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Can Non-Consciously Perceived Conditioned Fear be Generalized to Consciously Presented Concept Stimulus?
Zhou Yijia, Gao Caicai, Mei Ying, Lei Yi
Journal of Psychological Science ›› 2026, Vol. 49 ›› Issue (2) : 289-302.
PDF(1741 KB)
PDF(1741 KB)
Can Non-Consciously Perceived Conditioned Fear be Generalized to Consciously Presented Concept Stimulus?
Fear is an adaptive emotion that enables organisms to learn to distinguish threatening stimuli in complex natural environments. The "preparedness" theory posits that fear associations can be learned effortlessly, even without the conscious perception of fear-related stimuli. While previous studies have examined whether fear acquisition can be established without contingency awareness, this question remains largely unresolved. Several investigations have employed fear-related stimuli as conditioned stimuli (CS+) to study non-conscious fear acquisition. However, the preparedness theory itself lacks empirical validation, and no consensus exists on whether non-conscious fear acquisition necessarily requires fear-related stimuli. Generalized learning is defined as the retrieval of previously acquired stimulus information when responding to similar yet novel stimuli. Stimuli that humans encounter daily have specific meanings, and their retrieval depends both on conceptual relations and perceptual features. Previous studies mainly used perceptual materials with low ecological validity; therefore, examining the role of conceptual relations in generalization processes is essential for understanding fear overgeneralization in anxiety disorders. Fear can generalize to items that are conceptually linked to an initial fear experience. Concepts are organized either taxonomically through shared categorical features (e.g., fruit) or thematically through contextual associations within events or scenarios (e.g., desk and book). The focus of our study is to examine whether conditioned fear can be acquired by using fear-unrelated stimuli in the absence of awareness, and how different conceptual relations (thematic vs. taxonomic) and conceptual distance (near vs. far) influence subsequent fear generalization.
Twenty-seven healthy participants completed a fear generalization test with concurrent recording of neural activity via event-related potentials (ERPs). Shock expectancy ratings were used to assess the efficacy of non-conscious fear acquisition and examine conceptual generalization processes. The experimental design consisted of two consecutive phases: a non-conscious acquisition phase and a conscious generalization phase. During non-conscious acquisition, visual target stimuli were masked using a sandwich-masking paradigm; each presentation was preceded and followed by masking stimuli, rendering participants unaware of the conditioned stimuli and the CS-US contingency. Specifically, sparrow stimuli were designated as conditioned stimuli (CS+) paired with electric shocks (unconditioned stimulus, US), whereas car stimuli (CS-) remained unpaired. Stimulus assignment was counterbalanced across participants. To develop ecologically valid generalization stimuli (GS) based on conceptual relations, an independent cohort of 28 participants was recruited to complete a rating task. Forty potential stimulus exemplars per category were evaluated for their thematic or taxonomic association strength with the CS+ (sparrow). The three concepts demonstrating the highest and lowest thematic/taxonomic associations with the CS+ were selected as generalization stimuli (GS+ and GS-, respectively), thus yielding four stimulus classes: taxonomic GS+ (e.g., swan), taxonomic GS- (e.g., turtle), thematic GS+ (e.g., birdcage), and thematic GS- (e.g., sculpture).
Behavioral data reveal significantly higher shock expectancy for CS+ relative to CS- during non-conscious acquisition. ERP analyses demonstrate enhanced P300 amplitudes elicited by CS+ compared with CS-. During generalization, taxonomic relations evoke larger P2 components than thematic relations; notably, taxonomic GS+ stimuli produce significantly greater P2 amplitudes than thematic GS+ stimuli. Significantly larger P2 amplitudes are observed for taxonomic GS- relative to thematic GS-. When conditioned stimuli are presented supraliminally during generalization, the CS+ elicits higher shock expectancy and enhanced P600 components compared with the CS-.
These findings indicate that nonconscious fear acquisition can be established using neutral stimuli, thereby challenging the validity of the preparedness theory. Following non-conscious fear acquisition, broader generalization responses are elicited by taxonomic stimuli relative to thematic relations. Enhanced P600 amplitudes to the CS+ may reflect heightened semantic processing of the CS+ post-acquisition, which means non-consciously acquired fear demonstrates resistance to conscious extinction. These results demonstrate that fear acquisition occurs non-consciously with neutral stimuli, challenging preparedness theory, and reveal taxonomic relations drive broader fear generalization, elucidating mechanisms for anxiety interventions.
non-conscious fear acquisition / fear generalization / taxonomic relations / thematic relations / P2 / P600 / P300
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Fear generalization, in which conditioned fear responses generalize or spread to related stimuli, is a defining feature of anxiety disorders. The behavioral consequences of maladaptive fear generalization are that aversive experiences with one stimulus or event may lead one to regard other cues or situations as potential threats that should be avoided, despite variations in physical form. Theoretical and empirical interest in the generalization of conditioned learning dates to the earliest research on classical conditioning in nonhumans. Recently, there has been renewed focus on fear generalization in humans due in part to its explanatory power in characterizing disorders of fear and anxiety. Here, we review existing behavioral and neuroimaging empirical research on the perceptual and non-perceptual (conceptual and symbolic) generalization of fear and avoidance in healthy humans and patients with anxiety disorders. The clinical implications of this research for understanding the etiology and treatment of anxiety is considered and directions for future research described. Copyright © 2014. Published by Elsevier Ltd.
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Most theories of categorization posit feature-based representations. Markman and Stilwell (2001) argued that many natural categories name roles in relational systems and therefore they are role-governed categories. There is little extant empirical evidence to support the existence of role-governed categories. Three experiments examine predictions for ways that role-governed categories should differ from feature-based categories. Experiment 1 shows that our knowledge of role-governed categories, in contrast to feature-based categories, is largely about properties extrinsic to category members. Experiment 2 shows that role-governed categories have more prominent ideals than feature-based categories. Experiment 3 demonstrates that novel role-governed categories are licensed by the instantiation of novel relational structures. We then discuss broader implications for the study of categories and concepts.Copyright © 2010 Elsevier B.V. All rights reserved.
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Inductive reasoning can be performed in different contexts, but it is unclear whether the neural mechanism of reasoning performed in a thematic context (e.g., bee has x, so honey has x) is the same as that performed in a taxonomic context (e.g., bee has x, so butterfly has x). In the present study, participants were required to judge whether a conclusion was acceptable or not based on its premise, for which the taxonomic or thematic distances between premise and conclusion objects were either far or near. The Event related potential (ERP) results indicated that the effect of context (taxonomic vs. thematic) was initially observed in the P2 component; while the distance effect (far vs. near) was observed in N400 and late components. Moreover, the distance effect on thematic-based inductive reasoning was found in the anterior regions, while the distance effect on taxonomic-based inductive reasoning conditions was found in the posterior regions. These results support the view that inductive reasoning is performed differently under different semantic contexts.
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Despite the importance of semantic relationships to our understanding of semantic knowledge, the nature of the neural processes underlying these abilities are not well understood. In order to investigate these processes, 20 healthy adults listened to thematically related (e.g., leash-dog), taxonomically related (e.g., horse-dog), or unrelated (e.g., desk-dog) noun pairs as their EEG was recorded. The data were analyzed using both event-related potentials (ERP) and event-related spectral perturbation (ERSP) analyses. The spatiotemporal ERP and ERSP results were analyzed further with principal component analysis (PCA). When comparing unrelated to related word pairs, the expected N400 effect was confirmed, as well as differences in theta and alpha oscillations. When comparing thematically and taxonomically related word pairs, the ERP revealed no significant differences, but the ERSP did. Specifically, theta power increased over right frontal areas for thematic versus taxonomic relationships and alpha power increased over parietal areas for taxonomic versus thematic relationships. The different oscillatory patterns over different brain regions suggest that thematic and taxonomic relationships engage distinct neural processes. Specifically, thematic relationships engage memory processes, while taxonomic relationships may require additional inhibitory or attention processes.Copyright 2010 Elsevier Inc. All rights reserved.
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Fear learning reflects the adaptive ability to learn to anticipate aversive events and to display preparatory fear reactions based on prior experiences. Usually, these learning experiences are modeled in the lab with pairings between a neutral conditioned stimulus (CS) and an aversive unconditioned stimulus (US) (i.e., fear conditioning via CS-US pairings). Nevertheless, for humans, fear learning can also be based on verbal instructions. In this review, we consider the role of verbal instructions in laboratory fear learning. Specifically, we consider both the effects of verbal instructions on fear responses in the absence of CS-US pairings as well as the way in which verbal instructions moderate fear established via CS-US pairings. We first focus on the available empirical findings about both types of effects. More specifically, we consider how these effects are moderated by elements of the fear conditioning procedure (i.e., the stimuli, the outcome measures, the relationship between the stimuli, the participants, and the broader context). Thereafter, we discuss how well different mental-process models of fear learning account for these empirical findings. Finally, we conclude the review with a discussion of open questions and opportunities for future research.Copyright © 2018 Elsevier B.V. All rights reserved.
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Whether fear conditioning can take place without contingency awareness is a topic of continuing debate and conflicting findings have been reported in the literature. This systematic review provides a critical assessment of the available evidence. Specifically, a search was conducted to identify articles reporting fear conditioning studies in which the contingency between conditioned stimuli (CS) and the unconditioned stimulus (US) was masked, and in which CS-US contingency awareness was assessed. A systematic assessment of the methodological quality of the included studies (k = 41) indicated that most studies suffered from methodological limitations (i.e., poor masking procedures, poor awareness measures, researcher degrees of freedom, and trial-order effects), and that higher quality predicted lower odds of studies concluding in favor of contingency unaware fear conditioning. Furthermore, meta-analytic moderation analyses indicated no evidence for a specific set of conditions under which contingency unaware fear conditioning can be observed. Finally, funnel plot asymmetry and p-curve analysis indicated evidence for publication bias. We conclude that there is no convincing evidence for contingency unaware fear conditioning.Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.
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Posttraumatic stress disorder (PTSD) may develop when mechanisms for making accurate distinctions about threat relevance have gone awry. Generalization across conceptually related objects has been hypothesized based on clinical observation in PTSD, but the neural mechanisms remain unexplored. Recent trauma-exposed military veterans (n = 46) were grouped into PTSD (n = 23) and non-PTSD (n = 23). Participants learned to generalize fear across conceptual categories (animals or tools) of semantically related items that were partially reinforced by shock during functional magnetic resonance imaging. Conditioned fear learning was quantified by shock expectancy and skin conductance response (SCR). Relative to veteran controls, PTSD subjects exhibited a stronger neural response associated with fear generalization to the reinforced object category in the striatum, anterior cingulate cortex, amygdala, occipitotemporal cortex, and insula (Z > 2.3; p < 0.05; whole-brain corrected). Based on SCR, both groups generalized the shock contingency to the reinforced conceptual category, but learning was not significantly different between groups. We found that PTSD was associated with an enhanced neural response in fronto-limbic, midline, and occipitotemporal regions to a learned representation of threat that is based on previously established conceptual knowledge of the relationship between basic-level exemplars within a semantic category. Behaviorally, veterans with PTSD were somewhat slower to differentiate threat and safety categories as compared with trauma-exposed veteran controls owing in part to an initial overgeneralized behavioral response to the safe category. These results have implications for understanding how fear spreads across semantically related concepts in PTSD.
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The neuroplasticity hypothesis of depression proposes that a dysfunction of neural plasticity-the basic ability of living organisms to adapt their neural function and structure to external and internal cues-might represent a final common pathway underlying the biological and clinical characteristics of the disorder. This study examined learning and memory as correlates of long-term synaptic plasticity in humans to further test the neuroplasticity hypothesis of depression.Learning in three tasks, for which memory consolidation has been shown to depend on local synaptic refinement in areas of interest (hippocampus-dependent declarative word-pair learning, amygdala-dependent fear conditioning, and primary-cortex-dependent visual texture discrimination), was assessed in 23 inpatients who met International Classification of Disease, 10th Revision, criteria for severe unipolar depression and 35 nondepressed comparison subjects.Depressed subjects showed a significant deficit in declarative memory consolidation and enhanced fear acquisition as indicated by skin conductance responses to conditioned stimuli, in comparison with nondepressed subjects. Depressed subjects demonstrated impaired visual discrimination at baseline, not allowing for valid group comparisons of gradual improvement, the plasticity-dependent phase of the task.The results of the study are consistent with the neuroplasticity hypothesis of depression, showing decreased synaptic plasticity in a dorsal executive network that comprises the hippocampus and elevated synaptic plasticity in a ventral emotional network that includes the amygdala in depression. Evaluation of further techniques aimed at modulating synaptic plasticity might prove useful for developing novel treatments for major depressive disorder.Copyright © 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
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The structure of people's conceptual knowledge of concrete nouns has traditionally been viewed as hierarchical (Collins & Quillian, 1969). For example, superordinate concepts (vegetable) are assumed to reside at a higher level than basic-level concepts (carrot). A feature-based attractor network with a single layer of semantic features developed representations of both basic-level and superordinate concepts. No hierarchical structure was built into the network. In Experiment and Simulation 1, the graded structure of categories (typicality ratings) is accounted for by the flat attractor-network. Experiment and Simulation 2 show that, as with basic-level concepts, such a network predicts feature verification latencies for superordinate concepts (vegetable <is nutritious>). In Experiment and Simulation 3, counterintuitive results regarding the temporal dynamics of similarity in semantic priming are explained by the model. By treating both types of concepts the same in terms of representation, learning, and computations, the model provides new insights into semantic memory.
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Polycyclic aromatic compounds (PACs) are known due to their mutagenic activity. Among them, 2-nitrobenzanthrone (2-NBA) and 3-nitrobenzanthrone (3-NBA) are considered as two of the most potent mutagens found in atmospheric particles. In the present study 2-NBA, 3-NBA and selected PAHs and Nitro-PAHs were determined in fine particle samples (PM 2.5) collected in a bus station and an outdoor site. The fuel used by buses was a diesel-biodiesel (96:4) blend and light-duty vehicles run with any ethanol-to-gasoline proportion. The concentrations of 2-NBA and 3-NBA were, on average, under 14.8 µg g−1 and 4.39 µg g−1, respectively. In order to access the main sources and formation routes of these compounds, we performed ternary correlations and multivariate statistical analyses. The main sources for the studied compounds in the bus station were diesel/biodiesel exhaust followed by floor resuspension. In the coastal site, vehicular emission, photochemical formation and wood combustion were the main sources for 2-NBA and 3-NBA as well as the other PACs. Incremental lifetime cancer risk (ILCR) were calculated for both places, which presented low values, showing low cancer risk incidence although the ILCR values for the bus station were around 2.5 times higher than the ILCR from the coastal site.
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Wernicke (1900, as cited in G. H. Eggert, 1977) suggested that semantic knowledge arises from the interaction of perceptual representations of objects and words. The authors present a parallel distributed processing implementation of this theory, in which semantic representations emerge from mechanisms that acquire the mappings between visual representations of objects and their verbal descriptions. To test the theory, they trained the model to associate names, verbal descriptions, and visual representations of objects. When its inputs and outputs are constructed to capture aspects of structure apparent in attribute-norming experiments, the model provides an intuitive account of semantic task performance. The authors then used the model to understand the structure of impaired performance in patients with selective and progressive impairments of conceptual knowledge. Data from 4 well-known semantic tasks revealed consistent patterns that find a ready explanation in the model. The relationship between the model and related theories of semantic representation is discussed.
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Aversive pavlovian delay conditioning was investigated in a sample of 11 criminal psychopaths as identified by using the Psychopathy Checklist-Revised and 11 matched healthy controls. A painful electric stimulus served as unconditioned stimulus and neutral faces as conditioned stimuli. Event-related potentials, startle response potentiation, skin conductance response, corrugator activity, and heart rate were assessed, along with valence, arousal, and contingency ratings of the CS and US. Compared to healthy controls, psychopathic subjects failed to differentiate between the CS+/CS- as shown by an absence of a conditioned response in startle potentiation and skin conductance measures. Through use of a fear-eliciting US, these data confirm previous findings of a deficient capacity to form associations between neutral and aversive events in psychopathy that appears unrelated to cognitive deficits and is consistent with hypothesized frontolimbic deficits in the disorder.Copyright © 2012 Elsevier B.V. All rights reserved.
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Although the hippocampus is structurally quite different among reptiles, birds, and mammals, its function in spatial memory is said to be highly conserved. This is surprising, given that structural differences generally reflect functional differences. Here I review this enigma in some detail, identifying several evolutionary changes in hippocampal cytoarchitecture and connectivity. I recognize a lepidosaurid pattern of hippocampal organization (in lizards, snakes, and the tuatara Sphenodon) that differs substantially from the pattern of organization observed in the turtle/archosaur lineage, which includes crocodilians and birds. Although individual subdivisions of the hippocampus are difficult to homologize between these two patterns, both lack a clear homolog of the mammalian dentate gyrus. The strictly trilaminar organization of the ancestral amniote hippocampus was gradually lost in the lineage leading to birds, and birds expanded the system of intrahippocampal axon collaterals, relative to turtles and lizards. These expanded collateral axon branches resemble the extensive collaterals in CA3 of the mammalian hippocampus but probably evolved independently of them. Additional examples of convergent evolution between birds and mammals are the loss of direct inputs to the hippocampus from the primary olfactory cortex and the general expansion of telencephalic regions that communicate reciprocally with the hippocampus. Given this structural convergence, it seems likely that some similarities in the function of the hippocampus between birds and mammals, notably its role in the ability to remember many different locations without extensive training, likewise evolved convergently. The currently available data do not allow for a strong test of this hypothesis, but the hypothesis itself suggests some promising new research directions.© 2015 Wiley Periodicals, Inc.
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Many previous studies have demonstrated that the visual N1 component is larger for attended-location stimuli than for unattended-location stimuli. This difference is observed typically only for tasks involving a discrimination of the attended-location stimuli, suggesting that the N1 wave reflects a discrimination process that is applied to the attended location. The present study tested this hypothesis by examining the N1 component elicited by attended stimuli under conditions that either required or did not require the subject to perform a discrimination. Specifically, the N1 elicited by foveal stimuli during choice-reaction time (RT) tasks was compared with the N1 elicited by identical stimuli during simple-RT tasks. In three experiments, a larger posterior N1 was observed in choice-RT tasks than in simple-RT tasks, even when several potential confounds were eliminated (e.g., arousal and motor preparation). This N1 discrimination effect was observed even when no motor response was required and was present for both color- and form-based discriminations. Moreover, this discrimination effect was equally large for easy and difficult discriminations, arguing against a simple resource-based explanation of the present results. Instead, the results of this study are consistent with the hypothesis that the visual N1 component reflects the operation of a discrimination process within the focus of attention.
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Studies of human fear learning suggest that a reliable discrimination between safe and threatening stimuli is important for survival and mental health. In the current study, we applied the subsequent memory paradigm in order to identify neurophysiological correlates of successful threat and safety learning. We recorded event-related potentials, while participants incidentally learned associations between multiple neutral faces and an aversive outcome [unconditioned stimulus (US)/conditioned stimulus (CS)+] or no outcome (noUS/CS-). We found that an enhanced late positive potential (LPP) to both CS+ and CS- during learning predicted subsequent memory. A quadratic relationship between LPP and confidence in memory indicates a possible role in both correct and false fear memory. Importantly, the P300 to the omission of the US (following CS-) was enhanced for remembered CS-, while there was a positive correlation between P300 amplitude to both US occurrence and omission and individual memory performance. A following re-exposure phase indicated that memory was indeed related to subjective fear of the CS+/CS-. These results highlight the importance of cognitive resource allocation to both threat and safety for the acquisition of fear and suggest a potential role of the P300 to US omission as an electrophysiological marker of successful safety learning.© The Author(s) 2021. Published by Oxford University Press.
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The authors explored three properties of basic, unconsciously triggered affective reactions: They can influence consequential behavior, they work without eliciting conscious feelings, and they interact with motivation. The authors investigated these properties by testing the influence of subliminally presented happy versus angry faces on pouring and consumption of beverage (Study 1), perception of beverage value (Study 2), and reports of conscious feelings (both studies). Consistent with incentive motivation theory, the impact of affective primes on beverage value and consumption was strongest for thirsty participants. Subliminal smiles caused thirsty participants to pour and consume more beverage (Study 1) and increased their willingness to pay and their wanting more beverage (Study 2). Subliminal frowns had the opposite effect. No feeling changes were observed, even in thirsty participants. The results suggest that basic affective reactions can be unconscious and interact with incentive motivation to influence assessment of value and behavior toward valenced objects.
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Fear conditioning and generalization are well-known mechanisms in the pathogenesis of anxiety disorders. Extinction of conditioned fear responses is crucial for the psychotherapeutic treatment of these diseases. Anxious depression as a subtype of major depression shares characteristics with anxiety disorders. We therefore aimed to compare fear learning mechanisms in patients with anxious versus non-anxious depression. Fear learning mechanisms in patients with major depression (n = 79; for subgroup analyses n = 41 patients with anxious depression and n = 38 patients with non-anxious depression) were compared to 48 healthy participants. We used a well-established differential fear conditioning paradigm investigating acquisition, generalization, and extinction. Ratings of valence, arousal and probability of expected threat were assessed as well as skin conductance response as an objective psychophysiological measure. Patients with major depression showed impaired acquisition of conditioned fear. In addition, depressed patients showed impaired extinction of conditioned fear responses after successful fear conditioning. Generalization was not affected. However, there was no difference between patients with anxious and non-anxious depression. Results differed between objective and subjective measures. Our findings show altered fear acquisition and extinction in major depression as compared to healthy controls, but they do not favor differential fear learning and extinction mechanisms in the pathogenesis of anxious versus non-anxious depression. The results of impaired extinction warrant future studies addressing extinction learning elements in the treatment of depression.Copyright © 2021 Elsevier Ltd. All rights reserved.
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| [64] |
This study aims to examine the process of L2 novel word learning through the combination of episodic and semantic memory, and how the process differs between the formation of thematic and taxonomic relations. The major approach adopted was observing the neural effects of word learning, which is manifested in the N400 from event-related potentials (ERPs). Eighty-eight participants were recruited for the experiment. In the learning session, L2 contextual discourses related to novel words were learned by participants. In the testing session, discourses embedded with incongruous and congruous novel words in the final position were used for participants to judge the congruency which affected the N400 neural activity. The results showed that both recurrent and new-theme discourses elicited significant N400 effects, while taxonomic sentences did not. These results confirmed the formation of episodic and semantic memory during L2 new word learning, in which semantic memory was mainly supported by thematic relations.
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| [65] |
Major depressive disorder (MDD) is associated with behavioral and neurobiological evidences of negative bias in unconscious emotional processing. However, little is known about the time course of this deficit. The current study aimed to explore the unconscious processing of emotional facial expressions in MDD patients by means of event-related potentials (ERPs).The ERP responses to subliminally presented happy/neutral/sad faces were recorded in 26 medication-free patients and 26 healthy controls in a backward masking task. Three ERP components were compared between patients and controls.Detection accuracy was at chance level for both groups, suggesting that the process was performed in the absence of conscious awareness of the emotional stimuli. Robust emotion×group interactions were observed in P1, N170 and P3. Compared with the neutral faces, 1) the patients showed larger P1 for sad and smaller P1 for happy faces; however, the controls showed a completely inverse P1 pattern; 2) the controls exhibited larger N170 in the happy but not in the sad trials, whereas patients had comparable larger N170 amplitudes in sad and happy trials; 3) although both groups exhibited larger P3 for emotional faces, the patients showed a priority for sad trials while the controls showed a priority for happy trials.Our data suggested that negative processing bias exists on the unconscious level in individuals with MDD. The ERP measures indicated that the unconscious emotional processing in MDD patients has a time course of three-stage deflection.Copyright © 2016 Elsevier B.V. All rights reserved.
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