Multisensory Congruency as a Mechanism for Attentional Control over Perceptual Selection

The neural mechanisms underlying attentional selection of competing neural signals for awareness remains an unresolved issue. We studied attentional selection, using perceptually ambiguous stimuli in a novel multisensory paradigm that combined competing auditory and competing visual stimuli. We demonstrate that the ability to select, and attentively hold, one of the competing alternatives in either sensory modality is greatly enhanced when there is a matching cross-modal stimulus. Intriguingly, this multimodal enhancement of attentional selection seems to require a conscious act of attention, as passively experiencing the multisensory stimuli did not enhance control over the stimulus. We also demonstrate that congruent auditory or tactile information, and combined auditory–tactile information, aids attentional control over competing visual stimuli and visa versa. Our data suggest a functional role for recently found neurons that combine voluntarily initiated attentional functions across sensory modalities. We argue that these units provide a mechanism for structuring multisensory inputs that are then used to selectively modulate early (unimodal) cortical processing, boosting the gain of task-relevant features for willful control over perceptual awareness

Removal of monocular interactions equates rivalry behavior for monocular, binocular, and stimulus rivalries

When the two eyes are presented with conflicting stimuli, perception starts to fluctuate over time (i.e., binocular rivalry). A similar fluctuation occurs when two patterns are presented to a single eye (i.e., monocular rivalry), or when they are swapped rapidly and repeatedly between the eyes (i.e., stimulus rivalry). Although all these cases lead to rivalry, in quantitative terms these modes of rivalry are generally found to differ significantly. We studied these different modes of rivalry with identical intermittently shown stimuli while varying the temporal layout of stimulation. We show that the quantitative differences between the modes of rivalry are caused by the presence of monocular interactions between the rivaling patterns; the introduction of a blank period just before a stimulus swap changed the number of rivalry reports to the extent that monocular and stimulus rivalries were inducible over ranges of spatial frequency content and contrast values that were nearly identical to binocular rivalry. Moreover when monocular interactions did not occur the perceptual dynamics of monocular, binocular, and stimulus rivalries were statistically indistinguishable. This range of identical behavior exhibited a monocular (∼50 ms) and a binocular (∼350 ms) limit. We argue that a common binocular, or pattern-based, mechanism determines the temporal constraints for these modes of rivalry

Different signal enhancement pathways of attention and consciousness underlie perception in humans

It is not yet known whether attention and consciousness operate through similar or largely different mechanisms. Visual processing mechanisms are routinely characterized by measuring contrast response functions (CRFs). In this report, behavioral CRFs were obtained in humans (both males and females) by measuring afterimage durations over the entire range of inducer stimulus contrasts to reveal visual mechanisms behind attention and consciousness. Deviations relative to the standard CRF, i.e., gain functions, describe the strength of signal enhancement, which were assessed for both changes due to attentional task and conscious perception. It was found that attention displayed a response-gain function, whereas consciousness displayed a contrast-gain function. Through model comparisons, which only included contrast-gain modulations, both contrast-gain and response-gain effects can be explained with a two-level normalization model, in which consciousness affects only the first level and attention affects only the second level. These results demonstrate that attention and consciousness can effectively show different gain functions because they operate through different signal enhancement mechanisms

A Dissociation of Attention and Awareness in Phase-sensitive but Not Phase-insensitive Visual Channels

The elements most vivid in our conscious awareness are the ones to which we direct our attention. Scientific study confirms the impression of a close bond between selective attention and visual awareness, yet the nature of this association remains elusive. Using visual afterimages as an index, we investigate neural processing of stimuli as they enter awareness and as they become the object of attention. We find evidence of response enhancement accompanying both attention and awareness, both in the phase-sensitive neural channels characteristic of early processing stages and in the phase-insensitive channels typical of higher cortical areas. The effects of attention and awareness on phase-insensitive responses are positively correlated, but in the same experiments, we observe no correlation between the effects on phase-sensitive responses. This indicates independent signatures of attention and awareness in early visual areas yet a convergence of their effects at more advanced processing stages

Visual Rivalry Without Spatial Conflict

Visual rivalry has been extensively characterized in the literature. It is thought to require spatial conflict between overlapping visual presentations, even in studies that have found nonspatial (i.e. nonretinal) influences on rivalry. Unexpectedly, we identified visual rivalry in the complete absence of spatial conflict. Participants experienced visual rivalry when we placed a nonambiguous motion stimulus in a nonspatial (in our case, object-based) reference frame. Moreover, a stimulus that was displaced within a nonspatial reference frame did not induce rivalry despite the presence of spatial conflict. This finding shows that nonspatial, object-based processing can overrule retinotopic processing and prevent rivalry from occurring when a perceived stimulus exists unambiguously in an object-based reference frame. our results identify a potent high-level conflict-resolution stage independent of low-level spatial visual conflict. This independence of spatial overlap provides an advantage to the visual system, allowing conflict resolution when an object is nonstationary on the retina (e.g., during frequently occurring eye movements)

Stimulating situational interest and student questioning through three types of historical introductory texts

This study investigates questions students ask related to an introductory text about a new topic in the history classroom. The effects of a narrative, problematizing, and expository introductory text on the situational interest of students and the number and type of student-generated questions, are compared. Participants are 174 students in higher secondary education (16 years old). Student-generated questions are categorized in higher -and lower-order questions, in descriptive, explanative, comparative and evaluative questions, and in emotive and non-emotive questions. The type of introductory text had a significant effect on the level of situational interest and type of questions but not on the number of generated questions. Narrative and problematizing texts provoked more situational interest and more emotive questions than the expository text. We found a significant positive correlation between prior topic knowledge, interest in History, situational interest, and number of questions

Dutch students’ understanding of the interpretative nature of textbooks when comparing two texts about a significant event in the development of democracy

In history education, the deconstruction of narratives is an important skill for students. The skill teaches them to look critically at the offered texts. In this study, we investigated the extent to which students are able to critically analyse the narratives in their history textbooks. To answer this question, we asked 106 students in pre-university education (16–17 years of age) to read and compare two texts – from two different textbooks – about a turning point in the development of the Dutch state and democracy: the introduction of universal suffrage for men and women in 1917–19. One group of students (N=10) worked on the assignment while thinking aloud. We found that most students recognized the author’s voice in the selection of persons and dates and in the attention paid to a particular topic, but that they hardly mentioned recognizing the voice in aspects such as the choice of words or headings. The students who analysed and compared the texts while thinking aloud all indicated after the assignment that they understood that these texts are different interpretations of the same historical development