Wenbo Luo

Emotional conflict occurs at an early stage: evidence from the emotional face-word Stroop task.

The perceptual processing of emotional conflict was studied using electrophysiological techniques to measure event-related potentials (ERPs). The emotional face-word Stroop task in which emotion words are written in prominent red color across a face was use to study emotional conflict. In each trial, the emotion word and facial expression were either congruent or incongruent (in conflict). When subjects were asked to identify the expression of the face during a trial, the incongruent condition evoked a more negative N170 ERP component in posterior lateral sites than in the congruent condition. In contrast, when subjects were asked to identify the word during a trial, the incongruent condition evoked a less negative N170 component than the congruent condition. The present findings extend our understanding of the control processes involved in emotional conflict by demonstrating that differentiation of emotional congruency begins at an early perceptual processing stage.

Single-trial ERP analysis reveals facial expression category in a three-stage scheme ☆

Emotional faces are salient stimuli that play a critical role in social interactions. Following up on previous research suggesting that the event-related potentials (ERPs) show differential amplitudes in response to various facial expressions, the current study used trial-to-trial variability assembled from six discriminating ERP components to predict the facial expression categories in individual trials. In an experiment involved 17 participants, fearful trials were differentiated from non-fearful trials as early as the intervals of N1 and P1, with a mean predictive accuracy of 87%. Single-trial features in the occurrence of N170 and vertex positive potential could distinguish between emotional and neutral expressions (accuracy=90%). Finally, the trials associated with fearful, happy, and neutral faces were completely separated during the window of N3 and P3 (accuracy=83%). These categorization findings elucidated the temporal evolution of facial expression extraction, and demonstrated that the spatio-temporal characteristics of single-trial ERPs can distinguish facial expressions according to a three-stage scheme, with fear popup, emotional/unemotional discrimination, and complete separation as processing stages. This work constitutes the first examination of neural processing dynamics beyond multitrial ERP averaging, and directly relates the prediction performance of single-trial classifiers to the progressive brain functions of emotional face discrimination.

Linking brain electrical signals elicited by current outcomes with future risk decision-making

The experience of current outcomes influences future decisions in various ways. The neural mechanism of this phenomenon may help to clarify the determinants of decision-making. In this study, thirty-nine young adults finished a risky gambling task by choosing between a high- and a low-risk option in each trial during electroencephalographic data collection. We found that risk-taking strategies significantly modulated mean amplitudes of the event-related potential (ERP) component P3, particularly at the central scalp. The event-related spectral perturbation and the inter-trial coherence measurements of the independent component analysis (ICA) data indicated that the “stay” vs. “switch” electrophysiological difference associated with subsequent decision-making was mainly due to fronto-central theta and left/right mu independent components. Event-related cross-coherence results suggested that the neural information of action monitoring and updating emerged in the fronto-central cortex and propagated to sensorimotor area for further behavior adjustment. Based on these findings of ERP and event-related oscillation (ERO) measures, we propose a neural model of the influence of current outcomes on future decisions.

Emotional Noun Processing: An ERP Study with Rapid Serial Visual Presentation

Reading is an important part of our daily life, and rapid responses to emotional words have received a great deal of research interest. Our study employed rapid serial visual presentation to detect the time course of emotional noun processing using event-related potentials. We performed a dual-task experiment, where subjects were required to judge whether a given number was odd or even, and the category into which each emotional noun fit. In terms of P1, we found that there was no negativity bias for emotional nouns. However, emotional nouns elicited larger amplitudes in the N170 component in the left hemisphere than did neutral nouns. This finding indicated that in later processing stages, emotional words can be discriminated from neutral words. Furthermore, positive, negative, and neutral words were different from each other in the late positive complex, indicating that in the third stage, even different emotions can be discerned. Thus, our results indicate that in a three-stage model the latter two stages are more stable and universal.

The time course of emotional picture processing: an event-related potential study using a rapid serial visual presentation paradigm

The present study recorded event-related potentials using rapid serial visual presentation paradigm to explore the time course of emotionally charged pictures. Participants completed a dual-target task as quickly and accurately as possible, in which they were asked to judge the gender of the person depicted (task 1) and the valence (positive, neutral, or negative) of the given picture (task 2). The results showed that the amplitudes of the P2 component were larger for emotional pictures than they were for neutral pictures, and this finding represents brain processes that distinguish emotional stimuli from non-emotional stimuli. Furthermore, positive, neutral, and negative pictures elicited late positive potentials with different amplitudes, implying that the differences between emotions are recognized. Additionally, the time course for emotional picture processing was consistent with the latter two stages of a three-stage model derived from studies on emotional facial expression processing and emotional adjective processing. The results of the present study indicate that in the three-stage model of emotion processing, the middle and late stages are more universal and stable, and thus occur at similar time points when using different stimuli (faces, words, or scenes).

N170 changes reflect competition between faces and identifiable characters during early visual processing

According to the neuronal recycling hypothesis, brain circuits can gain new functions through cultural learning, which are distinct from their evolutionarily established functions, creating competition between processes such as facial and identifiable character processing. In the present study, event-related potential (ERP) recording was used to examine electrophysiological correlates of identification levels of Chinese characters as well as the competition between facial and Chinese character processing after the characters were learnt. Twenty volunteers performed a lateralized face detection task, and N170 responses were recorded when the participants viewed only Chinese characters (identifiable or unidentifiable in Xiaozhuan font), or Chinese characters and faces concurrently. Viewing identifiable Chinese characters bilaterally elicited larger N170 amplitudes than viewing unidentifiable ones. N170 amplitudes in response to faces bilaterally declined when identifiable Chinese characters and faces were viewed concurrently as compared to viewing unidentifiable Chinese characters and faces concurrently. These results indicate that the N170 component is modulated by the observers identification level of Chinese characters, and that identifiable Chinese characters compete with faces during early visual processing.

N170 effects during exact and approximate calculation tasks: an ERP study.

Event-related potentials were used to investigate the neural correlates of two-digit exact and approximate addition calculations. The results showed that the dissociation between exact and approximate calculations began at approximately 150 ms after stimulus. In the left hemisphere, N170 amplitude elicited by exact calculation was larger than that elicited by approximate calculation; however, in the right hemisphere, N170 amplitudes elicited by the two calculation strategies were not significantly different. Moreover, a larger P3 amplitude was elicited by exact calculation than by approximate calculation. In the 130–210 ms windows, dipole source analysis of the difference wave (exact calculation minus approximate calculation) indicated that the generator of N170 was localized in the left fusiform gyrus.

Emotional content modulates response inhibition and perceptual processing

In this study, event-related potentials were used to investigate the effect of emotion on response inhibition. Participants performed an emotional go/no-go task that required responses to human faces associated with a go valence (i.e., emotional, neutral) and response inhibition to human faces associated with a no-go valence. Emotional content impaired response inhibition, as evidenced by decreased response accuracy and N2 amplitudes in no-go trials. More importantly, emotional expressions elicited larger N170 amplitudes than neutral expressions, and this effect was larger in no-go than in go trials, indicating that the perceptual processing of emotional expression had priority in inhibitory trials. In no-go trials, correlation analysis showed that increased N170 amplitudes were associated with decreased N2 amplitudes. Taken together, our findings suggest that emotional content impairs response inhibition due to the prioritization of emotional content processing.

P1 and N170 components distinguish human-like and animal-like makeup stimuli

This study used event-related potentials to investigate the sensitivity of P1 and N170 components to human-like and animal-like makeup stimuli, which were derived from pictures of Peking opera characters. As predicted, human-like makeup stimuli elicited larger P1 and N170 amplitudes than did animal-like makeup stimuli. Interestingly, a right hemisphere advantage was observed for human-like but not for animal-like makeup stimuli. Dipole source analyses of 130–200-ms window showed that the bilateral fusiform face area may contribute to the differential sensitivity of the N170 component in response to human-like and animal-like makeup stimuli. The present study suggests that the amplitudes of both the P1 and the N170 are sensitive for the mouth component of face-like stimuli.

The neural processing of fearful faces without attention and consciousness: An event-related potential study

To investigate whether the non-conscious processing of fearful faces exist in unattended condition, event-related potentials (ERPs) were recorded in a facial expression detection task. Participants were asked to discriminate the facial expressions (fearful or neutral) at the attended location. Unattended faces were associated with a response that was either congruent or in conflict with the response to the attended face. ERP results showed that the trials with response conflict between attended and unattended faces enhanced the amplitude of the P3 component when the neutral face was presented at attended location and the fearful face was presented at the unattended location. Our findings imply that the non-conscious fearful faces can be processed in the unattended condition.