive and neural mechanisms that underlie phenomenal visual
awareness during the last decades. In this article, we provide an overview of
the latest research investigating important phenomena in conscious and
unconscious vision. We identify general principles to characterize conscious and
unconscious visual perception, which may serve as important building blocks for
a unified model to explain the plethora of findings. We argue that in particular
the integration of principles from both conscious and unconscious vision is
advantageous and provides critical constraints for developing adequate
theoretical models. Based on the principles identified in our review, we outline
essential components of a unified model of conscious and unconscious visual
perception. We propose that awareness refers to consolidated
visual representations, which are accessible to the entire brain and therefore
globally available. However, visual awareness not only depends
on consolidation within the visual system, but is additionally the result of a
post-sensory gating process, which is mediated by higher-level cognitive control
mechanisms. We further propose that amplification of visual representations by
attentional sensitization is not exclusive to the domain of conscious
perception, but also applies to visual stimuli, which remain unconscious.
Conscious and unconscious processing modes are highly interdependent with
influences in both directions. We therefore argue that exactly this
interdependence renders a unified model of conscious and unconscious visual
perception valuable. Computational modeling jointly with focused experimental
research could lead to a better understanding of the plethora of empirical
phenomena in consciousness research
Top-down contingent feature-specific orienting with and without awareness of the visual input
In the present article, the role of endogenous feature-specific orienting for
conscious and unconscious vision is reviewed. We start with an overview of
orienting. We proceed with a review of masking research, and the definition of
the criteria of experimental protocols that demonstrate endogenous and exogenous
orienting, respectively. Against this background of criteria, we assess studies
of unconscious orienting and come to the conclusion that so far studies of
unconscious orienting demonstrated endogenous feature-specific orienting. The
review closes with a discussion of the role of unconscious orienting in action
control
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