情绪面孔的意识神经相关物及其无意识自动加工：来自事件相关电位的证据

意识的神经相关物尚有争议, 且个体能否无意识自动检测视觉环境变化尚不清楚。本研究采用非注意视盲范式操控视觉意识, 并引入具有社会信息的情绪面孔, 探讨意识的神经相关物以及视觉意识与自动检测变化机制的关系。在A阶段, 部分被试对任务无关的情绪面孔处于无意识水平; 在B阶段, 所有被试对任务无关的情绪面孔处于意识水平; 在C阶段, 所有被试对任务相关的情绪面孔处于意识水平。结果显示, 任务无关的情绪面孔的意识过程诱发视觉意识负波(visual awareness negativity, VAN)、晚期正成分(late positivity, LP)和晚期枕区正成分(late occipital positivity, LOP)。此外, 无意识的情绪面孔能诱发视觉失匹配负波(visual mismatch negativity, vMMN), 且其幅值不受意识影响, 但是受任务相关性调制。这些结果提示对情绪面孔的视觉意识在不同的时间进程上有不同的ERP指标——VAN反映早期知觉经验, 而LP和LOP反映晚期意识过程, 而且面孔情绪信息的自动加工独立于视觉意识, 但是受视觉注意调制。     

The levels of perceptual processing and the neural correlates of increasing subjective visibility

According to the levels-of-processing hypothesis, transitions from unconscious to conscious perception may depend on stimulus processing level, with more gradual changes for low-level stimuli and more dichotomous changes for high-level stimuli. In an event-related fMRI study we explored this hypothesis using a visual backward masking procedure. Task requirements manipulated level of processing. Participants reported the magnitude of the target digit in the high-level task, its color in the low-level task, and rated subjective visibility of stimuli using the Perceptual Awareness Scale. Intermediate stimulus visibility was reported more frequently in the low-level task, confirming prior behavioral results. Visible targets recruited insulo-fronto-parietal regions in both tasks. Task effects were observed in visual areas, with higher activity in the low-level task across all visibility levels. Thus, the influence of level of processing on conscious perception may be mediated by attentional modulation of activity in regions representing features of consciously experienced stimuli.     

Tracking the processes behind conscious perception: a review of event-related potential correlates of visual consciousness

Event-related potential (ERP) studies have attempted to discover the processes that underlie conscious visual perception by contrasting ERPs produced by stimuli that are consciously perceived with those that are not. Variability of the proposed ERP correlates of consciousness is considerable: the earliest proposed ERP correlate of consciousness (P1) coincides with sensory processes and the last one (P3) marks postperceptual processes. A negative difference wave called visual awareness negativity (VAN), typically observed around 200 ms after stimulus onset in occipitotemporal sites, gains strong support for reflecting the processes that correlate with, and possibly enable, aware visual perception. Research suggests that the early parts of conscious processing can proceed independently of top-down attention, although top-down attention may modulate visual processing even before consciousness. Evidence implies that the contents of consciousness are provided by interactions in the ventral stream, but indispensable contributions from dorsal regions influence already low-level visual responses.     

ERP and MEG correlates of visual consciousness: The second decade

The first decade of event-related potential (ERP) research had established that the most consistent correlates of the onset of visual consciousness are the early visual awareness negativity (VAN), a posterior negative component in the N2 time range, and the late positivity (LP), an anterior positive component in the P3 time range. Two earlier extensive reviews ten years ago had concluded that VAN is the earliest and most reliable correlate of visual phenomenal consciousness, whereas LP probably reflects later processes associated with reflective/access consciousness. This article provides an update to those earlier reviews. ERP and MEG studies that have appeared since 2010 and directly compared ERPs between aware and unaware conditions are reviewed, and important new developments in the field are discussed. The result corroborates VAN as the earliest and most consistent signature of visual phenomenal consciousness, and casts further doubt on LP as an ERP correlate of phenomenal consciousness.     

The electrophysiological correlates of stimulus visibility and metacontrast masking

There are conflicting views concerning the electrophysiological correlates of visual consciousness. Whereas one view considers a relatively late positive deflection (LP) as a primary correlate of consciousness, another model links consciousness with earlier negativity (VAN). The present experiment utilized metacontrast masking in investigating the electrophysiological correlates of visual consciousness. The participants were presented with target-mask sequences in three stimulus onset asynchronies. The target stimuli were followed by either a metacontrast mask or a similar-looking, but ineffective pseudomask. The results showed that the first deflection that correlated with target visibility was VAN which was followed by LP. We argue that the VAN is the primary correlate target visibility, while the LP reflects later, postperceptual processing stages.     

Contextual illusions reveal the limit of unconscious visual processing

The perception of even the most elementary features of the visual environment depends strongly on their spatial context. In the study reported here, we asked at what level of abstraction such effects require conscious processing of the context. We compared two visual illusions that alter subjective judgments of brightness: the simultaneous brightness contrast illusion, in which two circles of identical physical brightness appear different because of different surround luminance, and the Kanizsa triangle illusion, which occurs when the visual system extrapolates a surface without actual physical stimulation. We used a novel interocular masking technique that allowed us to selectively render only the context invisible. Simultaneous brightness contrast persisted even when the surround was masked from awareness. In contrast, participants did not experience illusory contours when the inducing context was masked. Our findings show that invisible context is resolvable by low-level processes involved in surface-brightness perception, but not by high-level processes that assign surface borders through perceptual completion.     

Modulations of sensory-evoked brain potentials indicate changes in perceptual processing during visual-spatial priming.

Reaction time (RT) differences to visual stimuli as a function of expectancy have been attributed to changes in perceptual processing or entirely to shifts in decision and response criteria. To help distinguish between these competing interpretations, event-related brain potentials (ERPs) were recorded to lateralized flashes delivered to visual field locations precued by a central arrow (valid stimuli) or not precued (invalid stimuli). Validly cued stimuli in both simple and choice RT tasks elicited consistent amplitude enhancements of the early, sensory-evoked PI component of the ERP recorded at scalp sites overlying lateral prestriate visual cortex (90-130 ms poststimulus). In contrast, the subsequent N1 component (150-200 ms) was enhanced by validly cued stimuli in the choice RT task condition only. These electrophysiological findings support models proposing that the behavioral effects of precuing expected target locations are due, at least in part, to changes in sensory-perceptual processing. Furthermore, these data provide specific information regarding the neural mechanisms underlying such effects.     

Subjective visibility depends on level of processing

Is visual awareness graded or binary? Experimental work has provided support for both possibilities, leading to two coexisting but contradictory theoretical accounts. Here we propose a promising candidate factor through which to integrate both accounts: the depth of stimulus processing required by the task. We compared color identification (a low-level task) with numerical judgements (a high-level task) performed on the very same colored number stimuli. Psychophysical curves were analyzed for both objective discrimination performance and subjective visibility ratings on a trial-by trial basis. We observed a graded relationship between stimulus duration and visibility in the low-level task, but a more non-linear relationship in the high-level task. Both patterns of results have previously been consistently associated with the graded and the dichotomous account, respectively. Follow-up experiments that manipulate the level of processing can further unify previously inconsistent results, thus integrating two major theories of visual awareness.     

Non-conscious word processing in a mirror-masking paradigm causing attentional distraction: an ERP-study

In this event-related potential (ERP) study a masking technique that prevents conscious perception of words and non-words through attentional distraction was used to reveal the temporal dynamics of word processing under non-conscious and conscious conditions. In the non-conscious condition, ERP responses differed between masked words and non-words from 112 to 160 ms after stimulus-onset over posterior brain areas. The early onset of the word-non-word differences was compatible with previous studies that reported non-conscious access to orthographic information within this time period. Moreover, source localisations provided evidence for automatic activation of prelexical phonological information, whereas no evidence for non-conscious semantic processing was found. When subjects were informed about the masking technique, lexical differences occurred at later time intervals, suggesting conscious access to additional word related information. These results indicate that early visual word processing does not depend entirely on attentional resources, but that non-conscious processing probably is restricted to rather lower-level linguistic information.     

A review of abnormalities in the perception of visual illusions in schizophrenia

Specific abnormalities of vision in schizophrenia have been observed to affect high-level and some low-level integration mechanisms, suggesting that people with schizophrenia may experience anomalies across different stages in the visual system affecting either early or late processing or both. Here, we review the research into visual illusion perception in schizophrenia and the issues which previous research has faced. One general finding that emerged from the literature is that those with schizophrenia are mostly immune to the effects of high-level illusory displays, but this effect is not consistent across all low-level illusions. The present review suggests that this resistance is due to the weakening of top–down perceptual mechanisms and may be relevant to the understanding of symptoms of visual distortion rather than hallucinations as previously thought.     

The Sounds of Sentences: Differentiating the Influence of Physical Sound,Sound Imagery,and Linguistically Implied Sounds on Physical Sound Processing

Both the imagery literature and grounded models of language comprehension emphasize the tight coupling of high-level cognitive processes, such as forming a mental image of something or language understanding, and low-level sensorimotor processes in the brain. In an electrophysiological study, imagery and language processes were directly compared and the sensory associations of processing linguistically implied sounds or imagined sounds were investigated. Participants read sentences describing auditory events (e.g., “The dog barks”), heard a physical (environmental) sound, or had to imagine such a sound. We examined the influence of the 3 sound conditions (linguistic, physical, imagery) on subsequent physical sound processing. Event-related potential (ERP) difference waveforms indicated that in all 3 conditions, prime compatibility influenced physical sound processing. The earliest compatibility effect was observed in the physical condition, starting in the 80–110 ms time interval with a negative maximum over occipital electrode sites. In contrast, the linguistic and the imagery condition elicited compatibility effects starting in the 180–220 ms time window with a maximum over central electrode sites. In line with the ERPs, the analysis of the oscillatory activity showed that compatibility influenced early theta and alpha band power changes in the physical, but not in the linguistic and imagery, condition. These dissociations were further confirmed by dipole localization results showing a clear separation between the source of the compatibility effect in the physical sound condition (superior temporal area) and the source of the compatibility effect triggered by the linguistically implied sounds or the imagined sounds (inferior temporal area). Implications for grounded models of language understanding are discussed.     

Auditory awareness negativity is an electrophysiological correlate of awareness in an auditory threshold task

One theory of visual awareness proposes that electrophysiological activity related to awareness occurs in primary visual areas approximately 200 ms after stimulus onset (visual awareness negativity: VAN) and in fronto-parietal areas about 300 ms after stimulus onset (late positivity: LP). Although similar processes might be involved in auditory awareness, only sparse evidence exists for this idea. In the present study, we recorded electrophysiological activity while subjects listened to tones that were presented at their own awareness threshold. The difference in electrophysiological activity elicited by tones that subjects reported being aware of versus unaware of showed an early negativity about 200 ms and a late positivity about 300 ms after stimulus onset. These results closely match those found in vision and provide convincing evidence for an early negativity (auditory awareness negativity: AAN), as well as an LP. These findings suggest that theories of visual awareness are also applicable to auditory awareness.     

Domain specificity versus expertise: factors influencing distinct processing of faces

To explore face specificity in visual processing, we compared the role of task-associated strategies and expertise on the N170 event-related potential (ERP) component elicited by human faces with the ERPs elicited by cars, birds, items of furniture, and ape faces. In Experiment 1, participants performed a car monitoring task and an animacy decision task. In Experiment 2, participants monitored human faces while faces of apes were the distracters. Faces elicited an equally conspicuous N170, significantly larger than the ERPs elicited by non-face categories regardless of whether they were ignored or had an equal status with other categories (Experiment 1), or were the targets (in Experiment 2). In contrast, the negative component elicited by cars during the same time range was larger if they were targets than if they were not. Furthermore, unlike the posterior-temporal distribution of the N170, the negative component elicited by cars and its modulation by task were more conspicuous at occipital sites. Faces of apes elicited an N170 that was similar in amplitude to that elicited by the human face targets, albeit peaking 10 ms later. As our participants were not ape experts, this pattern indicates that the N170 is face-specific, but not specie-specific, i.e. it is elicited by particular face features regardless of expertise. Overall, these results demonstrate the domain specificity of the visual mechanism implicated in processing faces, a mechanism which is not influenced by either task or expertise. The processing of other objects is probably accomplished by a more general visual processor, which is sensitive to strategic manipulations and attention.     

Temporal dynamics of awareness for facial identity revealed with ERP

In this study, we investigated the scalp recorded event-related potential (ERP) responses related to visual awareness. A backward masking procedure was performed while high-density EEG recordings were carried out. Subjects were asked to detect a familiar face, presented at durations that varied parametrically between 16 and 266 ms. ERPs were computed and awareness was assessed using a sensitivity measure from signal detection theory (d'). Modifications in the electrical scalp topographies were found to reflect visual awareness of the stimulus. In particular, an early map topography was found to emerge progressively around 230 ms, showing a pattern of increase similar to the measure of visual awareness. This was followed by an increase in duration of a second, P300-like map. Source localisation for the early awareness-related topography revealed the activation of a distributed network of brain areas including frontal and temporo-occipital regions. Our results suggest that conscious experience emerges in parallel with the activation of a specific neural network that occurs in a time window beginning from about 200 ms.     

The influence of action observation on action execution: Dissociating the contribution of action on perception,perception on action,and resolving conflict

For more than 15 years, motor interference paradigms have been used to investigate the influence of action observation on action execution. Most research on so-called automatic imitation has focused on variables that play a modulating role or investigated potential confounding factors. Interestingly, furthermore, a number of functional magnetic resonance imaging (fMRI) studies have tried to shed light on the functional mechanisms and neural correlates involved in imitation inhibition. However, these fMRI studies, presumably due to poor temporal resolution, have primarily focused on high-level processes and have neglected the potential role of low-level motor and perceptual processes. In the current EEG study, we therefore aimed to disentangle the influence of low-level perceptual and motoric mechanisms from high-level cognitive mechanisms. We focused on potential congruency differences in the visual N190 ? a component related to the processing of biological motion, the Readiness Potential ? a component related to motor preparation, and the high-level P3 component. Interestingly, we detected congruency effects in each of these components, suggesting that the interference effect in an automatic imitation paradigm is not only related to high-level processes such as self-other distinction but also to more low-level influences of perception on action and action on perception. Moreover, we documented relationships of the neural effects with (autistic) behavior.     

Electrophysiological evidence for parallel and serial processing during visual search

Event-related potentials were recorded from young adults during a visual search task in order to evaluate parallel and serial models of visual processing in the context of Treisman's feature integration theory. Parallel and serial search strategies were produced by the use of feature-present and feature-absent targets, respectively. In the feature-absent condition, the slopes of the functions relating reaction time and latency of the P3 component to set size were essentially identical, indicating that the longer reaction times observed for larger set sizes can be accounted for solely by changes in stimulus identification and classification time, rather than changes in post-perceptual processing stages. In addition, the amplitude of the P3 wave on target-present trials in this condition increased with set size and was greater when the preceding trial contained a target, whereas P3 activity was minimal on target-absent trials. These effects are consistent with the serial self-terminating search model and appear to contradict parallel processing accounts of attention-demanding visual search performance, at least for a subset of search paradigms. Differences in ERP scalp distributions further suggested that different physiological processes are utilized for the detection of feature presence and absence.     

声乐与器乐情绪加工的ERP研究

借助跨通道情绪启动范式考察声乐与器乐情绪加工的电生理差异。启动刺激是声乐和器乐曲(小提琴演奏), 目标刺激是与音乐情绪一致或不一致的面孔表情图片。结果显示, 与一致条件相比, 与面孔情绪不一致的器乐曲诱发了N400, 而与面孔情绪不一致的声乐曲诱发了LPC。这些结果表明, 声乐与器乐情绪加工的电生理反应存在差异。     

Neural correlates of facial emotion processing in infancy

In the present study we examined the neural correlates of facial emotion processing in the first year of life using ERP measures and cortical source analysis. EEG data were collected cross‐sectionally from 5‐ (N = 49), 7‐ (N = 50), and 12‐month‐old (N = 51) infants while they were viewing images of angry, fearful, and happy faces. The N290 component was found to be larger in amplitude in response to fearful and happy than angry faces in all posterior clusters and showed largest response to fear than the other two emotions only over the right occipital area. The P400 and Nc components were found to be larger in amplitude in response to angry than happy and fearful faces over central and frontal scalp. Cortical source analysis of the N290 component revealed greater cortical activation in the right fusiform face area in response to fearful faces. This effect started to emerge at 5 months and became well established at 7 months, but it disappeared at 12 months. The P400 and Nc components were primarily localized to the PCC/Precuneus where heightened responses to angry faces were observed. The current results suggest the detection of a fearful face in infants’ brain can happen shortly (~200–290 ms) after the stimulus onset, and this process may rely on the face network and develop substantially between 5 to 7 months of age. The current findings also suggest the differential processing of angry faces occurred later in the P400/Nc time window, which recruits the PCC/Precuneus and is associated with the allocation of infants’ attention.     

Three kinds of rhymes: An ERP study

In a simple prime-target visual rhyming paradigm, pairs of words, nonwords, and single letters elicited similar event-related potential (ERP) rhyming effects in young adults. Within each condition, primes elicited contingent negative variation (CNV) while nonrhyming targets elicited more negative waveforms than rhyming targets within the 320-500ms (N400/N450) time window. The target rhyming effect, apparently primarily an index of phonological processing, was similar across conditions but tended to be smaller in mean amplitude for letters. One of the first reports of such a letter rhyming effect in the ERP literature, these findings could be important developmentally because letter rhyme tasks simultaneously index the two best predictors of ease of learning to read: letter name knowledge and phonological awareness.     

The role of activation charge in an emotional categorisation task for words: insight from the perspective of a dual process theory of the activation mechanisms

The role of activation (arousal and subjective significance) was investigated for word processing in an explicit emotional judgement task using a 3?×?3 manipulation. We expected to find dissociative effects for both factors. The behavioural results showed that the fraction of words perceived as emotional increases with increasing arousal or subjective significance. The electrophysiological (EEG) results showed that both factors influence ERP amplitudes. General effects of subjective significance were found for early (60–120?ms and 120–250?ms, low subjective significant stimuli evoked higher amplitude than other conditions) and late (350–490?ms, high subjective significant stimuli evoked higher amplitude than other conditions) time ranges. Localised arousal effects were found in 250–350?ms and 350–490?ms time ranges at posterior (amplitude for high arousing stimuli was less positive than for other conditions) and left frontal ROIs (diverse pattern). Localised subjective significance effects were found for the 350–490?ms time range at the posterior ROIs (amplitude for high subjective significant stimuli was more positive than for other conditions). The results of this study suggest that the effects of arousal reported in earlier studies might account for a more complex form of activation that was recently postulated, namely subjective significance.