Signature Of Consciousness Research Articles

The Arousal-Related "Central Thalamus" Stimulation Site Simultaneously Innervates Multiple High-Level Frontal and Parietal Areas.

In human and nonhuman primates, deep brain stimulation applied at or near the internal medullary lamina of the thalamus [a region referred to as "central thalamus," (CT)], but not at nearby thalamic sites, elicits major changes in the level of consciousness, even in some minimally conscious brain-damaged patients. The mechanisms behind these effects remain mysterious, as the connections of CT had not been specifically mapped in primates. In marmoset monkeys (Callithrix jacchus) of both sexes, we labeled the axons originating from each of the various CT neuronal populations and analyzed their arborization patterns in the cerebral cortex and striatum. We report that, together, these CT populations innervate an array of high-level frontal, posterior parietal, and cingulate cortical areas. Some populations simultaneously target the frontal, parietal, and cingulate cortices, while others predominantly target the dorsal striatum. Our data indicate that CT stimulation can simultaneously engage a heterogeneous set of projection systems that, together, target the key nodes of the attention, executive control, and working-memory networks of the brain. Increased functional connectivity in these networks has been previously described as a signature of consciousness.SIGNIFICANCE STATEMENT In human and nonhuman primates, deep brain stimulation at a specific site near the internal medullary lamina of the thalamus ["central thalamus," (CT)] had been shown to restore arousal and awareness in anesthetized animals, as well as in some brain-damaged patients. The mechanisms behind these effects remain mysterious, as CT connections remain poorly defined in primates. In marmoset monkeys, we mapped with sensitive axon-labeling methods the pathways originated from CT. Our data indicate that stimulation applied in CT can simultaneously engage a heterogeneous set of projection systems that, together, target several key nodes of the attention, executive control, and working-memory networks of the brain. Increased functional connectivity in these networks has been previously described as a signature of consciousness.

An academic survey on theoretical foundations, common assumptions and the current state of consciousness science.

We report the results of an academic survey into the theoretical and methodological foundations, common assumptions, and the current state of the field of consciousness research. The survey consisted of 22 questions and was distributed on two different occasions of the annual meeting of the Association of the Scientific Study of Consciousness (2018 and 2019). We examined responses from 166 consciousness researchers with different backgrounds (e.g. philosophy, neuroscience, psychology, and computer science) and at various stages of their careers (e.g. junior/senior faculty and graduate/undergraduate students). The results reveal that there remains considerable discussion and debate between the surveyed researchers about the definition of consciousness and the way it should be studied. To highlight a few observations, a majority of respondents believe that machines could have consciousness, that consciousness is a gradual phenomenon in the animal kingdom, and that unconscious processing is extensive, encompassing both low-level and high-level cognitive functions. Further, we show which theories of consciousness are currently considered most promising by respondents and how supposedly different theories cluster together, which dependent measures are considered best to index the presence or absence of consciousness, and which neural measures are thought to be the most likely signatures of consciousness. These findings provide us with a snapshot of the current views of researchers in the field and may therefore help prioritize research and theoretical approaches to foster progress.

Temporal irreversibility of neural dynamics as a signature of consciousness.

Dissipative systems evolve in the preferred temporal direction indicated by the thermodynamic arrow of time. The fundamental nature of this temporal asymmetry led us to hypothesize its presence in the neural activity evoked by conscious perception of the physical world, and thus its covariance with the level of conscious awareness. We implemented a data-driven deep learning framework to decode the temporal inversion of electrocorticography signals acquired from non-human primates. Brain activity time series recorded during conscious wakefulness could be distinguished from their inverted counterparts with high accuracy, both using frequency and phase information. However, classification accuracy was reduced for data acquired during deep sleep and under ketamine-induced anesthesia; moreover, the predictions obtained from multiple independent neural networks were less consistent for sleep and anesthesia than for conscious wakefulness. Finally, the analysis of feature importance scores highlighted transitions between slow ($\approx$20Hz) and fast frequencies (>40Hz) as the main contributors to the temporal asymmetry observed during conscious wakefulness. Our results show that a preferred temporal direction is manifest in the neural activity evoked by conscious mentation and in the phenomenology of the passage of time, establishing common ground to tackle the relationship between brain and subjective experience.

Signature of consciousness in brain-wide synchronization patterns of monkey and human fMRI signals

During the sleep-wake cycle, the brain undergoes profound dynamical changes, which manifest subjectively as transitions between conscious experience and unconsciousness. Yet, neurophysiological signatures that can objectively distinguish different consciousness states based are scarce. Here, we show that differences in the level of brain-wide signals can reliably distinguish different stages of sleep and anesthesia from the awake state in human and monkey fMRI resting state data. Moreover, a whole-brain computational model can faithfully reproduce changes in global synchronization and other metrics such as functional connectivity, structure-function relationship, integration and segregation across vigilance states. We demonstrate that the awake brain is close to a Hopf bifurcation, which naturally coincides with the emergence of globally correlated fMRI signals. Furthermore, simulating lesions of individual brain areas highlights the importance of connectivity hubs in the posterior brain and subcortical nuclei for maintaining the model in the awake state, as predicted by graph-theoretical analyses of structural data.

Cognitive Psychology of Activity: Attention as a Constructive Process

The problem of consciousness is one of the core problems in the contemporary cogni-tive science. Driven by the neuroimaging boom, most researchers look for the neural correlates or signatures of consciousness and awareness in the human brain. However, we believe that the explanatory potential of the cultural-historical activity approach to this problem is far from being exhausted. We propose Cognitive Psychology of Activity research program, or the activity theory-based constructivism as an attempt to account for multiple phenomena of human awareness and attention. This approach relies upon cultural-historical psychology and the concept of mediation by Lev S. Vygotsky, activity theory and the concept of image generation by Alexey N. Leontiev, the physiology of ac-tivity and the metaphor of movement construction by Nikolai A. Bernstein, transferred to the psychology of perception as image construction by a number of Russian researchers in 1960-es, and the understanding of attention as action by evolutionary cognitive psy-chologists of 1980-es. The central concept of our approach is a concept of task, defined by Leontiev as “a goal assigned in specific circumstances”. The goal determines choice and use of available cultural means (“mediators”) consistent with the circumstances or conditions of task performance, which in turn provide for the construction of processing units allowing for more successful (“attentive”) performance and for the awareness of visual stimuli which could otherwise be missed or ignored. The perceptual task accom-plishment is controlled at several levels organized heterarchically, with possible strategic reorganizations of this system demonstrating the constructive nature of human cognition.

The Conscious Infant

A new study finds a possible brain signature of consciousness in infants as young as five months

In Search of a Neuronal Signature of Consciousness – Facts, Hypotheses and Proposals

Evolution leads to more and more complex structures, e.g., molecules, cells and organisms. By means of such structures elementary dynamic bio-electrical fields originate in single cells. They further develop into neurons with neuronal fields, and these combine and integrate in brains into global neuro-electrical fields (NEF) as a medium for the fast representation of outer stimuli. The present hypothesis proposes a specific state of the global NEF in brains as the signature of consciousness. This NEF changes periodically between two states, a de- and a hyperpolarized brain state, and these in turn are paralleled intimately by transitions between consciousness and unconsciousness. In the hyperpolarized state the elementary neuronal fields are ‘enslaved’ and synchronized by strong oscillations, and under these conditions the NEF is of low information capacity. In the depolarized state, however, the elementary fields are freed to self-organize and superimpose into an integrated NEF rich in information. In this condition the NEF acquires a qualitatively new state variable: consciousness. This new variable is no longer physically measurable; it can only be perceived by introspection.