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

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)

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

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

Attending to auditory signals slows visual alternations in binocular rivalry

A previous study has shown that diverting attention from binocular rivalry to a visual distractor task results in a slowing of rivalry alternation rate between simple orthogonal orientations. Here, we investigate whether the slowing of visual perceptual alternations will occur when attention is diverted to an auditory distractor task, and we extend the investigation by testing this for two kinds of binocular rivalry stimuli and for the Necker cube. Our results show that doing the auditory attention task does indeed slow visual perceptual alternations, that the slowing effect is a graded function of attentional load, and that the attentional slowing effect is less pronounced for grating rivalry than for house/face rivalry and for the Necker cube. These results are explained in terms of supramodal attentional resources modulating a high-level interpretative process in perceptual ambiguity, together with a role for feedback to early visual processes in the case of binocular rivalry

Does It Matter Whether You or Your Brain Did It? An Empirical Investigation of the Influence of the Double Subject Fallacy on Moral Responsibility Judgments

Despite progress in cognitive neuroscience, we are still far from understanding the relations between the brain and the conscious self. We previously suggested that some neuroscientific texts that attempt to clarify these relations may in fact make them more difficult to understand. Such texts—ranging from popular science to high-impact scientific publications—position the brain and the conscious self as two independent, interacting subjects, capable of possessing opposite psychological states. We termed such writing ‘Double Subject Fallacy’ (DSF). We further suggested that such DSF language, besides being conceptually confusing and reflecting dualistic intuitions, might affect people’s conceptions of moral responsibility, lessening the perception of guilt over actions. Here, we empirically investigated this proposition with a series of three experiments (pilot and two preregistered replications). Subjects were presented with moral scenarios where the defendant was either (1) clearly guilty, (2) ambiguous, or (3) clearly innocent while the accompanying neuroscientific evidence about the defendant was presented using DSF or non-DSF language. Subjects were instructed to rate the defendant’s guilt in all experiments. Subjects rated the defendant in the clearly guilty scenario as guiltier than in the two other scenarios and the defendant in the ambiguously described scenario as guiltier than in the innocent scenario, as expected. In Experiment 1 (N = 609), an effect was further found for DSF language in the expected direction: subjects rated the defendant less guilty when the neuroscientific evidence was described using DSF language, across all levels of culpability. However, this effect did not replicate in Experiment 2 (N = 1794), which focused on different moral scenario, nor in Experiment 3 (N = 1810), which was an exact replication of Experiment 1. Bayesian analyses yielded strong evidence against the existence of an effect of DSF language on the perception of guilt. Our results thus challenge the claim that DSF language affects subjects’ moral judgments. They further demonstrate the importance of good scientific practice, including preregistration and—most critically—replication, to avoid reaching erroneous conclusions based on false-positive results

Consciousness and Attention: On Sufficiency and Necessity

Recent research has slowly corroded a belief that selective attention and consciousness are so tightly entangled that they cannot be individually examined. In this review, we summarize psychophysical and neurophysiological evidence for a dissociation between top-down attention and consciousness. The evidence includes recent findings that show subjects can attend to perceptually invisible objects. More contentious is the finding that subjects can become conscious of an isolated object, or the gist of the scene in the near absence of top-down attention; we critically re-examine the possibility of “complete” absence of top-down attention. We also cover the recent flurry of studies that utilized independent manipulation of attention and consciousness. These studies have shown paradoxical effects of attention, including examples where top-down attention and consciousness have opposing effects, leading us to strengthen and revise our previous views. Neuroimaging studies with EEG, MEG, and fMRI are uncovering the distinct neuronal correlates of selective attention and consciousness in dissociative paradigms. These findings point to a functional dissociation: attention as analyzer and consciousness as synthesizer. Separating the effects of selective visual attention from those of visual consciousness is of paramount importance to untangle the neural substrates of consciousness from those for attention

Estimated GFR, Albuminuria, and Cognitive Performance:The Maastricht Study

BACKGROUND: Reduced estimated glomerular filtration rate (eGFR) and albuminuria have been associated with worse cognitive performance. However, few studies have examined whether these associations are confined to older individuals or may be extended to the middle-aged population. STUDY DESIGN: Cross-sectional analyses of a prospective population-based cohort study. SETTING & PARTICIPANTS: 2,987 individuals aged 40 to 75 years from the general population (The Maastricht Study). PREDICTOR: eGFR and urinary albumin excretion (UAE). OUTCOMES: Memory function, information processing speed, and executive function. MEASUREMENTS: Analyses were adjusted for demographic variables (age, sex, and educational level), lifestyle factors (smoking behavior and alcohol consumption), depression, and cardiovascular disease risk factors (glucose metabolism status, waist circumference, total to high-density lipoprotein cholesterol ratio, triglyceride level, use of lipid-modifying medication, systolic blood pressure, use of antihypertensive medication, and prevalent cardiovascular disease). RESULTS: UAE was <15mg/24 h in 2,439 (81.7%) participants, 15 to <30 mg/24 h in 309 (10.3%), and ≥30mg/24 h in 239 (8.0%). In the entire study population, UAE≥30mg/24 h was associated with lower information processing speed as compared to UAE<15mg/24 h (β [SD difference] = -0.148; 95% CI, -0.263 to -0.033) after full adjustment, whereas continuous albuminuria was not. However, significant interaction terms (P for interaction < 0.05) suggested that albuminuria was most strongly and extensively associated with cognitive performance in older individuals. Mean (±SD) eGFR, estimated by the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine-cystatin C equation (eGFRcr-cys), was 88.4±14.6 mL/min/1.73m(2). eGFRcr-cys was not associated with any of the domains of cognitive performance after full adjustment. However, significant interaction terms (P for interaction < 0.05) suggested that eGFRcr-cys was associated with cognitive performance in older individuals. LIMITATIONS: Cross-sectional design, which limited causal inferences. CONCLUSIONS: In the entire study population, albuminuria was independently associated with lower information processing speed, whereas eGFRcr-cys was not associated with cognitive performance. However, both were more strongly and extensively associated with cognitive performance in older individuals