Development of emergent processes and threshold of consciousness with levels of processing.

Introduction: The transition of experience from unconscious to conscious, the emergent process, is a crucial topic in consciousness studies. Three frameworks exist to explain the process: (1) consciousness arises in an all-or-none manner; (2) consciousness arises gradually; (3) consciousness arises either all at once or gradually, depending on the level of stimulus processing (low- vs. high-level). However, the development of emergent processes of consciousness remains unclear. This study examines the development of emergent processes of consciousness based on the level of stimulus processing framework. Methods: Ninety-nine children (5-12 year-olds) and adults participated in two online discrimination tasks. These tasks involved color discrimination as lower-level processing and number magnitude discrimination as higher-level processing, as well as backward masking with stimulus onset asynchronies (SOAs) varying from 16.7 to 266.7 ms. We measured objective discrimination accuracy and used a 4-scale Perceptual Awareness Scale (PAS) to assess subjective awareness. We fit the data to a four-parameter nonlinear function to estimate the center of the slope (threshold) and the range of the slope (gradualness, the measure of emergent process of consciousness) of the model. Results: The results showed the threshold of objective discrimination was significantly higher in 5-6 year-olds than in 7-12 year-olds, but not of subjective awareness. The emergent process of objective discrimination in the number task was more gradual than in the color task. Discussion: The findings suggest that the thresholds of subjective awareness in 5-6 year-olds and objective discrimination in 7-9 year-olds are similar to those in adults. Moreover, the emergent processes of subjective awareness and objective discrimination in 5-6 year-olds are also similar to those in adults. Our results support the level of processing hypothesis but suggest that its effects may differ across developmental stages.

An embarrassment of richnesses: the PFC isn't the content NCC.

Recent years have seen the rise of several theories saying that the prefrontal cortex (PFC) is a neural correlate of visual consciousness (NCC). Especially popular here are theories saying that the PFC is the 'content NCC' for vision, i.e. it contains those brain areas that are not only necessary for consciousness, but also determine 'what' it is that we visually experience (e.g. whether we experience green or red). This article points out how this "upper-deck" form of PFC theory is at odds with the character of visual experience: on the one hand, visual consciousness appears to contain copious amounts of content, with many properties (such as object, shape, or color) being simultaneously represented in many parts of the visual field. On the other hand, the functions that the PFC carries out (e.g. attention and working memory) are each dedicated to processing only a relatively small subset of available visual stimuli. In short, the PFC probably does not produce enough or the right kind of visual representations for it to supply all of the content found in visual experience, in which case the idea that the PFC is the content NCC for vision is probably false. This article also discusses data thought to undercut the idea that visual experience is informationally rich (inattentional blindness, etc.), along with theories of vision according to which "ensemble statistics" are used to represent features in the periphery of the visual field. I'll argue that these lines of evidence fail to close the apparently vast gap between the amount of visual content represented in the visual experience and the amount represented in the PFC.

The involvement of the human prefrontal cortex in the emergence of visual awareness.

Exploring the neural mechanisms of awareness is a fundamental task of cognitive neuroscience. There is an ongoing dispute regarding the role of the prefrontal cortex (PFC) in the emergence of awareness, which is partially raised by the confound between report- and awareness-related activity. To address this problem, we designed a visual awareness task that can minimize report-related motor confounding. Our results show that saccadic latency is significantly shorter in the aware trials than in the unaware trials. Local field potential (LFP) data from six patients consistently show early (200-300ms) awareness-related activity in the PFC, including event-related potential and high-gamma activity. Moreover, the awareness state can be reliably decoded by the neural activity in the PFC since the early stage, and the neural pattern is dynamically changed rather than being stable during the representation of awareness. Furthermore, the enhancement of dynamic functional connectivity, through the phase modulation at low frequency, between the PFC and other brain regions in the early stage of the awareness trials may explain the mechanism of conscious access. These results indicate that the PFC is critically involved in the emergence of awareness.

Temporal integration by multi-level regularities fosters the emergence of dynamic conscious experience.

The relationship between integration and awareness is central to contemporary theories and research on consciousness. Here, we investigated whether and how information integration over time, by incorporating the underlying regularities, contributes to our awareness of the dynamic world. Using binocular rivalry, we demonstrated that structured visual streams, constituted by shape, motion, or idiom sequences containing perceptual- or semantic-level regularities, predominated over their nonstructured but otherwise matched counterparts in the competition for visual awareness. Despite the apparent resemblance, a substantial dissociation of the observed rivalry advantages emerged between perceptual- and semantic-level regularities. These effects stem from nonconscious and conscious temporal integration processes, respectively, with the former but not the latter being vulnerable to perturbations in the spatiotemporal integration window. These findings corroborate the essential role of structure-guided information integration in visual awareness and highlight a multi-level mechanism where temporal integration by perceptually and semantically defined regularities fosters the emergence of continuous conscious experience.

Young children's subjective and objective thresholds and emergent processes of visual consciousness using a backward masking task.

Visual consciousness studies in humans have primarily focused on adults. However, whether young children's visual consciousness is similar to or different from that of adults remains unknown. This study examined young children's and adults' subjective awareness and objective discrimination for thresholds and emergent processes of visual consciousness in two experiments. In Experiment 1, 20 5-6-year-olds and 20 adults attempted a figure discrimination task using a square or a diamond as the target stimulus and responded, using a two-point scale, to a question on subjective awareness of the target stimulus with stimulus onset asynchronies (SOA) from 20 to 260 ms. In Experiment 2, 31 5-6-year-olds and 16 adults attempted the task and responded, using a four-point scale, to a question on subjective awareness with SOA from 50 to 550 ms. We measured the discrimination accuracy and the awareness scale with SOA and fit them to the sigmoid function. The results showed that the objective accuracy threshold of young children was larger than that of adults. Moreover, young children's subjective awareness threshold was larger than that of adults in the four-point but not in the two-point scale responses. Finally, there were no age differences in the emergent process of consciousness. This study suggests that the emergent process of consciousness in young children is similar to that in adults, however, the threshold in young children is larger than that in adults.

From intermediate shape-centered representations to the perception of oriented shapes: response to commentaries.

In this response paper, we start by addressing the main points made by the commentators on the target article's main theoretical conclusions: the existence and characteristics of the intermediate shape-centered representations (ISCRs) in the visual system, their emergence from edge detection mechanisms operating on different types of visual properties, and how they are eventually reunited in higher order frames of reference underlying conscious visual perception. We also address the much-commented issue of the possible neural mechanisms of the ISCRs. In the final section, we address more specific and general comments, questions, and suggestions which, albeit very interesting, were less directly focused on the main conclusions of the target paper.

The functions of consciousness in visual processing.

Conscious experiences form a relatively diverse class of psychological phenomena, supported by a range of distinct neurobiological mechanisms. This diversity suggests that consciousness occupies a variety of different functional roles across different task domains, individuals, and species; a position I call functional pluralism. In this paper, I begin to tease out some of the functional contributions that consciousness makes to (human) visual processing. Consolidating research from across the cognitive sciences, I discuss semantic and spatiotemporal processing as specific points of comparison between the functional capabilities of the visual system in the presence and absence of conscious awareness. I argue that consciousness contributes a cluster of functions to visual processing; facilitating, among other things, (i) increased capacities for semantically processing informationally complex visual stimuli, (ii) increased spatiotemporal precision, and (iii) increased capacities for representational integration over large spatiotemporal intervals. This sort of analysis should ultimately yield a plurality of functional markers that can be used to guide future research in the philosophy and science of consciousness, some of which are not captured by popular theoretical frameworks like global workspace theory and information integration theory.

Effects of Moderate-to-Vigorous Acute Exercise on Conscious Perception and Visual Awareness.

Background: the effect of acute exercise on cognition covers almost all stages of information processing, but few studies have focused on visual awareness. Reports on the appearance of faint speed-changes in the perception of stimuli were used as an index for visual awareness. Visual awareness was assessed after exercise or rest. Aside from the detection of speed-changes, speed-change discrimination was added as an index of perception. Results: the results showed that reports on the appearance of faint speed-changes were affected by acute aerobic exercise. The d' index was higher after exercise. The hit rate for speed-change detection was marginally significantly higher after exercise than after the sedentary test condition. Analysis of the results obtained for the discrimination task showed that discrimination speed was boosted only when subjects were aware of the speed-change. Importantly, neither false alarm rate nor response bias was affected by exercise. Conclusions: acute moderate- to vigorous-intensity aerobic exercise improved subjects' awareness of speed changes. In addition, there was a perceptual advantage due to exercise.

InFoRM (Indicate-Follow-Replay-Me): A novel method to measure perceptual multistability dynamics using continuous data tracking and validated estimates of visual introspection.

Perceptual multistability, e.g. Binocular Rivalry, has been intensively used as a tool to study visual consciousness. Current methods to assess multistability do not capture all potentially occurring perceptual states, provide no estimate of introspection, and lack continuous, high-temporal resolution to resolve perceptual changes between states and within mixed perceptual states. We introduce InFoRM (Indicate-Follow-Replay-Me), a four-phase method that (1) trains a participant to self-generate estimates of perceptual introspection-maps that are (2) validated during a physical mimic task, (3) gathers perceptual multistability data, and (4) confirms their validity during a physical replay. 28 condition-blinded adults performed InFoRM while experiencing binocular rivalry evoked with orthogonal sinusoidal gratings. A 60 Hz joystick (3600 data samples/minute) was used to indicate continuously changes across six perceptual states within each 1 min trial. A polarized monitor system was used to present the stimuli dichoptically. Three contrast conditions were investigated: low vs low, high vs high, and low vs high. InFoRM replicates standard outcome measures, i.e. alternation rate, mean and relative proportions of perception, and distribution of exclusive percepts that are well fitted with gamma functions. Furthermore, InFoRM generates novel outcomes that deliver new insights in visual cognition via estimates of introspection maps, in ocular dominance via perceptual-state-specific dominance scores, in transitory dynamics between and within perceptual states, via techniques adopted from eye-tracking, and in rivalry-zone-size estimates utilizing InFoRM's ability to simulate piecemeal perception. The replay phase (physical replay of perceptual rivalry) confirmed good overall agreement (73% ±5 standard deviation). InFoRM can be applied to other multistable paradigms and can be used to study visual consciousness in typical and neuro-atypical populations.

The mechanisms of selective attention in phenomenal consciousness.

In three experiments we investigated the effects of selective attention in iconic memory and fragile-visual short-term memory (VSTM), which have been related to phenomenal consciousness. We used a novel retro-cue paradigm with different delays (early vs late) and object priorities (high vs equal vs low), to investigate (a) attentional costs and benefits and the role of (b) bottom-up factors and (c) fragile-VSTM in feature-based attentional selection. Experiment 1 showed that attentional costs modulate visual maintenance at longer delays, while Experiment 2 showed that by reducing the time exposure of the memory array from 250 ms to 100 ms, as a bottom-up factor, participants were not able to select the objects based on their priorities. Finally, Experiment 3 showed that a pattern mask presented before the transfer in visual working memory, attenuates the overall performance while preserving the priority effect. The implications for phenomenal consciousness before conscious access are discussed.

High spatial frequencies disrupt conscious visual recognition: evidence from an attentional blink paradigm.

In this article, we tested the respective importance of low spatial frequencies (LSF) and high spatial frequencies (HSF) for conscious visual recognition of emotional stimuli by using an attentional blink paradigm. Thirty-eight participants were asked to identify and report two targets (happy faces) embedded in a rapid serial visual presentation of distractors (angry faces). During attentional blink, conscious perception of the second target (T2) is usually altered when the lag between the two targets is short (200-500 ms) but is restored at longer lags. The distractors between T1 and T2 were either non-filtered (broad spatial frequencies, BSF), low-pass filtered (LSF), or high-pass filtered (HSF). Assuming that prediction abilities could be at the root of conscious visual recognition, we expected that LSF distractors could result in a greater disturbance of T2 reporting than HSF distractors. Results showed that both LSF and HSF play a role in the emergence of exogenous consciousness in the visual system. Furthermore, HSF distractors strongly affected T1 and T2 reporting irrespective of the lag between targets, suggesting their role for facial emotion processing. We discuss these results with regards to other models of visual recognition. .

High confidence and low accuracy in redundancy masking.

Visual scenes typically contain redundant information. One mechanism by which the visual system compresses such redundancies is 'redundancy masking' - the reduction of the perceived number of items in repeating patterns. For example, when presented with three lines in the periphery, observers frequently report only two lines. Redundancy masking is strong in radial arrangements and absent in tangential arrangements. Previous studies suggested that redundancy-masked percepts predominate in stimuli susceptible to redundancy masking. Here, we investigated whether strong redundancy masking is associated with high confidence in perceptual judgements. Observers viewed three to seven radially or tangentially arranged lines at 10° eccentricity. They first indicated the number of lines, and then rated their confidence in their responses. As expected, redundancy masking was strong in radial arrangements and weak in tangential arrangements. Importantly, with radial arrangements, observers were more confident in their responses when redundancy masking occurred (i.e., lower number of lines reported) than when it did not occur (i.e., correct number of lines reported). Hence, observers reported higher confidence for erroneous than for correct judgments. In contrast, with tangential arrangements, observers were similarly confident in their responses whether redundancy masking occurred or not. The inversion of confidence in the radial condition (higher confidence when accuracy was low and lower confidence when accuracy was high) suggests that redundancy-masked appearance trumps 'veridical' perception. The often-reported richness of visual consciousness may partly be due to overconfidence in erroneous judgments in visual scenes that are subject to redundancy masking.

Mapping the emergence of visual consciousness in the human brain via brain-wide intracranial electrophysiology.

Consciousness lies at the heart of our existence and experience. To probe how perceptual consciousness emerges in the brain, we recorded brain-wide intracranial electroencephalography signals from human patients while their perceptual consciousness was effectively manipulated using the continuous flash suppression paradigm. We observed substantial differences in brain activities when visual information gradually enters consciousness. Specifically, the functional connectivity first increases and then decreases, oscillations in the low-frequency band reduce in power, and those in the high-frequency band remain unchanged. We employed random forest-based classification to characterize the transitions from no perception to subconsciousness and then to consciousness, which showed an increase in signal variance at the second transition rather than the first. Further, the frontal-parietal junction dominates the first transition, whereas the temporal-frontal lobes dominate the second transition. Finally, we identified the most relevant neuronal features associated with consciousness. Altogether, these findings shed fresh light on the emergence of visual consciousness.

Shape-centered representations of bounded regions of space mediate the perception of objects.

We report the study of a woman who perceives 2D bounded regions of space ("shapes") defined by sharp edges of medium to high contrast as if they were rotated by 90, 180 degrees around their centre, mirrored across their own axes, or both. In contrast, her perception of 3D, strongly blurred or very low contrast shapes, and of stimuli emerging from a collection of shapes, is intact. This suggests that a stage in the process of constructing the conscious visual representation of a scene consists of representing mutually exclusive bounded regions extracted from the initial retinotopic space in "shape-centered" frames of reference. The selectivity of the disorder to shapes originally biased toward the parvocellular subcortical pathway, and the absence of any other type of error, additionally invite new hypotheses about the operations involved in computing these "intermediate shape-centered representations" and in mapping them onto higher frames for perception and action.

V1 as an egocentric cognitive map.

We typically distinguish between V1 as an egocentric perceptual map and the hippocampus as an allocentric cognitive map. In this article, we argue that V1 also functions as a post-perceptual egocentric cognitive map. We argue that three well-documented functions of V1, namely (i) the estimation of distance, (ii) the estimation of size, and (iii) multisensory integration, are better understood as post-perceptual cognitive inferences. This argument has two important implications. First, we argue that V1 must function as the neural correlates of the visual perception/cognition distinction and suggest how this can be accommodated by V1's laminar structure. Second, we use this insight to propose a low-level account of visual consciousness in contrast to mid-level accounts (recurrent processing theory; integrated information theory) and higher-level accounts (higher-order thought; global workspace theory). Detection thresholds have been traditionally used to rule out such an approach, but we explain why it is a mistake to equate visibility (and therefore the presence/absence of visual experience) with detection thresholds.

Continuous flash suppression: Known and unknowns.

Studies utilizing continuous flash suppression (CFS) provide valuable information regarding conscious and nonconscious perception. There are, however, crucial unanswered questions regarding the mechanisms of suppression and the level of visual processing in the absence of consciousness with CFS. Research suggests that the answers to these questions depend on the experimental configuration and how we assess consciousness in these studies. The aim of this review is to evaluate the impact of different experimental configurations and the assessment of consciousness on the results of the previous CFS studies. We review studies that evaluated the influence of different experimental configuration on the depth of suppression with CFS and discuss how different assessments of consciousness may impact the results of CFS studies. Finally, we review behavioral and brain recording studies of CFS. In conclusion, previous studies provide evidence for survival of low-level visual information and complete impairment of high-level visual information under the influence of CFS. That is, studies suggest that nonconscious perception of lower-level visual information happens with CFS, but there is no evidence for nonconscious high-level recognition with CFS.

The Relationship between Biological Motion-Based Visual Consciousness and Attention: An Electroencephalograph Study.

Understanding and predicting the intentions of others through limb movements are vital to social interaction. The processing of biological motion is unique from the processing of motion of inanimate objects. Presently, there is controversy over whether visual consciousness of biological motion is regulated by visual attention. In addition, the neural mechanisms involved in biological motion-related visual awareness are not known. In the current study, the relationship between visual awareness (aware vs unaware), represented by a point-light walker and biological-motion-based attention, manipulated by a difference in congruence (congruent, incongruent) between the direction of a pre-cue and that of biological motion was explored. The neural mechanisms involved in processing the stimuli were explored through electroencephalography. Both early (50-150 ms, 100-200 ms, and 174-226 ms after target presentation) and late (350-550 ms after target presentation) awareness-related neural processings were observed during a biological motion-based congruency task. Early processing was localized to occipital-parietal regions, such as the left postcentral gyrus, the left middle occipital gyrus, and the right precentral gyrus. In the 174-226-ms window, the activity in the occipital region was gradually replaced by activity in the parietal and frontal regions. Late processing was localized to frontal-parietal regions, such as the right dorsal superior frontal gyrus, the left medial superior frontal gyrus, and the occipito-temporal regions. Congruency-related processing occurred in the 246-260-ms window and was localized to the right superior occipital gyrus. In summary, due to its complexity, biological motion awareness has a unique neural basis.

In search of consciousness: Examining the temporal dynamics of conscious visual perception using MEG time-series data.

The mere presence of information in the brain does not always mean that this information is available to consciousness. Experiments using paradigms such as binocular rivalry, visual masking, and the attentional blink have shown that visual information can be processed and represented by the visual system without reaching consciousness. Using multivariate pattern analysis (MVPA) and magneto-encephalography (MEG), we investigated the temporal dynamics of information processing for unconscious and conscious stimuli. We decoded stimulus information from the brain recordings while manipulating visual consciousness by presenting stimuli at threshold contrast in a backward masking paradigm. Participants' consciousness was measured using both a forced-choice categorisation task and self-report. We show that brain activity during both conscious and non-conscious trials contained stimulus information and that this information was enhanced in conscious trials. Overall, our results indicate that visual consciousness is characterised by enhanced neural activity representing the visual stimulus and that this effect arises as early as 180 ms post-stimulus onset.

Does TMS on V3 block conscious visual perception?

Primary visual cortex (V1) and extrastriate V2 are necessary for the emergence of visual consciousness, but the effects of involvement of extrastriate V3 on visual consciousness is unclear. The objective of this study was to examine the causal role of V3 in visual consciousness in humans. We combined neuronavigated transcranial magnetic stimulation (TMS) with a computational model of the TMS-induced electric field to test whether or not the intact processing of visual input in V3, like in V1 and V2, is necessary for conscious visual perception. We targeted the stimulation both to V2 and to V3. If TMS of V3 blocks conscious visual perception of stimuli, then activation in V3 is a causally necessary prerequisite for conscious perception of stimuli. According to the alternative hypothesis, TMS of V3 will not block the conscious visual perception of stimuli, because the pathways from V1 to the higher cortical areas that go around V3 provide sufficient visual input for the emergence of conscious visual perception. The results showed that TMS interfered with conscious perception of features, detection of stimulus presence and the ability to discriminate the letter stimuli both when TMS was targeted either to V3 or to V2. For the conscious detection of stimulus presence, the effect was significantly stronger when V2 was stimulated than when V3 was stimulated. The results of the present study suggest that in addition to the primary visual cortex and V2, also V3 causally contributes to the generation of the most basic form of visual consciousness. Importantly, the results also indicate that V3 is necessary for visual perception in general, not only for visual consciousness.