Orbitofrontal cortex and dynamic filtering of emotional stimuli

Event-related potentials (ER) were recorded in response to mildly aversive somatosensory and auditory stimuli. Patients with orbitofrontal lesions exhited enhanced ERPs (i.e., P3 amplitudes), as compared with control subjects. Moreover, these patients did not habituate to somatoensory stimuli across blocks of trials. The results were specific to orbitofrontal damage, since patients with damage to the dorsolateral prefontal cortex did not exhibit enhanced P3 amplitudes. These findings suggest damage to the orbitofrontal cortex impairs the ability to modulate or inhibit neural responses to aversive stimuli. The findings are couched in terms of dynamic filtering theory, which suggests that the orbitofrontal cortex is involved in the selection and active inhibition of neural circuits associated with emotional responses.     

Flexible emotional responsiveness in trait resilience

Field studies and laboratory experiments have documented that a key component of resilience is emotional flexibility--the ability to respond flexibly to changing emotional circumstances. In the present study we tested the hypotheses that resilient people exhibit emotional flexibility: (a) in response to frequently changing emotional stimuli and (b) across multiple modalities of emotional responding. As participants viewed a series of emotional pictures, we assessed their self-reported affect, facial muscle activity, and startle reflexes. Higher trait resilience predicted more divergent affective and facial responses (corrugator and zygomatic) to positive versus negative pictures. Thus, compared with their low-resilient counterparts, resilient people appear to be able to more flexibly match their emotional responses to the frequently changing emotional stimuli. Moreover, whereas high-trait-resilient participants exhibited divergent startle responses to positive versus negative pictures regardless of the valence of the preceding trial, low-trait-resilient participants did not exhibit divergent startle responses when the preceding picture was negative. High-trait-resilient individuals, therefore, appear to be better able than are their low-resilient counterparts to either switch or maintain their emotional responses depending on whether the emotional context changes. The present findings broaden our understanding of the mechanisms underlying resilience by demonstrating that resilient people are able to flexibly change their affective and physiological responses to match the demands of frequently changing environmental circumstances.     

Differences in startle reactivity during the perception of angry and fearful faces

Emotion researchers often categorize angry and fearful face stimuli as "negative" or "threatening". Perception of fear and anger, however, appears to be mediated by dissociable neural circuitries and often elicit distinguishable behavioral responses. The authors sought to elucidate whether viewing anger and fear expressions produce dissociable psychophysiological responses (i.e., the startle reflex). The results of two experiments using different facial stimulus sets (representing anger, fear, neutral, and happy) indicated that viewing anger was associated with a significantly heightened startle response (p < .05) relative to viewing fear, happy, and neutral. This finding suggests that while anger and fear faces convey messages of "threat", their priming effect on startle circuitry differs. Thus, angry expressions, representing viewer-directed threat with an unambiguous source (i.e., the expresser), may more effectively induce a motivational propensity to withdraw or escape. The source of threat is comparatively less clear for fearful faces. The differential effects of these two facial threat signals on the defensive motivational system adds to growing literature highlighting the importance of distinguishing between emotional stimuli of similar valence, along lines of meaning and functional impact.     

Emotion elicitor or emotion messenger? Subliminal priming reveals two faces of facial expressions

Facial emotional expressions can serve both as emotional stimuli and as communicative signals. The research reported here was conducted to illustrate how responses to both roles of facial emotional expressions unfold over time. As an emotion elicitor, a facial emotional expression (e.g., a disgusted face) activates a response that is similar to responses to other emotional stimuli of the same valence (e.g., a dirty, nonflushed toilet). As an emotion messenger, the same facial expression (e.g., a disgusted face) serves as a communicative signal by also activating the knowledge that the sender is experiencing a specific emotion (e.g., the sender feels disgusted). By varying the duration of exposure to disgusted, fearful, angry, and neutral faces in two subliminal-priming studies, we demonstrated that responses to faces as emotion elicitors occur prior to responses to faces as emotion messengers, and that both types of responses may unfold unconsciously.     

“Remembering” emotional words is based on response bias,not recollection

Recent studies have demonstrated that emotional stimuli result in a higher proportion of recognized items that are “remembered” (e.g., Kensinger & Corkin, 2003; Ochsner, 2000), leading to greater estimates of recollection by the dual-process model (Yonelinas, 1994). This result suggests that recognition judgments to emotional stimuli depend on a recollection process. We challenge this conclusion with receiver operating characteristic (ROC) curve data from two experiments. In both experiments, subjects studied neutral and emotional words. During the recognition test, subjects made old-new confidence ratings as well as remember-know judgments. Four models of remember-know judgments were fit to individual subjects’ data: two versions of a one-dimensional signaldetection-based model (Donaldson, 1996; Wixted & Stretch, 2004), the dual-process model (Yonelinas, 1994), and the two-dimensional signal-detection-based model known as STREAK (Rotello, Macmillan, & Reeder, 2004). Consistent with the literature, we found that emotion increases subjective reports of “remembering.” However, our ROC analyses and modeling work reveal that the effect is due to response bias differences rather than sensitivity change or use of a high-threshold recollection process.     

Hearing others’ pain: neural activity related to empathy

The human voice is one of the principal conveyers of social and affective communication. Recent neuroimaging studies have suggested that observing pain in others activates neural representations similar to those from the first-hand experience of pain; however, studies on pain expressions in the auditory channel are lacking. We conducted a functional magnetic resonance imaging study to examine brain responses to emotional exclamations of others’ pain. The control condition comprised positive (e.g., laughing) or negative (e.g., snoring) stimuli of the human voice that were not associated with pain and suffering. Compared to these control stimuli, pain-related exclamations elicited increased activation in the superior and middle temporal gyri, left insula, secondary somatosensory cortices, thalamus, and right cerebellum, as well as deactivation in the anterior cingulate cortex. The left anterior insular and thalamic activations correlated significantly with the Empathic Concern subscale of the Interpersonal Reactivity Index. Thus, the brain regions involved in hearing others’ pain are similar to those activated in the empathic processing of visual stimuli. Additionally, the findings emphasise the modulating role of interindividual differences in affective empathy.     

Startle modulation in non-incarcerated men and women with psychopathic traits

Past research has demonstrated that individuals with psychopathic characteristics are under-responsive to aversive stimuli, however, much of this work has failed to include non-incarcerated samples, or to examine gender differences in this relationship. Additionally, few studies have examined the role of specific personality characteristics, as they relate to both psychopathic behavior and emotional responsiveness. The current study assessed emotional modulation of the startle response in a community sample of 108 men and women (99 with usable startle data) during perception of emotion-laden photographs. Consistent with previous work, men reporting high levels of psychopathy failed to show the typical increase in the startle response when exposed to aversive photographs, but only when responses were elicited relatively early in picture viewing (i.e., 2.0 s as compared to 4.5 s post-photograph onset). Additionally, both genders showed a significant effect of harm avoidance and anxiety on modulation of the startle response, such that individuals reporting low levels of each trait failed to show significant responses to aversive photographs. These results suggest that while deficits in emotional processing extend to non-incarcerated samples, the relationship may be influenced by additional factors including gender, personality, and attributes related to incarceration.     

Startle modulation in non-incarcerated men and women with psychopathic traits

Past research has demonstrated that individuals with psychopathic characteristics are under-responsive to aversive stimuli, however, much of this work has failed to include non-incarcerated samples, or to examine gender differences in this relationship. Additionally, few studies have examined the role of specific personality characteristics, as they relate to both psychopathic behavior and emotional responsiveness. The current study assessed emotional modulation of the startle response in a community sample of 108 men and women (99 with usable startle data) during perception of emotion-laden photographs. Consistent with previous work, men reporting high levels of psychopathy failed to show the typical increase in the startle response when exposed to aversive photographs, but only when responses were elicited relatively early in picture viewing (i.e., 2.0 s as compared to 4.5 s post-photograph onset). Additionally, both genders showed a significant effect of harm avoidance and anxiety on modulation of the startle response, such that individuals reporting low levels of each trait failed to show significant responses to aversive photographs. These results suggest that while deficits in emotional processing extend to non-incarcerated samples, the relationship may be influenced by additional factors including gender, personality, and attributes related to incarceration.     

Somatic markers,working memory,and decision making

The somatic marker hypothesis formulated by Damasio (e.g., 1994; Damasio, Tranel, & Damasio, 1991) argues that affective reactions ordinarily guide and simplify decision making. Although originally intended to explain decision-making deficits in people with specific frontal lobe damage, the hypothesis also applies to decision-making problems in populations without brain injury. Subsequently, the gambling task was developed by Bechara (Bechara, Damasio, Damasio, & Anderson, 1994) as a diagnostic test of decision-making deficit in neurological populations. More recently, the gambling task has been used to explore implications of the somatic marker hypothesis, as well as to study suboptimal decision making in a variety of domains. We examined relations among gambling task decision making, working memory (WM) load, and somatic markers in a modified version of the gambling task. Increased WM load produced by secondary tasks led to poorer gambling performance. Declines in gambling performance were associated with the absence of the affective reactions that anticipate choice outcomes and guide future decision making. Our experiments provide evidence that WM processes contribute to the development of somatic markers. If WM functioning is taxed, somatic markers may not develop, and decision making may thereby suffer.     

The effect of content and physical properties of affective pictures on emotional responses

The aim of this research was to study the influence of both the emotional content and the physical characteristics of affective stimuli on the psychophysiological, behavioral and cognitive indexes of the emotional response. We selected 54 pictures from the IAPS, depicting unpleasant, neutral, and pleasant contents, and used two picture sizes as experimental conditions (120 x 90 cm and 52 x 42 cm). Sixty-one subjects were randomly assigned to each experimental condition. We recorded the startle blink reflex, skin conductance response, heart rate, free viewing time, and picture valence and arousal ratings. In line with previous research (e.g., Bradley, Codispoti, Cuthbert, and Lang, 2001), our data showed an effect of the affective content on all the measurements recorded. Importantly, effects of the size of the affective pictures on emotional responses were not found, indicating that the emotional content is more important than the formal properties of the stimuli in evoking the emotional response.     

Meditation and the startle response: a case study

The effects of two kinds of meditation (open presence and focused) on the facial and physiological aspects of the defensive response to an aversive startle stimulus were studied in a Buddhist monk with approximately 40 years of meditation experience. The participant was exposed to a 115-db, 100-ms acoustic startle stimulus under the 2 meditation conditions, a distraction condition (to control for cognitive and attentional load) and an unanticipated condition (startle presented without warning or instruction). A completely counterbalanced 24-trial, single-subject design was used, with each condition repeated 6 times. Most aspects of the participant's responses in the unanticipated condition did not differ from those of a comparison group of 12 age-matched male controls. Both kinds of meditation produced physiological and facial responses to the startle that were smaller than in the distraction condition. Within meditation conditions, open presence meditation produced smaller physiological and facial responses than focused meditation. These results from a single highly expert meditator indicate that these 2 kinds of meditation can differentially alter the magnitude of a primitive defensive response.     

I know how you feel: Task-irrelevant facial expressions are spontaneously processed at a semantic level

Previous studies have demonstrated that emotions are automatically processed. Even with subliminal presentations, subjects involuntarily mimic specific facial expressions, are influenced by the valence of a preceding emotion during judgments, and exhibit slowed responses to personally meaningful emotions; these effects are due to reflexive mimicry, unconscious carryover of valence, and attentional capture, respectively. However, perception-action effects indicate that rapid processing should involve deep, semantic-level representations of emotion (e.g., “fear”), even in the absence of a clinical emotion disorder. To test this hypothesis, we developed an emotional Stroop task (Emostroop) in which subjects responded nonverbally to emotion words superimposed over task-irrelevant images of faces displaying congruent or incongruent emotional expressions. Subjects reliably responded more slowly to incongruent than to congruent stimuli, and this interference was related to trait measures of emotionality. Rapid processing of facial emotions spontaneously activates semantic, content-rich representations at the level of the specific emotion.     

Emotional appraisal is influenced by cardiac afferent information

Influential models highlight the central integration of bodily arousal with emotion. Some emotions, notably disgust, are more closely coupled to visceral state than others. Cardiac baroreceptors, activated at systole within each cardiac cycle, provide short-term visceral feedback. Here we explored how phasic baroreceptor activation may alter the appraisal of brief emotional stimuli and consequent cardiovascular reactions. We used functional MRI (fMRI) to measure brain responses to emotional face stimuli presented before and during cardiac systole. We observed that the processing of emotional stimuli was altered by concurrent natural baroreceptor activation. Specifically, facial expressions of disgust were judged as more intense when presented at systole, and rebound heart rate increases were attenuated after expressions of disgust and happiness. Neural activity within prefrontal cortex correlated with emotionality ratings. Activity within periaqueductal gray matter reflected both emotional ratings and their interaction with cardiac timing. Activity within regions including prefrontal and visual cortices correlated with increases in heart rate evoked by the face stimuli, while orbitofrontal activity reflected both evoked heart rate change and its interaction with cardiac timing. Our findings demonstrate that momentary physiological fluctuations in cardiovascular afferent information (1) influence specific emotional judgments, mediated through regions including the periaqueductal gray matter, and (2) shape evoked autonomic responses through engagement of orbitofrontal cortex. Together these findings highlight the close coupling of visceral and emotional processes and identify neural regions mediating bodily state influences on affective judgment.     

Common spatial organization of number and emotional expression: a mental magnitude line

Converging behavioral and neural evidence suggests that numerical representations are mentally organized in left-to-right orientation. Here we show that this format of spatial organization extends to emotional expression. In Experiment 1, right-side responses became increasingly faster as number (represented by Arabic numerals) or happiness (depicted in facial stimuli) increased, for judgments completely unrelated to magnitude. Additional experiments suggest that magnitude (i.e., more/less relations), not valence (i.e., positive/negative), underlies left-to-right orientation of emotional expression (Experiment 2), and that this orientation accommodates to the context-relevant emotion (e.g., happier faces are more rightward when judged on happiness, but more leftward when judged on angriness; Experiment 3). These findings show that people automatically extract magnitude from a variety of stimuli, representing such information in common left-to-right format, perhaps reflecting a mental magnitude line. We suggest that number is but one dimension in a hyper-general representational system uniting disparate dimensions of magnitude and likely subserved by common neural mechanisms in posterior parietal cortex.     

Emotionality,distinctiveness, and recollective experience

Two experiments investigated the effects of emotional stimuli on recollective experience in recognition memory. In Experiment 1, words judged to evoke a positive emotional response (e.g., warmth, freedom) or a negative emotional response (e.g., mucus, corpse) were associated with more “remember” responses than emotionally neutral words (e.g., crate, border) when presented in mixed lists. This effect was stronger with negative words than with positive words. In Experiment 2 the effects of emotional stimuli were eliminated when participants studied pure lists of either all emotional or all neutral words. These findings are discussed in relation to Rajaram's (1996) distinctiveness account of recollective experience.     

Editorial: Information Processing and the Emotional Disorders

Abstract

It is shown that emotions can usefully be considered as states produced by reinforcing stimuli. The ways in which a wide variety of emotions can be produced, and the functions of emotion, are considered. There is evidence that the amygdala is involved in the formation of stimulus-reinforcement associations, and the orbitofrontal cortex with correcting behavioural responses when these are no longer appropriate because previous reinforcement contingencies change. This evidence comes from the effects of damage to these structures, and from recording the activity of single neurons in these structures in the monkey during the formation and disconnection of stimulus-reinforcement associations. In so far as emotions can be defined as states produced by reinforcing stimuli, then the amygdala and orbitofrontal cortex are seen to be of great importance for emotions, in that they are involved respectively in the elicitation of learned emotional responses, and in the correction or adjustment of these emotional responses as the reinforcing value of environmental stimuli alters. One of the theses advanced is that the changes in emotional behaviour produced by damage to the brain can be analysed and understood by considering how different parts of it function in reinforcement and in the formation and disconnection of stimulus-reinforcement connections. Another thesis is that there is a population of neurons in the amygdala and parts of the temporal lobe visual cortex specialised to respond to faces, and that these neurons may be involved in social and emotional resposes to faces.

Some of the outputs of the amygdala and orbitofrontal cortex are directed to the hypothalamus, which not only provides one route for these reinforcing environmental events to produce autonomic responses, but also is implicated in the utilisation of such stimuli in motivational responses, such as feeding and drinking, and in emotional behaviour. Other outputs of the amygdala and orbitofrontal cortex which may enable them to influence behaviour are directed to the striatum, and also back towards some of the cortical regions from which they receive inputs. It is suggested that these latter projections are important in the effects which mood states have on cognitive processing.     

The Disruptive Adolescent as a Grown-Up: Predicting Adult Startle Responses to Violent and Erotic Films from Adolescent Conduct Problems and Callous-Unemotional Traits

The current study aimed to identify heterogeneous groups of adolescents differing on their levels of conduct problems (CP) and callous-unemotional (CU) traits, and compare them on startle reactivity to emotional videos (violent/erotic) during young adulthood. A Latent Profile Analysis, conducted among a longitudinal sample of 2306 adolescents, provided evidence for the existence of heterogeneous CP and CU subgroups (i.e., CP-only, CU-only, and CP+CU groups). Three years later, 82 young adults (Mage?=?19.95), randomly selected from the identified groups, participated in an experiment assessing their startle eye-blink responses during violent, erotic and neutral video scenes. Self-report ratings of fear, valence and arousal to affective scenes were also collected. Findings suggested that adolescents high on CP and low on CU traits showed high startle potentiation when viewing violent scenes during young adulthood, while those high on both CP and CU traits showed diminished startle reactivity to violent stimuli. Individuals high on CU traits without CP showed similar startle reactivity to controls. Further, the findings indicate that startle potentiation to violent stimuli can be a reliable physiological marker to distinguish antisocial individuals with and without CU traits. The finding that the CU only group was not differentiated from the control group on startle reactivity when viewing violent stimuli might explain their lower likelihood of engaging in antisocial behavior.     

Overt congruent facial reaction to dynamic emotional expressions in 9–10-month-old infants

The current study aimed to extend the understanding of the early development of spontaneous facial reactions toward observed facial expressions. Forty-six 9- to 10-month-old infants observed video clips of dynamic human facial expressions that were artificially created with morphing technology. The infants’ facial responses were recorded, and the movements of the facial action unit 12 (e.g., lip-corner raising, associated with happiness) and facial action unit 4 (e.g., brow-lowering, associated with anger) were visually evaluated by multiple naïve raters. Results showed that (1) infants make congruent, observable facial responses to facial expressions, and (2) these specific facial responses are enhanced during repeated observation of the same emotional expressions. These results suggest the presence of observable congruent facial responses in the first year of life, and that they appear to be influenced by contextual information, such as the repetition of presentation of the target emotional expressions.