Electrophysiological correlates of threat processing in spider phobics

The electrocortical correlates of the processing of feared/fear-relevant and neutral stimuli were investigated in a pictorial emotional Stroop paradigm with spider phobic, social phobic, and nonphobic subjects. Subjects identified either the color of red or blue pictures of spiders, birds, or flowers (emotional Stroop task) or the object itself (identification task) by pressing different buttons. No emotional Stroop interference was found for spider phobic subjects when identifying the color of spiders as opposed to neutral stimuli. However, in the object identification task, spider phobic subjects identified spiders significantly faster than birds or flowers. Parietal P300 and P400 amplitudes were enhanced independent of task in spider phobic but not in nonphobic subjects when viewing pictures of spiders, which is consistent with previous studies showing that highly unpleasant and arousing pictures affect parietal late positive potentials.     

Electromagnetic indication of hypervigilant responses to emotional stimuli in blood-injection-injury fear

Blood phobia differs from other phobias and anxiety disorders in that no attentional bias for blood-related stimuli has been consistently observed. The present study aimed at clarifying this characteristic by investigating electromagnetic brain activity to blood-related and -unrelated pictures in high blood-fearful and non-fearful individuals. Relative to non-fearful controls, high blood-fearful subjects displayed more intense occipito-parietal activation 190–250 ms after picture onset, which was interpreted as non-specifically enhanced sensory encoding of visual stimuli. Blood-related stimuli did not elicit different activity patterns in high blood-fearful subjects and controls, supporting the hypothesis that non-specific hypervigilance does not provide a basis for subsequent, specifically enhanced processing of fear-related contents.     

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.     

Affective picture processing: an integrative review of ERP findings

The review summarizes and integrates findings from 40 years of event-related potential (ERP) studies using pictures that differ in valence (unpleasant-to-pleasant) and arousal (low-to-high) and that are used to elicit emotional processing. Affective stimulus factors primarily modulate ERP component amplitude, with little change in peak latency observed. Arousal effects are consistently obtained, and generally occur at longer latencies. Valence effects are inconsistently reported at several latency ranges, including very early components. Some affective ERP modulations vary with recording methodology, stimulus factors, as well as task-relevance and emotional state. Affective ERPs have been linked theoretically to attention orientation for unpleasant pictures at earlier components (<300 ms). Enhanced stimulus processing has been associated with memory encoding for arousing pictures of assumed intrinsic motivational relevance, with task-induced differences contributing to emotional reactivity at later components (>300 ms). Theoretical issues, stimulus factors, task demands, and individual differences are discussed.     

Acute psychological stress promotes general alertness and attentional control processes: An ERP study

The current study investigated the influence of acute psychological stress on selective attention processes. After an acute stressor or a control condition, 20 participants performed an arrow-based version of the Eriksen flanker task, while ERPs (N1, N2, P3), reaction times, accuracy, subjective stress, and electrocardiogram signal were measured. Results showed elevated self-report stress, negative affect, state anxiety, heart rate, and reduced high-frequency heart rate variability in the stress block than in the control block, indicating that the flanker task was performed in a stressful situation. In the flanker task, faster response and larger flanker effect of accuracy were observed for the stress block relative to the control block, indicating increased arousal level and improved conflict detection under stress. Event-related potentials locked to target stimuli in the flanker task revealed that (a) frontal N1 was amplified in the stress block than in the control block, indicating elevated vigilance level under stress; (b) frontal N2 was increased in the stress block than in the control block for both congruent and incongruent trials, indicating more intensive attention control under stress; and (c) Increased P3 in the stress block than in the control block may reflect more allocation of neural resources as a consequence of improved attentional control under stress. These findings suggest that acute psychological stress increases general alertness and promotes attentional control in selective attention processes.     

When persons disagree: an ERP study of Unagreement in Spanish

Agreement is one of the main devices used by languages to signal grammatical relations. In this study, we investigated the neurophysiological processing correlates of subject-verb agreement in Spanish using Unagreement, a phenomenon characterized by a person mismatch between subject and verb that nonetheless produces a grammatical pattern. Unagreement was compared to well-formed sentences with full agreement, and ill-formed sentences with a person mismatch. Compared to control sentences, Unagreement produced a left posterior negativity followed by a more central negativity; no P600 effect was observed. In contrast, person violations generated a negativity that was widely distributed over the scalp, followed by a P600 effect. These data suggest that the comprehension of qualitatively different agreement patterns, which could reflect the performance of different processing routines, recruits different neural generators.     

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.     

Specific fear modulates attentional selectivity during visual search: Electrophysiological insights from the N2pc

In the present study, we used high‐density EEG during a visual search task to investigate the dynamics of spatial attention to fear‐relevant targets and background stimuli in small animal phobia during a visual search task. Twenty‐five spider fearful (22 females) and 25 healthy nonfearful participants (19 females) were measured, while searching for discrepant objects in visual arrays. Compared to nonfearful participants, s pider fearful individuals showed a more enhanced posterior N2pc to spider (vs. butterfly) targets in an array of flowers. Furthermore, spider fearful participants showed enhanced hypervigilance for all presented stimuli compared to controls as reflected by enhanced N1 amplitudes (160–200 ms). Our findings provide neural evidence for early, enhanced selective spatial attention for fear‐relevant stimuli.     

Time course of attentional bias in social anxiety: The effects of spatial frequencies and individual threats

Hypervigilance and attentional bias to threat faces with low-spatial-frequency (LSF) information have been found in individuals with social anxiety. The vigilance–avoidance hypothesis posits that socially anxious individuals exhibit initial vigilance and later avoidance to threatening cues. However, the temporal dynamics of these two processes in response to various LSF threats in social anxiety remain unclear. In the current study, we presented faces containing anger, disgust, and fear in high and low spatial frequencies and compared the neural correlates with sensory perception and attention in individuals with high versus low social anxiety (HSA/LSA, n = 24). A visual search task was used to investigate the attentional effects of threats and spatial frequencies, and event-related potentials, particularly, the visual components of P1 and P250, were measured to index visual perceptual and attentional processes, respectively. We found that HSA individuals showed pronounced P1 and reduced P250 to LSF (vs. HSF) faces, regardless of emotion type, suggesting a general pattern of initial vigilance and later avoidance to LSF faces in social anxiety. Furthermore, while LSA individuals showed enhanced P250 to both fear and disgust (vs. neutral) faces, HSA individuals showed pronounced P250 to disgust faces alone. Our results, thus, elucidate the temporal profile of early vigilance and later avoidance in social anxiety, highlighting its broad implication for all faces and predominance in the low spatial frequency. Considering individual threats, our results demonstrate specific attentional avoidance of fear faces in social anxiety.     

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.     

Infants' neutral facial expressions elicit the strongest initial attentional bias in adults: Behavioral and electrophysiological evidence

Recent studies that used adult faces as the baseline have revealed that attentional bias toward infant faces is the strongest for neutral expressions than for happy and sad expressions. However, the time course of the strongest attentional bias toward infant neutral expressions is unclear. To clarify this time course, we combined a behavioral dot-probe task with electrophysiological event-related potentials (ERPs) to measure adults' responses to infant and adult faces with happy, neutral, and sad expressions derived from the same face. The results indicated that compared with the corresponding expressions in adult faces, attentional bias toward infant faces with various expressions resulted in different patterns during rapid and prolonged attention stages. In particular, first, neutral expressions in infant faces elicited greater behavioral attentional bias and P1 responses than happy and sad ones did. Second, sad expressions in infant faces elicited greater N170 responses than neutral and happy ones did; notably, sad expressions elicited greater N170 responses in the left hemisphere in women than in men. Third, late positive potential (LPP) responses were greater for infant faces than for adult faces under each expression condition. Thus, we propose a three-stage model of attentional allocation patterns that reveals the time course of attentional bias toward infant faces with various expressions. This model highlights the prominent role of neutral facial expressions in the attentional bias toward infant faces.     

Excitatory versus inhibitory impairments in insomnia patients: An ERP study

According to the neurocognitive perspective on insomnia, conditioned arousal results in impairment of information processing, as such interfering with normal sleep processes. In the present study, evening event-related potentials N100 and P200 were evaluated to assess hyperarousal in patients with insomnia and controls. 13 patients (mean age = 40.8) with polysomnographically verified sleep disruptions and 11 good sleepers (mean age = 45.4) were included. An auditory oddball paradigm was administered the evening of the polysomnography. N100 and P200 mean amplitudes and peak latencies at Fz and Cz were analyzed as a measure of respectively general arousability and inhibition of information processing. Patients experiencing insomnia were characterized by decreased P200 amplitudes compared to good sleepers. No significant differences were found for N100 amplitudes and latencies of both ERP waves.     

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.     

Gender differences in emotional responses: A psychophysiological study

Gender differences in emotional responses have been investigated in two groups of students, 22 males and 21 females. Participants watched a set of sixty emotional standardized slides divided into pleasant, neutral and unpleasant, while Startle reflex, Evoked Potentials, Heart Rate, facial EMG and Skin Conductance were recorded. Startle reflex amplitude, an index modulated by amygdala and orbitofrontal cortex and sensitive to aversive emotional stimuli, was overall larger in women. In addition, startle emotion modulation was greater in women with respect to men. Slow Evoked Potentials (400–800 ms), a measure representing the cognitive component of the emotional response, revealed gender differences in the left prefrontal site, with women showing greater positivity to unpleasant compared with pleasant slides while men had greater positivity to pleasant vs. neutral slides. Women, compared with men, perceived all slides as less pleasant and reported greater arousal to unpleasant condition. Results are in line with known functional brain differences, at level of limbic and paralimbic structures, between men and women, and point to biologically grounded greater sensitivity and vulnerability of women to adverse/stressful events.     

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.     

Fear induced complexity loss in the electrocardiogram of flight phobics: a multiscale entropy analysis

In this study we explored the changes in the variability and complexity of the electrocardiogram (ECG) of flight phobics (N=61) and a matched non-phobic control group (N=58) when they performed a paced breathing task and were exposed to flight related stimuli. Lower complexity/entropy values were expected in phobics as compared to controls. The phobic system complexity as well as the heart rate variability (HRV) were expected to be reduced by the exposure to fearful stimuli. The multiscale entropy (MSE) analysis revealed lower entropy values in phobics during paced breathing and exposure, and a complexity loss was observed in phobics during exposure to threatening situations. The expected HRV decreases were not found in this study. The discussion is focused on the distinction between variability and complexity measures of the cardiac output, and on the usefulness of the MSE analysis in the field of anxiety disorders.     

Intentional forgetting might be more effortful than remembering: an ERP study of item-method directed forgetting

This study recorded ERPs while participants engaged in a procedure that combined semantic priming and item-method directed forgetting, aiming to investigate the issues of whether intentional forgetting demands cognitive efforts and modulates the semantic processing of to-be-remembered (TBR) and to-be-forgotten (TBF) items. Participants made lexical decisions to semantically related or unrelated prime and target words. A Remember/Forget cue, presented between the prime and target, designated the prime as TBR or TBF. When the cues were shown for 500 ms, targets preceded by Forget cues yielded a smaller P200 wave than those preceded by Remember cues. Furthermore, the topography of the N400 effect was different for targets preceded by Remember and Forget cues. The cues did not modulate the ERPs of the targets when they were shown for 1500 ms. Because P200 is sensitive to attention influence and the N400 effect reflects semantic processing, we conclude that forgetting is more effortful than remembering and that the semantic processing is different for TBR and TBF items. Nevertheless, there is a temporal limitation for the Remember/Forget cues to modulate the semantic processing and attentional resources in item-method directed forgetting.     

Age-related frontoparietal changes during the control of bottom-up and top-down attention: an ERP study

We investigated age-related changes in frontal and parietal scalp event-related potential (ERP) activity during bottom-up and top-down attention. Younger and older participants were presented with arrays constructed to induce either automatic “pop-out” (bottom-up) or effortful “search” (top-down) behavior. Reaction times (RTs) increased and accuracy decreased with age, with a greater age-related decline in accuracy for the search than for the pop-out condition. The latency of the P300 elicited by the visual search array was shorter in both conditions in the younger than in the older adults. Pop-out target detection was associated with greater activity at parietal than at prefrontal locations in younger participants and with a more equipotential prefrontal-parietal distribution in older adults. Search target detection was associated with greater activity at prefrontal than at parietal locations in older relative to younger participants. Thus, aging was associated with a more prefrontal P300 scalp distribution during the control of bottom-up and top-down attention. Early latency extrastriate potentials were enhanced and N2-posterior-contralateral (N2pc) was reduced in the older group, supporting the idea that the frontal enhancements may be due to a compensation for disinhibition and distraction in the older adults. Taken together these findings provide evidence that younger and older adults recruit different frontal-parietal networks during top-down and bottom-up attention, with older adults increasing their recruitment of a more frontally distributed network in both of these types of attention. This work is in accord with previous neuroimaging findings suggesting that older adults recruit more frontal activity in the service of a variety of tasks than younger adults.     

Earthquake experience interference effects in a modified Stroop task: An ERP study

The effects of the modified Stroop task on ERP were investigated in 20 subjects who had experienced the Sichuan earthquake and a matched control group. ERP data showed that Incongruent stimuli elicited a more negative ERP deflection (N300–450) than did Congruent stimuli between 300 and 450 ms post-stimulus in the earthquake group but not found in the control group, and the N300–450 might reflect conflict monitor (the information of color and meaning do not match) in the early phase of perception identification due to their sensitivity to the external stimulus. Then, Incongruent stimuli elicited a more negative ERP deflection than did Congruent stimuli between 450 and 650 ms post-stimulus in both the groups. Dipole source analysis showed that the N450–650 was mainly generated in the ACC contributed to this effect in the control group, which might be related to monitor and conflict resolution. However, in the earthquake group, the N450–650 was generated in the thalamus, which might be involved in inhibiting and compensating of the ACC which may be related to conflict resolution process.