The major brain networks of human visual consciousness

Understanding consciousness is one of the most important and challenging questions in modern science. Existing theories have pursued single unifying mechanisms but do not succeed in explaining consciousness. Importantly, the neural circuits that distinguish messages that arrive from the outside world and attain consciousness have remained unknown. Here we identify signals throughout the entire brain at high spatiotemporal resolution specifically related to consciousness. To accomplish this, we combined a large sample size of electrical and neuroimaging data with a novel experimental approach to remove confounding signal unrelated to consciousness1-3. We discovered three major brain networks driving conscious visual perception. First, we found increases in signal detection regions in visual, fusiform cortex, and frontal eye fields; and in arousal/salience networks involving midbrain, thalamus, nucleus accumbens, anterior cingulate, and anterior insula. Second, we found increases in frontoparietal attention and executive control networks and in the cerebellum. Finally, we found decreases in the default mode network. Our results identify subcortical and cortical networks designed for signal detection, attentional amplification, and perceptual processing that together can explain visual consciousness. These findings provide evidence that understanding consciousness can be reframed as requiring multiple overlapping brain networks to produce consciousness of visual events4.

Challenging the notion of a task-negative network: default mode network involvement under varying levels of cognitive effort

Everyday cognitive functioning is characterized by constant alternations between different modes of information processing, driven by fluctuations in environmental demands. At the neural level, this is realized through corresponding dynamic shifts in functional activation and network connectivity. A distinction is often made between the Default Mode Network (DMN) as a task-negative network that is upregulated in the absence of cognitive demands, and task-positive networks that are upregulated when cognitive demands such as attention and executive control are present. Such networks have been labelled the Extrinsic Mode Network (EMN). We investigated changes in brain activation and functional network connectivity during repeated alternations between levels of cognitive effort. Using fMRI and a block-design Stroop paradigm, participants switched back and forth between periods of no effort (resting), low effort (word reading, automatic processing) and high effort (color naming, cognitive control). Results showed expected EMN-activation for task versus rest, and likewise expected DMN-activation for rest versus task. The DMN was also more strongly activated during low effort contrasted with high effort, suggesting a gradual up- and down-regulation of the DMN, depending on the level of demand. The often reported anti-correlation between DMN and EMN was only present during periods of low effort, indicating intermittent contributions of both networks. These results challenge the traditional view of the DMN as solely a task-negative network. Instead, the present results suggest that both EMN and DMN may contribute to low-effort cognitive processing. In contrast, periods of resting and high effort are dominated by the DMN and EMN, respectively.

Executive and Attentional Resting-State Hubs of the Human Cortical Connectome Revealed by a Causal Discovery Method for Data-Driven Effective Connectivity Analysis

We introduce a data-driven causal discovery method (Greedy Adjacencies and Non-Gaussian Orientations; GANGO) for calculating a "causal connectome" of directed connectivity from resting-state fMRI data and characterizing hubs of directed information transfer across the human cortex. Prominent hubs of the causal connectome were situated in attentional (dorsal attention) and executive (frontoparietal and cingulo-opercular) networks. These hub networks had distinctly different connectivity profiles. Attentional networks shared incoming connections with sensory regions and outgoing connections with higher cognitive networks, while executive networks primarily connected to other higher cognitive networks and had a high degree of bidirected connectivity. Virtual lesion analyses accentuated these findings, demonstrating that attentional and executive hubs are points of critical vulnerability in the human causal connectome. These data highlight the central role of attention and executive control networks in the human cortical connectome and set the stage for future applications of data-driven causal ("effective") connectivity analysis in psychiatry.

Catching wandering minds with tapping fingers: Neural and behavioral insights into task-unrelated cognition

When the human mind wanders, it engages in episodes during which attention is focused on self-generated thoughts rather than on external task demands. Although the sustained attention to response task is commonly used to examine relationships between mind wandering and executive functions, limited executive resources are required for optimal task performance. In the current study, we aimed to investigate the relationship between mind wandering and executive functions more closely by employing a recently developed finger-tapping task to monitor fluctuations in attention and executive control through objective task performance and periodical experience sampling during concurrent fMRI and pupillometry. Our results show that mind wandering was preceded by increases in finger-tapping variability, which was correlated with activity in dorsal and ventral attention networks. The entropy of random finger-tapping sequences was related to activity in frontoparietal regions associated with executive control, demonstrating the suitability of this paradigm for studying executive functioning. The neural correlates of behavioral performance, pupillary dynamics, and self-reported attentional state diverged, indicating a dissociation between objective and subjective markers of mind wandering. Together, the investigation of these relationships at both the behavioral and neural level provided novel insights in the identification of underlying mechanisms of mind wandering.

The Link Between Obstructive Sleep Apnoea and Neurodegeneration and Cognition

Purpose of Review Obstructive sleep apnoea (OSA) is increasingly found to have an impact on neurodegeneration. In this review, we summarise recent findings on the association between OSA and brain morphology, cognition, and processes related to Alzheimer’s dementia (AD) and Parkinson’s disease (PD). Recent Findings Associations between OSA and alterations in grey and white matter, brain diffusivity, and deficits in memory, attention, and executive control were reported. Furthermore, OSA was correlated with higher risks of developing AD and PD and associated pathophysiology. Treatment was found to alleviate but not reverse some of the damage. Summary There are strong indications that OSA plays a major role in neurodegenerative processes. The broad picture however remains elusive, likely due to insufficient sample sizes, heterogeneous outcomes, and OSA definitions failing to quantify the disorder’s sub-processes. While studies resolving these issues are required, the available evidence shows OSA to be a promising target to slow neurodegeneration and delay the onset of related disorders.

A fájdalomélmény kialakulásának korszerű megközelítése

According to the basic assumption of pain research, the activity of pain matrix shows an increase in functional neuroimaging studies during nociceptive stimulation whose extent is correlated with the intensity of the stimulus and that of the emerged experience of pain. Research conducted over the past decade has questioned this assumption. In order to understand the controversial findings I have reviewed new results of pain research. In order to get to know more about “hardware”, I reviewed the direct relationships between members of the pain network. With a view to understand the mechanism of the development of pain perception, the “software”, I give a brief description of the functioning of the salient as well as attention and executive control network. To have a better understanding of “hardware”, I examined the behavior of the pain network of patients incapable of feeling pain in aversive situations. In the review I introduced the thought-provoking knowledge of the pain for all experts, regardless of this specialty by presenting the results of pain research.

Reward Influences Masked Free-Choice Priming

While it is known that reward induces attentional prioritization, it is not clear what effect reward-learning has when associated with stimuli that are not fully perceived. The masked priming paradigm has been extensively used to investigate the indirect impact of brief stimuli on response behavior. Interestingly, the effect of masked primes is observed even when participants choose their responses freely. While classical theories assume this process to be automatic, recent studies have provided evidence for attentional modulations of masked priming effects. Most such studies have manipulated bottom-up or top-down modes of attentional selection, but the role of “newer” forms of attentional control such as reward-learning and selection history remains unclear. In two experiments, with number and arrow primes, we examined whether reward-mediated attentional selection modulates masked priming when responses are chosen freely. In both experiments, we observed that primes associated with high-reward lead to enhanced free-choice priming compared to primes associated with no-reward. The effect was seen on both proportion of choices and response times, and was more evident in the faster responses. In the slower responses, the effect was diminished. Our study adds to the growing literature showing the susceptibility of masked priming to factors related to attention and executive control.

The effects of cognitive training on executive functions and reading in typically-developing children with varied socioeconomic status in Brazil

Recent findings show that children from low-socioeconomic status (SES) tend to have reduced performance on several tasks involving working memory, attention and executive control. In addition, researchers argue for the effectiveness of training of these same cognitive skills as a way to ameliorate children’s EF skills as well as scholastic outcomes. To investigate possible training effects and to study the impact of SES on scholastic achievement in Brazilian children, we trained 61 children for 5-7 weeks and compared their performance with that of 60 age-matched peers on measures of executive functions and reading. Our results demonstrate a general effect of SES for the dependent variables. Furthermore, our findings demonstrate a positive near transfer effect on a working memory and a selective attention test and a far transfer effect on the words and pseudowords reading measure.

Pulvino-cortical interaction: an integrative role in the control of attention

Selective attention is a fundamental cognitive function that guides behavior by selecting and prioritizing salient or relevant sensory information of our environment. Despite early evidence and theoretical proposal pointing to an implication of thalamic control in attention, most studies in the past two decades focused on cortical substrates, largely ignoring the contribution of subcortical regions as well as cortico-subcortical interactions. Here, we suggest a key role of the pulvinar in the selection of salient and relevant information via its involvement in priority maps computation. Prioritization may be achieved through a pulvinar- mediated generation of alpha oscillations, which may then modulate neuronal gain in thalamo-cortical circuits. Such mechanism might orchestrate the synchrony of cortico-cortical interaction, by rendering neural communication more effective, precise and selective. We propose that this theoretical framework will support a timely shift from the prevailing cortico- centric view of cognition to a more integrative perspective of thalamic contributions to attention and executive control processes.

The Correlation of Sorted Scores Rule

The worst performance rule (WPR) claims that subjects’ worst performance on multi-trial tasks, e.g. in reaction time, is more predictive of their general intelligence than better performances. A common interpretation of the WPR has been that it occurs because poor performances reflect momentary lapses in attention and executive control, which occur more frequently in individuals with low IQ. However, the present simulation study indicates that WPR like phenomena may arise whenever certain statistical relations between the intra-individual variance of multiple test scores and other measures of interest are present. Specifically, we propose that the WPR is a special case of a more general correlation of sorted scores rule (CSSR). According to the CSSR, a WPR (i.e. a negative correlation between the test score percentile of sorted scores, e.g. in reaction time, and the test score × construct (e.g. g) correlation), will be seen if the intra-individual variance on the tests has a negative correlation with the construct. However, if the latter correlation is positive, the CSSR predicts a positive association also between test score percentiles and test score × construct correlations, i.e. a “best performance rule”. A way to discriminate between a “true” WPR, which occurs independently of these statistical relations, and the CSSR is suggested.