Interference Control Modulations Over Conscious Perception

The influence of spatial and temporal attention on visual awareness-a behavioral and ERP study

Whether attention is a prerequisite of perceptual awareness or an independent and dissociable process remains a matter of debate. Importantly, understanding the relation between attention and awareness is probably not possible without taking into account the fact that both are heterogeneous and multifaceted mechanisms. Therefore, the present study tested the impact on visual awareness of two attentional mechanisms proposed by the Posner model: temporal alerting and spatio-temporal orienting. Specifically, we evaluated the effects of attention on the perceptual level, by measuring objective and subjective awareness of a threshold-level stimulus; and on the neural level, by investigating how attention affects two postulated event-related potential correlates of awareness. We found that alerting and orienting mechanisms additively facilitate perceptual consciousness, with activation of the latter resulting in the most vivid awareness. Furthermore, we found that late positivity is unlikely to constitute a neural correlate of consciousness as its amplitude was modulated by both attentional mechanisms, but early visual awareness negativity was independent of the alerting and orienting mechanisms. In conclusion, our study reveals a nuanced relationship between attention and awareness; moreover, by investigating the effect of the alerting mechanism, this study provides insights into the role of temporal attention in perceptual consciousness.

Functional networks in prolonged disorders of consciousness

Prolonged disorders of consciousness (DoC) are characterized by extended disruptions of brain activities that sustain wakefulness and awareness and are caused by various etiologies. During the past decades, neuroimaging has been a practical method of investigation in basic and clinical research to identify how brain properties interact in different levels of consciousness. Resting-state functional connectivity within and between canonical cortical networks correlates with consciousness by a calculation of the associated temporal blood oxygen level-dependent (BOLD) signal process during functional MRI (fMRI) and reveals the brain function of patients with prolonged DoC. There are certain brain networks including the default mode, dorsal attention, executive control, salience, auditory, visual, and sensorimotor networks that have been reported to be altered in low-level states of consciousness under either pathological or physiological states. Analysis of brain network connections based on functional imaging contributes to more accurate judgments of consciousness level and prognosis at the brain level. In this review, neurobehavioral evaluation of prolonged DoC and the functional connectivity within brain networks based on resting-state fMRI were reviewed to provide reference values for clinical diagnosis and prognostic evaluation.

EXPRESS: Attention does not always help: the role of expectancy, divided, and spatial attention on illusory conjunctions

Humans have the subjective impression of a rich perceptual experience, but this perception is riddled with errors that might be produced by top-down expectancies or failures in feature integration. The role of attention in feature integration is still unclear. Some studies support the importance of attention in feature integration (Paul & Schyns, 2003), whereas others suggest that feature integration does not require attention (Humphreys, 2016). Understanding attention as a heterogeneous system, in this study we explored the role of divided (as opposed to focused - Experiment 1) attention, and endogenous-exogenous spatial orienting (Experiments 2 and 3) in feature integration. We also explored the role of feature expectancy, by presenting stimulus features that were completely unexpected to the participants. Results demonstrated that both endogenous and exogenous orienting improved feature integration while divided attention did not. Moreover, a strong and consistent feature expectancy effect was observed, demonstrating perceptual completion when an unexpected perceptual feature was presented in the scene. These results support the feature confirmation account (Humphreys, 2016), which proposes that attention is important for top-down matching of stable representations.

Measuring the Impact of Bilingualism on Executive Functioning Via Inhibitory Control Abilities in Autistic Children

One factor that may influence how executive functions develop is exposure to more than one language in childhood. This study explored the impact of bilingualism on inhibitory control in autistic (n = 38) and non-autistic children (n = 51). Bilingualism was measured on a continuum of exposure to investigate the effects of language environment on two facets of inhibitory control. Behavioural control of motor impulses was modulated positively through increased bilingual exposure, irrespective of diagnostic status, but bilingual exposure did not significantly affect inhibition involving visual attention. The results partially support the hypothesis that bilingual exposure differentially affects components of inhibitory control and provides important evidence for families that bilingualism is not detrimental to their development.

Causal Contributions of the SMA to Alertness and Consciousness Interactions

Phasic alertness facilitates conscious perception through a fronto-striatal network, including the supplementary motor area (SMA). The functioning of the ventral attentional network has been related to the alerting system, overlapping with the ventral branch of the superior longitudinal fasciculus (SLF III). In this study, we use repetitive transcranial magnetic stimulation (rTMS) and a conscious detection task with near-threshold stimuli that could be preceded by an alerting tone to explore the causal implication of the SMA in the relationship between phasic alertness and conscious perception. Complementary to SMA stimulation, a sham and an active condition (left inferior parietal lobe; IPL) were included. Deterministic tractography was used to isolate the right and left SLF III. Behaviorally, the alerting tone enhanced conscious perception and confidence ratings. rTMS over the SMA reduced the alerting effect on the percentage of perceived stimuli while rTMS over the left IPL produced no modulations, demonstrating a region-specific effect. Additionally, a correlation between the rTMS effect and the integrity of the right SLF III was found. Our results highlight the causal implication of a frontal region, the SMA, in the relationship between phasic alertness and conscious perception, which is related to the white matter microstructure of the SLF III.

Connectivity of Frontoparietal Regions Reveals Executive Attention and Consciousness Interactions

The executive control network is involved in the voluntary control of novel and complex situations. Solving conflict situations or detecting errors have demonstrated to impair conscious perception of near-threshold stimuli. The aim of this study was to explore the neural mechanisms underlying executive control and its interaction with conscious perception using functional magnetic resonance imaging and diffusion-weighted imaging. To this end, we used a dual-task paradigm involving Stroop and conscious detection tasks with near-threshold stimuli. A set of prefrontal and frontoparietal regions were more strongly engaged for incongruent than congruent trials while a distributed set of frontoparietal regions showed stronger activation for consciously than nonconsciously perceived trials. Functional connectivity analysis revealed an interaction between executive control and conscious perception in frontal and parietal nodes. The microstructural properties of the middle branch of the superior longitudinal fasciculus were associated with neural measures of the interaction between executive control and consciousness. These results demonstrate that conscious perception and executive control share neural resources in frontoparietal networks, as proposed by some influential models.