Gastric myoelectrical activity as an index of emotional arousal.

Autonomic nervous system parameters such as electrodermal activity, heart rate, and facial EMG have been utilized extensively as measures of emotional arousal. One measure that has rarely been employed in this setting is gastric myoelectrical activity, despite the fact that "gut feelings" have an obvious and even profound role in everyday emotional life. It has been shown that the gastrointestinal system changes wall tonus and contraction rate during stressful tasks. However, the effects of emotionally salient stimuli on gastrointestinal motility have scarcely been studied. In the current study, emotional film clips designed to elicit happiness, disgust, fear, sadness, or no emotion (neutral) were presented to 16 normal participants. Electrogastrogram (EGG), skin conductance, and heart rate were measured while the participants viewed the film clips, and participants rated subjective arousal intensity and pleasantness of the film clips. We found that emotional film clips reliably induced the intended subjective feeling states. Also, EGG peak amplitudes in fear, disgust, sadness and happiness were higher than in the no emotion condition. There was a strong positive correlation (r=0.64) between EGG peak amplitude and subjective ratings of arousal. This is the first evidence that gastric myoelectrical activity is strongly correlated with arousal ratings to emotionally salient stimuli, and it suggests that EGG may add useful information about how the body contributes to the phenomenology of emotion and feeling.     

Event-related brain potentials and affective responses to threat in spider/snake-phobic and non-phobic subjects.

We investigated cortical responses and valence/arousal ratings of spider phobic, snake phobic, and healthy subjects while they were processing feared, fear-relevant, emotional neutral, and pleasant stimuli. Results revealed significantly larger amplitudes of late ERP components (P3 and late positive complex, LPC) but not of early components (N1, P2, N2) in phobics when subjects were processing feared stimuli. This fear-associated increase of amplitudes of late ERP components in phobic subjects was maximal at centro-parietal and occipital brain sites. Furthermore, phobics but not controls rated feared stimuli to be more negative and arousing than fear-relevant, emotional neutral, and pleasant stimuli. Since late ERP components and valence/arousal ratings were only significantly increased when phobic subjects but not when healthy controls were processing feared stimuli, the present data suggest that P3 and LPC amplitudes represent useful neural correlates of the emotional significance and meaning of stimuli.     

Affective modulation of brain potentials to painful and nonpainful stimuli

In accordance with the emotional priming hypothesis, emotions seem to modulate pain perception and pain tolerance thresholds. To further evaluate this association, event-related brain potentials (ERPs) elicited by painful and nonpainful electrical stimuli during processing of positive, neutral, and negative valenced pictures were recorded from 30 healthy volunteers. Valence of pictures affected pain ratings and the N150 elicited by painful stimuli, with lowest amplitudes for positive pictures and highest amplitudes for negative pictures. The P260 elicited by painful and nonpainful stimuli was modulated by arousal with reduced amplitudes with arousing (positive or negative) compared to neutral pictures. N150 amplitudes varying with picture valence seem to reflect an affective modulation of pain perception whereas P260 amplitudes varying with picture arousal rather reflect non-pain-specific attentional processes.     

Intact physiological response to arousal with impaired emotional recognition in alexithymia

BACKGROUND: The purpose of the present study was to clarify the relationship between the recognition of emotion and physiological response to emotion (i.e. arousal) in alexithymia. METHODS: This study investigated differences in physiological arousal state, as measured by continuous heart rate, electrodermal activity (EDA) and self-reported emotional intensity before and after exposure to an emotionally arousing or neutral videotape among 41 high- or low-alexithymic young adult participants. RESULTS: Across subjects, emotionally negative stimuli produced increased physiological arousal. However, high-alexithymic participants exposed to the arousing videotape did not report increased subjective emotional intensity, as did low-alexithymic participants. In addition, the baseline EDA of high-alexithymic participants was significantly higher than that of the low-alexithymic participants. CONCLUSIONS: Results support the prediction that alexithymia leads to a decoupling between subjective and physiological arousal when exposed to emotionally negative stimuli. This decoupling may increase alexithymic individuals' risks for stress-related illness.     

Stimulus-Preceding Negativity and heart rate changes in anticipation of affective pictures.

The aim of the present study was to investigate the affective modulation of the Stimulus-Preceding Negativity (SPN) and heart rate changes in anticipation of visual stimuli differing in emotional content. A S1-S2 task was employed with a word (S1) indicating the content of a subsequent emotional picture (S2). Both valence and arousal dimensions were manipulated by presenting positive and negative pictures, high and low in arousal. Irrespective of valence, the amplitude of the SPN resulted to be significantly larger preceding high rather than low arousal pictures, indicating that the SPN does reflect the intensity of the motivational engagement ascribed to affective stimuli. Heart rate responses showed a deceleration preceding S2, which was larger preceding high arousal stimuli in comparison with neutral stimuli. Results suggest a coherent response pattern in both cortical and peripheral measures during affective anticipation.     

Reduced positive emotion and underarousal are uniquely associated with subclinical depression symptoms: Evidence from psychophysiology,self‐report,and symptom clusters

Multiple models of aberrant emotional processing in depression have been advanced. However, it is unclear which of these models best applies to emotional disturbances in subclinical depressive symptoms. The current study employed a battery of psychophysiological measures and emotional ratings in a picture‐viewing paradigm to examine whether the underarousal, low positive emotion, heightened negative emotion, or emotion context insensitivity model of emotional dysfunction in subclinical depressive symptoms received greatest support. Postauricular reflex and skin conductance response potentiation for pleasant minus neutral pictures (measuring low positive emotion), overall skin conductance magnitude and late positive potential (LPP) amplitude (measuring underarousal), and pleasant minus aversive valence ratings (measuring emotion context insensitivity) and aversive minus neutral arousal ratings (measuring heightened negative emotionality) were all negatively related to depressive symptomatology. Of these, postauricular reflex potentiation and overall LPP amplitude were incrementally associated with depressive symptoms over the other measures. Postauricular reflex potentiation, overall skin conductance magnitude, and aversive minus neutral arousal ratings were incrementally associated with depressive symptomatology after controlling for other symptoms of internalizing disorders. Though no model was unequivocally superior, the low positive emotion and underarousal models received the most support from physiological measures and symptom reports, with self‐report data matching patterns consistent with the emotion context insensitivity model.     

Respiratory responses associated with affective processing of film stimuli

We investigated respiratory responses during film clip viewing and their relation to the affective dimensions of valence and arousal. Seventy-six subjects participated in a study using a between groups design. To begin with, all participants viewed an emotionally neutral film clip. Then, they were presented with one out of four emotional film clips: a positive high-arousal, a positive low-arousal, a negative high-arousal and a negative low-arousal clip. Respiration, skin conductance level, heart rate, corrugator activity and affective judgments were measured. Expiratory time was shorter and inspiratory duty cycle, mean expiratory flow and minute ventilation were larger during the high-arousal clips compared to the low-arousal clips. The pleasantness of the stimuli had no influence on any respiratory measure. These findings confirm the importance of arousal in respiratory responding but also evidence differences in comparison to previous studies using visual and auditory stimuli.     

Affective reactions to acoustic stimuli

Emotional reactions to naturally occurring sounds (e.g., screams, erotica, bombs, etc.) were investigated in two studies. In Experiment 1, subjects rated the pleasure and arousal elicited when listening to each of 60 sounds, followed by an incidental free recall task. The shape of the two-dimensional affective space defined by the mean ratings for each sound was similar to that previously obtained for pictures, and, like memory for pictures, free recall was highest for emotionally arousing stimuli. In Experiment 2, autonomic and facial electromyographic (EMG) activity were recorded while a new group of subjects listened to the same set of sounds; the startle reflex was measured using visual probes. Listening to unpleasant sounds resulted in larger startle reflexes, more corrugator EMG activity, and larger heart rate deceleration compared with listening to pleasant sounds. Electrodermal reactions were larger for emotionally arousing than for neutral materials. Taken together, the data suggest that acoustic cues activate the appetitive and defensive motivational circuits underlying emotional expression in ways similar to pictures.     

Age effects to negative arousal differ for self-report and electrodermal activity

Affective processing and emotional experience may change with age. Because findings of age differences in affective experiences are mixed even in studies using standardized stimuli, this study assessed age differences along gradual increases in negative arousal. Younger (20-30 years) and older (70-80 years) healthy adults (n=78) viewed 110 neutral to negative pictures (IAPS) while intensity ratings and electrodermal activity were recorded. Results showed that age had opposite effects on intensity ratings and electrodermal activity over gradual increases in normative arousal. Whereas older adults showed greater increases in intensity ratings than younger adults, they showed attenuated electrodermal activity, especially at high negative arousal. Because self-reports of arousal capture various aspects of affective processes (e.g., physiological changes as well as experience), effects of age may vary for these different aspects.     

Emotional & electroencephalographic responses during affective picture viewing after exercise

We examined the effects of 30 min of cycling exercise at a moderate intensity of 50% peak oxygen uptake, compared to 30 min of rest, on changes in emotional responses to pictorial foreground stimuli that reliably elicit unpleasant, neutral, and pleasant affect. Emotional responses were measured by self-reports of valence (unpleasant to pleasant) and arousal (low to high) and by hemispheric asymmetry (R-L) of frontal and parietal brain electroencephalographic (EEG) activity in 13 females and 21 males (24+/-3 y). Compared to after rest, self-reports of arousal in response to unpleasant slides were diminished after exercise, but self-reports of valence and frontal asymmetry of alpha frequencies were generally unchanged. Even so, there were differential responses in asymmetry in the beta frequencies in the frontal region and for alpha and beta frequencies in the parietal region, indicative of decreased activity in the left frontal and right parietal regions after exercise compared to after rest. We conclude that moderately intense cycling exercise generally does not alter emotional responding to pleasant and neutral pictures, but may reduce emotional arousal during exposure to unpleasant stimuli.     

Startle during backward evaluative conditioning is not modulated by instructions

Instructions highlighting that backward conditional stimuli (CSs) stop unconditional stimuli (USs) result in their acquiring valence opposite to that of the US on explicit measures of valence. We assessed whether such instructions would influence startle blink modulation in the same way. Two groups were presented with concurrent forward and backward evaluative conditioning (CS-US-CS) using cartoon aliens as CSs, and pleasant, neutral, and unpleasant sounds as USs. Startle magnitude was measured during conditioning and valence ratings were assessed after conditioning. Participants in the “start-stop” instructions group (n = 41) were instructed to learn whether CSs started or stopped US presentations, while participants in the “observe” instructions group (n = 41) were told to pay attention to the stimuli as they would be asked questions about them after the experiment. In the start-stop instructions group backward CSs paired with positive USs were rated as less pleasant than backward CSs paired with neutral and negative USs (contrast effect), whereas ratings of backward CSs did not differ in the observe instructions group. Startle magnitude was larger during backward CSs paired with positive USs in comparison to CSs paired with neutral or negative USs in both instruction groups. Startle blink modulation was unaffected by instructions, suggesting that startle indexes the emotional state at the time of probe presentation rather than CS valence based on propositional information about the function of the CS.     

Emotional qualities of odors and their influence on the startle reflex in humans

Recent human and animal research suggests that the startle reflex might serve as a psychophysiological indicator of the emotional valence of foreground stimulation. The present experiment was designed to evaluate the emotional effects of positive and negative odorant stimuli. We examined the effects of continuous hydrogen sulphide (H2S) and vanillin stimulation on the magnitude of the acoustic startle reflex (measured at the M. orbicularis oculi) and on ratings of subjective valence in 16 healthy subjects. In accordance with the view that odors have emotional qualities, we found that H2S, a presumed negative foreground stimulus, significantly enhanced the startle-reflex amplitude relative to neutral air stimulation, whereas vanillin, a positive foreground stimulus, tended to reduce the reflex amplitude compared with neutral air stimulation. Both odorant stimuli were rated as equally intense by the subjects, and heart rate and electrodermal activity were not affected differentially by the two odorants.     

Affective and physiological responses to environmental noises and music.

Research suggests that respiratory patterns may reflect general dimensions of emotional response. In this study, we investigated the relationships between judgments of affective valence (pleasantness) and arousal and respiratory responses to acoustic stimuli. Sixteen environmental noises and 16 musical fragments of 30 s duration were presented to 31 participants, while respiration, skin conductance level and heart rate were recorded. Judgments of valence and arousal were registered using the 9-point Self-Assessment Manikin. For noises, breathing accelerated and minute ventilation augmented with decreases in pleasantness for low-arousal stimuli and with increases in arousal for positive stimuli. For music, breathing accelerated and minute ventilation augmented with increases both in rated valence and arousal. Skin conductance level increased with arousal ratings for music but not for noises, whereas mean heart rate increased with rated arousal for noises but not for music. Although both noises and music are sound-vibrations, differences in the relationships between affective judgments and physiological responses were found suggesting differences in the processing of the two types of acoustic stimuli.     

Heart rate response after emotional picture presentation is modulated by interoceptive awareness.

The perception of visceral signals plays a crucial role in many theories of emotions. The present study was designed to investigate the relationship between interoceptive awareness, emotional experience and heart rate responses in an emotional stimulation paradigm. Based on their performance in a heartbeat perception task 38 participants (16 males, 22 females) were classified as subjects with either high (n=19; 8 males) or low interoceptive awareness (n=19; 8 males). 120 pictures (40 pleasant, 40 unpleasant, 40 neutral slides) from the International Affective Picture System served as emotional stimuli. Heart rate changes were recorded during baseline and during slide presentation. After each slide, the subjects had to rate emotional valence and arousal on a 9-point self-report scale. Statistical analyses revealed significantly stronger heart rate responses to pleasant and unpleasant stimuli in subjects with high interoceptive awareness. Furthermore, subjects with high interoceptive awareness rated pleasant and unpleasant slides as significantly more arousing; no differences were found in the emotional valence ratings. Heartbeat perception scores correlated significantly positive with both the mean arousal rating and with the mean heart rate changes. Our results demonstrate a strong relationship between the perception of cardiac signals and the peripheral processing of emotional stimuli.     

Distinct effects of attention and affect on pain perception and somatosensory evoked potentials

The influence of affect and attention on sensory and affective pain as well as on somatosensory evoked potentials in response to painful and nonpainful electrical stimuli was investigated in a single experimental design. Affect was induced by pictures from the International Affective Picture System; attention was manipulated by asking participants to focus attention either on the pictures or on the electrical stimuli. Sensory and affective pain ratings were generally lower during exposure to positive compared to negative and neutral pictures. Attention modulated only sensory pain ratings with lower ratings with an attention focus on pictures than with an attention focus on sensory pain. The N150 was modulated by picture valence, the P260 by picture arousal. Furthermore, the P260 was modulated by attention with highest amplitudes with an attention focus on the stimulus intensity. This study provides neurophysiological evidence that attention and affect have distinct effects on pain processing.     

Autonomic responding to aversive words without conscious valence discrimination.

A growing body of data suggests that the emotional dimension of a stimulus can be processed without conscious identification of the stimulus. The arousal system could be activated by unrecognised biologically significant stimuli through simple physical stimulus features related to threat, without any evaluation of the meaning of the stimulus. However, unconscious processing of emotionally laden words cannot rely only on perceptual features but must include some analysis of symbolic meaning. The first aim of the present study was to assess whether masked (unrecognised) aversive words can elicit enhanced skin conductance responses (SCRs), a major autonomic index of emotional arousal, in normal participants. Our second aim was to determine whether any autonomic activation related to affective value of words is independent from access of this value to consciousness. Thus, the presentation duration of masked aversive and neutral words was determined, for each participant, in such a way that (1) identification was precluded, (2) valence discrimination was at chance, as indicated by performance in a forced-choice two-alternative task and by confidence ratings of the responses, and (3) emotional and neutral words were not detected differentially. SCRs were recorded during masked and unmasked presentations of both types of word. SCRs elicited by unmasked words, and also by masked words, were of greater magnitude when the words were emotional than when they were neutral. Consequently, in normal participants, autonomic activation can be a discriminative marker of the affective dimension of unrecognised verbal material in the absence of conscious valence identification.     

The influence of facial expression at perceptual threshold on electrodermal activity and social comfort distance

Interpersonal distance, an essential component of social interaction, is modulated by the emotion conveyed by others and associated physiological response. However, in modern societies with overcrowded and hyperstimulating environments, we can only surreptitiously glimpse the faces of others in order to quickly make behavioral adjustments. How this impacts social interactions is not yet well understood. In the present study, we investigated this issue by testing whether facial expressions that are difficult to identify modify the physiological response (Electrodermal Activity, EDA) and subsequent judgment of interpersonal comfort distance. We recorded participants’ EDA while they provided comfort judgments to interpersonal distances with a Point-Light Walker (PLW). The PLW, with an emotionally neutral gait, moved toward and crossed participants at various distances after the latter were exposed to a negative (anger), positive (happiness) or neutral facial expression presented at the perceptual threshold. Bayesian analyses of the data revealed an increase versus decrease of interpersonal comfort distance with the PLW depending on the negative versus positive emotional valence of the facial expression. They also showed an increase in EDA when the approaching PLW violated interpersonal comfort distance after participants were exposed to an angry facial expression. These effects correlated with the subjective assessment of the arousal of facial expressions. Thus, previous exposure to barely visible facial expressions can alter the representation of social comfort space and the physiological response associated with a violation of interpersonal comfort distances, depending on the valence and arousal of the emotional social stimuli.     

Overnight emotional adaptation to negative stimuli is altered by REM sleep deprivation and is correlated with intervening dream emotions

Rapid eye movement (REM) sleep and dreaming may be implicated in cross-night adaptation to emotionally negative events. To evaluate the impact of REM sleep deprivation (REMD) and the presence of dream emotions on a possible emotional adaptation (EA) function, 35 healthy subjects randomly assigned to REMD ( n  = 17; mean age 26.4 ± 4.3 years) and control ( n  = 18; mean age 23.7 ± 4.4 years) groups underwent a partial REMD and control nights in the laboratory, respectively. In the evening preceding and morning following REMD, subjects rated neutral and negative pictures on scales of valence and arousal and EA scores were calculated. Subjects also rated dream emotions using the same scales and a 10-item emotions list. REMD was relatively successful in decreasing REM% on the experimental night, although a mean split procedure was applied to better differentiate subjects high and low in REM%. High and low groups differed – but in a direction contrary to expectations. Subjects high in REMD% showed greater adaptation to negative pictures on arousal ratings than did those low in REMD% ( P  < 0.05), even after statistically controlling sleep efficiency and awakening times. Subjects above the median on EA_valence had less intense overall dream negativity ( P  < 0.005) and dream sadness ( P  < 0.004) than subjects below the median. A correlation between the emotional intensities of the morning dream and the morning picture ratings supports a possible emotional carry-over effect. REM sleep may enhance morning reactivity to negative emotional stimuli. Further, REM sleep and dreaming may be implicated in different dimensions of cross-night adaptation to negative emotions.     

Affect, attention, or anticipatory arousal? Human blink startle modulation in forward and backward affective conditioning

Affect modulates the blink startle reflex in the picture-viewing paradigm, however, the process responsible for reflex modulation during conditional stimuli (CSs) that have acquired valence through affective conditioning remains unclear. In Experiment 1, neutral shapes (CSs) and valenced or neutral pictures (USs) were paired in a forward (CS-->US) manner. Pleasantness ratings supported affective learning of positive and negative valence. Post-acquisition, blink reflexes were larger during the pleasant and unpleasant CSs than during the neutral CS. Rather than affect, attention or anticipatory arousal were suggested as sources of startle modulation. Experiment 2 confirmed that affective learning in the picture-picture paradigm was not affected by whether the CS preceded the US. Pleasantness ratings and affective priming revealed similar extents of affective learning following forward, backward or simultaneous pairings of CSs and USs. Experiment 3 utilized a backward conditioning procedure (US-->CS) to minimize effects of US anticipation. Again, blink reflexes were larger during CSs paired with valenced USs regardless of US valence implicating attention rather than anticipatory arousal or affect as the process modulating startle in this paradigm.     

A startling absence of emotion effects: Active attention to the startle probe as a motor task cue appears to eliminate modulation of the startle reflex by valence and arousal

Research has shown that during emotional imagery, valence and arousal each modulate the startle reflex. Here, two imagery-startle experiments required participants to attend to the startle probe as a simple reaction time cue. In Experiment 1, four emotional conditions differing in valence and arousal were examined. Experiment 2, to accentuate potential valence effects, included two negative high arousal, a positive high arousal and a negative low arousal condition. Imagery effectively manipulated emotional valence and arousal, as indicated by heart rate and subjective ratings. Compared to baseline, imagery facilitated startle responses. However, valence and arousal failed to significantly affect startle magnitude in both experiments and startle latency in Experiment 1. Results suggest that emotional startle modulation is eclipsed when the probe is significant for task completion and/or cues a motor response. Findings suggest that an active, rather than defensive, response set may interfere with affective startle modulation, warranting further investigation.