Neuroscience of Consciousness最新文献

Evidence from temporal regularities in perception, temporal phenomenology, and neural dynamics indicate that our awareness evolves and devolves over several timescales. However, most theories of consciousness posit a single timescale of processing at the end of which a percept is rendered conscious. To show evidence for multiple timescales, we utilized continuous flash suppression (CFS). Based on a hierarchical framework of temporal phenomenology, we reasoned that different flicker rates (1, 4, 10, and 25 Hz) of the suppressor should be able to perturb phenomenologically distinct tasks. We designed four experiments that used different perceptual tasks (N = 48). The results showed that entry of contents into conscious awareness, their attentional sampling, perceptual grouping, and exiting from awareness were all maximally perturbed at distinct flicker frequencies of the suppressor in a CFS paradigm. Our demonstration shows that different flicker frequencies perturb different phenomenological aspects of awareness, and these flicker frequencies systematically map onto temporal hierarchies of timing of awareness.

Our subjective experience of the sensory information is rich and complex. Yet, typical cognitive and perception psychology paradigms reduce it to a few predefined discrete categories, like yes/no answers or the Likert scales. In the current study, we examined the complexity of subjective visual experience during binocular rivalry, a major experimental paradigm used to study conscious visual perception and its neural mechanisms. Binocular rivalry occurs when the two eyes are presented with two different images that cannot be fused into a uniform percept. As a result, the conscious perception alternates between the two images with brief transition phases in between. Fifty-two subjects viewed binocular rivalry produced by pairs of stimuli with different visual information (images, orthogonal gratings, or moving dots). After each rivalry period, they indicated how many different transition types they perceived and described their perception of each transition type. Using content analysis, we identified 20 unique categories over all subjects, sessions, and stimuli. On average, participants reported 2-3 unique transition categories for each visual stimulus combination. The categories were consistent for each observer over time but varied across participants and stimulus content. Our results show that perceptual transitions during binocular rivalry appear in different forms and depend on the specific visual stimulus content that induces rivalry. Our findings have implications for neuroimaging studies of binocular rivalry, which may yield different results depending on the exact experience of transitions. They also demonstrate how the complexity of subjective visual experience may be underestimated in traditional perception paradigms.

Background: Human predictive capacity underlies its adaptive strength but also the potential for existential terror. Grounded in the predictive processing framework of brain function, we recently showed using a magnetoencephalogram visual mismatch-response (vMMR) paradigm that prediction-based self-specific neural mechanisms shield the self from existential threat-at the level of perception-by attributing death to the 'other' (nonself). Here we test the preregistered hypothesis that insight meditation grounded on mindful awareness is associated with a reduction in the brain's defensiveness toward mortality. In addition, we examine whether these neurophysiological markers of death-denial are associated with the phenomenology of meditative self-dissolution (embodied training in impermanence).

Methods: Thirty-eight meditators pooled from a previous project investigating self-dissolution neurophenomenology underwent the vMMR task, as well as self-report measures of mental health, and afterlife beliefs. Results were associated with the previously-reported phenomenological dimensions of self-dissolution.

Results: Meditators' brains responded to the coupling of death and self-stimuli in a manner indicating acceptance rather than denial, corresponding to increased self-reported well-being. Additionally, degree of death acceptance predicted positively valenced meditation-induced self-dissolution experiences, thus shedding light on possible mechanisms underlying wholesome vs. pathological disruptions to self-consciousness.

Conclusions: The findings provide empirical support for the hypothesis that the neural mechanisms underlying the human tendency to avoid death are not hard-wired but are amenable to mental training, one which is linked with meditating on the experience of the embodied self's impermanence. The results also highlight the importance of assessing and addressing mortality concerns when implementing psychopharmacological or contemplative interventions with the potential of inducing radical disruptions to self-consciousness.

Dissociations in types of memory tasks emerge when comparing feeling-of-knowing (FOK) judgments, predictions of upcoming performance, and retrospective confidence. This pattern has been used to construct theories of metacognitive access to memory, particularly in memory-impaired groups. In particular, older adults' metacognitive sensitivity appears to vary between episodic (impaired) and semantic (intact) memory. However, this could be explained by the limitations of metacognitive measures and/or memory differences. We aimed to test these dissociations of metacognition with aging by comparing metacognitive efficiency in episodic and semantic tasks using two types of judgment: retrospective confidence judgments (RCJs) and FOK judgments. Metacognitive efficiency was estimated in 240 participants aged 19-79 years using a hierarchical Bayesian framework. Results showed that metacognitive efficiency for RCJs declined with age in the semantic task, even though task performance increased with age, while metacognitive efficiency was stable in the episodic task. Surprisingly, metacognitive efficiency was very low (although significantly higher than zero) for both FOK tasks regardless of age compared to similar previous studies. We suggested this might be due to the online testing. These results point to metacognition being multifaceted and varying according to judgment, domains, and populations.

How is it that psychedelics so profoundly impact brain and mind? According to the model of "Relaxed Beliefs Under Psychedelics" (REBUS), 5-HT2a agonism is thought to help relax prior expectations, thus making room for new perspectives and patterns. Here, we introduce an alternative (but largely compatible) perspective, proposing that REBUS effects may primarily correspond to a particular (but potentially pivotal) regime of very high levels of 5-HT2a receptor agonism. Depending on both a variety of contextual factors and the specific neural systems being considered, we suggest opposite effects may also occur in which synchronous neural activity becomes more powerful, with accompanying "Strengthened Beliefs Under Psychedelics" (SEBUS) effects. Such SEBUS effects are consistent with the enhanced meaning-making observed in psychedelic therapy (e.g. psychological insight and the noetic quality of mystical experiences), with the imposition of prior expectations on perception (e.g. hallucinations and pareidolia), and with the delusional thinking that sometimes occurs during psychedelic experiences (e.g. apophenia, paranoia, engendering of inaccurate interpretations of events, and potentially false memories). With "Altered Beliefs Under Psychedelics" (ALBUS), we propose that the manifestation of SEBUS vs. REBUS effects may vary across the dose-response curve of 5-HT2a signaling. While we explore a diverse range of sometimes complex models, our basic idea is fundamentally simple: psychedelic experiences can be understood as kinds of waking dream states of varying degrees of lucidity, with similar underlying mechanisms. We further demonstrate the utility of ALBUS by providing neurophenomenological models of psychedelics focusing on mechanisms of conscious perceptual synthesis, dreaming, and episodic memory and mental simulation.

Consciously perceived emotional relative to neutral facial expressions evoke stronger early and late event-related potential (ERP) components. However, the extent of nonconscious neural processing of emotional information in faces is still a matter of debate. One possible reason for conflicting findings might relate to threshold effects depending on the sensory strength of stimuli. In the current study, we investigated this issue by manipulating the contrast of fearful and neutral faces presented with or without continuous flash suppression (CFS). Low, medium, and high contrasts were calibrated individually so that faces were consciously perceived at all contrast levels if presented without CFS. With CFS, however, low- and medium-contrast faces remained nonconscious, while high-contrast faces broke the suppression. Without CFS, ERPs showed an increased early negativity and late positivity in response to fearful vs. neutral faces regardless of contrast. Under CFS, we observed differential early negativities for suppression-breaking high-contrast fearful vs. neutral faces. For nonconscious faces, however, the contrast level modulated the difference between fearful and neutral faces, showing enhanced early negativities only at medium contrast and an inverted effect at low contrast. Additional analysis of late positivities provided evidence for the absence of an effect at low and medium contrast, while at high-contrast, fearful faces elicited a larger positivity than neutral ones. Taken together, our findings demonstrate the significance of stimulus strength for nonconscious emotion processing under CFS, implying that early negative ERP differences between neutral and fearful faces depend on stimulus contrast near the detection threshold.

This paper explores the relationship between intuition and flow from a neurodynamics perspective. Flow and intuition represent two cognitive phenomena rooted in nonconscious information processing; however, there are clear differences in both their phenomenal characteristics and, more broadly, their contribution to action and cognition. We propose, extrapolating from dual processing theory, that intuition serves as a rapid, nonconscious decision-making process, while flow facilitates this process in action, achieving optimal cognitive control and performance without [conscious] deliberation. By exploring these points of convergence between flow and intuition, we also attempt to reconcile the apparent paradox of the presence of enhanced intuition in flow, which is also a state of heightened cognitive control. To do so, we utilize a revised dual-processing framework, which allows us to productively align and differentiate flow and intuition (including intuition in flow). Furthermore, we draw on recent work examining flow from an active inference perspective. Our account not only heightens understanding of human cognition and consciousness, but also raises new questions for future research, aiming to deepen our comprehension of how flow and intuition can be harnessed to elevate human performance and wellbeing.

We apply the methodology of no-go theorems as developed in physics to the question of artificial consciousness. The result is a no-go theorem which shows that under a general assumption, called dynamical relevance, Artificial Intelligence (AI) systems that run on contemporary computer chips cannot be conscious. Consciousness is dynamically relevant, simply put, if, according to a theory of consciousness, it is relevant for the temporal evolution of a system's states. The no-go theorem rests on facts about semiconductor development: that AI systems run on central processing units, graphics processing units, tensor processing units, or other processors which have been designed and verified to adhere to computational dynamics that systematically preclude or suppress deviations. Whether our result resolves the question of AI consciousness on contemporary processors depends on the truth of the theorem's main assumption, dynamical relevance, which this paper does not establish.

This paper explores the limitations of neurobiological approaches to human emotional experience, focusing on the case of grief. We propose that grief is neither an episodic emotion nor a longer-term mood but instead a heterogeneous, temporally extended process. A grief process can incorporate all manner of experiences, thoughts, and activities, most or all of which are not grief-specific. Furthermore, its course over time is shaped in various different ways by interpersonal, social, and cultural environments. This poses methodological challenges for any attempt to relate grief to the brain. Grief also illustrates wider limitations of approaches that conceive of emotions as brief episodes, abstracted from the dynamic, holistic, longer-term organization of human emotional life.

Despite the dramatic rise of surveillance in our societies, only limited research has examined its effects on humans. While most research has focused on voluntary behaviour, no study has examined the effects of surveillance on more fundamental and automatic aspects of human perceptual awareness and cognition. Here, we show that being watched on CCTV markedly impacts a hardwired and involuntary function of human sensory perception-the ability to consciously detect faces. Using the method of continuous flash suppression (CFS), we show that when people are surveilled (N = 24), they are quicker than controls (N = 30) to detect faces. An independent control experiment (N = 42) ruled out an explanation based on demand characteristics and social desirability biases. These findings show that being watched impacts not only consciously controlled behaviours but also unconscious, involuntary visual processing. Our results have implications concerning the impacts of surveillance on basic human cognition as well as public mental health.