Neuroscience of Consciousness最新文献

A key question in consciousness studies is what is distinct about a conscious as opposed to a sub-conscious percept. The experiments presented here provide evidence for the hypothesis that only conscious percepts enable the formation of episodic memories. We do this by assessing proactive interference (PI) in rapid serial visual presentation (RSVP) streams. Specifically, in a post-stream recognition memory test, we quantify memory for items presented in the RSVP stream close in time to the memory test. PI is demonstrated if performance on long RSVP streams is worse than on short streams, where long streams have many more items presented before the item probed in the recognition memory test. We demonstrate PI on reaction times for slow streams [stimulus onset asynchrony (SOA) 350 ms], but not for fast streams (SOA 83 or 100 ms). We investigate the implications of this reaction time difference by fitting drift diffusion models. The failure to see PI in fast streams raises the possibility that stimuli presented below the threshold of awareness are not episodically encoded.

Disruption of conscious access contributes to the advent of psychotic symptoms in schizophrenia and could also explain lack of insight in other psychiatric disorders. In this study, we explored how insight and psychotic symptoms related to disruption of consciousness in obsessive-compulsive disorder (OCD) and schizophrenia, respectively. Patients with schizophrenia, and patients with OCD with good versus poor insight and matched controls underwent clinical assessments and performed a visual masking task. We used a principal component analysis to reduce symptom dimensionality. We found that clinical dimensions could be isolated by principal components that correlated with consciousness measures. More specifically, positive symptoms were associated with impaired conscious access in patients with schizophrenia, whereas the level of insight delineated two subtypes of OCD patients, those with poor insight who had consciousness impairments similar to patients with schizophrenia, and those with good insight who resemble healthy controls. Our study provides new insights about consciousness disruption in psychiatric disorders, showing that it relates to positive symptoms in schizophrenia and with insight in OCD. In OCD, it revealed a distinct subgroup sharing neuropathological features with schizophrenia. Our findings refine the mapping between symptoms and cognition and confirm that consciousness disruption can be observed in various psychiatric disorders.

There is an ongoing debate about the extent to which faces are processed if they are not consciously perceived. In the present study, we used event-related potentials (ERPs) to investigate neural responses to faces and two types of control stimuli (monochrome color-matched ovals and Fourier phase-scrambled faces), which allowed us to dissociate low-level and high-level face processing. Based on a pre-registered sequential Bayesian sampling protocol, we recorded the electroencephalogram (EEG) from 40 participants and compared the average amplitude of early components of the ERP (P1, N170) between faces, scrambles, and blanks presented for 17 ms, while the mask followed directly or 200 ms after the target stimulus. Participants were asked to rate their subjective perception after each trial on a perceptual awareness scale, and only trials with the lowest rating in the masked condition were considered as subjectively nonconscious. Matching the pre-registered hypotheses, P1 amplitudes were higher for faces and scrambles compared to blanks but did not differ between faces and scrambles. This pattern was found for conscious and nonconscious faces, however, with smaller yet reliable differences in the latter case. In contrast, the N170 reliably differentiated between faces and both types of control stimuli (scrambles and blanks), again for conscious and, with attenuated differences, also for nonconscious faces. Findings support the hypothesis of two early stages of face processing, which are at least partially independent of consciousness awareness of stimuli. The P1 stage is associated with low-level processing, while the N170 reflects processing of face-related configural information.

A Ganzfeld is a homogeneous, unstructured visual field that is known to induce visual hallucinations. Aside from visual percepts emerging in participants' awareness, Ganzfeld viewing is characterized by decays of color and brightness. The studies dedicated to this topic from the 20^th century have focused on these decays, although they have been reported in a confusing way, with different terms for these decaying experiences. This paper synthesizes the current state of the Ganzfeld literature going back to the 1930s with the purpose of clarifying the terminology of the phenomena that have largely retained their mysterious aspects. We built a Ganzfeld space to study the phenomenology without the restricted feeling of a confined space that translucent Ganzfeld goggles cause. Employing a multi-method approach, we combined quantitative and qualitative measures to better grasp the number, kind and temporal dynamics of the experienced phenomena as well as their experiential characteristics. We offer more insight into the different kinds of visual percepts that emerge in participants' awareness, induced by the Ganzfeld, and we identified three distinct types of decays of color and brightness. Based on previously used terminology, we propose to employ the terms 'fade-out', 'black-out' and 'blank-out', and present both the prevalence as well as the qualitative characteristics of these decays. Finally, we shed some light onto the role of eye movements and blinks on the experienced phenomena. All of this is relevant groundwork to be able to study the dynamics of different Ganzfeld experiences, in relation to different states of consciousness and their neural correlates in future work.

Previous studies examining confidence in perceptual completion in vision showed that observers can be unaware of missing sensory information and be even more confident in perceptually completed stimuli than veridical stimuli. In the current study, we aimed to investigate if auditory filling-in mechanisms would result in similar confidence biases. In two separate experiments, participants listened to continuous (uninterrupted) or discontinuous (interrupted) tones that were accompanied by noise. We examined confidence for continuity-discontinuity decisions by collecting confidence ratings (Experiment 1) and forced-choice confidence judgments (Experiment 2). Participants reported the interrupted sounds with masking noise more as uninterrupted, showing auditory filling-in. Confidence ratings in the first experiment followed response consistency. Forced-choice confidence judgments in the second experiment showed that participants were not able to distinguish the filled-in stimulus from a continuous stimulus with similar masking noise. Most importantly, there was no clear preference for a veridical compared to a perceptually completed stimulus. These results, extending findings from the visual modality, are the first to demonstrate that listeners are unaware of auditory filling-in and trust filled-in information almost as much as veridical information in the auditory sense.

The integration of imagination with perception of reality is associated with numerous neurocognitive and biological adaptive functions. Given the overlap between neural processes and regions governing internally versus externally generated imagery, the interaction between these processual components of high-level vision has been studied for over a century, without yielding a satisfactory account. Opposite to traditional theories like the Perky effect or sensory boost, we hypothesized that voluntary conscious mental imagery of an object enhances the processing of unconscious incoming visual spatial information. Hence, aspects of internal imagery such as vividness or motion should drive such an interaction. We probed how subliminal spatial information might be influenced under imagery conditions. Using behavioural data, we show that imagery improves the unconscious concurrent perception of visual spatial information. This priming effect seems driven by the gradient of imagery vividness: both explicitly required by task demands and implicitly generated. We found that imagery can direct visual perception when the visual system is strongly biased towards predicting that an object is present. Because the observed results vary systematically with self-reported vividness, rather than being epiphenomenal, the subjective experience of vividness is a deterministic condition for imagery priming.

Exposure to rapid and bright stroboscopic light has long been reported to induce vivid visual hallucinations of colour and geometric formations. This phenomenon was first documented by Purkinje over 200 years ago. Since then, significant progress has been made in understanding the effects of stroboscopic light and the experiences it induces through multiple waves of interest from the scientific, therapeutic, and broader cultural communities. Despite these advances, fundamental questions remain unanswered, including comprehensive characterizations of its phenomenology, its precise physiological origins, under which conditions it may lead to altered states of consciousness phenomena, and potential clinical or therapeutic applications. This narrative review provides a historical summary of research into stroboscopic light stimulation (SLS) alongside its use in recreation and lay-therapeutic contexts. It also discusses the phenomenology of these experiences, current perspectives on the potential neural mechanisms of stroboscopically induced experiences, and provides an outlook for future research in this field.

Recent studies on brief scene perception have revealed that adults discriminate between what they see and do not see in a photograph with varying degrees of confidence. In this study, we attempt to extend previous studies by asking if these perceptual/cognitive abilities are already established in preschool and school-aged children. In Experiment 1 (n = 122) and 2 (n = 205, registered report), using an online experiment, we briefly presented a natural scene (267 ms in Experiment 1 and 133 ms in Experiment 2) to participants and, subsequently, asked them if a small patch was included in the original scene. Experiment 2 was a registered report. We tested various patch locations to probe "how much" the participants can see and report about it with graded levels of confidence. In Experiment 1, discriminative performance was nearly saturated (the area under the receiver operating characteristic curve (AUC)) = 0.9 across age groups) with no effects of ages, but metacognition slightly improved across ages (AUC = 0.74 in 5-6-year-olds to 0.79 in adults). In a critical registered report (Experiment 2), with reduced stimulus duration, we found a developmental effect (AUC = 0.73 in 5-6-year-olds to 0.91 in adults), and, again, metacognitive accuracy was constant across development (AUC = 0.73 in 5-6-year-olds to 0.75 in adults). Additionally, our analysis of semantic congruence between objects and scenes revealed age-related differences in performance. Contrary to our expectation, the size of the image modification strongly affected task performance, uniformly across ages. Overall, we conclude that 5-6-year-olds' perceptual and metacognitive abilities are much better than we expected when they were tested with briefly presented natural scenes, although their performances were generally lower than adults.

Historically, voluntary action and volition more generally have been investigated through the lens of meaningless decisions. Importantly, these findings have been used in the debate about key notions like free will and moral responsibility. However, more recent claims have challenged the possibility of generalizing findings from a meaningless context to a more meaningful one. The current study investigates the markers of volition, specifically comparing meaningful and meaningless decisions. In an effort to maximize their monetary gain, 50 participants repeatedly deliberated between two options, making either rewarded choices-hard-deliberation decisions (where the options differed along two dimensions) or easy-deliberation decisions (where the options differed along a single dimension)-or unrewarded choices, a.k.a. arbitrary decision. This enabled us to contrast rewarded and unrewarded decisions as well as the degree of deliberation between easy- and hard-deliberation choices. We found evidence that rewarded and unrewarded decisions differed along several measures related to volition: participants reported a higher sense of volition, exhibited a stronger Readiness Potential, had increased temporal binding (mostly inconclusive), and demonstrated increased Effort Exerted in the rewarded condition. In contrast, we found evidence for similarity across these measures between easy-deliberation and hard-deliberation conditions. Our results suggest that it is not the complexity of the deliberation process prior to the action that makes it more volitional, but rather that the decision serves a meaningful goal. Our study also introduced a new implicit measure of volition- effort exerted-that well aligned with other measures of volition and should therefore prove useful in future studies.

The immersive environments of virtual reality (VR) have potential to engender a vast range of experiences. Although participants recognize these experiences as artificial, the consequences can still be profound. Compared to VR, lucid dreams-characterized by awareness that one is dreaming-potentially allow for even more expansive explorations of immersive multisensory experience. Furthermore, lucid dreaming could conceivably enhance the impact of a prior VR experience, producing more profound effects than the VR experience alone. As an initial step along those lines, we attempted to induce lucid dreams about a VR experience called Ripple, with the goal of documenting the impact of the combination. In prior research, Ripple by itself was shown to reduce self-other boundaries and enhance interconnectedness. We recruited four frequent lucid dreamers to experience Ripple on two occasions, followed by an overnight session with sounds from Ripple presented quietly during polysomnographically verified rapid eye movement (REM) sleep. Three participants experienced lucid dreams about Ripple that night, and all four reported dreams containing elements of Ripple. The lucid dreams were validated in real time by physiological signals from the dreamers to indicate their concurrent experience of lucidity in the dream, followed by signals of dreaming about the VR experience. On this basis, we can confirm that it was possible in these circumstances for people to have lucid dreams recapitulating elements of the prior VR experience. Our findings also showcase how the synergistic combination of VR and lucid dreaming could be strongly beneficial.