Fleeting images: a new look at early emotion discrimination

The visual brain quickly sorted stimuli for emotional impact despite high-speed presentation (3 or 5 per s) in a sustained, serial torrent of 700 complex pictures. Event-related potentials, recorded with a dense electrode array, showed selective discrimination of emotionally arousing stimuli from less affective content. Primary sources of this activation were over the occipital cortices, extending to right parietal cortex, suggesting a processing focus in the posterior visual system. Emotion discrimination was independent of formal pictorial properties (color, brightness. spatial frequency, and complexity). The data support the hypothesis of a very short-term conceptual memory store (M. C. Potter, 1999)-shown here to include a fleeting but reliable assessment of affective meaning.     

Rapid picture processing: affective primes and targets

In rapid serial visual presentation of pictures, an early ERP component shows enlarged negativity over occipital regions for emotional, compared to neutral, pictures. The present study examined the processing of emotional target pictures as a function of the hedonic valence of a preceding prime picture. Dense sensor ERPs were measured while subjects viewed a continuous stream of pleasant, neutral, and unpleasant pictures, presented for 335 ms each. Two main findings were observed: First, replicating previous results, emotional target pictures were associated with a larger posterior negativity, compared to neutral pictures. Second, the emotional content of the preceding prime picture affected target processing, with pleasant or unpleasant primes resulting in reduced negativity of the following picture, irrespective of its emotional valence. These findings are discussed within a framework of competition among successive pictures.     

The pupil's response to affective pictures: Role of image duration,habituation, and viewing mode

The pupil has been shown to be sensitive to the emotional content of stimuli. We examined this phenomenon by comparing fearful and neutral images carefully matched in the domains of luminance, image contrast, image color, and complexity of content. The pupil was more dilated after viewing affective pictures, and this effect was (a) shown to be independent of the presentation time of the images (from 100–3,000 ms), (b) not diminished by repeated presentations of the images, and (c) not affected by actively naming the emotion of the stimuli in comparison to passive viewing. Our results show that the emotional modulation of the pupil is present over a range of variables that typically vary from study to study (image duration, number of trials, free viewing vs. task), and encourages the use of pupillometry as a measure of emotional processing in populations where alternative techniques may not be appropriate.     

Effects of a varying stimulus context on habituation and sensitization of the OR

Twelve male subjects were tested in an experiment which investigated the habituation and sensitization processes of the orienting response (OR) in a varying stimulus context. Visual stimuli which varied along information and contour dimensions were presented in four blocks of 10 stimuli each. A tone served as the sensitizing stimulus and was presented before the fourth stimulus in each block. In two blocks the 5th, 6th and 7th stimuli were omitted (“blanks” condition) while in the other two blocks all stimuli were presented(“no blanks” condition). OR frequency and skin conductance levels indicated that the tone produced sensitization. Despite this, there was no evidence of dishabituation to the following stimuli. OR frequency to the 8th stimulus was significantly higher if the preceding three stimuli had been omitted. This result does not support a dual-process theory of habituation. However, rather than being contradictory, these findings are interpreted as further demonstration that laws governing habituation processes during repeated presentations of an identical stimulus do not apply in a context of repeated presentations of a varying stimulus.     

A multi-process account of startle modulation during affective perception

Modulation of the startle reflex by sensory, attentional, and emotional processes was explored by presenting acoustic startle probes at various delays following picture onset. Within 500 ms of onset, blinks were first greatly facilitated and then inhibited, indicating prepulse facilitation and prepulse inhibition that did not vary with affect. Attention allocation to the picture continued across the viewing interval and was most pronounced for emotional pictures, as determined by attenuation of the P3 component to the startle probe. Startle potentiation for unpleasant pictures occurred later in the viewing interval and was strongest for highly arousing pictures. Taken together, the startle reflex during picture viewing is modulated by sequential and sometimes concurrent processes of prepulse facilitation, prepulse inhibition, attentional inhibition, and affective modulation, with reflex magnitude reflecting the net effect of multiple processes.     

Repetitive exposure: Brain and reflex measures of emotion and attention

Effects of massed repetition on the modulation of the late positive potential elicited during affective picture viewing were investigated in two experiments. Despite a difference in the number of repetitions across studies (from 5 to 30), results were quite similar: The late positive potential continued to be enhanced when participants viewed emotional, compared to neutral, pictures. On the other hand, massed repetition did prompt a reduction in the late positive potential that was most pronounced for emotional pictures. Startle probe P3 amplitude generally increased with repetition, suggesting diminished attention allocation to repeated pictures. The blink reflex, however, continued to be modulated by hedonic valence, despite massive massed repetition. Taken together, the data suggest that the amplitude of the late positive potential during picture viewing reflects both motivational significance and attention allocation.     

Image motion and context: a between- and within-subjects comparison

In two previous experiments, we studied how stimulus motion affects both the self-report of emotion experience and the physiological sequelae of emotion. In both studies, image motion intensified emotional responding, and the effect of motion was relatively specific to the arousal dimension of the emotion; there was little evidence that image motion altered the valence of the image. Moving images also appeared to sustain the attention of the participants for a longer period of time than did the still images. In these two experiments, however, image motion was manipulated within participants. In the present experiment, we used a between-subjects manipulation of image motion and found a nearly identical pattern of results. These data indicate that motion inherently increments the arousal value of an image and that this increment is not dependent on the context in which motion is introduced.     

Unmasking emotion: Exposure duration and emotional engagement

Effects of exposure duration on emotional reactivity were investigated in two experiments that parametrically varied the duration of exposure to affective pictures from 25–6000 ms in the presence or absence of a visual mask. Evaluative, facial, autonomic, and cortical responses were measured. Results demonstrated that, in the absence of a visual mask (Experiment 1), emotional content modulated evaluative ratings, cortical, autonomic, and facial changes even with very brief exposures, and there was little evidence that emotional engagement increased with longer exposure. When information persistence was reduced by a visual mask (Experiment 2), differences as a function of hedonic content were absent for all measures when exposure duration was 25 ms but statistically reliable when exposure duration was 80 ms. Between 25–80 ms, individual differences in discriminability were critical in observing affective reactions to masked pictures.     

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.     

Emotional reactions in children: verbal, physiological, and behavioral responses to affective pictures

Many studies have shown a consistent pattern in adults' responses to affective pictures and there is growing evidence of gender differences, as well. Little is known, though, about children's verbal, behavioral, and physiological responses to affective pictures. Two experiments investigated children's responses to pictures. In Experiment 1, children, adolescents, and adults viewed pictures varying in affective content and rated them for pleasure, arousal, and dominance. Results indicated that children and adolescents rated the pictures similarly to adults. In Experiment 2, physiological responses, self-report, and viewing time were measured while children viewed affective pictures. As with adults, children's responses reflected the affective content of the pictures. Gender differences in affective evaluations, corrugator activity, skin conductance, startle modulation, and viewing time indicated that girls were generally more reactive to unpleasant materials.     

Modulation of the initial light reflex during affective picture viewing

An initial reflexive constriction of the pupil to stimulation—the light reflex—is primarily modulated by brightness, but is attenuated when participants are under threat of shock (i.e., fear‐inhibited light reflex). The present study assessed whether the light reflex is similarly attenuated when viewing emotional pictures. Pupil diameter was recorded while participants viewed erotic, violent, and neutral scenes that were matched in brightness; scrambled versions identical in brightness were also presented as an additional control. Compared to viewing neutral scenes, the light reflex was reliably modulated by hedonic content, with significant attenuation both when viewing unpleasant as well as pleasant pictures. No differences in the light reflex were found among scrambled versions. Thus, emotional modulation of the initial light reflex is not confined to a context of fear and is not indicative of brightness differences when viewing pictures of natural scenes.     

Natural selective attention: orienting and emotion

The foundations of orienting and attention are hypothesized to stem from activation of defensive and appetitive motivational systems that evolved to protect and sustain the life of the individual. Motivational activation initiates a cascade of perceptual and motor processes that facilitate the selection of appropriate behavior. Among these are detection of significance, indexed by a late centro-parietal positivity in the event-related potential, enhanced perceptual processing, indexed by a initial cardiac deceleration, and preparation for action, indexed by electrodermal changes. Data exploring the role of stimulus novelty and significance in orienting are presented that indicate different components of the orienting response habituate at different rates. Taken together, it is suggested that orienting is mediated by activation of fundamental motivational systems that have evolved to support survival.     

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.     

Affective Prime and Target Picture Processing: An ERP Analysis of Early and Late Interference Effects

Viewing emotionally arousing compared to neutral pictures is associated with differential electrophysiological activity in early (“early posterior negativity”, EPN), as well as later time-windows (“late positive potential”, LPP). A previous study revealed that the EPN is reduced when the preceding prime picture was emotional. The present study explored whether sequential interference effects are specific for early processing stages or extend to later processing stages. Dense sensor ERPs were measured while subjects viewed a continuous stream of pleasant, neutral, and unpleasant pictures, presented for 660 ms each. Previous results were replicated in that emotional pictures were associated with enlarged EPN and LPP amplitudes compared to neutral pictures. Furthermore, the EPN to emotional and neutral pictures was reduced when preceded by pleasant prime pictures. The novel finding was that emotional compared to neutral prime pictures were associated with reduced LPP amplitudes to the subsequently presented picture irrespective of its emotional valence (pleasant, neutral, unpleasant). These results demonstrate sustained interference effects in serial picture presentations discussed within a framework of resource competition among successive pictures.     

Parallel processing of affective visual stimuli

Event-related potential (ERP) studies of affective picture processing have demonstrated an early posterior negativity (EPN) for emotionally arousing pictures that are embedded in a rapid visual stream. The present study examined the selective processing of emotional pictures while systematically varying picture presentation rates between 1 and 16 Hz. Previous results with presentation rates up to 5 Hz were replicated in that emotional compared to neutral pictures were associated with a greater EPN. Discrimination among emotional and neutral contents was maintained up to 12 Hz. To explore the notion of parallel processing, convolution analysis was used: EPNs generated by linear superposition of slow rate ERPs explained 70%–93% of the variance of measured EPNs, giving evidence for an impressive capacity of parallel affective discrimination in rapid serial picture presentation.     

Distinct control networks for cognition and emotion in the prefrontal cortex

The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engagement of a control mechanism for top-down biasing of context processing in resource-demanding memory tasks. Here we tested the hypothesis that the dlPFC subserves a similar function also in attention and emotion tasks. 18 healthy young adults were tested in a functional magnetic resonance imaging (fMRI) study where the demands for context processing were manipulated in three different cognitive domains: auditory attention, episodic retrieval, and emotion regulation. We found that the right dlPFC was jointly sensitive to increased cognitive demands in the attention and memory tasks. By contrast, increased demands in the emotion task (reappraisal) were associated with increased activity in ventromedial PFC along with decreased amygdala activity. Our findings of divergent prefrontal control networks for cognitive and emotional control extend previous separations of cognition and emotion in the anterior cingulate cortex.     

Respiratory sinus arrhythmia responses to induced emotional states: effects of RSA indices, emotion induction method, age, and sex

The literature shows large inconsistencies in respiratory sinus arrhythmia (RSA) responses to induced emotional states. This may be caused by differences in emotion induction methods, RSA quantification, and non-emotional demands of the situation. In 83 healthy subjects, we studied RSA responses to pictures and film fragments eliciting six different discrete emotions relative to neutral baseline stimuli. RSA responses were quantified in the time and frequency domain and were additionally corrected for differences in mean heart rate and respiration rate, resulting in eight different RSA response measures. Subjective ratings of emotional stimuli and facial electromyographic responses indicated that pictures and film fragments elicited the intended emotions. Although RSA measures showed various emotional effects, responses were quite heterogeneous and frequently nonsignificant. They were substantially influenced by methodological factors, in particular time vs. frequency domain response measures, correction for changes in respiration rate, use of pictures vs. film fragments, and sex of participants.     

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.     

Probe P3 and blinks: Two measures of affective startle modulation

Two concurrent measures of the evoked startlé 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.     

Parent-child emotion communication,attachment, and affective narratives

Forty-four pre-schoolers (ages 4.3 to 5.8 years) and their primary caregivers participated in a study on the connections between parent-child emotion communication and a narrative assessment of pre-schoolers' attachment. Children completed the Separation Anxiety Test (SAT), a narrative assessment of children's responses to attachment-related separations (including self-reliance, avoidance, attachment and coherence scores). Several aspects of parent-child discussions of emotion-eliciting events were also assessed in the Emotion Communication Task. Results indicated that SAT coherence was positively related to SAT attachment and negatively related to SAT avoidance. Furthermore, SAT coherence was positively related to parental scaffolding and negatively related to parental and child negativity during the Emotion Communication Task. Parental scaffolding and child reciprocity were positively related to each other and, in general, were negatively related to parental and child negativity. Discussion focused on the potential contributions of children's interactions with caregivers to the development of children's attachment narratives and emotion-related understanding.