Emotion processing and the amygdala: from a 'low road' to 'many roads' of evaluating biological significance

A brain network instantiating approach and avoidance motivation

Research indicates that dorsolateral prefrontal cortex (DLPFC) is important for pursuing goals, and areas of DLPFC are differentially involved in approach and avoidance motivation. Given the complexity of the processes involved in goal pursuit, DLPFC is likely part of a network that includes orbitofrontal cortex (OFC), cingulate, amygdala, and basal ganglia. This hypothesis was tested with regard to one component of goal pursuit, the maintenance of goals in the face of distraction. Examination of connectivity with motivation-related areas of DLPFC supported the network hypothesis. Differential patterns of connectivity suggest a distinct role for DLPFC areas, with one involved in selecting approach goals, one in selecting avoidance goals, and one in selecting goal pursuit strategies. Finally, differences in trait motivation moderated connectivity between DLPFC and OFC, suggesting that this connectivity is important for instantiating motivation.

Threat, domain-specificity and the human amygdala

It is well documented that the human amygdala responds strongly to human faces, especially when depicting negative emotions. The extent to which the amygdala also responds to other animate entities - as well as to inanimate objects - and how that response is modulated by the object's perceived affective valence and arousal value remains unclear. To address these issues, subjects performed a repetition detection task to photographs of negative, neutral, and positive faces, animals, and manipulable objects equated for emotional valence and arousal level. Both the left and right amygdala responded more to animate entities than manipulable objects, especially for negative objects (fearful faces, threatening animals, versus weapons) and to neutral stimuli (faces with neutral expressions, neutral animals, versus tools). Thus, in the absence of contextual cues, the human amygdala responds to threat associated with some object categories (animate things) but not others (weapons). Although failing to activate the amygdala, relative to viewing other manipulable objects, viewing weapons did elicit an enhanced response in dorsal stream regions linked to object action. Thus, our findings suggest two circuits underpinning an automatic response to threatening stimuli; an amygdala-based circuit for animate entities, and a cortex-based circuit for responding to manmade, manipulable objects.

Spatial Frequency Tuning during the Conscious and Non-Conscious Perception of Emotional Facial Expressions - An Intracranial ERP Study

Previous studies have shown that complex visual stimuli, such as emotional facial expressions, can influence brain activity independently of the observers’ awareness. Little is known yet, however, about the “informational correlates” of consciousness – i.e., which low-level information correlates with brain activation during conscious vs. non-conscious perception. Here, we investigated this question in the spatial frequency (SF) domain. We examined which SFs in disgusted and fearful faces modulate activation in the insula and amygdala over time and as a function of awareness, using a combination of intracranial event-related potentials (ERPs), SF Bubbles (Willenbockel et al., 2010a), and Continuous Flash Suppression (CFS; Tsuchiya and Koch, 2005). Patients implanted with electrodes for epilepsy monitoring viewed face photographs (13° × 7°) that were randomly SF filtered on a trial-by-trial basis. In the conscious condition, the faces were visible; in the non-conscious condition, they were rendered invisible using CFS. The data were analyzed by performing multiple linear regressions on the SF filters from each trial and the transformed ERP amplitudes across time. The resulting classification images suggest that many SFs are involved in the conscious and non-conscious perception of emotional expressions, with SFs between 6 and 10 cycles per face width being particularly important early on. The results also revealed qualitative differences between the awareness conditions for both regions. Non-conscious processing relied on low SFs more and was faster than conscious processing. Overall, our findings are consistent with the idea that different pathways are employed for the processing of emotional stimuli under different degrees of awareness. The present study represents a first step to mapping how SF information “flows” through the emotion-processing network with a high temporal resolution and to shedding light on the informational correlates of consciousness in general.

Turn down the volume or change the channel? Emotional effects of detached versus positive reappraisal

Cognitive reappraisal, or changing one's interpretation of an event in order to alter the emotional response to it, is thought to be a healthy and an effective emotion regulation strategy. Although researchers recognize several distinct varieties of reappraisal, few studies have explicitly compared the effects of multiple reappraisal strategies on emotional responding. The present study compares the effects of detached and positive reappraisal on thought content, subjective emotional experience, physiological reactivity, and facial expressions of emotion while viewing film clips evoking sadness and disgust. Although both forms of reappraisal reduced overall emotional responding to unpleasant stimuli, the effects of detached reappraisal were stronger in this regard, and positive reappraisal was more likely to maintain subjective experience and facial expression of stimulus-appropriate positive emotions. The two reappraisal strategies also produced somewhat different profiles of physiological responding. Differences between detached and positive reappraisal with respect to subjective experience and facial expression were more pronounced among men than women; the reverse was true for differences with respect to physiological responding. Beyond these effects on individual emotion response systems, detached and positive reappraisal also had somewhat different effects on coherence in change across response systems. Implications for our understanding of emotion regulation processes, and for emotion theory more broadly, are discussed.

Neural substrates of childhood anxiety disorders: a review of neuroimaging findings

The development of fear is a normative process, and significant progress has been made in identifying fear neurocircuitry. The normal development of fear goes awry in children who develop anxiety disorders, and dysfunction in fear circuitry is likely. In this article, the authors present current knowledge about the neural basis of normal fear development and reviews findings from structural and functional neuroimaging studies of childhood anxiety disorders.

Acquired fears reflected in cortical sensory processing: a review of electrophysiological studies of human classical conditioning

The capacity to associate neutral stimuli with affective value is an important survival strategy that can be accomplished by cell assemblies obeying Hebbian learning principles. In the neuroscience laboratory, classical fear conditioning has been extensively used as a model to study learning-related changes in neural structure and function. Here, we review the effects of classical fear conditioning on electromagnetic brain activity in humans, focusing on how sensory systems adapt to changing fear-related contingencies. By considering spatiotemporal patterns of mass neuronal activity, we illustrate a range of cortical changes related to a retuning of neuronal sensitivity to amplify signals consistent with fear-associated stimuli at the cost of other sensory information. Putative mechanisms that may underlie fear-associated plasticity at the level of the sensory cortices are briefly considered, and several avenues for future work are outlined.

Affect-biased attention as emotion regulation

The affective biasing of attention is not typically considered to be a form of emotion regulation. In this article, we argue that 'affect-biased attention' - the predisposition to attend to certain categories of affectively salient stimuli over others - provides an important component of emotion regulation. Affect-biased attention regulates subsequent emotional responses by tuning one's filters for initial attention and subsequent processing. By reviewing parallel research in the fields of emotion regulation and affect-biased attention, as well as clinical and developmental research on individual differences in attentional biases, we provide convergent evidence that habitual affective filtering processes, tuned and re-tuned over development and situation, modulate emotional responses to the world. Moreover, they do so in a manner that is proactive rather than reactive.

Pathways for emotions and attention converge on the thalamic reticular nucleus in primates

How do emotional events readily capture our attention? To address this question we used neural tracers to label pathways linking areas involved in emotional and attentional processes in the primate brain (Macaca mulatta). We report that a novel pathway from the amygdala, the brain's emotional center, targets the inhibitory thalamic reticular nucleus (TRN), a key node in the brain's attentional network. The amygdalar pathway formed unusual synapses close to cell bodies of TRN neurons and had more large and efficient terminals than pathways from the orbitofrontal cortex and the thalamic mediodorsal nucleus, which similarly innervated extensive TRN sites. The robust amygdalar pathway provides a mechanism for rapid shifting of attention to emotional stimuli. Acting synergistically, pathways from the amygdala and orbitofrontal cortex provide a circuit for purposeful assessment of emotional stimuli. The different pathways to TRN suggest distinct mechanisms of attention to external and internal stimuli that may be differentially disrupted in anxiety and mood disorders and may be selectively targeted for therapeutic interventions.

Top-down modulation of the perception of other people in schizophrenia and autism

Accurately and efficiently perceiving social cues such as body movements and facial expressions is important in social interaction. Accurate social perception of this kind does not solely rely on “bottom-up” visual processing but is also subject to modulation by “top-down” signals. For example, if instructed to look for signs of happiness rather than fear, participants are more likely to categorize facial expressions as happy—this prior expectation biases subsequent perception. Top-down modulation is also important in our reactions to others. For example, top-down control over imitation plays an important role in the development of smooth and harmonious social interactions. This paper highlights the importance of top-down modulation in our perception of, and reactions to, others. We discuss evidence that top-down modulation of social perception and imitation is atypical in Autism Spectrum Conditions and in schizophrenia, and we consider the effect this may have on the development of social interactions for individuals with these developmental disorders.

Revise the revised? New dimensions of the neuroanatomical hypothesis of panic disorder

In 2000, Gorman et al. published a widely acknowledged revised version of their 1989 neuroanatomical hypothesis of panic disorder (PD). Herein, a 'fear network' was suggested to mediate fear- and anxiety-related responses: panic attacks result from a dysfunctional coordination of 'upstream' (cortical) and 'downstream' (brainstem) sensory information leading to heightened amygdala activity with subsequent behavioral, autonomic and neuroendocrine activation. Given the emergence of novel imaging methods such as fMRI and the publication of numerous neuroimaging studies regarding PD since 2000, a comprehensive literature search was performed regarding structural (CT, MRI), metabolic (PET, SPECT, MRS) and functional (fMRI, NIRS, EEG) studies on PD, which will be reviewed and critically discussed in relation to the neuroanatomical hypothesis of PD. Recent findings support structural and functional alterations in limbic and cortical structures in PD. Novel insights regarding structural volume increase or reduction, hyper- or hypoactivity, laterality and task-specificity of neural activation patterns emerged. The assumption of a generally hyperactive amygdala in PD seems to apply more to state than trait characteristics of PD, and involvement of further areas in the fear circuit, such as anterior cingulate and insula, is suggested. Furthermore, genetic risk variants have been proposed to partly drive fear network activity. Thus, the present state of knowledge generally supports limbic and cortical prefrontal involvement as originally proposed in the neuroanatomical hypothesis. Some modifications might be suggested regarding a potential extension of the fear circuit, genetic factors shaping neural network activity and neuroanatomically informed clinical subtypes of PD potentially guiding future treatment decisions.

Dynamic modulation of emotional processing

Recent findings suggest the processing of emotional stimuli is prioritized compared to neutral stimuli; however, it is not necessarily automatic and depends on several modulating factors. The current paper highlights three major factors that affect the reactions to emotional stimuli: (i) stimulus properties, (ii) task demands and attention, and (iii) individual characteristics. The evidence reviewed here suggests that individual characteristics shape the structure, function and connectivity within a neural network that is involved in the reactions to emotional stimuli. This neural network includes regions related to emotion and attention, in line with evidence for reciprocal connections between these two processes. Activation in this network further depends on the emotional value of a certain item, as well as physical features of the stimulus. This integrative view can lead to better understanding of the underlying mechanisms of emotional reactions, as well as better therapeutic approaches.

The brain basis of emotion: a meta-analytic review

Researchers have wondered how the brain creates emotions since the early days of psychological science. With a surge of studies in affective neuroscience in recent decades, scientists are poised to answer this question. In this target article, we present a meta-analytic summary of the neuroimaging literature on human emotion. We compare the locationist approach (i.e., the hypothesis that discrete emotion categories consistently and specifically correspond to distinct brain regions) with the psychological constructionist approach (i.e., the hypothesis that discrete emotion categories are constructed of more general brain networks not specific to those categories) to better understand the brain basis of emotion. We review both locationist and psychological constructionist hypotheses of brain-emotion correspondence and report meta-analytic findings bearing on these hypotheses. Overall, we found little evidence that discrete emotion categories can be consistently and specifically localized to distinct brain regions. Instead, we found evidence that is consistent with a psychological constructionist approach to the mind: A set of interacting brain regions commonly involved in basic psychological operations of both an emotional and non-emotional nature are active during emotion experience and perception across a range of discrete emotion categories.

The influence of prior expectations on emotional face perception in adolescence

Prior expectations influence the way incoming stimuli are processed. A standard, validated way of manipulating prior expectations is to bias participants to perceive a stimulus by instructing them to look out for this type of stimulus. Here, we investigated the influence of prior expectations on the processing of incoming stimuli (emotional faces) in adolescence. Using functional magnetic resonance imaging, we assessed activity and functional connectivity in 13 adolescents and 13 healthy adults (matched for gender and intelligence quotient), while they were presented with sequences of emotional faces (happy, fearful, or angry). A specific instruction at the start of each sequence instructed the participants to look out for fearful or angry faces in the subsequent sequence. Both groups responded more accurately and with shorter reaction times (RTs) to faces that were congruent with the instruction. For anger, this bias was lower in the adolescents (for RTs), and adults demonstrated greater activation than adolescents in the ventro-medial prefrontal cortex (vMPFC) and greater functional connectivity between the vMPFC and the thalamus when the face was congruent with the instruction. Our results demonstrate that the influence of prior expectations (in the form of an instruction) on the subsequent processing of face stimuli is still developing in the adolescent brain.

Brain circuitries involved in semantic interference by demands of emotional and non-emotional distractors

BACKGROUND

Previous studies have indicated that the processes leading to the resolution of emotional and non-emotional interference conflicts are unrelated, involving separate networks. It is also known that conflict resolution itself suggests a considerable overlap of the networks. Our study is an attempt to examine how these findings may be related.

METHODOLOGY/PRINCIPAL FINDINGS

We used functional magnetic resonance imaging (fMRI) to study neural responses of 24 healthy subjects to emotional and non-emotional conflict paradigms involving the presentation of congruent and incongruent word-face pairs based on semantic incompatibility between targets and distractors. In the emotional task, the behavioral interference conflict was greater (compared to the non-emotional task) and was paralleled by involvement of the extrastriate visual and posterodorsal medial frontal cortices. In both tasks, we also observed a common network including the dorsal anterior cingulate, the supplemental motor area, the anterior insula and the inferior prefrontal cortex, indicating that these brain structures are markers of experienced conflict. However, the emotional task involved conflict-triggered networks to a considerably higher degree.

CONCLUSIONS/SIGNIFICANCE

Our findings indicate that responses to emotional and non-emotional distractors involve the same systems, which are capable of flexible adjustments based on conflict demands. The function of systems related to conflict resolution is likely to be adjusted on the basis of an evaluation process that primarily involves the extrastriate visual cortex, with target playing a significant role.

Signature movements lead to efficient search for threatening actions

The ability to find and evade fighting persons in a crowd is potentially life-saving. To investigate how the visual system processes threatening actions, we employed a visual search paradigm with threatening boxer targets among emotionally-neutral walker distractors, and vice versa. We found that a boxer popped out for both intact and scrambled actions, whereas walkers did not. A reverse correlation analysis revealed that observers' responses clustered around the time of the “punch", a signature movement of boxing actions, but not around specific movements of the walker. These findings support the existence of a detector for signature movements in action perception. This detector helps in rapidly detecting aggressive behavior in a crowd, potentially through an expedited (sub)cortical threat-detection mechanism.

Beyond brain regions: Network perspective of cognition–emotion interactions

Lindquist et al. provide a convincing case against what they call the locationist account of emotion. Their quantitative approach elegantly illustrates the shortcomings of this still-entrenched viewpoint. Here, I discuss how a network perspective will advance our understanding of structure-function mappings in general, and the relationship between emotion and cognition in the brain.

Quantitative meta-analysis of neural activity in posttraumatic stress disorder

BACKGROUND

In recent years, neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have played a significant role in elucidating the neural underpinnings of posttraumatic stress disorder (PTSD). However, a detailed understanding of the neural regions implicated in the disorder remains incomplete because of considerable variability in findings across studies. The aim of this meta-analysis was to identify consistent patterns of neural activity across neuroimaging study designs in PTSD to improve understanding of the neurocircuitry of PTSD.

METHODS

We conducted a literature search for PET and fMRI studies of PTSD that were published before February 2011. The article search resulted in 79 functional neuroimaging PTSD studies. Data from 26 PTSD peer-reviewed neuroimaging articles reporting results from 342 adult patients and 342 adult controls were included. Peak activation coordinates from selected articles were used to generate activation likelihood estimate maps separately for symptom provocation and cognitive-emotional studies of PTSD. A separate meta-analysis examined the coupling between ventromedial prefrontal cortex and amygdala activity in patients.

RESULTS

Results demonstrated that the regions most consistently hyperactivated in PTSD patients included mid- and dorsal anterior cingulate cortex, and when ROI studies were included, bilateral amygdala. By contrast, widespread hypoactivity was observed in PTSD including the ventromedial prefrontal cortex and the inferior frontal gyrus. Furthermore, decreased ventromedial prefrontal cortex activity was associated with increased amygdala activity.

CONCLUSIONS

These results provide evidence for a neurocircuitry model of PTSD that emphasizes alteration in neural networks important for salience detection and emotion regulation.

Social anxiety modulates subliminal affective priming

Background

It is well established that there is anxiety-related variation between observers in the very earliest, pre-attentive stage of visual processing of images such as emotionally expressive faces, often leading to enhanced attention to threat in a variety of disorders and traits. Whether there is also variation in early-stage affective (i.e. valenced) responses resulting from such images, however, is not yet known. The present study used the subliminal affective priming paradigm to investigate whether people varying in trait social anxiety also differ in their affective responses to very briefly presented, emotionally expressive face images.

Methodology/Principal Findings

Participants (n = 67) completed a subliminal affective priming task, in which briefly presented and smiling, neutral and angry faces were shown for 10 ms durations (below objective and subjective thresholds for visual discrimination), and immediately followed by a randomly selected Chinese character mask (2000 ms). Ratings of participants' liking for each Chinese character indicated the degree of valenced affective response made to the unseen emotive images. Participants' ratings of their liking for the Chinese characters were significantly influenced by the type of face image preceding them, with smiling faces generating more positive ratings than neutral and angry ones (F(2,128) = 3.107, p<0.05). Self-reported social anxiety was positively correlated with ratings of smiling relative to neutral-face primed characters (Pearson's r = .323, p<0.01). Individual variation in self-reported mood awareness was not associated with ratings.

Conclusions

Trait social anxiety is associated with individual variation in affective responding, even in response to the earliest, pre-attentive stage of visual image processing. However, the fact that these priming effects are limited to smiling and not angry (i.e. threatening) images leads us to propose that the pre-attentive processes involved in generating the subliminal affective priming effect may be different from those that generate attentional biases in anxious individuals.

Response of neural reward regions to food cues in autism spectrum disorders

Background

One hypothesis for the social deficits that characterize autism spectrum disorders (ASD) is diminished neural reward response to social interaction and attachment. Prior research using established monetary reward paradigms as a test of non-social reward to compare with social reward may involve confounds in the ability of individuals with ASD to utilize symbolic representation of money and the abstraction required to interpret monetary gains. Thus, a useful addition to our understanding of neural reward circuitry in ASD includes a characterization of the neural response to primary rewards.

Method

We asked 17 children with ASD and 18 children without ASD to abstain from eating for at least four hours before an MRI scan in which they viewed images of high-calorie foods. We assessed the neural reward network for increases in the blood oxygenation level dependent (BOLD) signal in response to the food images

Results

We found very similar patterns of increased BOLD signal to these images in the two groups; both groups showed increased BOLD signal in the bilateral amygdala, as well as in the nucleus accumbens, orbitofrontal cortex, and insula. Direct group comparisons revealed that the ASD group showed a stronger response to food cues in bilateral insula along the anterior-posterior gradient and in the anterior cingulate cortex than the control group, whereas there were no neural reward regions that showed higher activation for controls than for ASD.

Conclusion

These results suggest that neural response to primary rewards is not diminished but in fact shows an aberrant enhancement in children with ASD.

Disturbance of emotion processing in frontotemporal dementia: a synthesis of cognitive and neuroimaging findings

Accurate processing of emotional information is a critical component of appropriate social interactions and interpersonal relationships. Disturbance of emotion processing is present in frontotemporal dementia (FTD) and is a clinical feature in two of the three subtypes: behavioural-variant FTD and semantic dementia. Emotion processing in progressive nonfluent aphasia, the third FTD subtype, is thought to be mostly preserved, although current evidence is scant. This paper reviews the literature on emotion recognition, reactivity and expression in FTD subtypes, although most studies focus on emotion recognition. The relationship between patterns of emotion processing deficits and patterns of neural atrophy are considered, by integrating evidence from recent neuroimaging studies. The review findings are discussed in the context of three contemporary theories of emotion processing: the limbic system model, the right hemisphere model and a multimodal system of emotion. Results across subtypes of FTD are most consistent with the multimodal system model, and support the presence of somewhat dissociable neural correlates for basic emotions, with strongest evidence for the emotions anger and sadness. Poor emotion processing is evident in all three subtypes, although deficits are more widespread than what would be predicted based on studies in healthy cohorts. Studies that include behavioural and imaging data are limited. Future investigations combining these approaches will help improve the understanding of the neural network underlying emotion processing. Presently, longitudinal investigations of emotion processing in FTD are lacking, and studies investigating emotion processing over time are critical to understand the clinical manifestations of disease progression in FTD.

The role of low and high spatial frequencies in exogenous attention to biologically salient stimuli

Exogenous attention can be understood as an adaptive tool that permits the detection and processing of biologically salient events even when the individual is engaged in a resource-consuming task. Indirect data suggest that the spatial frequency of stimulation may be a crucial element in this process. Behavioral and neural data (both functional and structural) were analyzed for 36 participants engaged in a digit categorization task in which distracters were presented. Distracters were biologically salient or anodyne images, and had three spatial frequency formats: intact, low spatial frequencies only, and high spatial frequencies only. Behavior confirmed enhanced exogenous attention to biologically salient distracters. The activity in the right and left intraparietal sulci and the right middle frontal gyrus was associated with this behavioral pattern and was greater in response to salient than to neutral distracters, the three areas presenting strong correlations to each other. Importantly, the enhanced response of this network to biologically salient distracters with respect to neutral distracters relied on low spatial frequencies to a significantly greater extent than on high spatial frequencies. Structural analyses suggested the involvement of internal capsule, superior longitudinal fasciculus and corpus callosum in this network. Results confirm that exogenous attention is preferentially captured by biologically salient information, and suggest that the architecture and function underlying this process are low spatial frequency-biased.

Hypervigilance for fear after basolateral amygdala damage in humans

Recent rodent research has shown that the basolateral amygdala (BLA) inhibits unconditioned, or innate, fear. It is, however, unknown whether the BLA acts in similar ways in humans. In a group of five subjects with a rare genetic syndrome, that is, Urbach-Wiethe disease (UWD), we used a combination of structural and functional neuroimaging, and established focal, bilateral BLA damage, while other amygdala sub-regions are functionally intact. We tested the translational hypothesis that these BLA-damaged UWD-subjects are hypervigilant to facial expressions of fear, which are prototypical innate threat cues in humans. Our data indeed repeatedly confirm fear hypervigilance in these UWD subjects. They show hypervigilant responses to unconsciously presented fearful faces in a modified Stroop task. They attend longer to the eyes of dynamically displayed fearful faces in an eye-tracked emotion recognition task, and in that task recognize facial fear significantly better than control subjects. These findings provide the first direct evidence in humans in support of an inhibitory function of the BLA on the brain's threat vigilance system, which has important implications for the understanding of the amygdala's role in the disorders of fear and anxiety.

Immature integration and segregation of emotion-related brain circuitry in young children

The human brain undergoes protracted development, with dramatic changes in expression and regulation of emotion from childhood to adulthood. The amygdala is a brain structure that plays a pivotal role in emotion-related functions. Investigating developmental characteristics of the amygdala and associated functional circuits in children is important for understanding how emotion processing matures in the developing brain. The basolateral amygdala (BLA) and centromedial amygdala (CMA) are two major amygdalar nuclei that contribute to distinct functions via their unique pattern of interactions with cortical and subcortical regions. Almost nothing is currently known about the maturation of functional circuits associated with these amygdala nuclei in the developing brain. Using intrinsic connectivity analysis of functional magnetic resonance imaging data, we investigated developmental changes in functional connectivity of the BLA and CMA in twenty-four 7- to 9-y-old typically developing children compared with twenty-four 19- to 22-y-old healthy adults. Children showed significantly weaker intrinsic functional connectivity of the amygdala with subcortical, paralimbic, and limbic structures, polymodal association, and ventromedial prefrontal cortex. Importantly, target networks associated with the BLA and CMA exhibited greater overlap and weaker dissociation in children. In line with this finding, children showed greater intraamygdala connectivity between the BLA and CMA. Critically, these developmental differences were reproducibly identified in a second independent cohort of adults and children. Taken together, our findings point toward weak integration and segregation of amygdala circuits in young children. These immature patterns of amygdala connectivity have important implications for understanding typical and atypical development of emotion-related brain circuitry.

Emotional perception: correspondence of early and late event-related potentials with cortical and subcortical functional MRI

This research examines the relationship between brain activity recorded with functional magnetic resonance imaging (fMRI) and event related potentials (ERP) as these responses varied over a series of emotionally evocative and neutral pictures. We investigate the relationship of early occipitotemporal and later centroparietal emotion-modulated ERPs in one sample to fMRI estimates of neural activity in another sample in a replicated experiment. Using this approach, we aimed to link effects found in time-resolved electrocortical measures to specific neural structures across individual emotional and nonemotional picture stimuli. The centroparietal late positive potential (LPP) showed covariation with emotion-modulated regions of hemodynamic activation across multiple dorsal and ventral visual cortical structures, while the early occipitotemporal potential was not reliably associated. Subcortical and corticolimbic structures involved in the perception of motivationally relevant stimuli also related to modulation of the LPP, and were modestly associated to the amplitude of the early occipitotemporal potential. These data suggest that early occipitotemporal potentials may reflect multiple sources of modulation including motivational relevance, and supports the perspective that the slow-wave LPP represents aggregate cortical and subcortical structures involved in emotional discrimination.

Out of sight but not out of mind: unseen affective faces influence evaluations and social impressions

Using Continuous Flash Suppression (CFS), we demonstrated in four experiments that affective information extracted from unseen faces influences both affective and personality judgments of neutral faces. In four experiments, participants judged neutral faces as more pleasant or unpleasant (Studies 1 and 2) or as more or less trustworthy, likable, and attractive (Study 3) or as more or less competent or interpersonally warm (Study 4) when paired with unseen smiling or scowling faces compared to when paired with unseen neutral faces. These findings suggest that affective influences are a normal part of everyday experience and provide evidence for the affective foundations consciousness. Affective misattribution arises even when affective changes occur after a neutral stimulus is presented, demonstrating that these affective influences cannot be explained as a simple semantic priming effect. These findings have implications for understanding the constructive nature of experience, as well as the role of affect in social impressions.

The hippocampus reevaluated in unconscious learning and memory: at a tipping point?

Classic findings from the neuropsychological literature invariably indicated that performances on tests of memory that can be accomplished without conscious awareness were largely spared in amnesia, while those that required conscious retrieval (e.g., via recognition or recall) of information learned in the very same sessions was devastatingly impaired. Based on reports of such dissociations, it was proposed that one of the fundamental distinctions between memory systems is whether or not they support conscious access to remembered content. Only recently have we come to realize that the putative systemic division of labor between conscious and unconscious memory is not so clean. A primary goal of this review is to examine recent evidence that has been advanced against the view that the hippocampus is selectively critical for conscious memory. Along the way, consideration is given to criticisms that have been levied against these findings, potential explanations for differences in the reported results are proposed, and methodological pitfalls in investigations of unconscious memory are discussed. Ultimately, it is concluded that a tipping point has been reached, and that while conscious recollection depends critically on hippocampal integrity, the reach of the hippocampus extends to unconscious aspects of memory performance when relational memory processing and representation are required.

Attention biases, anxiety, and development: toward or away from threats or rewards?

Research on attention provides a promising framework for studying anxiety pathophysiology and treatment. The study of attention biases appears particularly pertinent to developmental research, as attention affects learning and has down-stream effects on behavior. This review summarizes recent findings about attention orienting in anxiety, drawing on findings in recent developmental psychopathology and affective neuroscience research. These findings generate specific insights about both development and therapeutics. The review goes beyond a traditional focus on biased processing of threats and considers biased processing of rewards. Building on this work, we then turn to the treatment of pediatric anxiety, where manipulation of attention to threat and/or reward may serve a therapeutic role as a component of Attention Bias Modification Therapy.

Does emotional memory enhancement assist the memory-impaired?

We review recent work on emotional memory enhancement in older adults and patients with mild cognitive impairment (MCI) or Alzheimer dementia (AD) and evaluate the viability of incorporating emotional components into cognitive rehabilitation for these groups. First, we identify converging evidence regarding the effects of emotional valence on working memory in healthy aging. Second, we introduce work that suggests a more complex role for emotional memory enhancement in aging and identify a model capable of unifying disparate research findings. Third, we survey the neuroimaging literature for evidence of a special role for the amygdala in MCI and early AD in emotional memory enhancement. Finally, we assess the theoretical feasibility of incorporating emotional content into cognitive rehabilitation given all available evidence.

Decoding unattended fearful faces with whole-brain correlations: an approach to identify condition-dependent large-scale functional connectivity

Processing of unattended threat-related stimuli, such as fearful faces, has been previously examined using group functional magnetic resonance (fMRI) approaches. However, the identification of features of brain activity containing sufficient information to decode, or "brain-read", unattended (implicit) fear perception remains an active research goal. Here we test the hypothesis that patterns of large-scale functional connectivity (FC) decode the emotional expression of implicitly perceived faces within single individuals using training data from separate subjects. fMRI and a blocked design were used to acquire BOLD signals during implicit (task-unrelated) presentation of fearful and neutral faces. A pattern classifier (linear kernel Support Vector Machine, or SVM) with linear filter feature selection used pair-wise FC as features to predict the emotional expression of implicitly presented faces. We plotted classification accuracy vs. number of top N selected features and observed that significantly higher than chance accuracies (between 90-100%) were achieved with 15-40 features. During fearful face presentation, the most informative and positively modulated FC was between angular gyrus and hippocampus, while the greatest overall contributing region was the thalamus, with positively modulated connections to bilateral middle temporal gyrus and insula. Other FCs that predicted fear included superior-occipital and parietal regions, cerebellum and prefrontal cortex. By comparison, patterns of spatial activity (as opposed to interactivity) were relatively uninformative in decoding implicit fear. These findings indicate that whole-brain patterns of interactivity are a sensitive and informative signature of unattended fearful emotion processing. At the same time, we demonstrate and propose a sensitive and exploratory approach for the identification of large-scale, condition-dependent FC. In contrast to model-based, group approaches, the current approach does not discount the multivariate, joint responses of multiple functional connections and is not hampered by signal loss and the need for multiple comparisons correction.

Cortical functional connectivity decodes subconscious, task-irrelevant threat-related emotion processing

It is currently unclear to what extent cortical structures are required for and engaged during subconscious processing of biologically salient affective stimuli (i.e. the 'low-road' vs. 'many-roads' hypotheses). Here we show that cortical-cortical and cortical-subcortical functional connectivity (FC) contain substantially more information, relative to subcortical-subcortical FC (i.e. 'subcortical alarm' and other limbic regions), that predicts subliminal fearful face processing within individuals using training data from separate subjects. A plot of classification accuracy vs. number of selected whole-brain FC features revealed 92% accuracy when learning was based on the top 8 features from each training set. The most informative FC was between right amygdala and precuneus, which increased during subliminal fear conditions, while left and right amygdala FC decreased, suggesting a bilateral decoupling of this key limbic region during processing of subliminal fear-related stimuli. Other informative FC included angular gyrus, middle temporal gyrus and cerebellum. These findings identify FC that decodes subliminally perceived, task-irrelevant affective stimuli, and suggest that cortical structures are actively engaged by and appear to be essential for subliminal fear processing.

Hemispheric asymmetry and visuo-olfactory integration in perceiving subthreshold (micro) fearful expressions

Multisensory integration is ubiquitous, facilitating perception beyond the limit of individual senses. This mechanism is especially salient when individual sensory input is weak (i.e., the principle of inverse effectiveness), fusing subthreshold cues into tangible percepts. Nevertheless, it is unclear how this rule applies to threat perception, synthesizing elusive, discrete traces of a threat into a discernible danger signal. In light of hemispheric asymmetry in threat processing, we combined parafoveal stimulus presentation and the contralateral P1 visual event-related potential to investigate how aversive olfactory inputs enhance visual perception of highly degraded, subthreshold fearful expressions. The dominant right hemisphere exhibited early visual discrimination between subtle fear and neutral expressions, independently of accompanying odors. In the left hemisphere, differential visual processing occurred only at the convergence of negative odors and minute facial fear, highlighting the success and necessity of visuo-olfactory threat integration in this disadvantaged hemisphere. Reaction time data from a subsequent dot-detection task complemented these neural findings, revealing odor-dependent and hemisphere-specific modulation of spatial attention to facial expressions. Our evidence thus indicates cross-modal threat integration in basic visual perception in humans that captures minimal threat information, especially in the blind right hemifield. Critically, this interaction between multisensory synergy and hemispheric asymmetry in threat perception may underlie the multifaceted fear experiences of everyday life.

See what you think: reappraisal modulates behavioral and neural responses to social stimuli

The social environment requires people to quickly form contextually appropriate social evaluations. Models of social cognition suggest that this ability depends on the interaction of automatic and controlled evaluative systems. However, controlled processes, such as reappraisal of an initial response, have rarely been studied in the context of social evaluation. In the two studies reported here, participants reappraised or simply observed angry or neutral faces. In Study 1, reappraisal modulated evaluations of angry faces on explicit as well as implicit behavioral levels. In Study 2, reappraisal altered both early and late phases of evaluative electrocortical processing. These studies suggest that controlled processes, such as reappraisal, can quickly and substantially modulate early evaluative processes in the context of biologically significant social stimuli.

Emotion processing in women with schizophrenia is menstrual cycle phase and affective valence dependent: an FMRI study

Despite a large number of functional neuroimaging investigations of emotion processing in schizophrenia, very few have included women. In the present study 21 schizophrenia and 23 healthy women underwent functional MRI (3T) on two occasions (during the follicular and luteal phase of their menstrual cycle) while viewing blocks of emotionally negative, positive and neutral images. During exposure to negatively charged images patients showed relatively less activations than controls during the luteal phase, but no between-group differences were observed during the follicular phase. In contrast, the exposure to positively valenced material produced no significant interaction, but the main effect of group; schizophrenia patients exhibited less activation than healthy controls during both phases of the menstrual cycle. This is the first study demonstrating that atypical neural activations associated with emotion processing in women diagnosed with schizophrenia depend on the menstrual cycle phase and on the affective valence of presented stimuli.

Brain mechanisms for emotional influences on perception and attention: what is magic and what is not

The rapid and efficient selection of emotionally salient or goal-relevant stimuli in the environment is crucial for flexible and adaptive behaviors. Converging data from neuroscience and psychology have accrued during the last decade to identify brain systems involved in emotion processing, selective attention, and their interaction, which together act to extract the emotional or motivational value of sensory events and respond appropriately. An important hub in these systems is the amygdala, which may not only monitor the emotional value of stimuli, but also readily project to several other areas and send feedback to sensory pathways (including striate and extrastriate visual cortex). This system generates saliency signals that modulate perceptual, motor, as well as memory processes, and thus in turn regulate behavior appropriately. Here, we review our current views on the function and properties of these brain systems, with an emphasis on their involvement in the rapid and/or preferential processing of threat-relevant stimuli. We suggest that emotion signals may enhance processing efficiency and competitive strength of emotionally significant events through gain control mechanisms similar to those of other (e.g. endogenous) attentional systems, but mediated by distinct neural mechanisms in amygdala and interconnected prefrontal areas. Alterations in these brain mechanisms might be associated with psychopathological conditions, such as anxiety or phobia. We conclude that attention selection and awareness are determined by multiple attention gain control systems that may operate in parallel and use different sensory cues but act on a common perceptual pathway.

Serotonin transporter genotype modulates cognitive reappraisal of negative emotions: a functional magnetic resonance imaging study

A functional polymorphism within the serotonin transporter gene (5-HTTLPR) has been reported to modulate emotionality and risk for affective disorders. The short (S) allele has less functional efficacy than the long (L) allele and has been associated with enhanced emotional reactivity. One possible contributing factor to the high emotionality in S carriers may be inefficient use of cognitive strategies such as reappraisal to regulate emotional responses. The aim of the present study was to test whether the 5-HTTLPR genotype modulates the neural correlates of emotion regulation. To determine neural differences between S and L allele carriers during reappraisal of negative emotions, 15 homozygous S (S'/S') and 15 homozygous L (L'/L') carriers underwent functional magnetic resonance imaging (fMRI), while performing an instructed emotion regulation task including downregulation, upregulation and passive viewing of negative emotional pictures. Compared to L'/L' allele carriers, subjects who carry the S'/S' allele responded with lower posterior insula and prefrontal brain activation during passive perception of negative emotional information but showed greater prefrontal activation and anterior insula activation during down- and upregulation of negative emotional responses. The current results support and extend previous findings of enhanced emotionality in S carriers by providing additional evidence of 5-HTTLPR modulation of volitional emotion regulation.

Emotional targets: evaluative categorization as a function of context and content

Event-related potential (ERP) studies of early evaluative categorization have often used variants of an oddball paradigm to assess attention to target stimuli as a function of content (i.e., valence) and context (e.g., presentation among non-targets differing in valence). However, most previous studies have not fully crossed content and context, and have not examined the time-course of these effects. The purpose of the current study was to investigate these two issues in an effort to further clarify the nature of evaluative categorization as reflected in the late positive potential (LPP). Pleasant, neutral, and unpleasant images served as both targets and non-targets in an emotional oddball task. Results indicate additive effects of emotional content and target status on the early portion of the LPP; however, the LPP did not differ between pleasant and unpleasant stimuli. Only target status modulated the later portion of the LPP, suggesting different contributions of cognitive-affective processes over time during evaluative categorization.

Neural systems approaches to understanding major depressive disorder: an intrinsic functional organization perspective

Recent research detailing the intrinsic functional organization of the brain provides a unique and useful framework to gain a better understanding of the neural bases of Major Depressive Disorder (MDD). In this review, we first present a brief history of neuroimaging research that has increased our understanding of the functional macro-architecture of the brain. From this macro-architectural perspective, we examine the extant body of functional neuroimaging research assessing MDD with a specific emphasis on the contributions of default-mode, executive, and salience networks in this debilitating disorder. Next, we describe recent investigations conducted in our laboratory in which we explicitly adopt a neural-system perspective in examining the relations among these networks in MDD. Finally, we offer directions for future research that we believe will facilitate the development of more detailed and integrative models of neural dysfunction in depression.

Introspective minds: using ALE meta-analyses to study commonalities in the neural correlates of emotional processing, social & unconstrained cognition

Previous research suggests overlap between brain regions that show task-induced deactivations and those activated during the performance of social-cognitive tasks. Here, we present results of quantitative meta-analyses of neuroimaging studies, which confirm a statistical convergence in the neural correlates of social and resting state cognition. Based on the idea that both social and unconstrained cognition might be characterized by introspective processes, which are also thought to be highly relevant for emotional experiences, a third meta-analysis was performed investigating studies on emotional processing. By using conjunction analyses across all three sets of studies, we can demonstrate significant overlap of task-related signal change in dorso-medial prefrontal and medial parietal cortex, brain regions that have, indeed, recently been linked to introspective abilities. Our findings, therefore, provide evidence for the existence of a core neural network, which shows task-related signal change during socio-emotional tasks and during resting states.

Common and distinct neural correlates of emotional processing in Bipolar Disorder and Major Depressive Disorder: a voxel-based meta-analysis of functional magnetic resonance imaging studies

Neuroimaging studies have consistently shown functional brain abnormalities in patients with Bipolar Disorder (BD) and Major Depressive Disorder (MDD). However, the extent to which these two disorders are associated with similar or distinct neural changes remains unclear. We conducted a systematic review of functional magnetic resonance imaging studies comparing BD and MDD patients to healthy participants using facial affect processing paradigms. Relevant spatial coordinates from twenty original studies were subjected to quantitative Activation Likelihood Estimation meta-analyses based on 168 BD and 189 MDD patients and 344 healthy controls. We identified common and distinct patterns of neural engagement for BD and MDD within the facial affect processing network. Both disorders were associated with increased engagement of limbic regions. Diagnosis-specific differences were observed in cortical, thalamic and striatal regions. Decreased ventrolateral prefrontal cortical engagement was associated with BD while relative hypoactivation of the sensorimotor cortices was seen in MDD. Increased responsiveness in the thalamus and basal ganglia were associated with BD. These findings were modulated by stimulus valence. These data suggest that whereas limbic overactivation is reported consistently in patients with mood disorders, future research should consider the relevance of a wider network of regions in formulating conceptual models of BD and MDD.

Cognition-emotion integration in the anterior insular cortex

Both cognitive and affective processes require mental resources. However, it remains unclear whether these 2 processes work in parallel or in an integrated fashion. In this functional magnetic resonance imaging study, we investigated their interaction using an empathy-for-pain paradigm, with simultaneous manipulation of cognitive demand of the tasks and emotional valence of the stimuli. Eighteen healthy adult participants viewed photographs showing other people's hands and feet in painful or nonpainful situations while performing tasks of low (body part judgment) and high (laterality judgment) cognitive demand. Behavioral data showed increased reaction times and error rates for painful compared with nonpainful stimuli under laterality judgment relative to body part judgment, indicating an interaction between cognitive demand and stimulus valence. Imaging analyses showed activity in bilateral anterior insula (AI) and primary somatosensory cortex (SI), but not posterior insula, for main effects of cognitive demand and stimulus valence. Importantly, cognitive demand and stimulus valence showed a significant interaction in AI, SI, and regions of the frontoparietal network. These results suggest that cognitive and emotional processes at least partially share common brain networks and that AI might serve as a key node in a brain network subserving cognition-emotion integration.

The processing bias for threatening cues revealed by event-related potential and event-related oscillation analyses

The processing bias of threat is crucial for survival. However, the neurophysiological underpinnings of this bias are not fully understood. To contribute to a better understanding of the processing bias for threat, both event-related potential (ERP) and event-related oscillation (ERO) analyses were applied to the electroencephalography (EEG) data recorded from subjects while performing a go/no-go variant of the dot-probe task. In the task, subjects responded to the infrequent target stimuli and didn't respond to the standard stimuli. Both target and standard stimuli were preceded by a bilateral picture pair [one emotional (threatening or pleasant) and one neutral] as an emotional cue. The behavioral data and the P1 elicited by standard stimuli didn't show any significant main effect or interaction. The mean amplitude of N1 was greater negative for threatening cues than pleasant cues with the most significant effect in the fronto-central region, indicating a processing bias for threat related to early attention processing. In addition, the theta synchronization was stronger for threatening cues than pleasant cues with significant effect in posterior regions, suggesting that the posterior theta synchronization reflects the evaluation of emotional significance of stimuli. Taken together, the ERP and ERO analyses provide some independent insights into the processing bias for threatening cues and illustrate this bias more comprehensively.