Music-induced mood modulates the strength of emotional negativity bias: an ERP study

The present study investigated the effect of music-elicited moods on the subsequent affective processing through a music-primed valence categorization task. Event-related potentials were recorded for positive and negative emotional pictures that were primed by happy or sad music excerpts. The reaction time data revealed longer reaction times (RTs) for pictures following negative versus positive music pieces, irrespective of the valence of the picture. Additionally, positive pictures elicited faster response latencies than negative pictures, irrespective of the valence of the musical prime. Moreover, the main effect of picture valence, and the music by picture valence interaction effect were both significant for P2 amplitudes and for the averaged amplitudes at 500-700ms interval. Negative pictures elicited smaller P2 amplitudes than positive pictures, and the amplitude differences between negative and positive pictures were larger with negative musical primes than with positive musical primes. Similarly, compared to positive pictures, negative pictures elicited more negative deflections during the 500-700ms interval across prime types. The amplitude differences between negative and positive pictures were again larger under negative versus positive music primes at this interval. Therefore, the present study observed a clear emotional negativity bias during either prime condition, and extended the previous findings by showing increased strength of the negative bias under negative mood primes. This suggests that the neural sensitivity of the brain to negative stimuli varies with individuals' mood states, and this bias is particularly intensified by negative mood states.     

Time course of affective processing bias in major depression: An ERP study

The current study investigated the time course of the affective processing bias in major depressive disorder (MDD) in a visual three-stimulus semantic oddball task using event-related potentials (ERPs). MDD patients showed decreased P1 latency over right posterior regions to negative relative to positive target stimuli, reflecting a very early onset of the negativity bias in emotional perception. Compared to controls, MDD patients showed enlarged anterior P2 amplitude to positive target stimuli, reflecting an affective bias in the early attentional stages of processing. In addition, MDD patients showed relatively high N2 and reduced P3 amplitudes to negative compared with positive target stimuli, as well as marginally reduced N2 amplitude to positive target stimuli compared with controls. This suggests that the negativity bias also occurs during later strategic evaluation stages. Therefore, the present study extended previous findings by demonstrating that the affective processing bias in MDD begins in the early stages of perceptual processing and continues at later cognitive stages.     

Intentional modulation of emotional responding to unpleasant pictures: an ERP study

Intentionally altering responses to unpleasant stimuli affects physiological and hemodynamic activity associated with emotional and cognitive processing. In the present experiment, we measured the late-positive potential (LPP) of the visually evoked event-related brain potential to examine the effects of intentional emotion modulation on electrophysiological correlates of emotional and cognitive processing. Seventeen participants received instructions to view, suppress, and enhance emotional responses to unpleasant stimuli. Results revealed significantly decreased electrophysiological activity during suppression of emotional responses beginning around 250 ms poststimulus and lasting several hundred milliseconds. These data suggest that ERPs are sensitive to emotion modulation/regulation processes.     

Emotional sensitization highlights the attentional bias in blood-injection-injury phobics: an ERP study

The presence of an attentional bias towards disorder-related stimuli has not been consistently demonstrated in blood phobics. The present study was aimed at investigating whether or not an attentional bias, as measured by event-related potentials (ERPs), could be highlighted in blood phobics by inducing cognitive-emotional sensitization through the repetitive presentation of different disorder-related pictures. The mean amplitudes of the N100, P200, P300 and late positive potentials to picture onset were assessed along with subjective ratings of valence and arousal in 13 blood phobics and 12 healthy controls. Blood phobics, but not controls, showed a linear increase of subjective arousal over time, suggesting that cognitive-emotional sensitization did occur. The analysis of cortical responses showed larger N100 and smaller late positive potentials in phobics than in controls in response to mutilations. These findings suggest that cognitive-emotional sensitization induced an attentional bias in blood phobics during picture viewing, involving early selective encoding and late cognitive avoidance of disorder-related stimuli depicting mutilations.     

Discrimination of emotional facial expressions in a visual oddball task: an ERP study

Several ERP studies have shown an orienting complex, the N2/P3a, associated to the detection of stimulus novelty. Its role consists in preparing the organism to process and react to biologically prepotent stimuli. Whether this N2/P3a: (1) could be obtained with complex visual stimuli, such as with emotional facial expressions; and (2) could take part in a complex discrimination process has yet to be determined. To investigate this issue, event-related potentials were recorded in response to repetitions of a particular facial expression (e.g. sadness) and in response to two different deviant (rare) stimuli, one depicting the same emotion as the frequent stimulus, while the other depicted a different facial expression (e.g. fear). As expected, deviant stimuli evoked an N2/P3a complex of larger amplitude than frequent stimuli. But more interestingly, when the deviant stimulus depicted the same emotion as the frequent stimulus the N2/P3a was delayed compared to the response elicited by the different-emotion deviant. The N2/P3a was thus implicated in the detection of physical facial changes, with a higher sensitivity to changes related to a new different emotional content, perhaps leading to faster adaptive reactions.     

Categorization of unilaterally presented emotional words: an ERP analysis

This study is intended to clarify the functional role of different ERP components as indicators of the processing of emotions. The effect of emotional connotation of words on hemispheric lateralization is also explored. Visual ERPs were recorded to unilaterally presented positive, negative, and neutral words that should be categorized according to their emotional connotation. The P2 amplitude was larger to positive than to negative words whereas P3 amplitude was larger to positive words compared with neutral ones. The slow positive wave (SPW) was influenced by words emotionality at anterior and posterior sites differently. The amplitude of the N1 component was larger in the left hemisphere to contralaterally presented words. The P2 and P3 components were larger over the left hemisphere whereas the N3 and N4 components were larger over the right hemisphere to ipsilateral stimulation. The results support our hypotheses on the functional role of positive ERP components in the processing of an affective words connotation: the P2 wave reflects a general evaluation of emotional significance, the P3 a task-related decision, and the SPW an additional decision control in the context of the emotional experience of an individual. Neither the "right hemisphere hypothesis" nor "valence hypothesis" on lateralization of the processing of emotions were confirmed. Each hemisphere seems to exert its effect on emotion through specific hemispheric resources that are unequally allocated along the different stages of task processing and may cause alternation of hemispheric dominance.     

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.     

Up-regulation of emotional responses to reward-predicting stimuli: An ERP study

Altered reward processing is a hallmark symptom of many psychiatric disorders. It has recently been shown that people are capable of down-regulating reward processing. Here, we examined whether people are capable of up-regulating emotional responses to reward-predicting stimuli. Participants passively viewed colored squares that predicted a reward or no reward, and up- or down-regulated their emotional responses to these reward-predicting stimuli by focusing on the reward meaning or the color of the squares respectively. The amplitude of the late positive potential (LPP) was taken as an objective index of regulation success. The LPP in response to reward-predicting squares was enhanced by up-regulation, suggesting that up-regulation of emotional responses to reward-predicting stimuli using a cognitive strategy is feasible. These results are highly relevant for the treatment of disorders characterized by diminished motivation, and for reward-based decision making in daily life.     

Shyness and emotional face processing in schizophrenia: An ERP study

Shyness in healthy controls has been related to early event-related potential (ERP) responses to emotional faces. Patients with schizophrenia typically demonstrate increased shyness that is stable and related to reduced social functioning. We indexed early ERP responses to emotional faces in relation to shyness in 40 outpatients with schizophrenia and 39 healthy controls. Patients with low-to-medium shyness showed reductions in P100 amplitude to emotional compared to neutral faces as shyness increased. Patients reporting medium-to-high shyness demonstrated the opposite pattern; P100 amplitude sharply increased as shyness increased, possibly reflecting heightened vigilance. When a restricted range of shyness scores was used to equalize scores between groups, patients showed increased N170 amplitude to emotional faces as shyness increased, whereas controls demonstrated the opposite pattern. The implications of the findings are discussed with respect to informing vulnerability to social functioning impairment and psychosocial stress in this population.     

Impact of meditation on emotional processing--a visual ERP study

Impact of meditation on emotional processing, and its clinical applications, has recently drawn significant interest. In this visual event-related potential (ERP) study we investigated whether long-term meditation practitioners exhibit different ERP responses to the emotional load of stimuli (IAPS pictures) than control subjects with no experience in meditation. Differences were observed in the late positive potential (LPP). LPP amplitude is typically greater in ERPs evoked by emotionally arousing scenes, specifically negative images, compared to neutral scenes. This effect was also replicated in our study, but not in case of meditators’ frontal scalp regions, who differed significantly in this respect from control subjects. Our findings provide support for different emotional processing in meditation practitioners: at high levels of processing meditators are less affected by stimuli with adverse emotional load, while processing of positive stimuli remains unaltered. To further confirm this observation, a long-term longitudinal random assignment study would be desirable.     

Sad benefit in face working memory: an emotional bias of melancholic depression

Emotion biases feature prominently in cognitive theories of depression and are a focus of psychological interventions. However, there is presently no stable neurocognitive marker of altered emotion-cognition interactions in depression. One reason may be the heterogeneity of major depressive disorder. Our aim in the present study was to find an emotional bias that differentiates patients with melancholic depression from controls, and patients with melancholic from those with non-melancholic depression. We used a working memory paradigm for emotional faces, where two faces with angry, happy, neutral, sad or fearful expression had to be retained over one second. Twenty patients with melancholic depression, 20 age-, education- and gender-matched control participants and 20 patients with non-melancholic depression participated in the study. We analysed performance on the working memory task using signal detection measures. We found an interaction between group and emotion on working memory performance that was driven by the higher performance for sad faces compared to other categories in the melancholic group. We computed a measure of "sad benefit", which distinguished melancholic and non-melancholic patients with good sensitivity and specificity. However, replication studies and formal discriminant analysis will be needed in order to assess whether emotion bias in working memory may become a useful diagnostic tool to distinguish these two syndromes.     

Visual categorization during childhood: an ERP study

Categorization is a basic means of organizing the world around us and offers a simple way to process the mass of stimuli one perceives every day. The ability to categorize appears early in infancy, and has important ramifications for the acquisition of other cognitive capacities, but little is known of its development during childhood. We studied 48 children (7-15 years of age) and 14 adults using an animal/nonanimal visual categorization task while event-related potentials (ERPs) were recorded. Three components were measured: P1, N2, and P3. Behaviorally, the children performed the task very similarly to adults, although the children took longer to make categorization responses. Decreases in latencies (N2, P3) and amplitudes (P1, N2, P3) with age indicated that categorization processes continue to develop through childhood. P1 latency did not differ between the age groups. N2 latency, which is associated with stimulus categorization, reached adult levels at 9 years and P3 latency at 11 years of age. Age-related amplitude decreases started after the maturational changes in latencies were finished.     

Somatosensory off-response in humans: an ERP study

Quick detection of changes in the sensory environment is very important for survival, resulting in automatic shifts of attention to the event and the facilitation of subsequent processes to execute appropriate behaviors. The abrupt onset or offset of a sensory stimulus should also activate the neural network detecting changes. To test this hypothesis, we compared cortical on- and off-responses using somatosensory-evoked potentials (SEPs) elicited by a train of electrical pulses delivered to the right hand in eight healthy volunteers. SEPs were recorded from 15 electrodes on the scalp at three different interstimulus intervals (ISIs, 50, 20, and 10 ms) under two sets of conditions (attended and unattended). Both the onset and offset of stimulation evoked two similar components, P100 and N140, in the attended and unattended conditions. The latency of P100 and N140 in response to stimulus onset did not differ among the three ISIs, while the latency of both components in response to stimulus offset was significantly longer for the longer ISI; that is, detection of the cessation of the stimulation was based on short-term memory of the stimulus frequency. The present results supported a cortical network triggered by both the onset and offset of sensory stimulation. In this network, the change is automatically detected using a memory trace by comparing the abrupt event (on or off) with the preceding condition (silent or repetitive stimuli).     

The time course of building discourse coherence in schizophrenia: an ERP investigation

Impairments in the buildup and use of context may lead to disorders of thought and language in schizophrenia. To test this hypothesis, event-related potentials (ERPs) were measured while patients and healthy controls read sentences that were highly causally related, intermediately related, or unrelated to preceding contexts. Although patients were slower than controls, both groups used the discourse context similarly as evidenced by similar reaction time patterns across conditions. Neurally however, different patterns emerged between patients and controls: within the N400 time window, patients failed to modulate their neural responses across conditions. This failure to differentiate between conditions was specifically correlated with positive thought disorder. Results suggest that schizophrenia patients, particularly those with positive thought disorder, fail to make immediate use of discourse context to build up semantic coherence in the brain.     

The case of letter rhyming: an ERP study

Previous visual event-related potential (ERP) studies using prime-target pairs of word and pseudoword stimuli have reported a robust rhyming effect such that nonrhyming targets elicit a larger N450 than rhyming targets. However, results of similar studies using simpler linguistic stimuli-single letters-are equivocal. We used lowercase and uppercase letter pairs in a simple ERP prime-target rhyming paradigm to further investigate whether single letters could elicit the typical rhyming effect and, if so, whether the rhyming effect was sensitive to physical orthography (which differed between the case conditions). The typical N450 rhyming effect was observed in both the lowercase and uppercase letter pair conditions, with similar amplitude and latency between conditions. This pattern of results suggests that the N450 rhyming effect is not sensitive to physical (case) orthography and likely primarily indexes phonological processing related to the rhyme task.     

Decomposition of the ERP late posterior negativity: effects of retrieval and response fluency

Negativity elicited by recognized items over posterior sites--the late posterior negativity (LPN)--has been linked to action monitoring, task "uncertainty," and contextual retrieval. Four recognition tests required retrieval of encoding operations. Task fluency was assumed to increase with each block. The responses assigned to the episodic sources were reversed in Block 3 to reduce response fluency. Dissociable LPNs were identified; the 1200-1900-ms LPN was insensitive to task and response fluency and may reflect the maintenance of a retrieved episode. The 600-1200-ms LPN was sensitive to task fluency and may index the search for episodic information. A response-related LPN was sensitive to response fluency and was consistent with an action monitoring role. The findings confirm that the LPN is functionally heterogeneous, and comprises subcomponents sensitive to retrieval fluency, action monitoring, and postretrieval processing respectively.     

ERP correlates of Remember/Know decisions: association with the late posterior negativity

A number of studies have utilized the Remember/Know paradigm to determine event-related potential (ERP) correlates of recollection and familiarity. However, no prior work has been specifically directed at examining the processing involved in making the Remember/Know distinction. The following study employed a two-step recognition memory test in which participants first decided whether they recognized a word from a prior study list (Old/New decision); if they did, they then determined whether it was recognized on the basis of recollection ('Remember' responses) or familiarity ('Know' responses). By time-locking ERPs to the initial Old/New decision, processing related to making the introspective Remember/Know judgment was isolated. This methodology revealed a posterior negativity that was largest for 'Remember' responses. Previous work has described a late posterior negativity which appears to be related to the search for and recapitulation of study details. Such processing may be critical in making Remember/Know determinations.     

An ERP study on the time course of facial trustworthiness appraisal

The neuropeptide galanin has been recognized as a possible neurotransmitter/neuromodulator, and in addition has been implicated in anxiety- and depression-related behaviors. The present study demonstrates increased locomotion and rearing after galanin (0.3 mg/kg) that was given intraperitoneally (i.p.) to intact Wistar rats which were tested 1 h later in the open field (OF). These effects, which suggest an anxiolytic-like action, were blocked by i.p. administered peptidic galanin antagonist M40. Further, the locomotion increase caused by galanin and the inhibitory effect of M40 persisted for 48 h without additional treatment. Rats exposed to restraint stress (lasting 60 min) for three consecutive days and tested 1 h after stress termination exhibited reduced locomotion and exploration in the OF. Galanin (0.3 and 1.0 mg/kg) given immediately after each stress exposure prevented the decrease of locomotion and exploration induced by stress in all trials. When the test was repeated 6 days later without stress and galanin treatment the reduction of locomotion produced by stress persisted; the anti-stress behavioral effects of both galanin doses were also present. Testing performed on the 12th day after the last stress and galanin treatment with 0.3 mg/kg revealed an increased locomotion compared with unstressed and stress-exposed rats. Our results demonstrate that behavioral effects of the peptide galanin are evident even after i.p. administration. These results also suggest that galanin elicits stress-modulatory action, and support the notion that the galaninergic system may serve as a drug target in stress-related conditions.     

An ERP study on the time course of facial trustworthiness appraisal

The importance of facial trustworthiness for human interaction and communication is difficult to exaggerate. Reflections on daily experience indicate that the presence of a human face elicits rapid appraisals of its trustworthiness. Relatively little is known, however, about the exact brain processes related to this response. In the present study, event-related brain potentials were recorded during trustworthiness appraisals of various emotionally neutral faces. On the one hand, trustworthy faces elicited a more positive C1 than untrustworthy faces; a finding that might be related to initial stages of perceptual processing that categorizes faces on the basis of structural properties. On the other hand, untrustworthy faces elicited a more positive late positive component (LPC) than trustworthy faces, indicating that greater amounts of motivated attention are allocated to faces appearing to be untrustworthy. The LPC effect in this study was consistent with the prediction of the emotion overgeneralization hypothesis of trustworthy face evaluation.     

Brain electrical correlates of dimensional weighting: an ERP study

In visual search, there is a reaction time (RT) cost for targets on a given trial if the previous target was defined in a different dimension. According to the "dimension-weighting" account (Müller, Heller, & Ziegler, 1995), limited attentional weight needs to be shifted to the new dimension, resulting in slower RTs. The present study aimed at identifying brain electrical correlates associated with the weight shift. Analyses of ERPs revealed several components to reflect dimension changes whether the task was to detect the target or to identify its defining dimension. N2 amplitudes were more negative whenever the dimension changed. The P3 exhibited latency differences that mirrored RTs in both tasks, but the amplitudes showed no direct relation to stimulus- or response-related processes. Finally, slow-wave amplitudes were enhanced for dimension changes. Taken together, the results provide support for relatively early, perceptual processes underlying dimension change costs.