Repetition and ERPs during emotional scene processing: A selective review

A set of studies are reviewed that investigate the effects of repetition during scene perception on event-related potentials, elucidating perceptual, memory and emotional processes. Repetition suppression was consistently found for the amplitude of early frontal N2 and posterior P2 components, which was greatly enhanced for massed, compared to distributed, repetition. Both repetition suppression and enhancement of the amplitude of a centro-parietal positive potential (LPP) were found in specific contexts. Suppression was reliably found following a massive number of repetitions of few items, whereas enhancement is found when repetitions are spaced; enhancement was apparent both during simple free viewing as well as on an explicit recognition test. Regardless of repetition, an enhanced LPP was always found for emotional, compared to neutral, scenes. Taken together, the data suggest that different effects of massed and distributed repetitions on specific ERP components index perceptual priming, habituation, and spontaneous episodic retrieval.

Beyond Feelings:

Emotion and emotion-related processes lie at the heart of counseling, yet there is scant evidence that counseling psychology has a substantial curricular, scientific, or psychotherapeutic commitment to the psychological science of emotion. Likewise, social psychology and other fields involved with emotion science often avoid researching counseling-relevant topics and disseminate their findings in outlets and formats not likely to be accessed by or useful to counseling psychologists. This article identifies a series of impediments that may be responsible for these and related problems and proposes potential solutions.

Motivational engagement in Parkinson's disease: Preparation for motivated action

The current study investigated whether motivational dysfunction in Parkinson's patients is related to a deficit in preparing for motivated behavior. Based on previous studies, it was hypothesized that PD patients would show reduced preparation for action specifically when faced with threat (of loss) and that reduced action preparation would relate to self-report of apathy symptoms. The study measured an electrocortical correlate of preparation for action (CNV amplitude) in PD patients and healthy controls, as well as defensive and appetitive activation during emotional perception (LPP amplitude). The sample included 18 non-demented PD patients (tested on dopaminergic medications) and 15 healthy controls who responded as quickly as possible to cues signaling threat of loss or reward, in which the speed of the response determined the outcome. Results indicated that, whereas PD patients showed similar enhanced action preparation with the addition of incentives to controls, PD patients showed generally reduced action preparation, evidenced by reduced CNV amplitude overall. Results suggest that PD patients may have behavioral issues due to globally impaired action preparation but that this deficit is not emotion-specific, and movement preparation may be aided by incentive in PD patients.

Prediction and perception: Defensive startle modulation

Previous research indicates that predictive cues can dampen subsequent defensive reactions. The present study investigated whether effects of cuing are specific to aversive stimuli, using modulation of the blink startle reflex as a measure of emotional reactivity. Participants viewed pictures depicting violence, romance/erotica, or mundane content. On half of all trials, a cue (color) predicted the content of the upcoming picture; on the remaining trials, scenes were presented without a cue. Acoustic startle probes were presented during picture viewing on trials with predictive cues and trials without a cue. Replicating previous studies, blink reflexes elicited when viewing violent pictures that had not been preceded by a cue were potentiated compared to uncued mundane scenes, and reflexes were attenuated when viewing scenes of erotica/romance that had not been cued. On the other hand, reflex potentiation when viewing scenes of violence (relative to mundane scenes) was eliminated when these pictures were preceded by a predictive cue, whereas scenes of romance prompted reliable reflex attenuation regardless of whether pictures were cued or not. Taken together, the data suggest that cuing elicits an anticipatory coping process that is specific to aversive stimuli.

Selective looking at natural scenes: Hedonic content and gender

Choice viewing behavior when looking at affective scenes was assessed to examine differences due to hedonic content and gender by monitoring eye movements in a selective looking paradigm. On each trial, participants viewed a pair of pictures that included a neutral picture together with an affective scene depicting either contamination, mutilation, threat, food, nude males, or nude females. The duration of time that gaze was directed to each picture in the pair was determined from eye fixations. Results indicated that viewing choices varied with both hedonic content and gender. Initially, gaze duration for both men and women was heightened when viewing all affective contents, but was subsequently followed by significant avoidance of scenes depicting contamination or nude males. Gender differences were most pronounced when viewing pictures of nude females, with men continuing to devote longer gaze time to pictures of nude females throughout viewing, whereas women avoided scenes of nude people, whether male or female, later in the viewing interval. For women, reported disgust of sexual activity was also inversely related to gaze duration for nude scenes. Taken together, selective looking as indexed by eye movements reveals differential perceptual intake as a function of specific content, gender, and individual differences.

Massed and distributed repetition of natural scenes: Brain potentials and oscillatory activity

Neural measures of repetition can result in either repetition suppression or enhancement effects, with enhancement sometimes interpreted as indicating episodic retrieval, rather than stimulus habituation. Here, we manipulated whether repetitions were massed (consecutive) or distributed (intermixed) and measured event-related potentials and oscillatory activity, investigating the question of whether there is evidence of "spontaneous" episodic retrieval for distributed, but not massed, repetition. Results showed that distributed repetition uniquely prompted a significant centroparietal old-new effect as well as enhanced theta, compared to either novel presentations or massed repetitions, consistent with a hypothesis of spontaneous retrieval. Massed repetition, on the other hand, prompted repetition suppression and reduction of the N2/P2. Taken together, the data suggest that distributed repetition may facilitate later memory performance because it spontaneously retrieves prior representations.

Imaging distributed and massed repetitions of natural scenes: spontaneous retrieval and maintenance

Repetitions that are distributed (spaced) across time prompt enhancement of a memory-related event-related potential, compared to when repetitions are massed (contiguous). Here, we used fMRI to investigate neural enhancement and suppression effects during free viewing of natural scenes that were either novel or repeated four times with massed or distributed repetitions. Distributed repetition was uniquely associated with a repetition enhancement effect in a bilateral posterior parietal cluster that included the precuneus and posterior cingulate and which has previously been implicated in episodic memory retrieval. Unique to massed repetition, conversely, was enhancement in a right dorsolateral prefrontal cluster that has been implicated in short-term maintenance. Repetition suppression effects for both types of spacing were widespread in regions activated during novel picture processing. Taken together, the data are consistent with a hypothesis that distributed repetition prompts spontaneous retrieval of prior occurrences, whereas massed repetition prompts short-term maintenance of the episodic representation, due to contiguous presentation. These processing differences may mediate the classic spacing effect in learning and memory.

From threat to safety: instructed reversal of defensive reactions

Cues that signal the possibility of receiving an electric shock reliably induce defensive activation. To determine whether cues can also easily reverse defensive reactions, a threat reversal paradigm was developed in which a cue signaling threat of shock reversed its meaning across the course of the study. This allowed us to contrast defensive reactions to threat cues that became safe cues, with responses to cues that continued to signal threat or safety. Results showed that, when participants were instructed that a previously threatening cue now signaled safety, there was an immediate and complete attenuation of defensive reactions compared to threat cues that maintained their meaning. These findings highlight the role that language can play both in instantiating and attenuating defensive reactions, with implications for understanding emotion regulation, social communication, and clinical phenomena.

Pathological anxiety and function/dysfunction in the brain's fear/defense circuitry

Research from the University of Florida Center for the Study of Emotion and Attention aims to develop neurobiological measures that objectively discriminate among symptom patterns in patients with anxiety disorders. From this perspective, anxiety and mood pathologies are considered to be brain disorders, resulting from dysfunction and maladaptive plasticity in the neural circuits that determine fearful/defensive and appetitive/reward behavior (Insel et al., 2010). We review recent studies indicating that an enhanced probe startle reflex during the processing of fear memory cues (mediated by cortico-limbic circuitry and thus indicative of plastic brain changes), varies systematically in strength over a spectrum-wide dimension of anxiety pathology-across and within diagnoses-extending from strong focal fear reactions to a consistently blunted reaction in patients with more generalized anxiety and comorbid mood disorders. Preliminary studies with functional magnetic resonance imaging (fMRI) encourage the hypothesis that fear/defense circuit dysfunction covaries with this same dimension of psychopathology. Plans are described for an extended study of the brain's motivation circuitry in anxiety spectrum patients, with the aim of defining the specifics of circuit dysfunction in severe disorders. A sub-project explores the use of real-time fMRI feedback in circuit analysis and as a modality to up-regulate circuit function in the context of blunted affect.

Startle modulation during emotional anticipation and perception

The startle reflex is potentiated when anticipating emotional, compared to neutral, pictures. This study investigated the time course of reflex modulation during anticipation and the impact of informative cuing on picture perception. Colors were used to signal the thematic content of emotional and neutral scenes; blink response modulation was measured by presenting acoustic startle probes 3, 2, or 1 s before picture onset or 2 s after picture onset. During anticipation of neutral scenes, blink magnitude showed increasing attenuation as picture onset approached, consistent with a modality-directed vigilance account. Conversely, when anticipating emotional scenes, reflex magnitude did not change over time, and blinks elicited closest to picture onset were potentiated compared to neutral. During perception, the expected reflex potentiation for unpleasant pictures was not found, suggesting that cuing may dampen defensive activation.

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.

Encoding and reinstatement of threat: recognition potentials

On a recognition test, stimuli originally encoded in the context of shock threat show an enhanced late parietal positivity during later recognition compared to stimuli encoded during safety, particularly for emotionally arousing stimuli. The present study investigated whether this ERP old/new effect is further influenced when a threat context is reinstated during the recognition test. ERPs were measured in a yes-no recognition test for words rated high or low in emotional arousal that were encoded and recognized in the context of cues that signaled threat of shock or safety. Correct recognition of words encoded under threat, irrespective of reinstatement, was associated with an enhanced old-new ERP difference (500-700ms; centro-parietal), and this difference was only reliable for emotionally arousing words. Taken together, the data suggest that information processed in a stressful context are associated with better recollection on later recognition, an effect that was not modulated by reinstating the stressful context at retrieval.

Repetition and brain potentials when recognizing natural scenes: task and emotion differences

Repetition has long been known to facilitate memory performance, but its effects on event-related potentials (ERPs), measured as an index of recognition memory, are less well characterized. In Experiment 1, effects of both massed and distributed repetition on old-new ERPs were assessed during an immediate recognition test that followed incidental encoding of natural scenes that also varied in emotionality. Distributed repetition at encoding enhanced both memory performance and the amplitude of an old-new ERP difference over centro-parietal sensors. To assess whether these repetition effects reflect encoding or retrieval differences, the recognition task was replaced with passive viewing of old and new pictures in Experiment 2. In the absence of an explicit recognition task, ERPs were completely unaffected by repetition at encoding, and only emotional pictures prompted a modestly enhanced old-new difference. Taken together, the data suggest that repetition facilitates retrieval processes and that, in the absence of an explicit recognition task, differences in old-new ERPs are only apparent for affective cues.

Explicit and spontaneous retrieval of emotional scenes: electrophysiological correlates

When event-related potentials (ERP) are measured during a recognition task, items that have previously been presented typically elicit a larger late (400-800 ms) positive potential than new items. Recent data, however, suggest that emotional, but not neutral, pictures show ERP evidence of spontaneous retrieval when presented in a free-viewing task (Ferrari, Bradley, Codispoti, Karlsson, & Lang, 2012). In two experiments, we further investigated the brain dynamics of implicit and explicit retrieval. In Experiment 1, brain potentials were measured during a semantic categorization task, which did not explicitly probe episodic memory, but which, like a recognition task, required an active decision and a button press, and were compared to those elicited during recognition and free viewing. Explicit recognition prompted a late enhanced positivity for previously presented, compared with new, pictures regardless of hedonic content. In contrast, only emotional pictures showed an old-new difference when the task did not explicitly probe episodic memory, either when making an active categorization decision regarding picture content, or when simply viewing pictures. In Experiment 2, however, neutral pictures did prompt a significant old-new ERP difference during subsequent free viewing when emotionally arousing pictures were not included in the encoding set. These data suggest that spontaneous retrieval is heightened for salient cues, perhaps reflecting heightened attention and elaborative processing at encoding.

Appetitive and Defensive Motivation: Goal-Directed or Goal-Determined?

Our view is that fundamental appetitive and defensive motivation systems evolved to mediate a complex array of adaptive behaviors that support the organism's drive to survive-defending against threat and securing resources. Activation of these motive systems engages processes that facilitate attention allocation, information intake, sympathetic arousal, and, depending on context, will prompt tactical actions that can be directed either toward or away from the strategic goal, whether defensively or appetitively determined. Research from our laboratory that measures autonomic, central, and somatic reactions when processing emotional scenes is described which indicates that motivationally relevant cues, whether appetitive or defensive, capture attention preferentially, prompt enhanced perceptual processing and information gathering, and occasion metabolic arousal that mobilizes the organism for coping actions.

The late positive potential, emotion and apathy in Parkinson's disease

Parkinson's disease is associated with emotional changes including depression, apathy, and anxiety. The current study investigated emotional processing in non-demented individuals with Parkinson disease (PD) using an electrophysiological measure, the centro-parietal late positive potential (LPP). Non-demented patients with Parkinson's disease (n=17) and healthy control participants (n=16) viewed pleasant, neutral, and unpleasant pictures while EEG was recorded from a 64-channel geodesic net. The Parkinson patients did not differ from controls in terms of early electrophysiological components that index perceptual processing (occipital P100, N150, P250). Parkinson patients, however, showed reduced LPP amplitude specifically when viewing unpleasant, compared to pleasant, pictures as well as when compared to controls, consistent with previous studies suggesting a specific difference in aversive processing between PD patients and healthy controls. Importantly, LPP amplitude during unpleasant picture viewing was most attenuated for patients reporting high apathy. The data suggest that apathy in PD may be related to a deficit in defensive activation, and may be indexed cortically using event-related potentials.

Orienting and emotional perception: facilitation, attenuation, and interference

Human emotions are considered here to be founded on motivational circuits in the brain that evolved to protect (defensive) and sustain (appetitive) the life of individuals and species. These circuits are phylogenetically old, shared among mammals, and involve the activation of both subcortical and cortical structures that mediate attention, perception, and action. Circuit activation begins with a feature-match between a cue and an existing representation in memory that has motivational significance. Subsequent processes include rapid cue-directed orienting, information gathering, and action selection - What is it? Where is it? What to do? In our studies of emotional perception, we have found that measures that index orienting to emotional cues generally show enhanced circuit activation and response facilitation, relative to orienting indicators occasioned by affectively neutral cues, whether presented concurrently or independently. Here, we discuss these findings, considering both physiological reflex and brain measures as they are modulated during orienting and emotional perception.

The effect of anxiety on respiratory sensory gating measured by respiratory-related evoked potentials

Respiratory sensory gating is evidenced by decreased amplitudes of the respiratory-related evoked potentials (RREP) N1 peak for the second (S2) compared to the first occlusion (S1) when two paired occlusions are presented with a 500-millisecond (ms) inter-stimulus-interval during one inspiration. Because anxiety is prevalent in respiratory diseases and associated with altered respiratory perception, we tested whether anxiety can modulate individuals' respiratory neural gating mechanism. By using high-density EEG, RREPs were measured in a paired inspiratory occlusion paradigm in 11 low and 10 higher anxious individuals with normal lung function. The N1 peak gating S2/S1 ratio and the N1 S2 amplitudes were greater in higher compared to low anxious individuals (p's<0.05). In addition, higher anxiety levels were correlated with greater S2/S1 ratios (r=0.54, p<0.05) and S2 amplitudes (r=-0.49, p<0.05). The results demonstrate that anxiety is associated with reduced respiratory sensory gating which might underlie altered respiratory symptom perception in anxious individuals.

Defensive mobilization in specific phobia: fear specificity, negative affectivity, and diagnostic prominence

BACKGROUND

Understanding of exaggerated responsivity in specific phobia-its physiology and neural mediators-has advanced considerably. However, despite strong phenotypic evidence that prominence of specific phobia relative to co-occurring conditions (i.e., principal versus nonprincipal disorder) is associated with dramatic differences in subjective distress, there is yet no consideration of such comorbidity issues on objective defensive reactivity.

METHODS

A community sample of specific phobia (n = 74 principal; n = 86 nonprincipal) and control (n = 76) participants imagined threatening and neutral events while acoustic startle probes were presented and eyeblinks (orbicularis occuli) recorded. Changes in heart rate, skin conductance level, and facial expressivity were also measured.

RESULTS

Principal specific phobia patients far exceeded control participants in startle reflex and autonomic reactivity during idiographic fear imagery. Distinguishing between single and multiple phobias within principal phobia and comparing these with nonprincipal phobia revealed a continuum of decreasing defensive mobilization: single patients were strongly reactive, multiple patients were intermediate, and nonprincipal patients were attenuated-the inverse of measures of pervasive anxiety and dysphoria (i.e., negative affectivity). Further, as more disorders supplanted specific phobia from principal disorder, overall defensive mobilization was systematically more impaired.

CONCLUSIONS

The exaggerated responsivity characteristic of specific phobia is limited to those patients for whom circumscribed fear is the most impairing condition and coincident with little additional affective psychopathology. As specific phobia is superseded in severity by broad and chronic negative affectivity, defensive reactivity progressively diminishes. Focal fears may still be clinically significant but not reflected in objective defensive mobilization.

Affective engagement for facial expressions and emotional scenes: the influence of social anxiety

Pictures of emotional facial expressions or natural scenes are often used as cues in emotion research. We examined the extent to which these different stimuli engage emotion and attention, and whether the presence of social anxiety symptoms influences responding to facial cues. Sixty participants reporting high or low social anxiety viewed pictures of angry, neutral, and happy faces, as well as violent, neutral, and erotic scenes, while skin conductance and event-related potentials were recorded. Acoustic startle probes were presented throughout picture viewing, and blink magnitude, probe P3 and reaction time to the startle probe also were measured. Results indicated that viewing emotional scenes prompted strong reactions in autonomic, central, and reflex measures, whereas pictures of faces were generally weak elicitors of measurable emotional response. However, higher social anxiety was associated with modest electrodermal changes when viewing angry faces and mild startle potentiation when viewing either angry or smiling faces, compared to neutral. Taken together, pictures of facial expressions do not strongly engage fundamental affective reactions, but these cues appeared to be effective in distinguishing between high and low social anxiety participants, supporting their use in anxiety research.

When fear forms memories: threat of shock and brain potentials during encoding and recognition

The anticipation of highly aversive events is associated with measurable defensive activation, and both animal and human research suggests that stress-inducing contexts can facilitate memory. Here, we investigated whether encoding stimuli in the context of anticipating an aversive shock affects recognition memory. Event-related potentials (ERPs) were measured during a recognition test for words that were encoded in a font color that signaled threat or safety. At encoding, cues signaling threat of shock, compared to safety, prompted enhanced P2 and P3 components. Correct recognition of words encoded in the context of threat, compared to safety, was associated with an enhanced old-new ERP difference (500-700 msec; centro-parietal), and this difference was most reliable for emotional words. Moreover, larger old-new ERP differences when recognizing emotional words encoded in a threatening context were associated with better recognition, compared to words encoded in safety. Taken together, the data indicate enhanced memory for stimuli encoded in a context in which an aversive event is merely anticipated, which could assist in understanding effects of anxiety and stress on memory processes.

Tagging cortical networks in emotion: a topographical analysis

Viewing emotional pictures is associated with heightened perception and attention, indexed by a relative increase in visual cortical activity. Visual cortical modulation by emotion is hypothesized to reflect re-entrant connectivity originating in higher-order cortical and/or limbic structures. The present study used dense-array electroencephalography and individual brain anatomy to investigate functional coupling between the visual cortex and other cortical areas during affective picture viewing. Participants viewed pleasant, neutral, and unpleasant pictures that flickered at a rate of 10 Hz to evoke steady-state visual evoked potentials (ssVEPs) in the EEG. The spectral power of ssVEPs was quantified using Fourier transform, and cortical sources were estimated using beamformer spatial filters based on individual structural magnetic resonance images. In addition to lower-tier visual cortex, a network of occipito-temporal and parietal (bilateral precuneus, inferior parietal lobules) structures showed enhanced ssVEP power when participants viewed emotional (either pleasant or unpleasant), compared to neutral pictures. Functional coupling during emotional processing was enhanced between the bilateral occipital poles and a network of temporal (left middle/inferior temporal gyrus), parietal (bilateral parietal lobules), and frontal (left middle/inferior frontal gyrus) structures. These results converge with findings from hemodynamic analyses of emotional picture viewing and suggest that viewing emotionally engaging stimuli is associated with the formation of functional links between visual cortex and the cortical regions underlying attention modulation and preparation for action.

Emotion and ocular responses in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease that affects motor, cognitive, and emotional functioning. Previous studies reported reduced skin conductance responses in PD patients, compared to healthy older adults when viewing emotionally arousing pictures. Attenuated skin conductance changes in PD may reflect peripheral autonomic dysfunction (e.g., reduced nerve endings at the sweat gland) or, alternatively, a more central emotional deficit. The aim of the current study was to investigate a second measure of sympathetic arousal-change in pupil dilation. Eye movements, a motor-based correlate of emotional processing, were also assessed. Results indicated that pupil dilation was significantly greater when viewing emotional, compared to neutral pictures for both PD patients and controls. On the other hand, PD patients made fewer fixations with shorter scan paths, particularly when viewing pleasant pictures. These results suggest that PD patients show normal sympathetic arousal to affective stimuli (indexed by pupil diameter), but differences in motor correlates of emotion (eye movements).

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.