The Neural Correlates of Access Consciousness and Phenomenal Consciousness Seem to Coincide and Would Correspond to a Memory Center, an Activation Center and Eight Parallel Convergence Centers

A global workspace model for phenomenal and access consciousness

<i>Human and Animal Minds: The Consciousness Questions Laid to Rest</i>

自传体记忆作为一个复杂的，涉及众多因素的长时记忆成分，具有独特的记忆结构；相应地，自传体记忆的神经机制也包括了众多脑区。基于自传体记忆的复杂性，本文总结了先前对于自传体记忆及其神经机制的研究，从记忆系统的角度对自传体记忆包含的认知加工成分及相应的神经机制进行了归纳总结，并就各认知加工成分间的相互联系和相互作用进行了详尽的分析；同时分析了目前自传体记忆神经机制研究存在的一些局限性，包括偏重强调实验条件间差异性而对不同认知加工成分脑机制间的相互联系分析不足，只关注脑区激活的空间定位而忽视时间维度的差异信息等。最后本文提出在将来的研究中需要更多地从系统的观点出发，重视认知加工成分间的相互联系，引入多体素分析和时间序列分析以便能为自传体记忆神经机制研究提供更深入的证据。 Autobiographical memory, with special inherent structure, is a complex component of long-term memory. It has a close relationship with semantic memory and episodic memory and is also connected with many other psychological cognitive processes, such as the emotional process, self-referential process etc. Accordingly, the neural correlates of autobiographical memory consist of many brain areas, including the frontal lobe, temporal lobe, superior parietal lobe and the adjacent occipital area etc. All of the brain areas mentioned above are mainly on the left hemisphere. This article summarizes the previous researches on autobiographical memory and its neural correlates. Given the complexity of autobiographical memory, we divide different cognitive processes of autobiographical memory into 5 operating components from the perspective of memory-system. These operating components include semantic component, episodic component, self-referential component, emotional component and general cognitive processing component (cognitive process related to general memory retrieval), and each component has its underlying neural correlates. What is more important, these operating components interact with each other coherently within the autobiographical memory system and this article discusses these interactions and connections in depth. These interactions analyzed in this article includes the semantic & episodic interaction, the self-referential processing & general cognitive processing interaction, the emotional & episodic interaction, the general cognitive processing & episodic interaction and the general cognitive processing & emotional interaction. By taking the interactions among the operating components into consideration, different ideas and opinions to integrate the experiment findings are offered, and new ways and solutions to settle some heating debates in the field of autobiographical memory are proposed. Furthermore, this article points out that even though the operating components of autobiographical memory system are closely connected with one another, the previous researches didn’t pay enough attention to it. This article analyzes two problems existing in the previous studies. First, most of the previous researches spent much effort in analyzing the different activated brain areas among different experiment tasks, while leaving the common brain activation alone, which might reflect the interaction and connection among the operating components. Second, those studies investigating neural correlates of autobiographical memory using brain imaging techniques tended to overlook the different brain activations at different time points, and these temporal differences may carry important information about the neural mechanism of autobiographical memory. Finally, the article proposes two analytical methods in order to solve the problems mentioned above to some extent. First is using multi-voxel analysis instead of the conventional analysis method to reveal the useful information held by the common activated brain areas, second is employing time series analysis to analyze the changes of brain activation pattern in the temporal dimension. In sum, if researchers are going to investigate the neural mechanism of autobiographical memory thoroughly and offered more convincing evidence, they should treat the various cognitive processes of autobiographical memory as a whole, take the interactions among different components into consideration and pay more attention to the neural correlates underlying these interactions.

Although deficits in learning and retrieving new information are well characterized in dementia with Lewy bodies, autobiographical memory has never been explored in this disease. Yet, autobiographical memory impairments are a pervasive feature of dementia, well characterized in other neurodegenerative diseases. Moreover, autobiographical memory corresponds to an extension over time of the self, which we hypothesize is altered in dementia with Lewy bodies and impairment of which could be linked to the insular atrophy occurring from an early stage of the disease. In this study, we sought to characterize autobiographical memory impairments and explore their neural correlates in dementia with Lewy bodies, on the assumption that insular damage could impact the self, including its most elaborate components, such as autobiographical memory. Twenty patients with prodromal to mild dementia with Lewy bodies were selected to participate in this exploratory study along with 20 healthy control subjects. The Autobiographical Interview was used to assess autobiographical memory. Performances were compared between patients and control subjects, and an analysis across life periods and recall conditions was performed. 3D magnetic resonance images were acquired for all participants, and correlational analyses were performed in the patient group using voxel-based morphometry. The behavioural results of the Autobiographical Interview showed that autobiographical memory performances were significantly impaired in dementia with Lewy body patients compared to control subjects in a temporally ungraded manner, for both the free recall and the specific probe conditions (P < 0.0001), though with greater improvement after probing in the patient group. Furthermore, autobiographical memory impairments were correlated with grey matter volume within right insular cortex, temporoparietal junction, precuneus, putamen, left temporal cortex, bilateral parahippocampus and cerebellum, using a threshold of P = 0.005 uncorrected. The behavioural results confirm the existence of temporally ungraded autobiographical memory impairments in dementia with Lewy bodies, from the early stage of the disease. As we expected, neuroimaging analysis revealed a role for the insula and the precuneus in autobiographical memory retrieval, two regions associated with elementary aspects of the self, among other brain regions classically associated with autobiographical memory, such as medial temporal lobe and temporoparietal junction. Our findings provide important insights regarding the involvement of the insula in the self and suggest that insular damage could lead to a global collapse of the self, including its more elaborated components, such as autobiographical memory.

Despite that leading theories of consciousness make diverging predictions for where and how neural activity gives rise to subjective experience, they all seem to partially agree that the neural correlates of consciousness (NCC) require globally integrated brain activity across a network of functionally specialized modules. However, it is not clear yet whether such functional configurations would be able to identify the NCC. We scanned resting-state fMRI data from 21 subjects during wakefulness, propofol-induced sedation, and anesthesia. Graph-theoretical analyses were conducted on awake fMRI data to search for the NCC candidates as brain regions that exhibit both high rich-clubness and high modular variability, which were found to locate in prefrontal and temporoparietal cortices. Another independent data set of 10 highly-sampled subjects was used to validate the NCC distribution at the individual level. Brain module-based dynamic analysis revealed two discrete reoccurring brain states, one of which was dominated by the NCC candidates (state 1), while the other state was predominately composed of primary sensory/motor regions (state 2). Moreover, state 1 appeared to be temporally more stable than state 2, suggesting that the identified NCC members could sustain conscious content as metastable network representations. Finally, we showed that the identified NCC was modulated in terms of functional connectedness and modular variability in response to the loss of consciousness induced by propofol anesthesia. This work offers a framework to search for neural correlates of consciousness by charting the brain network topology and provides new insights into understanding the roles of different regions in underpinning human consciousness.

The distinction between phenomenal and access consciousness is central to debates about consciousness and its neural correlates. However, this distinction has often been limited to the domain of perceptual (visual) experiences. On the basis of dream phenomenology and neuroscientific findings this paper suggests a theoretical framework which extends this distinction to dreaming, also in terms of plausible neural correlates. In this framework, phenomenal consciousness is involved in both waking perception and dreaming, whereas access consciousness is weakened, but not fully eliminated, during dreaming. However, access consciousness is more active during lucid dreaming. The proposed framework accounts for different aspects of dream phenomenology, including levels of integration of perceptual, cognitive and affective features in dreams, bizarreness, dream amnesia and the occurrence of meta-awareness and accessibility in lucid dreaming. Self-related experiences and their neural substrates are suggested to be differently involved in waking cognition and dreaming. Further, phenomenal consciousness during both waking and dream experiences involve widespread recurrent interactions and convergence-divergence zones in the thalamo-cortico-limbic system, activated before conscious access in global workspace areas. Finally, we discuss the relationships of the proposed framework with other neurocognitive theories and models of consciousness and major theories of dreaming, and propose novel experimental predictions.

Autobiographical memory relies on complex interactions between episodic memory contents, associated emotions and a sense of self-continuity along the time axis of one's life history. The neural correlates underlying autobiographical memory are known to primarily comprise areas of prefrontal cortex, medial and lateral temporal cortex, as well as posterior cingulate and retrosplenial cortex. By contrast, the effect of encoding and/or storage parameters such as the emotional tone of the memories retrieved or the length of the time-interval between the initial encoding of information and retrieval remains to be clarified. Using blocked design functional MRI and statistical parametric mapping, we investigated the impact of remoteness (factor 1: recent, remote) and emotional valence (factor 2: positive, negative) on the neural correlates of autobiographical memory retrieval. Changes in neural activity (P < 0.05, corrected) related to autobiographical memory retrieval (irrespective of remoteness and emotional tone) relative to baseline were observed bilaterally in medial and lateral temporal, temporal-occipital, posterior cingulate and frontal cortices. Recent (relative to remote) memories were associated with differentially increased neural activity bilaterally in the retrosplenial cortex and the hippocampal region, whereas remote (relative to recent) memories did not show any statistically significant differential neural activations. Positive (relative to negative) memories bilaterally activated the orbitofrontal cortex, the temporal pole, as well as medial temporal areas, with the activation peak being in the entorhinal region. By contrast, negative (relative to positive) memories differentially increased neural activity in the right middle temporal gyrus only. The data suggest differential functional roles for temporal, prefrontal and retrosplenial regions during autobiographical memory retrieval depending on the remoteness and the emotional valence of the memories retrieved. In particular, our findings support the 'classic' model of long-term memory processing, which suggests a time-limited differential involvement of the hippocampus in memory consolidation. Interestingly, the observation of such a time-dependent involvement of the hippocampal region in memory consolidation corresponds to the course of retrograde amnesia observed in demented patients, with the loss of recent memories appearing during early stages of the disease when conspicuous neurofibrillary changes are restricted mainly to the hippocampal and parahippocampal regions. Only during later stages, as the neurofibrillary changes spread out to neocortical association areas, do remote memories also become impaired. We conclude that the brain regions involved in autobiographical memory retrieval are influenced by the triggered memories' emotional significance and their relationship to the individual time axis.

Humans have conscious experiences of the events in their environment. Previous research from electroencephalography (EEG) has shown visual awareness negativity (VAN) at about 200 ms to be a neural correlate of consciousness (NCC). However, when considering VAN as an NCC, it is important to explore which particular experiences are associated with VAN. Recent research proposes that VAN is an NCC of lower-level experiences (detection) rather than higher-level experiences (identification). However, previous results are mixed and have several limitations. In the present study, the stimulus was a ring with a Gabor patch tilting either left or right. On each trial, subjects rated their awareness on a three-level perceptual awareness scale that captured both detection (something vs. nothing) and identification (identification vs. something). Separate staircases were used to adjust stimulus opacity to the detection threshold and the identification threshold. Bayesian linear mixed models provided extreme evidence (BF10 = 131) that VAN was stronger at the detection threshold than at the identification threshold. Mean VAN decreased from -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}2.12 microV [-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}2.86, -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}1.42] at detection to -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}0.46 microV [-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}0.79, -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}0.11] at identification. These results strongly support the claim that VAN is an NCC of lower-level experiences of seeing something rather than of higher-level experiences of specific properties of the stimuli. Thus, results are consistent with recurrent processing theory in that phenomenal visual consciousness is reflected by VAN. Further, results emphasize that it is important to consider the level of experience when searching for NCC.

1. Acknowledgments 2. The constitution of visual and phenomenal consciousness: An introduction (by Miller, Steven M.) 3. The scientific study of consciousness 4. Theories and methods in the scientific study of consciousness (by Klink, P. Christiaan) 5. The scientific study of coma and related states (by Charland-Verville, Vanessa) 6. De-confounding the neural constitution of phenomenal consciousness from attention, report and memory (by Boxtel, Jeroen J.A. van) 7. The correlation/constitution distinction problem: Foundations, limits and explanation in consciousness science (by Miller, Steven M.) 8. The neural correlates of consciousness: Causes, confounds and constituents (by Hohwy, Jakob) 9. On the various neural correlates of consciousness: Are they distinguishable? (by Graaf, Tom A. de) 10. On why the unconscious prerequisites and consequences of consciousness might derail us from unraveling the neural correlates of consciousness (by Aru, Jaan) 11. The neuroevolutionary sources of mind: The ancestral constitution of affective consciousness and the core-SELF (by Panksepp, Jaak) 12. The future of consciousness science: From empirical correlations to theoretical explanation (by Revonsuo, Antti) 13. Philosophy of mind 14. The philosophy of phenomenal consciousness: An introduction (by Drayson, Zoe) 15. The philosophy of mind needs a better metaphysics (by Mahner, Martin) 16. The scientific evidence for materialism about pains (by Melnyk, Andrew) 17. The status of consciousness in nature (by Brogaard, Berit) 18. Identity over time, constitution and the problem of personal identity (by Curtis, Benjamin L.) 19. Constitution, realization and identity: Empirical implications for three theories of the metaphysics of consciousness (by Keaton, Douglas) 20. Correlation, causation, constitution: On the interplay between the science and philosophy of consciousness (by Kozuch, Benjamin P.) 21. The material constitution of phenomenal consciousness (by Pereboom, Derk) 22. Material constitution, the neuroscience of consciousness, and the temporality of experience (by Curtis, Benjamin L.) 23. The structure of phenomenal consciousness (by Opie, Jonathan P.) 24. Index

It has been shown that three-dimensional self-assembled multicellular structures derived from human pluripotent stem cells show electrical activity similar to EEG. More recently, neurons were successfully embedded in digital game worlds. The biologically inspired neural network (BNN), expressing human cortical cells, was able to show internal modification and learn the task at hand (predicting the trajectory of a digital ball while moving a digital paddle). In other words, the system allowed to read motor information and write sensory data into cell cultures. In this article, we discuss Neural Correlates of Consciousness (NCC) theories, and their capacity to predict or even allow for consciousness in a BNN. We found that Information Integration Theory (IIT) is the only NCC that offers the possibility for a BNN to show consciousness, since the Φ value in the BNN is >0. In other words, the recording of real-time neural activity responding to environmental stimuli. IIT argues that any system capable of integrating information will have some degree of phenomenal consciousness. We argue that the pattern of activity appearing in the BNN, with increased density of sensory information leading to better performance, implies that the BNN could be conscious. This may have profound implications from a psychological, philosophical, and ethical perspective.

In the present communication, phenomenal consciousness, access consciousness and the closely related concept of working memory are presented in the context of a neurocognitive model-the REF (reorganization of elementary functions) framework. The REF framework is based on connectionist networks within which the 'units' are advanced processing modules called elementary functions (EFs). In this framework, the focus is on dynamically changeable 'strategies'-based on reorganizations of the connectivity between EFs-rather than on the more traditional 'cognitive functions'. The background for the REF framework and especially how the neural correlate of consciousness is understood within these models is summarized. According to the REF framework, phenomenal consciousness cannot 'overflow' availability of information for action. Phenomenal consciousness may, however, overflow working memory because working memory in the present context is seen as a surface phenomenon reflecting underlying dynamic strategies-influenced by both experience and situational factors.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

In the last decades, the neural correlates of consciousness (NCCs) have been explored using both invasive and non-invasive recordings by comparing the brain activity elicited by seen versus unseen visual stimuli (i.e., the contrastive analysis). Here, we review a selection of these studies and discuss a set of considerations to improve the search for the NCCs using the contrastive analysis. In particular, we first argue in favor of implementing paradigms where different perceptual outputs are obtained using identical visual inputs. Second, we propose that the large disagreement in the field -in terms of the dissimilar neural patterns proposed as NCCs- is partially explained by the fact that different studies report the neural correlates of different conscious processes in the brain. More specifically, we distinguish between the perceptual awareness of a visual stimulus, associated to a boost in object-selective neural assemblies, and a more elaborate process (contextual awareness) that we argue is reflected in the firing of concept neurons in the medial temporal lobe, triggering a rich representation of the context, associations, and memories linked to the specific stimulus.

Phenomenal consciousness, what it is like to have or undergo an experience, is typically understood as an empirical item – an actual or possible object of consciousness. Accordingly, the problem posed by phenomenal consciousness for materialist accounts of the mind is usually understood as an empirical problem: a problem of showing how one sort of empirical item – a conscious state – is produced or constituted by another – a neural process. The development of this problem, therefore, has usually consisted in the articulation of an intuition: no matter how much we know about the brain, this will not allow us to see how it produces or constitutes phenomenal consciousness. Developing a theme first explored by Kant, and then later by Sartre, this paper argues that the real problem posed by phenomenal consciousness is quite different. Consciousness, it will be argued, is not an empirical but a transcendental feature of the world. That is, what it is like to have an experience is not something of which we are aware in the having of that experience, but an item in virtue of which the genuine (non-phenomenal) objects of our consciousness are revealed as being the way they are. Phenomenal consciousness, that is, is not an empirical object of awareness but a transcendental condition of the possibility of there being empirical objects of awareness.

Neural correlates of autobiographical memory retrieval: An SDM neuroimaging meta-analysis

Memory Strength and Repetition Suppression: Multimodal Imaging of Medial Temporal Cortical Contributions to Recognition