Dissociable effects of arousal and valence on prefrontal activity indexing emotional evaluation and subsequent memory: an event-related fMRI study

Prefrontal cortex (PFC) activity associated with emotional evaluation and subsequent memory was investigated with event-related functional MRI (fMRI). Participants were scanned while rating the pleasantness of emotionally positive, negative, and neutral pictures, and memory for the pictures was tested after scanning. Emotional evaluation was measured by comparing activity during the picture rating task relative to baseline, and successful encoding was measured by comparing activity for subsequently remembered versus forgotten pictures (Dm effect). The effect of arousal on these measures was indicated by greater activity for both positive and negative pictures than for neutral ones, and the effect of valence was indicated by differences in activity between positive and negative pictures. The study yielded three main results. First, consistent with the valence hypothesis, specific regions in left dorsolateral PFC were more activated for positive than for negative picture evaluation, whereas regions in right ventrolateral PFC showed the converse pattern. Second, dorsomedial PFC activity was sensitive to emotional arousal, whereas ventromedial PFC activity was sensitive to positive valence, consistent with evidence linking these regions, respectively, to emotional processing and self-awareness or appetitive behavior. Finally, successful encoding (Dm) activity in left ventrolateral and dorsolateral PFC was greater for arousing than for neutral pictures. This finding suggests that the enhancing effect of emotion on memory formation is partly due to an augmentation of PFC-mediated strategic, semantic, and working memory operations. These results underscore the critical role of PFC in emotional evaluation and memory, and disentangle the effects of arousal and valence across PFC regions associated with different cognitive functions.     

Valence-specific regulation effects in a working memory task with emotional context

The modulatory effects of emotional context on episodic memory have been shown recently. We were interested whether working memory is similarly susceptible to emotional context or whether working memory helps to distract from emotion, i.e. serves to downregulate emotional reactions in order to sustain the prior intention. We tested the effects of emotional stimulation during active maintenance of information by modulating the emotional context of maintenance processes in a Sternberg item recognition task with two load conditions. Behavioral data revealed no impairment of working memory performance during emotional context. Actually, behavioral performance was better for emotional compared to neutral context during high load. Furthermore, emotional context had no interference effect on working memory-related brain activation. Instead, we found a valence-specific regulation effect: High cognitive effort was associated with reduced activity in emotion processing regions, i.e. the amygdala and ventral striatum. This effect was mediated by different prefrontal regions, i.e. by left inferior PFC for negative and left superior PFC for positive valence. Furthermore, our results reveal an integration effect of emotion and cognition in right dorsolateral prefrontal cortex showing increased recruitment with increasing complexity of the task. The results presented here are of relevance for the understanding of regulatory mechanisms and diseases characterized by increased susceptibility to emotional distraction.     

Functional association of the amygdala and ventral prefrontal cortex during cognitive evaluation of facial expressions primed by masked angry faces: an event-related fMRI study

The present study examined the functional association of the amygdala and right ventral prefrontal cortex (PFC) during cognitive evaluation of facial expressions. A situation was created where emotional valence of the stimuli was unconsciously manipulated by using subliminal affective priming. Twelve healthy volunteers were asked to evaluate the facial expressions of a target face (500-ms duration) such as "anger", "neutral", or "happy". All target faces expressed relatively weak anger. Just before the presentation of the target face, a prime of three conditions of 35-ms duration, angry face, neutral face, and white blank was presented. The subjects could not consciously identify the primes in this procedure. Activity in the right amygdala was greater with subliminal presentation of the angry prime compared with subliminal presentation of a neutral face or white-blank stimuli. Most importantly, the degree of activation of the right amygdala was negatively correlated with that of the right ventral PFC only with the anger prime. Furthermore, activation of the amygdala was positively correlated with rate of judgment when the subjects recognized anger in the target faces. These results are discussed in terms of the functional association between the right PFC and the amygdala and its influence on cognitive processing.     

Emotional context modulates subsequent memory effect

Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying these modulatory effects is largely unknown. Using event-related functional magnetic resonance imaging (fMRI), we investigated whether the context of emotional encoding modulates brain activation predictive for subsequent recall of emotionally neutral material. While inferior frontal activation predicted recall in general, our data show that in a positive encoding context, recall was predicted by activation of right anterior parahippocampal and extrastriate visual brain areas, whereas in a negative encoding context, recall was predicted by activation of the amygdala. Thus, we could demonstrate that successful episodic encoding is differentially modulated by emotional context. These results contribute to the understanding of the interaction of emotion and cognition and moreover are of general relevance for studies of episodic memory.     

Reactivation of visual cortex during memory retrieval: content specificity and emotional modulation

Studies on memory retrieval suggest a reactivation of cortical regions engaged during encoding, such that visual or auditory areas reactivate for visual or auditory memories. The content specificity and any emotion dependency of such reactivations are still unclear. Because distinct visual areas are specialized in processing distinct stimulus categories, we tested for face and word specific reactivations during a memory task using functional magnetic resonance imaging (fMRI). Furthermore, because visual processing and memory are both modulated by emotion, we compared reactivation for stimuli encoded in a neutral or emotionally significant context. In the learning phase, participants studied pairs of stimuli that consisted of either a scene and a face, or a scene and a word. Scenes were either neutral or negative, but did not contain faces or words. In the test phase scenes were presented alone (one in turn), and participants indicated whether it was previously paired with a face, a word, or was new. Results from the test phase showed activation in a functionally defined face-responsive region in the right fusiform gyrus, as well as in a word-responsive region in the left inferior temporal gyrus, for scenes previously paired with faces and words, respectively. Reactivation tended to be larger in both the face- and word-responsive regions when the associated scene was negative as compared to neutral. However, relative to neutral context, the recall of faces and words paired with a negative context produced smaller activations in brain regions associated with social and semantic processing, respectively, as well as poorer memory performance overall. Taken together, these results support the idea of cortical memory reactivations, even at a content-specific level, and further suggest that emotional context may produce opposite effects on reactivations in early sensory areas and more elaborate processing in higher-level cortical areas.     

The influence of emotional priming on the neural substrates of memory: a prospective fMRI study using portrait art stimuli

Events coupled with an emotional context seem to be better retained than non-emotional events. The aim of our study was to investigate whether an emotional context could influence the neural substrates of memory associations with novel portrait art stimuli. In the current prospective fMRI study, we have investigated for one specific visual art form (modern artistic portraits with a high degree of abstraction) whether memory is influenced by priming with emotional facial pictures. In total forty healthy female volunteers in the same age range were recruited for the study. Twenty of these women participated in a prospective brain imaging memory paradigm and were asked to memorize a series of similar looking, but different portraits. After randomization, for twelve participants (Group 1), a third of the portraits was emotionally primed with approach-related pictures (smiling baby faces), a third with withdrawal-related pictures (baby faces with severe dermatological conditions), and another third with neutral images. Group 2 consisted of eight participants and they were not primed. Then, during an fMRI session 2h later, these portraits were viewed in random order intermixed with a set of new (previously unseen) ones, and the participants had to decide for each portrait whether or not they had already been seen. In a separate experiment, a different sample of twenty healthy females (Group 3) rated their mood after being exposed to the same art stimuli, without priming. The portraits did not evoke significant mood changes by themselves, supporting their initial neutral emotional character (Group 3). The correct decision on whether the portraits were Familiar of Unfamiliar led to similar neuronal activations in brain areas implicated in visual and attention processing for both groups (Groups 1 and 2). In contrast, whereas primed participants showed significant higher neuronal activities in the left midline superior frontal cortex (Brodmann area (BA) 6), unprimed volunteers displayed higher right medial frontal cortical (BA 10) activities. Furthermore, specifically in Group 1, correct retrieval of negatively primed portraits evoked increased neuronal activity in the left medial orbitofrontal cortex (BA 11) and in the right (posterior) insula, suggesting enhanced stress-related responses to the memory of withdrawal-related primed modern artistic portraits in this group. Our prospective memory data in healthy females indicate that, to reach a correct retrieval decision, different midline anterior neuronal networks are recruited for portraits that were emotionally primed than for the unprimed ones. Importantly, our results also suggest that the negative emotional context leads to the formation of associations that are reactivated during memory retrieval processes of the initially neutral art portraits. When correctly recognized, the portraits evoke neuronal activities consistent with the withdrawal-related character of the emotional visual stimuli with which they have been associated. Although our results show that abstract portrait art can be associated with emotional primes this doesn't mean that this effect is specific for art images.     

Effects of semantic relatedness on age-related associative memory deficits: the role of theta oscillations

Growing evidence suggests that age-related deficits in associative memory are alleviated when the to-be-associated items are semantically related. Here we investigate whether this beneficial effect of semantic relatedness is paralleled by spatio-temporal changes in cortical EEG dynamics during incidental encoding. Young and older adults were presented with faces at a particular spatial location preceded by a biographical cue that was either semantically related or unrelated. As expected, automatic encoding of face-location associations benefited from semantic relatedness in the two groups of age. This effect correlated with increased power of theta oscillations over medial and anterior lateral regions of the prefrontal cortex (PFC) and lateral regions of the posterior parietal cortex (PPC) in both groups. But better-performing elders also showed increased brain-behavior correlation in the theta band over the right inferior frontal gyrus (IFG) as compared to young adults. Semantic relatedness was, however, insufficient to fully eliminate age-related differences in associative memory. In line with this finding, poorer-performing elders relative to young adults showed significant reductions of theta power in the left IFG that were further predictive of behavioral impairment in the recognition task. All together, these results suggest that older adults benefit less than young adults from executive processes during encoding mainly due to neural inefficiency over regions of the left ventrolateral prefrontal cortex (VLPFC). But this associative deficit may be partially compensated for by engaging preexistent semantic knowledge, which likely leads to an efficient recruitment of attentional and integration processes supported by the left PPC and left anterior PFC respectively, together with neural compensatory mechanisms governed by the right VLPFC.     

Increased neural response related to neutral faces in individuals at risk for psychosis

OBJECTIVE: The reliable discrimination of emotional expressions in faces is essential for adequate social interaction. Deficits in facial emotion processing are an important impairment in schizophrenia with major consequences for social functioning and subjective well-being. Whether neural circuits underlying emotion processing are already altered before illness onset is yet unclear. Investigating neural correlates of emotion processing in individuals clinically at risk for psychosis offers the possibility to examine neural processes unchanged by the manifest disorder and to study trait aspects of emotion dysfunctions. MATERIAL AND METHODS: Twelve subjects clinically at risk for psychosis and 12 matched control subjects participated in this study. fMRI data were acquired during an emotion discrimination task consisting of standardized photographs of faces displaying different emotions (happiness, sadness, anger, fear) as well as faces with neutral facial expression. RESULTS: There were no group differences in behavioral performance. Emotion discrimination was associated with hyperactivations in high-risk subjects in the right lingual and fusiform gyrus as well as the left middle occipital gyrus. Further, high-risk compared to control subjects exhibited stronger activation related to neutral faces relative to emotional faces in the inferior and superior frontal gyri, the cuneus, the thalamus and the hippocampus. CONCLUSIONS: The present study indicates that individuals clinically at risk for psychosis show differences in brain activation associated with processing of emotional and--more pronounced--neutral facial expressions despite an adequate behavioral performance. The proneness to attribute salience to neutral stimuli might indicate a biological risk marker for psychosis.     

Incongruence effects in crossmodal emotional integration

Emotions are often encountered in a multimodal fashion. Consequently, contextual framing by other modalities can alter the way that an emotional facial expression is perceived and lead to emotional conflict. Whole brain fMRI data was collected when 35 healthy subjects judged emotional expressions in faces while concurrently being exposed to emotional (scream, laughter) or neutral (yawning) sounds. The behavioral results showed that subjects rated fearful and neutral faces as being more fearful when accompanied by screams than compared to yawns (and laughs for fearful faces). Moreover, the imaging data revealed that incongruence of emotional valence between faces and sounds led to increased activation in the middle cingulate cortex, right superior frontal cortex, right supplementary motor area as well as the right temporoparietal junction. Against expectations no incongruence effects could be found in the amygdala. Further analyses revealed that, independent of emotional valence congruency, the left amygdala was consistently activated when the information from both modalities was emotional. If a neutral stimulus was present in one modality and emotional in the other, activation in the left amygdala was significantly attenuated. These results indicate that incongruence of emotional valence in audiovisual integration activates a cingulate-fronto-parietal network involved in conflict monitoring and resolution. Furthermore in audiovisual pairing amygdala responses seem to signal also the absence of any neutral feature rather than only the presence of an emotionally charged one.     

Distinct neural correlates of associative working memory and long-term memory encoding in the medial temporal lobe

Increasing evidence suggests a role for the hippocampus not only in long-term memory (LTM) but also in relational working memory (WM) processes, challenging the view of the hippocampus as being solely involved in episodic LTM. However, hippocampal involvement reported in some neuroimaging studies using "classical" WM tasks may at least partly reflect incidental LTM encoding. To disentangle WM processing and LTM formation we administered a delayed-match-to-sample associative WM task in an event-related fMRI study design. Each trial of the WM task consisted of four pairs of faces and houses, which had to be maintained during a delay of 10s. This was followed by a probe phase consisting of three consecutively presented pairs; for each pair participants were to indicate whether it matched one of the pairs of the encoding phase. After scanning, an unexpected recognition-memory (LTM) task was administered. Brain activity during encoding was analyzed based on WM and LTM performance. Hence, encoding-related activity predicting WM success in the absence of successful LTM formation could be isolated. Furthermore, regions critical for successful LTM formation for pairs previously correctly processed in WM were analyzed. Results showed that the left parahippocampal gyrus including the fusiform gyrus predicted subsequent accuracy on WM decisions. The right anterior hippocampus and left inferior frontal gyrus, in contrast, predicted successful LTM for pairs that were previously correctly classified in the WM task. Our results suggest that brain regions associated with higher-level visuo-perceptual processing are involved in successful associative WM encoding, whereas the anterior hippocampus and left inferior frontal gyrus are involved in successful LTM formation during incidental encoding.     

Time-dependent neural activations related to recognition of people's names in emotional and neutral face-name associative learning: an fMRI study

Previous data have indicated that the left anterior temporal lobe contributes to the retrieval of familiar people's names, and that the extended network including the bilateral anterior temporal lobe plays an important role in the retrieval of newly learned people's names. However, there has been no direct evidence for time-dependent change in brain activation in face-name associations. In addition, previous studies have demonstrated that emotional information such as emotional faces may contribute to the organization of long-lasting episodic memory. In the present study, we investigated the activations related to the recognition of people's names in the context of emotional and neutral face-name associative learning. Before fMRI scanning, subjects learned face-name associations that included emotionally positive and neutral facial expressions. In immediate (5 min later) and delayed (2 weeks later) recognition with fMRI scanning, subjects were presented with studied faces with two names, and were asked to choose the correct associative name learned previously. Recognition-related activations were identified in the anterior part of bilateral temporal lobe for immediate recognition and only in the left temporal lobe for delayed recognition. Further analysis confirmed the time-dependent change in activation of the right anterior temporal lobe. Activation related to the processing of faces with positive expressions were observed in the left periamygdaloid area and temporal pole, although emotional information did not have an influence on task performance in this study. These findings suggest that the neural network involving the bilateral temporal lobe contributes to the retrieval of newly learned people's names, and that the left temporal lobe has a crucial and stable role in retrieval of people's names from faces, whereas the role of the right temporal lobe in retrieval of people's names may decrease with the time course.     

Neural systems for orienting attention to the location of threat signals: an event-related fMRI study

Attention may reflexively shift towards the location of perceived threats, but it is still unclear how these spatial biases recruit the distributed fronto-parietal cortical networks involved in other aspects of selective attention. We used event-related fMRI to determine how brain responses to a neutral visual target are influenced by the emotional expression of faces appearing at the same location during a covert orienting task. On each trial, two faces were briefly presented, one in each upper visual field (one neutral and one emotional, fearful or happy), followed by a unilateral target (a small horizontal or vertical bar) replacing one of the faces. Participants had to discriminate the target orientation, shown on the same (valid) or opposite (invalid) side as the emotional face. Trials with faces but no subsequent target (cue-only trials) were included to disentangle activation due to emotional cues from their effects on target detection. We found increased responses in bilateral temporo-parietal areas and right occipito-parietal cortex for fearful faces relative to happy faces, unrelated to the subsequent target and cueing validity. More critically, we found a selective modulation of intraparietal and orbitofrontal cortex for targets following an invalid fearful face, as well as an increased visual response in right lateral occipital cortex for targets following a valid fearful face. No such effects were observed with happy faces. These results demonstrate that fearful faces can act as exogenous cues by increasing sensory processing in extrastriate cortex for a subsequent target presented at the same location, but also produce a cost in disengaging towards another location by altering the response of IPS to invalidly cued targets. Neural mechanisms responsible for orienting attention towards emotional vs. non-emotional stimuli are thus partly shared in parietal and visual areas, but also partly distinct.     

Crossmodal interactions in audiovisual emotion processing

Emotion in daily life is often expressed in a multimodal fashion. Consequently emotional information from one modality can influence processing in another. In a previous fMRI study we assessed the neural correlates of audio-visual integration and found that activity in the left amygdala is significantly attenuated when a neutral stimulus is paired with an emotional one compared to conditions where emotional stimuli were present in both channels. Here we used dynamic causal modelling to investigate the effective connectivity in the neuronal network underlying this emotion presence congruence effect. Our results provided strong evidence in favor of a model family, differing only in the interhemispheric interactions. All winning models share a connection from the bilateral fusiform gyrus (FFG) into the left amygdala and a non-linear modulatory influence of bilateral posterior superior temporal sulcus (pSTS) on these connections. This result indicates that the pSTS not only integrates multi-modal information from visual and auditory regions (as reflected in our model by significant feed-forward connections) but also gates the influence of the sensory information on the left amygdala, leading to attenuation of amygdala activity when a neutral stimulus is integrated. Moreover, we found a significant lateralization of the FFG due to stronger driving input by the stimuli (faces) into the right hemisphere, whereas such lateralization was not present for sound-driven input into the superior temporal gyrus. In summary, our data provides further evidence for a rightward lateralization of the FFG and in particular for a key role of the pSTS in the integration and gating of audio-visual emotional information.     

The effect of appraisal level on processing of emotional prosody in meaningless speech

In visual perception of emotional stimuli, low- and high-level appraisal processes have been found to engage different neural structures. Beyond emotional facial expression, emotional prosody is an important auditory cue for social interaction. Neuroimaging studies have proposed a network for emotional prosody processing that involves a right temporal input region and explicit evaluation in bilateral prefrontal areas. However, the comparison of different appraisal levels has so far relied upon using linguistic instructions during low-level processing, which might confound effects of processing level and linguistic task. In order to circumvent this problem, we examined processing of emotional prosody in meaningless speech during gender labelling (implicit, low-level appraisal) and emotion labelling (explicit, high-level appraisal). While bilateral amygdala, left superior temporal sulcus and right parietal areas showed stronger blood oxygen level-dependent (BOLD) responses during implicit processing, areas with stronger BOLD responses during explicit processing included the left inferior frontal gyrus, bilateral parietal, anterior cingulate and supplemental motor cortex. Emotional versus neutral prosody evoked BOLD responses in right superior temporal gyrus, bilateral anterior cingulate, left inferior frontal gyrus, insula and bilateral putamen. Basal ganglia and right anterior cingulate responses to emotional versus neutral prosody were particularly pronounced during explicit processing. These results are in line with an amygdala-prefrontal-cingulate network controlling different appraisal levels, and suggest a specific role of the left inferior frontal gyrus in explicit evaluation of emotional prosody. In addition to brain areas commonly related to prosody processing, our results suggest specific functions of anterior cingulate and basal ganglia in detecting emotional prosody, particularly when explicit identification is necessary.     

阿尔茨海默病情绪记忆相关脑灰质体积改变

目的 探讨阿尔茨海默病（AD）患者情绪记忆改变与灰质容积变化的相关性。方法 对25例AD患者（AD组）及25名正常对照（NC组）进行情绪记忆行为学检测,获取行为学成绩。采用MRI 3D结构相用VBM8和SPM8软件处理,得到相对灰质体积改变的脑区,做为ROI,采用REST软件提值,并与行为学成绩行相关性分析。结果 AD组受试对负性与中性图片反应正确率差异无统计学意义（P=0.56）。与NC组比较,AD组灰质体积缩小的脑区包括双侧颞下回、颞中回、海马、海马旁回、杏仁核、梭状回、楔前叶、后扣带回、左侧脑岛、右侧舌回、左侧额叶眶内侧回、左侧内侧前额叶、右侧额下回岛盖部、左侧中央前回及右侧丘脑（FWE校正,P<0.025）;其中双侧杏仁核、双侧后扣带回、左侧海马、左侧脑岛、左侧颞下回、左侧颞中回、左侧额叶眶内侧回、右侧额下回岛盖部、左侧内侧前额叶的相对灰质体积与情绪图片记忆反应正确率呈正相关（P均<0.05）。结论 AD患者负性图片情绪增强效应损害,可能与杏仁核和海马等情绪记忆系统脑区萎缩有关。     

Very early modulation of brain responses to neutral faces by a single prior association with an emotional context: evidence from MEG

Recent electrophysiological studies have demonstrated modulations of the very first stages of visual processing (<100 ms) due to prior experience. This indicates an influence of a memory trace on the earliest stages of stimulus processing. Here we investigated if emotional audio-verbal information associated with faces on first encounter can affect the very early responses to those faces on subsequent exposure. We recorded magneto-encephalographic (MEG) responses to neutral faces that had been previously associated with positive (happy), negative (angry) or neutral auditory verbal emotional contexts. Our results revealed a very early (30-60 ms) difference in the brain responses to the neutral faces according to the type of previously associated emotional context, with a clear dissociation between the faces previously associated to positive vs. negative or neutral contexts. Source localization showed that two main regions were involved in this very early association effect: the bilateral ventral occipito-temporal regions and the right anterior medial temporal region. These results provide evidence that the memory trace of a face integrates positive emotional cues present in the context of prior encounter and that this emotional memory can influence the very first stages of face processing. These experimental findings support the idea that face perception can be shaped by experience from its earliest stages and in particular through emotional association effects.     

Emotion suppression reduces hippocampal activity during successful memory encoding

People suppressing their emotions while facing an emotional event typically remember it less well. However, the neural mechanisms underlying the impairing effect of emotion suppression on successful memory encoding are not well understood. Because successful memory encoding relies on the hippocampus and the amygdala, we hypothesized that memory impairments due to emotion suppression are associated with down-regulated activity in these brain areas. 59 healthy females were instructed either to simply watch the pictures or to down-regulate their emotions by using a response-focused emotion suppression strategy. Brain activity was recorded using functional magnetic resonance imaging (fMRI), and free recall of pictures was tested afterwards. As expected, suppressing one's emotions resulted in impaired recall of the pictures. On the neural level, the memory impairments were associated with reduced activity in the right hippocampus during successful encoding. No significant effects were observed in the amygdala. In addition, functional connectivity between the hippocampus and the right dorsolateral prefrontal cortex was strongly reduced during emotion suppression, and these reductions predicted free-recall performance. Our results indicate that emotion suppression interferes with memory encoding on the hippocampal level, possibly by decoupling hippocampal and prefrontal encoding processes, suggesting that response-focused emotion suppression might be an adaptive strategy for impairing hippocampal memory formation in highly arousing situations.     

Retrieving accurate and distorted memories: neuroimaging evidence for effects of emotion

While limbic activity is known to be associated with successful encoding of emotional information, it is less clear whether it is related to successful retrieval. The present fMRI study assessed the effects of emotion on the neural processes engaged during retrieval of accurate compared to distorted memories. Prior to the scan, participants (16 young adults) viewed names of neutral (e.g., frog) and emotional (e.g., snake) objects and formed a mental image of the object named. They were shown photos of half of the objects. During the fMRI scan, participants saw object names and indicated whether or not they had seen the corresponding photo. Memory distortions (misattributions) occurred when participants incorrectly indicated whether or not a photo had been studied. Activity in some regions (e.g., L anterior hippocampus) was related to accurate retrieval (correct attributions > misattributions) for emotional and neutral items. However, activity in other regions corresponded with accurate retrieval specifically for emotional items (e.g., in R amygdala/periamygdaloid cortex and L orbitofrontal cortex) or for neutral items (e.g., in lateral inferior prefrontal cortex and R posterior hippocampus). Results indicate that emotional salience modulates the processes engaged during accurate retrieval and that activity in limbic regions corresponds with accurate memory assignment for emotional items. To our knowledge, this study is the first to demonstrate a link between limbic engagement at retrieval and accurate memory attribution.     

Cognitive versus automatic mechanisms of mood induction differentially activate left and right amygdala

The amygdala plays a key role in emotional processing. The specific contribution of the amygdala during the experience of one's own emotion, however, remains controversial and requires clarification. There is a long-standing debate on hemispheric lateralization of emotional processes, yet few studies to date directly investigated differential activation patterns for the left and right amygdala. Limited evidence supports right amygdala involvement in automatic processes of emotion and left amygdala involvement in conscious and cognitively controlled emotion processing. The present study investigated differential contributions of the left and right amygdala to cognitive and automatic mechanisms of mood induction. Using functional magnetic resonance imaging (fMRI), we examined hemispheric amygdala responses during two mood induction paradigms: a purely visual method presenting face stimuli and an audiovisual method using faces and music. Amygdala responses in 30 subjects (16 females) showed differences in lateralization patterns depending on the processing mode. The left amygdala exhibited comparable activation levels for both methods. The right amygdala, in contrast, showed increased activity only for the audiovisual condition and this activity was increasing over time. The left amygdala showed augmented activity with higher intensity ratings of negative emotional valence. These results support a left-lateralized cognitive and intentional control of mood and a right-sided more automatic induction of emotion that relies less on explicit reflection processes. The modulation of the left amygdala responses by subjective experience may reflect individual differences in the cognitive effort used to induce the mood. Thus, the central role of the amygdala may not be restricted to the perception of emotion in others but also extend into processes involved in regulation of mood.     

The temporal dynamics of insula activity to disgust and happy facial expressions: A magnetoencephalography study

The insula has consistently been shown to be involved in processing stimuli that evoke the emotional response of disgust. Recently, its specificity for processing disgust has been challenged and a broader role of the insula in the representation of interoceptive information has been suggested. Studying the temporal dynamics of insula activation during emotional processing can contribute valuable information pertaining to this issue. Few studies have addressed the insula's putative specificity to disgust and the dynamics of its underlying neural processes. In the present study, neuromagnetic responses of 13 subjects performing an emotional continuous performance task (CPT) to faces with disgust, happy, and neutral expressions were obtained. Magnetic field tomography extracted the time course of bilateral insula activities. Right insula activation was stronger to disgust and happy than neutral facial expressions at about 200 ms after stimulus onset. Later only at about 350 ms after stimulus onset the right insula was activated stronger to disgust than happy facial expressions. Thus, the early right insula response reflects activation to emotionally arousing stimuli regardless of valence, and the later right insula response differentiates disgust from happy facial expressions. Behavioral performance but not the insula activity differed between 100 ms and 1000 ms presentation conditions. Present findings support the notion that the insula is involved in the representation of interoceptive information.