Rapid discrimination of visual scene content in the human brain

The rapid evaluation of complex visual environments is critical for an organism's adaptation and survival. Previous studies have shown that emotionally significant visual scenes, both pleasant and unpleasant, elicit a larger late positive wave in the event-related brain potential (ERP) than emotionally neutral pictures. The purpose of the present study was to examine whether neuroelectric responses elicited by complex pictures discriminate between specific, biologically relevant contents of the visual scene and to determine how early in the picture processing this discrimination occurs. Subjects (n = 264) viewed 55 color slides differing in both scene content and emotional significance. No categorical judgments or responses were required. Consistent with previous studies, we found that emotionally arousing pictures, regardless of their content, produce a larger late positive wave than neutral pictures. However, when pictures were further categorized by content, anterior ERP components in a time window between 200 and 600 ms following stimulus onset showed a high selectivity for pictures with erotic content compared to other pictures regardless of their emotional valence (pleasant, neutral, and unpleasant) or emotional arousal. The divergence of ERPs elicited by erotic and non-erotic contents started at 185 ms post-stimulus in the fronto-central midline region, with a later onset in parietal regions. This rapid, selective, and content-specific processing of erotic materials and its dissociation from other pictures (including emotionally positive pictures) suggests the existence of a specialized neural network for prioritized processing of a distinct category of biologically relevant stimuli with high adaptive and evolutionary significance.     

Low spatial frequency filtering modulates early brain processing of affective complex pictures

Recent research on affective processing has suggested that low spatial frequency information of fearful faces provide rapid emotional cues to the amygdala, whereas high spatial frequencies convey fine-grained information to the fusiform gyrus, regardless of emotional expression. In the present experiment, we examined the effects of low (LSF, <15 cycles/image width) and high spatial frequency filtering (HSF, >25 cycles/image width) on brain processing of complex pictures depicting pleasant, unpleasant, and neutral scenes. Event-related potentials (ERP), percentage of recognized stimuli and response times were recorded in 19 healthy volunteers. Behavioral results indicated faster reaction times in response to unpleasant LSF than to unpleasant HSF pictures. Unpleasant LSF pictures and pleasant unfiltered pictures also elicited significant enhancements of P1 amplitudes at occipital electrodes as compared to neutral LSF and unfiltered pictures, respectively; whereas no significant effects of affective modulation were found for HSF pictures. Moreover, mean ERP amplitudes in the time between 200 and 500 ms post-stimulus were significantly greater for affective (pleasant and unpleasant) than for neutral unfiltered pictures; whereas no significant affective modulation was found for HSF or LSF pictures at those latencies. The fact that affective LSF pictures elicited an enhancement of brain responses at early, but not at later latencies, suggests the existence of a rapid and preattentive neural mechanism for the processing of motivationally relevant stimuli, which could be driven by LSF cues. Our findings confirm thus previous results showing differences on brain processing of affective LSF and HSF faces, and extend these results to more complex and social affective pictures.     

Emotional memories are resilient to time: evidence from the parietal ERP old/new effect

Emotional memories can be extremely robust and long-lasting and can contribute to the development of anxiety disorders. Despite tremendous work on neural responses underlying the memory formation of emotional events, less is known about long-term retention. In the present study, behavioral and electrophysiological measures were used to investigate long-term recognition memory for emotional (unpleasant and pleasant) and neutral pictures after two retention intervals (1 week vs. 1 year) in 21 male subjects. The results show enhanced recognition performance for emotional relative to neutral pictures for both test delays. On the neural side, the retrieval of emotional pictures compared to neutral pictures was accompanied after 1 week by an enhanced old/new effect (500-800 ms), originating in the parietal cortex. After 1-year retention delay, only unpleasant but not pleasant pictures were different from neutral pictures in the recollection-sensitive ERP component. Analysis of the subjective awareness (confidence ratings) during recognition indicated that behavioral and electrocortical response patterns were exclusively driven by high confidence responses, an indication for recollection-based recognition. These results suggest that high arousing emotional memories were highly consistent over time relative to neutral memories.     

Cerebral blood flow changes associated with attribution of emotional valence to pleasant, unpleasant, and neutral visual stimuli in a PET study of normal subjects.

OBJECTIVE: To assist in the development of a model for the psychopathology of emotions, the present study sought to identify the neural circuits associated with the evaluation of visual stimuli for emotional valence. METHOD: Seventeen healthy individuals were shown three sets of emotionally laden pictures carrying pleasant, unpleasant, and neutral content. While subjects evaluated the picture set for emotional valence, regional cerebral blood flow was measured with the use of [15O] water positron emission tomography. Subjective ratings of the emotional valence of the picture sets were recorded. Data were analyzed by comparing the images acquired during the neutral condition with the unpleasant and pleasant image sets and the unpleasant and pleasant conditions with each other. RESULTS: Processing of pleasant stimuli was associated with increased blood flow in the dorsal-lateral, orbital, and medial frontal cortex relative to the unpleasant condition and in the cingulate, precuneus, and visual cortex relative to the neutral condition. Evaluation of unpleasant stimuli activated the amygdala, visual cortex, and cerebellum relative to the pleasant condition and the nucleus accumbens, precuneus, and visual cortex relative to the neutral condition. CONCLUSIONS: Observing and assigning emotional value to unpleasant stimuli produced activations in subcortical limbic regions, whereas evaluation of pleasant stimuli produced activations in cortical limbic areas. These findings are consistent with the notion of a subcortical and archaic danger recognition system and a system detecting pleasantness in events and situations that is phylogenetically younger, involving primarily the prefrontal cortex.     

Effects of emotional arousal in the cerebral hemispheres: a study of oscillatory brain activity and event-related potentials.

OBJECTIVE: The present study aimed at examining the time course and topography of oscillatory brain activity and event-related potentials (ERPs) in response to laterally presented affective pictures. METHODS: Electroencephalography was recorded from 129 electrodes in 10 healthy university students during presentation of pictures from the international affective picture system. Frequency measures and ERPs were obtained for pleasant, neutral, and unpleasant pictures. RESULTS: In accordance with previous reports, a modulation of the late positive ERP wave at parietal recording sites was found as a function of emotional arousal. Early mid gamma band activity (GBA; 30-45 Hz) at 80 ms post-stimulus was enhanced in response to aversive stimuli only, whereas the higher GBA (46-65 Hz) at 500 ms showed an enhancement of arousing, compared to neutral pictures. ERP and late gamma effects showed a pronounced right-hemisphere preponderance, but differed in terms of topographical distribution. CONCLUSIONS: Late gamma activity may represent a correlate of widespread cortical networks processing different aspects of emotionally arousing visual objects. In contrast, differences between affective categories in early gamma activity might reflect fast detection of aversive stimulus features.     

Affective context-induced modulation of the error-related negativity

The error-related negativity putatively reflects the activity of performance-monitoring processes influenced by motivational factors, and is overactive in certain anxiety states, suggesting that affective factors affect its generation. We examined the effects of emotionally arousing and neutral task-irrelevant backgrounds on the error-related negativity to determine whether an affective context 'mismatch' alters error-related neural processing. Event-related potentials were acquired while healthy participants performed a modified Eriksen flanker task wherein flanker stimuli were superimposed on neutral, pleasant, and unpleasant pictures. The error-related negativity varied as a function of picture valence, peaking both earlier and larger in the context of pleasant backgrounds than neutral or unpleasant backgrounds. Findings support the hypothesis that affective factors influence the error-related negativity, potentially reflecting an affective mismatch associated with performance monitoring.     

Nonlinear relationship between emotional valence and brain activity: Evidence of separate negative and positive valence dimensions

Emotion plays a significant role in goal‐directed behavior, yet its neural basis is yet poorly understood. In several psychological models the cardinal dimensions that characterize the emotion space are considered to be valence and arousal. Here 3T functional magnetic resonance imaging (fMRI) was used to reveal brain areas that show valence‐ and arousal‐dependent blood oxygen level dependent (BOLD) signal responses. Seventeen healthy adults viewed pictures from the International Affective Picture System (IAPS) for brief 100 ms periods in a block design paradigm. In many brain regions BOLD signals correlated significantly positively with valence ratings of unpleasant pictures. Interestingly, partly in the same regions but also in several other regions BOLD signals correlated negatively with valence ratings of pleasant pictures. Therefore, there were several areas where the correlation across all pictures was of inverted U‐shape. Such correlations were found bilaterally in the dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex (DMPFC) extending to anterior cingulate cortex (ACC), and insula. Self‐rated arousal of those pictures which were evaluated to be unpleasant correlated with BOLD signal in the ACC, whereas for pleasant pictures arousal correlated positively with the BOLD signal strength in the right substantia innominata. We interpret our results to suggest a major division of brain mechanisms underlying affective behavior to those evaluating stimuli to be pleasant or unpleasant. This is consistent with the basic division of behavior to approach and withdrawal, where differentiation of hostile and hospitable stimuli is crucial. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.     

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. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.     

Why don’t you feel how I feel? Insight into the absence of empathy after severe Traumatic Brain Injury

Although the existence of empathy deficits in people with traumatic brain injury (TBI) is generally well accepted, it has been a topic of limited investigation. The current study examined the relationship between self-reported emotional and cognitive empathy and psychophysiological responding to emotionally evocative pictures in 20 patients with severe TBI and 22 control participants. Eighteen pictures with alternating pleasant, unpleasant and neutral content selected from the International Affective Picture System (IAPS) were presented whilst facial muscle responses, skin conductance, and valence and arousal ratings were measured. Self-reported emotional and cognitive empathy questionnaires were also administered. In comparison to control participants, those in the TBI group displayed a reduction in the ability to empathize both emotionally and cognitively, and evidence that these two aspects of empathy may be interconnected was established. Further, TBI participants showed reduced facial responding to unpleasant pictures, while also rating them as less unpleasant and arousing than controls. In addition, they exhibited lowered autonomic arousal to all pictures, regardless of affective valence. Interestingly, hypoarousal to pleasant pictures in particular was found to be related to the absence of empathy observed after TBI, and is consistent with the view that impaired emotional responsivity is associated with impairment to the empathy network. The results represent a further step towards understanding what processes shape empathy.     

Neural correlates of preparatory and regulatory control over positive and negative emotion

This study used functional magnetic resonance imaging to investigate brain activation during preparatory and regulatory control while participants (N = 24) were instructed either to simply view or decrease their emotional response to, pleasant, neutral or unpleasant pictures. A main effect of emotional valence on brain activity was found in the right precentral gyrus, with greater activation during positive than negative emotion regulation. A main effect of regulation phase was evident in the bilateral anterior prefrontal cortex (PFC), precuneus, posterior cingulate cortex, right putamen and temporal and occipital lobes, with greater activity in these regions during preparatory than regulatory control. A valence X regulation interaction was evident in regions of ventromedial PFC and anterior cingulate cortex, reflecting greater activation while regulating negative than positive emotion, but only during active emotion regulation (not preparation). Conjunction analyses revealed common brain regions involved in differing types of emotion regulation including selected areas of left lateral PFC, inferior parietal lobe, temporal lobe, right cerebellum and bilateral dorsomedial PFC. The right lateral PFC was additionally activated during the modulation of both positive and negative valence. Findings demonstrate significant modulation of brain activity during both preparation for, and active regulation of positive and negative emotional states.     

Representation of perceived sound valence in the human brain

Perceived emotional valence of sensory stimuli influences their processing in various cortical and subcortical structures. Recent evidence suggests that negative and positive valences are processed separately, not along a single linear continuum. Here, we examined how brain is activated when subjects are listening to auditory stimuli varying parametrically in perceived valence (very unpleasant-neutral-very pleasant). Seventeen healthy volunteers were scanned in 3 Tesla while listening to International Affective Digital Sounds (IADS-2) in a block design paradigm. We found a strong quadratic U-shaped relationship between valence and blood oxygen level dependent (BOLD) signal strength in the medial prefrontal cortex, auditory cortex, and amygdala. Signals were the weakest for neutral stimuli and increased progressively for more unpleasant or pleasant stimuli. The results strengthen the view that valence is a crucial factor in neural processing of emotions. An alternative explanation is salience, which increases with both negative and positive valences.     

Modulation of subthalamic alpha activity to emotional stimuli correlates with depressive symptoms in Parkinson's disease1

Background : Deep brain stimulation of the subthalamic nucleus is an effective treatment for patients with advanced Parkinson's disease. However, affective side effects following subthalamic deep brain stimulation have been reported. Here, we aim to elucidate the influence of affective state on emotional processing as indexed by local field potential activity and to identify neurophysiological markers in patients at risk of developing depressive symptoms during subthalamic deep brain stimulation. Methods : Subthalamic local field potentials were directly recorded via electrodes implanted for deep brain stimulation in 12 Parkinson's disease patients while viewing emotionally salient and neutral pictures. Parkinson's disease patients were assessed for depressive symptoms using the Beck depression inventory at the time of operation and 3 months after continuous subthalamic nucleus deep brain stimulation. Results : We found a significant event‐related desynchronization in the local alpha frequency band (8–12 Hz) for emotionally arousing but not neutral pictures. The the event‐related desynchronization (ERD) in the alpha frequency band was reduced for pleasant stimuli in patients with mild to moderate depressive symptoms compared with patients without depression. The alpha‐ERD to unpleasant stimuli showed the opposite pattern. Consistently, the index of event‐related alpha desynchronization (alpha ERD for pleasant stimuli minus alpha ERD for unpleasant stimuli) correlated with the Beck depression inventory at the time of the recordings and at 3 months after continuous deep brain stimulation. The alpha ERD to unpleasant pictures correlated significantly with the Beck depression inventory score at 3 months after chronic deep brain stimulation. Discusion : In conclusion, we found mood‐congruent stimulus processing in the subthalamic nucleus of Parkinson's disease patients. Electrophysiological markers such as event‐related desynchronization of subthalamic alpha activity reflect state‐dependent emotional processing and may potentially be used to predict depressive mood disturbances in Parkinson's disease patients with chronic subthalamic deep brain stimulation at an early stage. © 2011 Movement Disorder Society     

Extent and time‐course of competition in visual cortex between emotionally arousing distractors and a concurrent task

Emotionally arousing cues automatically attract attentional resources, which may be at the cost of processing task‐related information. Of central importance is how the visual system resolves competition for processing resources among stimuli differing in motivational salience. Here, we assessed the extent and time‐course of competition between emotionally arousing distractors and task‐related stimuli in a frequency‐tagging paradigm. Steady‐state visual evoked potentials (ssVEPs) were evoked using random‐dot kinematograms that consisted of rapidly flickering (8.57 Hz) dots, superimposed upon emotional or neutral distractor pictures flickering at 12 Hz. The time‐varying amplitude of the ssVEP evoked by the motion detection task showed a significant reduction to the task‐relevant stream while emotionally arousing pictures were presented as distractors. Competition between emotionally arousing pictures and moving dots began 450 ms after picture onset and persisted for an additional 2600 ms. Competitive effects of the overlapping task and picture stream revealed cost effects for the motion detection task when unpleasant pictures were presented as distractors between 450 and 1650 ms after picture onset, where an increase in ssVEP amplitude to the flickering picture stimulus was at the cost of ssVEP amplitude to the flickering dot stimulus. Cost effects were generalized to all emotionally arousing contents between 1850 and 3050 ms after picture onset, where the greatest amount of competition was evident for conditions in which emotionally arousing pictures, compared to neutral, served as distractors. In sum, the processing capacity of the visual system as measured by ssVEPs is limited, resulting in prioritized processing of emotionally relevant cues.     

The subthalamic region is activated during valence-related emotional processing in patients with Parkinson's disease

Visual stimuli are judged for their emotional significance based on two fundamental dimensions, valence and arousal, and may lead to changes in neural and body functions like attention, affect, memory and heart rate. Alterations in behaviour and mood have been encountered in patients with Parkinson's disease (PD) undergoing functional neurosurgery, suggesting that electrical high-frequency stimulation of the subthalamic nucleus (STN) may interfere with emotional information processing. Here, we use the opportunity to directly record neuronal activity from the STN macroelectrodes in patients with PD during presentation of emotionally laden and neutral pictures taken from the International Affective Picture System (IAPS) to further elucidate the role of the STN in emotional processing. We found a significant event-related desynchronization of STN alpha activity with pleasant stimuli that correlated with the individual valence rating of the pictures. Our findings suggest involvement of the human STN in valence-related emotional information processing that can potentially be altered during high-frequency stimulation of the STN in PD leading to behavioural complications.     

Motivated attention to cocaine and emotional cues in abstinent and current cocaine users--an ERP study

Event-related potentials (ERPs) are a direct measure of neural activity and are ideally suited to study the time-course of attentional engagement with emotional and drug-related stimuli in addiction. In particular, the late positive potential (LPP) appears to be enhanced following cocaine-related compared with neutral stimuli in human participants with cocaine use disorders (CUD). However, previous studies have not directly compared cocaine-related with emotional stimuli while examining potential differences between abstinent and current cocaine users. The present study examined ERPs in 55 CUD (27 abstinent and 28 current users) and 29 matched healthy controls while they passively viewed pleasant, unpleasant, neutral and cocaine-related pictures. To examine the time-course of attention to these stimuli, we analysed both an early and later window in the LPP as well as the early posterior negativity (EPN), established in assessing motivated attention. Cocaine pictures elicited increased electrocortical measures of motivated attention in ways similar to affectively pleasant and unpleasant pictures in all CUD, an effect that was no longer discernible during the late LPP window for the current users. This group also exhibited deficient processing of the other emotional stimuli (early LPP window - pleasant pictures; late LPP window - pleasant and unpleasant pictures). Results were unique to the LPP and not EPN. Taken together, results support a relatively early attention bias to cocaine stimuli in cocaine-addicted individuals, further suggesting that recent cocaine use decreases such attention bias during later stages of processing but at the expense of deficient processing of other emotional stimuli.     

Preserved emotional modulation of motor response time despite psychomotor slowing in young-old adults

Whereas aging affects cognitive and psychomotor processes negatively, the impact of aging on emotional processing is less clear. Using an "old-new" binary decision task, we ascertained the modulation of response latencies after presentation of neutral and emotional pictures in "young" (M = 27.1 years) and "young-old" adults with a mean age below 60 (M = 57.7 years). Stimuli varied on valence (pleasant, neutral, and unpleasant) and arousal (high and low) dimensions. Young-old adults had significantly longer reaction times. However, young and young-old adults showed the exact same pattern of response time modulation by emotional stimuli: Response latencies were longer for high-arousal than for low-arousal pictures and longer for negative than for positive or neutral stimuli. This result suggests that the specific effects of implicitly processed emotional valence and arousal information on behavioral response time are preserved in young-old adults despite significant age-related psychomotor decline.     

情绪词汇加工的事件相关电位的时空模式研究

目的 通过事件相关电位(ERP)的时空模式探讨不同知觉条件下情绪词汇加工的神经机制.方法 11名受试者从事情绪词汇加工后呈现的面孔照片组合的面孔性别判别任务.对不同知觉条件下情绪词与中性词的ERP差异波采用2(知觉:非觉察、觉察)×2(情绪词:正/中性、负/中性)重复测量方差分析,利用F值的统计参数映像呈现结果 .结果 F值统计参数映像显示:(1)显著交互效应(知觉×情绪)主要出现在左侧额颞区及右侧枕区(60～80ms);(2)显著知觉效应主要出现在双侧额区和右颞区(110～150 ms);(3)显著情绪效应主要出现在左右半球的广泛区域(60～90ms).结论 ERP的时空模式提示了非觉察和觉察条件下情绪词汇加工早期激活同一神经网络,前者的激活强度较后者弱.     

Transient interference of right hemispheric function due to automatic emotional processing

We examined the effects of emotional stimuli on right and left hemisphere detection performance in a hemifield visual discrimination task. A group of 18 healthy subjects were asked to discriminate between upright and inverted triangles (target). Targets were randomly presented in the left or right visual hemifield (150 ms target duration). A brief emotional picture (pleasant or unpleasant; 150 ms stimulus duration) or neutral picture selected from the International Affective Picture System was randomly presented either in the same (47%) or the opposite (47%) spatial location to the subsequent target. Emotional or neutral stimuli offset 150 ms prior to the subsequent target. Subjects were instructed to ignore the pictures and respond to the targets as quickly and accurately as possible. Independent of field of presentation, emotional stimuli prolonged reaction times (P < 0.01) to LVF targets, with unpleasant stimuli showing a greater effect than pleasant stimuli. The current study shows that brief emotional stimuli selectively impair right hemispheric visual discrimination capacity. The findings suggest automatic processing of emotional stimuli captures right hemispheric processing resources and transiently interferes with other right hemispheric functions.     

Expecting unpleasant stimuli – An fMRI study

Expecting forthcoming events and preparing adequate responses are important cognitive functions that help the individual to deal with the environment. The emotional valence of an event is decisive for the resulting action. Revealing the underlying mechanisms may help to understand the dysfunctional information processing in depression and anxiety that are associated with negative expectation of the future. We were interested in selective brain activity during the expectation of unpleasant visual stimuli. Twelve healthy female subjects were biased to expect and then perceive emotionally unpleasant, pleasant or neutral stimuli during functional magnetic resonance imaging. Expecting unpleasant stimuli relative to expecting pleasant and neutral stimuli resulted in activation of mainly cingulate cortex, insula, prefrontal areas, thalamus, hypothalamus and striatum. While certain areas were also active during subsequent presentation of the emotional stimuli, distinct regions of the anterior cingulate gyrus and the thalamus were solely active during expectation of the unpleasant stimuli. The identified areas may reflect a network for internal adaptation and preparation processes in order to react adequately to expected unpleasant events. They are known as well to be altered in depression. Disorders of this network may be relevant for psychiatric disorders such as depression.     

Expecting unpleasant stimuli--an fMRI study

Expecting forthcoming events and preparing adequate responses are important cognitive functions that help the individual to deal with the environment. The emotional valence of an event is decisive for the resulting action. Revealing the underlying mechanisms may help to understand the dysfunctional information processing in depression and anxiety that are associated with negative expectation of the future. We were interested in selective brain activity during the expectation of unpleasant visual stimuli. Twelve healthy female subjects were biased to expect and then perceive emotionally unpleasant, pleasant or neutral stimuli during functional magnetic resonance imaging. Expecting unpleasant stimuli relative to expecting pleasant and neutral stimuli resulted in activation of mainly cingulate cortex, insula, prefrontal areas, thalamus, hypothalamus and striatum. While certain areas were also active during subsequent presentation of the emotional stimuli, distinct regions of the anterior cingulate gyrus and the thalamus were solely active during expectation of the unpleasant stimuli. The identified areas may reflect a network for internal adaptation and preparation processes in order to react adequately to expected unpleasant events. They are known as well to be altered in depression. Disorders of this network may be relevant for psychiatric disorders such as depression.