Probing affective pictures: attended startle and tone probes

Reflexive eyeblinks to a startle probe vary with the pleasantness of affective pictures, whereas the corresponding P300 varies with emotional arousal. The impact of attention to the probe on these effects was examined by varying task and probe type. Probes were either nonstartling tones or startling noises presented during affective picture viewing. Half the participants performed a task requiring attention to the probes; the other participants were told to ignore the probes. Blinks to the startle probe varied with picture pleasantness for both task and nontask conditions. In contrast, P300 magnitudes for both startle and tone probes were reduced during emotionally arousing pictures, irrespective of pleasantness, in task and nontask conditions. Further, attending to the startle probe prompted an augmentation of N100 during unpleasant pictures. The data suggest that affective modulation of probe responses reflects obligatory processes in picture perception.

Emotional arousal and activation of the visual cortex: an fMRI analysis

Functional activity in the visual cortex was assessed using functional magnetic resonance imaging technology while participants viewed a series of pleasant, neutral, or unpleasant pictures. Coronal images at four different locations in the occipital cortex were acquired during each of eight 12-s picture presentation periods (on) and 12-s interpicture interval (off). The extent of functional activation was larger in the right than the left hemisphere and larger in the occipital than in the occipitoparietal regions during processing of all picture contents compared with the interpicture intervals. More importantly, functional activity was significantly greater in all sampled brain regions when processing emotional (pleasant or unpleasant) pictures than when processing neutral stimuli. In Experiment 2, a hypothesis that these differences were an artifact of differential eye movements was ruled out. Whereas both emotional and neutral pictures produced activity centered on the calcarine fissure (Area 17), only emotional pictures also produced sizable clusters bilaterally in the occipital gyrus, in the right fusiform gyrus, and in the right inferior and superior parietal lobules.

Neuroanatomical correlates of pleasant and unpleasant emotion

Substantial evidence suggests that a key distinction in the classification of human emotion is that between an appetitive motivational system association with positive or pleasant emotion and an aversive motivational system associated with negative or unpleasant emotion. To explore the neural substrates of these two systems, 12 healthy women viewed sets of pictures previously demonstrated to elicit pleasant, unpleasant and neutral emotion, while positron emission tomographic (PET) measurements of regional cerebral blood flow were obtained. Pleasant and unpleasant emotions were each distinguished from neutral emotion conditions by significantly increased cerebral blood flow in the vicinity of the medial prefrontal cortex (Brodmann's area 9), thalamus, hypothalamus and midbrain (P < 0.005). Unpleasant was distinguished from neutral or pleasant emotion by activation of the bilateral occipito-temporal cortex and cerebellum, and left parahippocampal gyrus, hippocampus and amygdala (P < 0.005). Pleasant was also distinguished from neutral but not unpleasant emotion by activation of the head of the left caudate nucleus (P < 0.005). These findings are consistent with those from other recent PET studies of human emotion and demonstrate that there are both common and unique components of the neural networks mediating pleasant and unpleasant emotion in healthy women.

Integrated RF coil with stabilization for fMRI human cortex

Functional brain imaging of the human cortex is limited by poor contrast to noise ratio (CNR) and image degradation due to subject motion during the acquisition period. The work described here combines the use of closely coupled phased array receiver coils with a stabilization system to address these needs. Several phased array designs are evaluated and compared with the conventional "birdcage" design. Coil performance is reported in terms of relative SNR and fMRI results. Relative improvements of up to 360% are obtained for the occipital region and 180% in the temporal region. More modest gains of 10-30% were obtained for a "dome"-shaped birdcage volume coil covering the entire cortex.

Probe P3 and blinks: two measures of affective startle modulation

Two concurrent measures of the evoked startle response, the elicited blink reflex and the event-related potential, were measured while individuals viewed pictures that varied in pleasure and arousal. Replicating previous findings, the blink response was modulated by picture pleasantness, with larger reflexes elicited in the context of viewing unpleasant versus pleasant pictures. However, the probe P3 was primarily modulated by picture arousal, with smaller P3 responses elicited when viewing affective (pleasant or unpleasant) than when viewing neutral pictures. Both modulatory effects were sustained for probes presented in a subsequent picture imagery period. These data suggest that two measurable responses to the same startle probe are differentially modified by emotional context, with blink magnitude varying with pleasure and probe P3 varying with stimulus arousal.

Picture media and emotion: effects of a sustained affective context

Pleasant, neutral, or unpleasant pictures were presented in a continuous series, and the effects of repetitive exposure to pictures of the same affective valence were assessed in somatic (corrugator electromyographic [EMG] activity) and visceral (heart rate and skin conductance) systems. Probe stimuli (startle or reaction time probes) were presented to index emotional and attentional concomitants of processing. Affective discrimination was maintained across time in all response systems, and sensitization was found for the corrugator EMG response. Responses to reaction time probes indexed differences in attentional allocation as a function of cognitive and affective variables in this paradigm. Taken together, the data suggest that presentation of a series of affective pictures of similar valence produces emotional reactions that are either maintained or sensitized across the temporal intervals used here but that do not habituate.

Probing picture perception: activation and emotion

When acoustic startle probes are presented during picture viewing, the blink reflex is augmented for unpleasant foreground stimuli and reduced during pleasant stimuli. The present experiment assessed the hypothesis that this affect-startle effect increases as pictures are judged to be more arousing. Eyeblinks elicited by startle probes of three different intensities were recorded while subjects viewed pictures varying in both pleasure (pleasant, neutral, and unpleasant) and arousal (low, moderate, and high). Both blink potentiation during unpleasant content and blink diminution during pleasant content were clearly strongest for picture contents high in arousal. The effect was present for all probe intensities tested.

Lateralized startle probes in the study of emotion

Two experiments are reported in which affective modulation of the startle reflex elicited by monaurally presented acoustic probes was further examined. An earlier study in our laboratory obtained significant modulation by affect for probes presented to the left ear, but no significant effect for probes presented to the right ear. Experiment 1 replicated the procedures used in that experiment and obtained the same pattern of effects. Experiment 2 changed the presentation of monaural probes from a blocked to a mixed presentation and again obtained a similar pattern. Modulatory differences in reflex magnitude between pleasant and unpleasant stimuli were consistently large and reliable for reflexes elicited by left ear probes but weak and unreliable for reflexes elicited by right ear probes.

Modulation of spinal reflexes: arousal, pleasure, action

The human startle reflex is reliably modulated by the affective valence of foreground pictures, with larger reflexes elicited when viewing unpleasant relative to pleasant scenes. If this modulation is due to priming of the defensive startle reflex by an aversive foreground, a different pattern should occur for a reflex that is not inherently defensive in nature. In the current study, affective modulation was investigated using the spinal tendinous (T) reflex, which is well documented as sensitive to differences in arousal and is involved in actions that are both appetitively defensively motivated. As such, T reflexes elicited during unpleasant pictures were not expected to be augmented relative to those elicited in the context of pleasant pictures. Results showed that T reflexes were facilitated during processing of arousing stimuli-either pleasant or unpleasant relative to low-arousal neutral materials. These effects of emotional stimuli on T-reflex amplitude are consistent with hypothesis that motivational priming underlies affective reflex modulation.

The emotion probe. Studies of motivation and attention

Emotions are action dispositions--states of vigilant readiness that vary widely in reported affect, physiology, and behavior. They are driven, however, by only 2 opponent motivational systems, appetitive and aversive--subcortical circuits that mediate reactions to primary reinforcers. Using a large emotional picture library, reliable affective psychophysiologies are shown, defined by the judged valence (appetitive/pleasant or aversive/unpleasant) and arousal of picture percepts. Picture-evoked affects also modulate responses to independently presented startle probe stimuli. In other words, they potentiate startle reflexes during unpleasant pictures and inhibit them during pleasant pictures, and both effects are augmented by high picture arousal. Implications are elucidated for research in basic emotions, psychopathology, and theories of orienting and defense. Conclusions highlight both the approach's constraints and promising paths for future study.

The emotion probe. Studies of motivation and attention

Emotions are action dispositions--states of vigilant readiness that vary widely in reported affect, physiology, and behavior. They are driven, however, by only 2 opponent motivational systems, appetitive and aversive--subcortical circuits that mediate reactions to primary reinforcers. Using a large emotional picture library, reliable affective psychophysiologies are shown, defined by the judged valence (appetitive/pleasant or aversive/unpleasant) and arousal of picture percepts. Picture-evoked affects also modulate responses to independently presented startle probe stimuli. In other words, they potentiate startle reflexes during unpleasant pictures and inhibit them during pleasant pictures, and both effects are augmented by high picture arousal. Implications are elucidated for research in basic emotions, psychopathology, and theories of orienting and defense. Conclusions highlight both the approach's constraints and promising paths for future study.

Emotion in the criminal psychopath: fear image processing

We tested the hypothesis that the response mobilization that normally accompanies imagery of emotional situations is deficient in psychopaths. Cardiac, electrodermal, and facial muscle responses of 54 prisoners, assigned to low- and high-psychopathy groups using R. D. Hare's (1991) Psychopathy Checklist--Revised, were recorded while subjects imagined fearful and neutral scenes in a cued sentence-processing task. Groups did not differ on self-ratings of fearfulness, imagery ability, or imagery experience. Low-psychopathy subjects showed larger physiological reactions during fearful imagery than high-psychopathy subjects. Extreme scores on the antisocial behavior factor of psychopathy predicted imagery response deficits. Results are consistent with the idea that semantic and emotional processes are dissociated in psychopaths.

Emotion in the criminal psychopath: fear image processing

We tested the hypothesis that the response mobilization that normally accompanies imagery of emotional situations is deficient in psychopaths. Cardiac, electrodermal, and facial muscle responses of 54 prisoners, assigned to low- and high-psychopathy groups using R. D. Hare's (1991) Psychopathy Checklist--Revised, were recorded while subjects imagined fearful and neutral scenes in a cued sentence-processing task. Groups did not differ on self-ratings of fearfulness, imagery ability, or imagery experience. Low-psychopathy subjects showed larger physiological reactions during fearful imagery than high-psychopathy subjects. Extreme scores on the antisocial behavior factor of psychopathy predicted imagery response deficits. Results are consistent with the idea that semantic and emotional processes are dissociated in psychopaths.

Emotion, novelty, and the startle reflex: habituation in humans

Previous research with both animal and human subjects has shown that startle reflex magnitude is potentiated in an aversive stimulus context, relative to responses elicited in a neutral or appetitive context. In the present experiment, the same pleasant, unpleasant, and neutral picture stimuli were repeatedly presented to human subjects. Startle reflex habituation was assessed in each stimulus context and was compared with the habituation patterns of heart rate, electrodermal, and facial corrugator muscle responses. All systems showed initial differentiation among affective picture contents and general habituation over trials. The startle reflex alone, however, continued to differentiate among pleasant, neutral, and unpleasant pictures throughout the presentation series. These results suggest that (a) the startle probe reflex is relatively uninfluenced by stimulus novelty, (b) the startle modulatory circuit (identified with amygdala-reticular connections in animals) varies systematically with affective valence, and (c) the modulatory influence is less subject to habituation than is the obligatory startle pathway or responses in other somatic and autonomic systems.

The varieties of emotional experience: a meditation on James-Lange theory

James-Lange theory influenced a century of emotion research. This article traces the theory's origins in philosophical psychology, considers differences in the thinking of James and Lange, and assesses Cannon's early critique and the resulting debate. Research is reviewed evaluating physiological patterns in emotion, the discordance of reported feelings and visceral reactivity, and the role of generalized arousal. NeoJamesian theories of attribution and appraisal--and alternative views based on dynamic psychology--are critically examined. A conception of emotion is presented, on the basis of developments unknown to James in conditioning theory, information processing, and neuroscience. Computational models of mentation are discussed, and implications are drawn for the classical debate on cognition and emotion. In concluding, new paths for emotion research are outlined and homage paid to the inspiration of William James.

Measuring emotion: the Self-Assessment Manikin and the Semantic Differential

The Self-Assessment Manikin (SAM) is a non-verbal pictorial assessment technique that directly measures the pleasure, arousal, and dominance associated with a person's affective reaction to a wide variety of stimuli. In this experiment, we compare reports of affective experience obtained using SAM, which requires only three simple judgments, to the Semantic Differential scale devised by Mehrabian and Russell (An approach to environmental psychology, 1974) which requires 18 different ratings. Subjective reports were measured to a series of pictures that varied in both affective valence and intensity. Correlations across the two rating methods were high both for reports of experienced pleasure and felt arousal. Differences obtained in the dominance dimension of the two instruments suggest that SAM may better track the personal response to an affective stimulus. SAM is an inexpensive, easy method for quickly assessing reports of affective response in many contexts.

Emotion, novelty, and the startle reflex: habituation in humans

Previous research with both animal and human subjects has shown that startle reflex magnitude is potentiated in an aversive stimulus context, relative to responses elicited in a neutral or appetitive context. In the present experiment, the same pleasant, unpleasant, and neutral picture stimuli were repeatedly presented to human subjects. Startle reflex habituation was assessed in each stimulus context and was compared with the habituation patterns of heart rate, electrodermal, and facial corrugator muscle responses. All systems showed initial differentiation among affective picture contents and general habituation over trials. The startle reflex alone, however, continued to differentiate among pleasant, neutral, and unpleasant pictures throughout the presentation series. These results suggest that (a) the startle probe reflex is relatively uninfluenced by stimulus novelty, (b) the startle modulatory circuit (identified with amygdala-reticular connections in animals) varies systematically with affective valence, and (c) the modulatory influence is less subject to habituation than is the obligatory startle pathway or responses in other somatic and autonomic systems.

Emotional learning, hedonic change, and the startle probe

A multiple-response analysis of aversive learning was conducted in human subjects. For each subject, two pictorial stimuli were presented--one paired with electric shock. After training, the magnitude of the acoustic startle eyeblink reflex elicited in the context of the shocked picture increased dramatically and was significantly larger than for reflexes elicited during the nonshocked stimulus. Five different picture contents were tested in separate groups: Reflex potentiation was larger for pictures rated as pleasant than pictures rated as unpleasant. Conditioned responses were also evident for skin conductance, heart rate, and affective judgments. Different systems reflected different aspects of the acquired fear response: Conductance change covaried with arousal, and startle probe magnitude varied with affective valence (pleasure). The neurophysiological implications of the data are elucidated, and parallels drawn between animal and human subjects findings.

Pictures as prepulse: attention and emotion in startle modification

The effects of an emotional stimulus prepulse on probe startle response were examined here. Pleasant, neutral and unpleasant pictures were viewed for 6 s, and an acoustic startle probe was presented either 300, 800, 1,300, or 3,800 ms after slide onset, or 300 or 3,800 ms after slide offset. Blink magnitude and onset latency demonstrated (a) an early (prepulse) inhibition effect in which reflexes elicited immediately after slide onset were smaller than reflexes elicited later in the viewing interval, and (b) affective modulation, in which unpleasant stimuli prompted larger reflexes than pleasant. Interactive effects of probe time and picture valence indicated attention/arousal effects early and pleasantness effects late in the picture interval. Effects of both attention and emotion can be simultaneously measured using this startle-probe paradigm, encouraging its use in both basic and clinical contexts.

Emotional learning, hedonic change, and the startle probe

A multiple-response analysis of aversive learning was conducted in human subjects. For each subject, two pictorial stimuli were presented--one paired with electric shock. After training, the magnitude of the acoustic startle eyeblink reflex elicited in the context of the shocked picture increased dramatically and was significantly larger than for reflexes elicited during the nonshocked stimulus. Five different picture contents were tested in separate groups: Reflex potentiation was larger for pictures rated as pleasant than pictures rated as unpleasant. Conditioned responses were also evident for skin conductance, heart rate, and affective judgments. Different systems reflected different aspects of the acquired fear response: Conductance change covaried with arousal, and startle probe magnitude varied with affective valence (pleasure). The neurophysiological implications of the data are elucidated, and parallels drawn between animal and human subjects findings.

Emotional imagery in simple and social phobia: fear versus anxiety

In a first study, phobic volunteer subjects (N = 60) reacted psychophysiologically with greater vigor to imagery of their own phobic content than to other fearful or nonaffective images. Imagery heart rate responses were largest in subjects with multiple phobias. For simple (dental) phobics, cardiac reactivity was positively correlated with reports of imagery vividness and concordant with reports of affective distress; these relationships were not observed for social (speech) phobics. In a second study, these phobic volunteers were shown to be similar on most measures to an outpatient clinically phobic sample. In an analysis of the combined samples, fearful and socially anxious subtypes were defined by questionnaires. Only the fearful subtype showed a significant covariation among physiological responses, imagery vividness, and severity of phobic disorder. This fearful-anxious distinction seems to cut across diagnostic categories, providing a heuristic perspective from which to view anxiety disorders.

Emotional imagery in simple and social phobia: fear versus anxiety

In a first study, phobic volunteer subjects (N = 60) reacted psychophysiologically with greater vigor to imagery of their own phobic content than to other fearful or nonaffective images. Imagery heart rate responses were largest in subjects with multiple phobias. For simple (dental) phobics, cardiac reactivity was positively correlated with reports of imagery vividness and concordant with reports of affective distress; these relationships were not observed for social (speech) phobics. In a second study, these phobic volunteers were shown to be similar on most measures to an outpatient clinically phobic sample. In an analysis of the combined samples, fearful and socially anxious subtypes were defined by questionnaires. Only the fearful subtype showed a significant covariation among physiological responses, imagery vividness, and severity of phobic disorder. This fearful-anxious distinction seems to cut across diagnostic categories, providing a heuristic perspective from which to view anxiety disorders.

Looking at pictures: affective, facial, visceral, and behavioral reactions

Colored photographic pictures that varied widely across the affective dimensions of valence (pleasant-unpleasant) and arousal (excited-calm) were each viewed for a 6-s period while facial electromyographic (zygomatic and corrugator muscle activity) and visceral (heart rate and skin conductance) reactions were measured. Judgments relating to pleasure, arousal, interest, and emotional state were measured, as was choice viewing time. Significant covariation was obtained between (a) facial expression and affective valence judgments and (b) skin conductance magnitude and arousal ratings. Interest ratings and viewing time were also associated with arousal. Although differences due to the subject's gender and cognitive style were obtained, affective responses were largely independent of the personality factors investigated. Response specificity, particularly facial expressiveness, supported the view that specific affects have unique patterns of reactivity. The consistency of the dimensional relationships between evaluative judgments (i.e., pleasure and arousal) and physiological response, however, emphasizes that emotion is fundamentally organized by these motivational parameters.

Emotion in the criminal psychopath: startle reflex modulation

Startle-elicited blinks were measured during presentation of affective slides to test hypotheses concerning emotional responding in psychopaths. Subjects were 54 incarcerated sexual offenders divided into nonpsychopathic, psychopathic, and mixed groups based on file and interview data. Consistent with findings for normal college students, nonpsychopaths and mixed subjects showed a significant linear relationship between slide valence and startle magnitude, with startle responses largest during unpleasant slides and smallest during pleasant slides. This effect was absent in psychopaths. Group differences in startle modulation were related to affective features of psychopathy, but not to antisocial behavior per se. Psychopathy had no effect on autonomic or self-report responses to slides. These results suggest an abnormality in the processing of emotional stimuli by psychopaths that manifests itself independently of affective report.

Emotion in the criminal psychopath: startle reflex modulation

Startle-elicited blinks were measured during presentation of affective slides to test hypotheses concerning emotional responding in psychopaths. Subjects were 54 incarcerated sexual offenders divided into nonpsychopathic, psychopathic, and mixed groups based on file and interview data. Consistent with findings for normal college students, nonpsychopaths and mixed subjects showed a significant linear relationship between slide valence and startle magnitude, with startle responses largest during unpleasant slides and smallest during pleasant slides. This effect was absent in psychopaths. Group differences in startle modulation were related to affective features of psychopathy, but not to antisocial behavior per se. Psychopathy had no effect on autonomic or self-report responses to slides. These results suggest an abnormality in the processing of emotional stimuli by psychopaths that manifests itself independently of affective report.

Remembering pictures: pleasure and arousal in memory

Incidental memory performance for pictures that varied along the affective dimensions of pleasantness and arousal was assessed. For both an immediate and delayed (1 year later) free-recall task, only the arousal dimension had a stable effect on memory performance: Pictures rated as highly arousing were remembered better than low-arousal stimuli. This effect was corroborated in a speeded recognition test, in which high-arousal materials encoded earlier in the experiment produced faster reaction times than their low-arousal counterparts. Pleasantness affected reaction time decisions only for pictures not encoded earlier. These results suggest that whereas both the dimensions of pleasantness and arousal are processed at initial encoding, long-term memory performance is mainly affected by arousal.

Relationship between facial expressiveness and sympathetic activation in emotion: A critical review, with emphasis on modeling underlying mechanisms and individual differences

Two important questions bearing on personality processes and individual differences are how do facial expressiveness and sympathetic activation vary as a function of the intensity of an emotional stimulus, and what is the functional mechanism underlying facial expressiveness and sympathetic activation in emotion? A formulation is proposed that is based on 2 propositions: (a) All strong emotions result in some degree of activation of the organism (i.e., principle of stimulus dynamism) and (b) there are individual differences in the gain (amplification) operating on the facial expressive and sympathetic response channels (i.e., principle of individual response uniqueness). This formulation organizes much of the existing data on internalizers and externalizers and yields novel predictions regarding the subpopulation labeled as generalizers.

Remembering pictures: Pleasure and arousal in memory

Incidental memory performance for pictures that varied along the affective dimensions of pleasantness and arousal was assessed. For both an immediate and delayed (1 year later) free-recall task, only the arousal dimension had a stable effect on memory performance: Pictures rated as highly arousing were remembered better than low-arousal stimuli. This effect was corroborated in a speeded recognition test, in which high-arousal materials encoded earlier in the experiment produced faster reaction times than their low-arousal counterparts. Pleasantness affected reaction time decisions only for pictures not encoded earlier. These results suggest that whereas both the dimensions of pleasantness and arousal are processed at initial encoding, long-term memory performance is mainly affected by arousal.

Relationship between facial expressiveness and sympathetic activation in emotion: a critical review, with emphasis on modeling underlying mechanisms and individual differences

Two important questions bearing on personality processes and individual differences are how do facial expressiveness and sympathetic activation vary as a function of the intensity of an emotional stimulus, and what is the functional mechanism underlying facial expressiveness and sympathetic activation in emotion? A formulation is proposed that is based on 2 propositions: (a) All strong emotions result in some degree of activation of the organism (i.e., principle of stimulus dynamism) and (b) there are individual differences in the gain (amplification) operating on the facial expressive and sympathetic response channels (i.e., principle of individual response uniqueness). This formulation organizes much of the existing data on internalizers and externalizers and yields novel predictions regarding the subpopulation labeled as generalizers.

Startle and emotion: lateral acoustic probes and the bilateral blink

The affect-startle effect describes the modulation of the reflexive eyeblink response to a probe startle stimulus as a function of foreground emotional valence. Larger blinks occur during viewing of unpleasant slide foregrounds, relative to positive foregrounds. This effect has been obtained repeatedly using binaural acoustic startle probes. The current study examines this phenomenon for monaural probes administered to the left and right ears in separate blocks. Startle probes were presented during and between exposures to pleasant, neutral, and unpleasant slides, with the ear of presentation counterbalanced across subjects. Left monaural probes produced blink magnitudes that increased linearly from pleasant to unpleasant slide foregrounds, and appeared to be independent of attention or interest. Right monaural probes did not vary with foreground valence. These findings suggest that the startle probe indexes emotional processing that is lateralized in the central nervous system.

The fear potentiated startle effect. Blink reflex modulation as a result of classical aversive conditioning

A differential conditioning study examined whether an acoustic startle probe, presented during extinction of an aversively conditioned visual stimulus, potentiated the reflex eyeblink response in humans and whether this potentiation varied with the change in affective valence of the conditioned stimulus. Sixty college students were randomly assigned to view a series of two slides, depicting either unpleasant/highly arousing, unpleasant/moderate arousing, neutral/calm, pleasant/moderate arousing or pleasant/highly arousing scenes and objects (duration: 8 sec). During preconditioning (8 trials) and extinction (24 trials) acoustic startle probes (white noise bursts [50 ms; 95 dBA] were administered during and between slide presentation). During acquisition (16 trials) CS+ was reinforced by an electric shock. Startle response magnitudes significantly increased from preconditioning to extinction and were substantially larger to CS+. Conditioned startle reflex augmentation linearly increased with the pleasantness of the slides. Furthermore, subjects showed a greater post-conditioning increase of judged aversiveness to slides that they had previously reported to be more pleasant, exactly paralleling the startle reflex results.

Startle reflex modification: emotion or attention?

Alternative interpretations of startle probe modulation by a pictorial foreground were tested: Either reflex amplitude varies as a function of modality-determined attention allocation, or, regardless of probe modality, reflex amplitude varies with the emotional valence of the foreground content. Thirty-six subjects viewed a series of 54 slides, divided into two 27-slide blocks. Each block consisted of nine exemplars of three independently rated emotional content categories--pleasant, neutral, and unpleasant. Startle probes, half visual (flashgun) and half acoustic (white noise), were presented unpredictably during and between slide presentations. Eyeblink reflexes, corrugator and orbicularis oculi muscle tension, heart rate, and skin conductance were recorded during a 6-s slide interval. Subjects subsequently rated the slides for emotional valence and arousal, and interest value. Free-viewing times were also recorded. Analysis of reflex response and all ancillary measures supported the hypothesis that the primary determinant of startle modulation was the emotional valence of foreground content.

Emotion, attention, and the startle reflex

This theoretical model of emotion is based on research using the startle-probe methodology. It explains inconsistencies in probe studies of attention and fear conditioning and provides a new approach to emotional perception, imagery, and memory. Emotions are organized biphasically, as appetitive or aversive (defensive). Reflexes with the same valence as an ongoing emotional state are augmented; mismatched reflexes are inhibited. Thus, the startle response (an aversive reflex) is enhanced during a fear state and is diminished in a pleasant emotional context. This affect-startle effect is not determined by general arousal, simple attention, or probe modality. The effect is found when affects are prompted by pictures or memory images, changes appropriately with aversive conditioning, and may be dependent on right-hemisphere processing. Implications for clinical, neurophysiological, and basic research in emotion are outlined.

Fear imagery and the startle-probe reflex

Blink reflexes to acoustic probes, heart rate, and subjective reports were studied during affective memory imagery. Thirty-six undergraduates memorized 6 pairs of neutral and fearful sentences. After learning each pair, they relaxed and listened to a series of uniform tones, one every 6 s. A change in tone pitch (higher or lower) cued recall of one of the two sentences. At the first cue tone, groups (n = 12) were under different instructions: (a) ignore the sentence and relax, (b) silently articulate the sentence, and (c) imagine the sentence content as a personal experience. At the second cue tone, all subjects performed the imagery task. Startle probes (50-ms, 95-dB white noise) were presented unpredictably during relaxation and recall trials. Probe blink reflexes were larger and cardiac rate faster at fear sentence recall than at neutral sentence recall or relaxation. For probe reflexes, this effect was greater for imagery than for nonsemantic recall tasks.

Fear imagery and the startle-probe reflex

Blink reflexes to acoustic probes, heart rate, and subjective reports were studied during affective memory imagery. Thirty-six undergraduates memorized 6 pairs of neutral and fearful sentences. After learning each pair, they relaxed and listened to a series of uniform tones, one every 6 s. A change in tone pitch (higher or lower) cued recall of one of the two sentences. At the first cue tone, groups (n = 12) were under different instructions: (a) ignore the sentence and relax, (b) silently articulate the sentence, and (c) imagine the sentence content as a personal experience. At the second cue tone, all subjects performed the imagery task. Startle probes (50-ms, 95-dB white noise) were presented unpredictably during relaxation and recall trials. Probe blink reflexes were larger and cardiac rate faster at fear sentence recall than at neutral sentence recall or relaxation. For probe reflexes, this effect was greater for imagery than for nonsemantic recall tasks.

Fear conditioning, meaning, and belongingness: A selective association analysis

Twenty-three subjects rated the belongingness of pairs of conditionable (photographic slides) and unconditioned (e.g., shock, tone, human scream) stimuli. Forty new subjects were then classically conditioned, using rating-defined high (angry face/scream) and low (landscape/scream) belongingness pairs. Finger-pulse responses to the high-belongingness pairs showed superior acquisition and resistance to extinction. Another 40 subjects were conditioned to compound stimuli: a slide (either landscape or angry face) that was the same over trials, and a yellow or blue background that was the discriminant cue for the unconditioned stimulus (scream). When the angry face (the high-belongingness slide) was the invariant part of the compound, relatively poorer differential pulse-volume and skin-conductance conditioning was observed. Thus, depending on the task, a priori belongingness rendered stimuli selectively conditionable, either enhancing or inhibiting visceral response associations.

Slow brain potentials, imagery and hemispheric differences

On the basis of Lang's (1979) theory of emotional imagery three experiments were conducted to investigate the relationship between slow cortical potentials (SP) and emotional imagery. According to the assumptions of Lang's theory and our model (Rockstroh et al., 1982) of SP-function imagery ability should be related to a person's capacity to generate and suppress preparatory activity in cortical networks "on demand." In order to test this hypothesis subjects in Experiment I were trained to regulate right- versus left-hemispheric SP-differentiation within an instrumental learning paradigm. Thirty-four subjects were reinforced for achieving maximal SP-differences between electrode locations C3-C4 over a 6 s interval across 120 trials. Success in the SP-regulation task correlated significantly (r = .37) with the capacity for vivid imagery as measured with the Questionnaire for Mental Imagery (QMI). In Experiment II instructions to imagine right- versus left-hand movements were introduced successively over 5 sessions of SP-self-regulation. Imagery clearly modified right- versus left-hand EMG-differentiation but had no influence on cortical SP-differentiation. Experiment III tested the influence of already achieved SP-regulation at the vertex on the perceived vividness of emotional images introduced after the SP-biofeedback training. Again, clear effects of imagery content on autonomic variables (HR, SCR) were found. However, SP-amplitude and SP-polarity had no effect on perceived vividness, arousal or emotional content. It may be concluded from the results of Experiment II and III that SPs either are not the crucial parameter to represent the cortical efferent outflow component of imagery, or that the dual task of SP-self-regulation and imagery prevented covariations to show up. Experiment I, on the other hand, points toward a positive relation of imagery-ability as a trait-variable and brain-self-regulation abilities.