Activation of the visual cortex in motivated attention

Functional activation (measured with fMRI) in occipital cortex was more extensive when participants view pictures strongly related to primary motive states (i.e., victims of violent death, viewer-directed threat, and erotica). This functional activity was greater than that observed for less intense emotional (i.e., happy families or angry faces) or neutral images (i.e., household objects, neutral faces). Both the extent and strength of functional activity were related to the judged affective arousal of the different picture contents, and the same pattern of functional activation was present whether pictures were presented in color or in grayscale. It is suggested that more extensive visual system activation reflects "motivated attention," in which appetitive or defensive motivational engagement directs attention and facilitates perceptual processing of survival-relevant stimuli.     

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.     

Erotic and disgust-inducing pictures--differences in the hemodynamic responses of the brain

The aim of this fMRI study was to explore brain structures that are involved in the processing of erotic and disgust-inducing pictures. The stimuli were chosen to trigger approach and withdrawal tendencies, respectively. By adding sadomasochistic (SM) scenes to the design and examining 12 subjects with and 12 subjects without sadomasochistic preferences, we introduced a picture category that induced erotic pleasure in one sample and disgust in the other sample. Since we also presented neutral pictures, all subjects viewed pictures of four different categories: neutral, disgust-inducing, erotic, and SM erotic pictures. The analysis indicated that several brain structures are commonly involved in the processing of disgust-inducing and erotic pictures (occipital cortex, hippocampus, thalamus, and the amygdala). The ventral striatum was specifically activated when subjects saw highly sexually arousing pictures. This indicates the involvement of the human reward system during the processing of visual erotica.     

Temporal course of emotional startle modulation in schizophrenia patients.

The temporal course of startle reflex modulation to emotional pictures was investigated in 49 relatively asymptomatic schizophrenia outpatients and 46 normal controls. Participants viewed pleasant, neutral and unpleasant pictures, which were presented for 6 s and acoustic startle probes were delivered at five different times after picture onset. Replicating previous findings schizophrenia patients showed the same affective modulation of the startle reflex as healthy controls when probes were presented later during the picture-viewing period (3800 ms). For the early probe times (300 and 800 ms), affective pictures proved to be the effective prepulse stimuli resulting in a clear Prepulse inhibition (PPI) effect in both groups. In contrast to previous findings, the PPI of startle response was not stronger during processing emotional stimuli relative to neutral stimuli. For control subjects, blink reflexes were larger for unpleasant pictures compared with neutral and pleasant pictures, representing an early activation of motivational systems. Schizophrenia patients on the other hand, did not show this early affective modulation of the acoustic startle reflex.     

Distant influences of amygdala lesion on visual cortical activation during emotional face processing

Emotional visual stimuli evoke enhanced responses in the visual cortex. To test whether this reflects modulatory influences from the amygdala on sensory processing, we used event-related functional magnetic resonance imaging (fMRI) in human patients with medial temporal lobe sclerosis. Twenty-six patients with lesions in the amygdala, the hippocampus or both, plus 13 matched healthy controls, were shown pictures of fearful or neutral faces in task-releant or task-irrelevant positions on the display. All subjects showed increased fusiform cortex activation when the faces were in task-relevant positions. Both healthy individuals and those with hippocampal damage showed increased activation in the fusiform and occipital cortex when they were shown fearful faces, but this was not the case for individuals with damage to the amygdala, even though visual areas were structurally intact. The distant influence of the amygdala was also evidenced by the parametric relationship between amygdala damage and the level of emotional activation in the fusiform cortex. Our data show that combining the fMRI and lesion approaches can help reveal the source of functional modulatory influences between distant but interconnected brain regions.     

Elevated response of human amygdala to neutral stimuli in mild post traumatic stress disorder: neural correlates of generalized emotional response

Previous evidence from functional magnetic resonance imaging (fMRI) studies has shown that amygdala responses to emotionally neutral pictures are exaggerated at a group level in patients with severe post-traumatic stress disorder (PTSD) [Hendler T, Rotshtein P, Yeshurun Y, Weizmann T, Kahn I, Ben-Bashat D, Malach R, Bleich A (2003) Neuroimage 19(3):587–600]. The present fMRI study tested the hypothesis that amygdala responses are elevated not only in response to negative pictures but also to neutral pictures as a function of disease severity in patients with mild symptoms and in subjects who did not develop symptoms. To this end, fMRI scans were performed in 10 patients with mild PTSD and 10 healthy controls (both victims of a bank robbery), during the execution of a visuo-attentional task in which they were asked to observe emotionally negative or neutral pictures. Control subjects showed enhanced amygdala responses to emotionally negative stimuli compared to neutral stimuli. On the contrary, PTSD patients were characterized by high amygdala responses to both neutral and emotional pictures, with no statistically significant difference between the two classes of stimuli. In the entire group, we found correlations among the severity of the PTSD symptoms, task performance, and amygdala activation during the processing of neutral stimuli. Results of this study suggest that amygdala responses and the selectivity of the emotional response to neutral stimuli are elevated as a function of disease severity in PTSD patients with mild symptoms.     

Novel fearful faces activate the amygdala in healthy young and elderly adults

Activation of the amygdala to emotionally valenced stimuli, and particularly to fearful faces, has been widely demonstrated in healthy young adults. However, recent studies assessing amygdala responses to fearful emotional faces in the normal elderly have not shown similar results. The reason for this is uncertain, but it may relate to life-span developmental changes in processing emotional stimuli or structural alterations in the amygdala with aging. In order to examine whether the amygdala could be activated in the elderly, we developed a paradigm designed to engage the amygdala on several levels. Based on recent imaging work indicating that novelty and stimulus change activates the amygdala, we assessed amygdala responses in young and elderly adults to novel fearful faces (versus familiar neutral ones). We demonstrate a robust activation in both groups, indicating that the amygdala remains responsive in aging. This activation did not differ between the two groups when we examined regions of interest in the amygdala based on functional or structural criteria. However, there were significantly greater activations in the inferior temporal cortex in the young versus elderly subjects.     

Effects of aging on functional connectivity of the amygdala during negative evaluation: a network analysis of fMRI data

Previous evidence has suggested both preserved emotional function in aging and age-related differences in emotional processing, but the neural networks underlying such processing alterations in the context of preserved affective function are not clear. Using event-related fMRI, we scanned young and older adults while they made valence ratings for emotional pictures. Behavioral results showed a similar pattern of emotional evaluation, but older adults experienced negatively valenced pictures as being less negative. Consistent with behavioral findings, we identified common activity in the right amygdala, but age-related differences in the functional connectivity of this region with the rest of the brain. Compared to young adults, older adults had greater functional connectivity between the right amygdala and ventral anterior cingulate cortex, possibly reflecting increased emotional regulation. Conversely, older adults showed decreased functional connectivity with posterior brain regions, likely reflecting decreased perceptual processing. Thus, age-related differences in evaluating negatively valenced stimuli might reflect decreased perceptual processing of these stimuli, as well as the engagement of control processes that inhibit the response to negative emotion.     

Stimulus type and design influence hemodynamic responses towards visual disgust and fear elicitors.

The question to what extent emotion-related brain activation depends upon the presentation design (block design vs. event-related design) and the stimulus type (scene pictures vs. pictures with facial mimic) has hardly been addressed in previous functional magnetic resonance imaging (fMRI) research. In the present fMRI experiment, 40 right-handed subjects viewed pictures with fear-inducing and disgust-inducing content as well as facial expressions of fear and disgust. Pictures of neutral objects and neutral facial mimic were used as control stimuli. The pictures were presented in a block design for half of the subjects; the other half viewed the same stimuli as singular events in randomized sequence. The participants had been instructed to passively view the pictures. Disgust-evoking scenes provoked activation in the amygdala, the insula and the orbitofrontal cortex (OFC). This applied to the blocked as well as to the event-related design. Fear-relevant scenes were associated with activity in the insula, the OFC and the middle temporal gyri in the event-related design. The presentation in a block design only led to activation in the middle temporal gyri. Facial expressions of disgust and fear did not trigger significant activation neither in the blocked nor event-related design. This surprising outcome may be a result of context and task effects. The face stimuli which were presented together with the more complex scenes in a passive viewing paradigm possibly were not salient enough to trigger emotional processing.     

Scan patterns when viewing natural scenes: emotion, complexity, and repetition

Eye movements were monitored during picture viewing, and effects of hedonic content, perceptual composition, and repetition on scanning assessed. In Experiment 1, emotional and neutral pictures that were figure-ground compositions or more complex scenes were presented for a 6-s free viewing period. Viewing emotional pictures or complex scenes prompted more fixations and broader scanning of the visual array, compared to neutral pictures or simple figure-ground compositions. Effects of emotion and composition were independent, supporting the hypothesis that these oculomotor indices reflect enhanced information seeking. Experiment 2 tested an orienting hypothesis by repeatedly presenting the same pictures. Although repetition altered specific scan patterns, emotional, compared to neutral, picture viewing continued to prompt oculomotor differences, suggesting that motivationally relevant cues enhance information seeking in appetitive and defensive contexts.     

Attentional modulation of emotional stimulus processing in patients with major depression—Alterations in prefrontal cortical regions

Patients with depression show an impaired ability to modulate emotional states and to process positive emotional information. Here we examined expectancy-induced modulation of emotional picture processing in major depression. We hypothesized alterations in the medial prefrontal cortex. During fMRI, 15 depressed and 21 healthy control subjects passively viewed affective photographs. Half of the pictures were preceded by an expectancy cue signaling whether an emotionally salient or neutral picture would follow. The contrast ‘cued versus uncued emotional picture viewing’ was used to study modulation of emotional picture processing by preceding attention. Healthy individuals showed enhanced activation in the dorsomedial prefrontal cortex and decreased activation in the dorsolateral prefrontal cortex during cued compared to uncued emotional picture perception. The group comparison revealed that these modulatory effects were significantly attenuated in depressed patients. This attenuation was particularly observed in the positive compared to the negative picture condition and tended to normalize in the dorsomedial prefrontal cortex after remission of symptoms. Altered prefrontal modulation in depression may contribute to impaired affect modulation and related clinical symptoms, such as anhedonia.     

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.     

Negative expectations influence behavioral and ERP responses in the subsequent recognition of expectancy-incongruent neutral events

Previous studies have shown that expectancy incongruence in emotional stimuli influences the encoding (i.e., the first stage of memory processing) of the stimuli. However, it is unknown about whether expectancy incongruence influences later stages of memory processing, such as recognition. To this end, expectancy cues were presented prior to emotional pictures. Most often, the cues accurately indicated the emotional consequences of the pictures, but in some cases the consequence was incongruent with the expectations, and a picture from another emotional category was presented. Afterward, participants completed an unexpected recognition task in which old and novel pictures were not preceded by expectancy cues. The results showed that, in the encoding phase, expectancy incongruence reduced response accuracy when categorizing pictorial emotions, and the effect was smaller for neutral pictures than for negative pictures. ERP results showed stronger and weaker responses to expectancy incongruent pictures compared to congruent pictures in time ranges related to the encoding-related early and middle late positive potential (LPP), respectively. In the subsequent recognition phase, d′ scores were higher for incongruent neutral pictures than for congruent ones. Expectancy incongruence enlarged the P2 response but reduced the recognition-related early LPP response for neutral pictures. However, effects of expectancy incongruence were not seen for negative pictures. Therefore, the findings in the present study indicate that negative expectations influence the later recognition of expectancy incongruent neutral events, whereas negative events are more resistant to the effects of expectation incongruence.     

Postauricular reflexes elicited by soft acoustic clicks and loud noise probes: Reliability,prepulse facilitation,and sensitivity to picture contents

The startle blink reflex is facilitated during early picture viewing, then inhibited by attention during pleasant and aversive pictures compared to neutral pictures, and finally potentiated during aversive pictures specifically. However, it is unclear whether the postauricular reflex, which is elicited by the same loud acoustic probe as the startle blink reflex but enhanced by appetitive instead of defensive emotion, has the same pattern and time course of emotional modulation. We examined this issue in a sample of 90 undergraduates using serially presented soft acoustic clicks that elicited postauricular (but not startle blink) reflexes in addition to standard startle probes. Postauricular reflexes elicited by both clicks and probes correlated during food and nurturant contents, during which they were potentiated compared to neutral pictures, suggesting clicks effectively elicit emotionally modulated postauricular reflexes. The postauricular reflex was initially facilitated during the first 500 ms of picture processing but was larger during pleasant than neutral pictures throughout picture processing, with larger effect sizes during the latter half of picture processing. Across reflexes and eliciting stimuli, measures of emotional modulation had higher coefficient alphas than magnitudes during specific picture contents within each valence, indicating that only emotional modulation measures assess higher‐order appetitive or defensive processing.     

The interaction of anticipatory anxiety and emotional picture processing: An event‐related brain potential study

The present study examined the interaction of anticipatory anxiety and selective emotion processing. Toward this end, a rapid stream of pleasant, neutral, and unpleasant pictures was presented in alternating blocks of threat‐of‐shock or safety, which were signaled by colored picture frames. The main finding is that pleasant pictures elicited a sustained negative difference potential over occipital regions during threat as compared to safety periods. In contrast, unpleasant and neutral picture processing did not vary as a function of threat‐of‐shock. Furthermore, in both the safety and threat‐of‐shock conditions, emotional pictures elicited an enlarged early posterior negativity and late positive potential. These data show that the activation of the fear/anxiety network exerts valence‐specific effects on affective picture processing. Pleasant stimuli mismatching the current state of anticipatory anxiety apparently draw more attentional resources.     

Hemodynamic responses to fear and disgust-inducing pictures: an fMRI study

The majority of neuroimaging studies on affective processing have indicated that there are specific brain structures, which are selectively responsive to fear and disgust. Whereas the amygdala is assumed to be fear-related, the insular cortex is most likely involved in disgust processing. Since these findings are mainly a result of studies focusing exclusively either on fear, or on disgust, but rarely on both emotions together, the present experiment explored the neural effects of viewing disgusting and fear-inducing pictures in contrast to neutral pictures. This was done by means of functional magnetic resonance imaging (fMRI) with 19 subjects (nine males, ten females), who also gave affective ratings for the presented pictures. The fear and the disgust pictures were able to induce the target emotions and they received comparable valence and arousal ratings. The processing of both aversive picture types was associated with an increased brain activation in the occipital–temporal lobe, in the prefrontal cortex, and in the thalamus. The amygdala was significantly activated by disgusting, but not by fear-inducing, pictures. Thus, our data are in contrast with the idea of highly emotion-specific brain structures and rather suggest the existence of a common affective circuit.     

Event‐related potentials of emotional and neutral memories: The role of encoding position and delayed testing

Previous research found that memory is not only better for emotional information but also for neutral information that has been encoded in the context of an emotional event. In the present ERP study, we investigated two factors that may influence memory for neutral and emotional items: temporal proximity between emotional and neutral items during encoding, and retention interval (immediate vs. delayed). Forty‐nine female participants incidentally encoded 36 unpleasant and 108 neutral pictures (36 neutral pictures preceded an unpleasant picture, 36 followed an unpleasant picture, and 36 neutral pictures were preceded and followed by neutral pictures) and participated in a recognition memory task either immediately (N = 24) or 1 week (N = 25) after encoding. Results showed better memory for emotional pictures relative to neutral pictures. In accordance, enhanced centroparietal old/new differences (500–900 ms) during recognition were observed for unpleasant compared to neutral pictures, most pronounced for the 1‐week interval. Picture position effects, however, were only subtle. During encoding, late positive potentials for neutral pictures were slightly lower for neutral pictures following unpleasant ones, but only at trend level. To summarize, we could replicate and extend previous ERP findings showing that emotionally arousing events are better recollected than neutral events, particularly when memory is tested after longer retention intervals. Picture position during encoding, however, had only small effects on elaborative processing and no effects on memory retrieval.     

More is less: Emotion induced prefrontal cortex activity habituates in aging

Several recent studies have documented age-related changes in brain activity—less amygdala activity and higher prefrontal activity in response to emotional stimuli. Using functional magnetic resonance imaging (fMRI), we examined whether aging also affects the maintenance of activity to emotional stimuli and whether maintenance differs by the valence (negative, neutral and positive) of the pictures. Younger participants had a larger volume of activity in the amygdala but less in the prefrontal cortex than the old. The old showed more habituation to highly arousing negative but not positive or neutral stimuli in prefrontal cortex as compared to younger participants. Thus prefrontal cortex activity indexes emotion in the elderly, but not the young. Amplified prefrontal activity suggests elderly increase cognitive control for negative, highly arousing emotional stimuli, but it is not maintained. Taken together, age-related increases in prefrontal activity and reduced amygdala activity may underlie observed affective changes in aging.     

Affective picture processing as a function of preceding picture valence: an ERP analysis

Event-related brain potential (ERP) studies consistently revealed that a relatively early (early posterior negativity; EPN) and a late (late positive potential; LPP) ERP component differentiate between emotional and neutral picture stimuli. Two studies examined the processing of emotional stimuli when preceded either by pleasant, neutral, or unpleasant context images. In both studies, distinct streams of six pictures were shown. In Study 1, hedonic context was alternated randomly across the 180 picture streams. In Study 2, hedonic context sequences were blocked, resulting in 60 preceding sequences of pleasant, neutral, and unpleasant context valence, respectively. The main finding was that the valence of the preceding picture sequence had no significant effect on the emotional modulation of the EPN and LPP components. However, previous results were replicated in that emotional stimulus processing was associated with larger EPN and LPP components as compared to neutral pictures. These findings suggest that the prioritized processing of emotional stimuli is primarily driven by the valence of the current picture.