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Two studies examined emotional responding to food cues. In experiment 1, normal college students were assigned to 0-, 6- or 24-h of food deprivation prior to presentations of standard emotional and food-related pictures. Food deprivation had no impact on responses elicited by standard emotional pictures. However, subjective and psychophysiological reactions to food pictures were affected significantly by deprivation. Importantly, food-deprived subjects viewing food pictures showed an enhanced startle reflex and increased heart rate. Experiment 2 replicated the food deprivation effects from experiment 1, and examined participants reporting either a habitual pattern of restrained (anorexia-like) or binge (bulimia-like) eating. Food-deprived and binge eater groups showed startle potentiation to food cues, and rated these stimuli as more pleasant, relative to restrained eaters and control subjects. The results are interpreted from the perspective that startle modulation reflects activation of defensive or appetitive motivation. Implications of the data for understanding eating disorders are considered.

Startle modulation was investigated as participants first anticipated and then viewed affective pictures in order to determine whether affective modulation of the startle reflex is similar in these different task contexts. During a 6-s anticipation period, a neutral light cue signaled whether the upcoming picture would portray snakes, erotica, or household objects; at the end of the anticipatory period, a picture in the signaled category was viewed for 6 s. Male participants highly fearful of snakes were recruited to maximize emotional arousal during anticipation and perception. Results indicated that the startle reflex was potentiated when anticipating either unpleasant (phobic) or pleasant (erotic) pictures, compared to neutral stimuli, whereas during perception, reflexes were potentiated when viewing unpleasant stimuli, and reduced when viewing pleasant pictures. The startle reflex is modulated by hedonic valence in picture perception, and by emotional arousal in a task context involving picture anticipation.

This study investigated the size of, and relationship between, different modulatory effects of aversive stimulation on the acoustic startle reflex. This reflex is potentiated by shock exposure and associative shock conditioning (in animals and human volunteers) and unpleasant pictures (in human volunteers). In this study, dramatic sensitization of the probe-startle response was observed after shock exposure but not after a control task. Magnitude of sensitization was significantly larger than associative shock conditioning and picture modulation effects (also significant). Sensitization and conditioning scores showed modest, significant correlations with one another but not with picture modulation scores, consistent with animal data showing that partially overlapping brain mechanisms (i.e., amygdaloid-reticular projections) mediate these effects. The present results also indicate that sensitization of startle in human volunteers is a relatively more robust defensive response to aversive stimulation.

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.

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.

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.

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 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.

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.

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.

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.

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.

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.

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.

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.