A cross-linguistic examination of cortical auditory evoked potentials for a categorical voicing contrast

Behavioral perceptions and cortical auditory evoked potentials (CAEPs) from native English (N=10) and Spanish speakers (N=10) were recorded for speech stimuli that constitute phonetically relevant categories of voicing. The stimuli were synthesized bilabial stop consonant-vowel syllables in a continuum ranging from/ba/to/pa/that varied in voice onset time (VOT) from 0 to 60 ms. Different behavioral perceptions were evidenced by significantly different categorical phonetic boundaries between the two groups (p<.0001). In contrast, there were no significant differences in CAEP component P1, N1, and P2 mean latencies or P1-N1 and N1-P2 amplitudes between groups (p>.05). Peak P1, N1, and P2 response latencies and P1-N1 and N1-P2 amplitudes increased significantly with increasing VOTs (p<.0001 and p<.001, respectively). There were no systematic changes in CAEP morphology that corresponded to listeners' perceptual categorical boundaries. These findings are consistent with the notion that changes in morphology of the P1-N1-P2 response are related to acoustical changes in speech sounds and are independent of phonetic categorization of voicing cues across language groups.     

Beware misleading cues: perceptual similarity modulates the N2/P3 complex

Event-related potentials were used to investigate neural processes relating perceptual similarity to action control. To assess whether perceptual overlap among targets and nontargets would modulate the N2/P3 complex, the present study used multiple nontarget categories varying in their targetlike characteristics. Participants made one (relatively rare) response to a low-probability stimulus (target), and they made a different (relatively common) response to all other stimuli (nontargets). The critical nontarget categories had equivalent probability (.10) but varied in their targetlike characteristics. Supporting the N2 component as sensitive to the strength of conflicting action imperatives, perceptual overlap among targets and nontargets elicited a prominent N2. In contrast, amplitude of the P3 component appeared most sensitive to the extent of cognitive processing needed for categorization.     

Impaired perceptual processing of facial expression categorization in social anhedonia

The current event-related potential study investigated the perceptual processing of the categorization advantage of happy over sad faces in social anhedonia with a nonclinical sample. A high social anhedonia (HSA, N = 25) group and a low social anhedonia (LSA, N = 27) group performed a facial expression categorization task during which they classified facial expressions (happy, neutral, sad), irrespective of face orientation (upright, upside-down). Behaviorally, happy faces were identified more quickly than sad ones in the upright but not inverted orientation. Electrophysiologically, the LSA group showed earlier N170 latencies for happy than for sad faces in the upright but not upside-down orientation, whereas the HSA group did not show any expression effect on N170 latencies. Moreover, N170 and P2 amplitude results revealed that HSA relative to LSA individuals showed delayed neural discrimination between happy and sad faces. These results suggest that social anhedonia is associated with a deficit of perceptual processing during facial expression categorization.     

Electrophysiological indexes of option characteristic processing

Decision making is vital to human behavior and can be divided into multiple stages including option assessment, behavioral output, and feedback evaluation. Studying how people evaluate option characteristics in the option assessment stage would provide important knowledge on human decision making. Using the event‐related potential (ERP) method, the present study investigated the neural mechanism of evaluating two types of option characteristics (i.e., reward magnitude and degree of uncertainty) in the temporal dimension. Thirty‐five volunteers participated in a monetary gambling task, where they either accepted or rejected gambles. The ERP results showed a double dissociation pattern, with the early P1 component being sensitive to magnitude but insensitive to degree of uncertainty, while both the N2 and P3 components showed the opposite pattern. The results suggest that these two fundamental option features are assessed rapidly and separately in the human brain. Specifically, small magnitude elicited a larger P1 than did large magnitude, indicating that the perceptual and attentional processing of options is modulated by magnitude. Both the N2 and P3 amplitudes evoked by the risky context were larger than those evoked by the ambiguous one, reflecting that more cognitive conflicts and resources are involved in the former condition. Furthermore, the P1, but not the N2 or P3, amplitude was sensitive to decisions, suggesting that early attentional processes may contribute to human decision making. These findings may provide insight into the temporal mechanisms of option characteristic processing.     

The influence of stimulus valence on perceptual processing of facial expressions and subsequent response inhibition

The constant interplay between affective processing and cognitive control supports emotion regulation and appropriate social functioning. Even when affective stimuli are processed implicitly, threat-related stimuli are prioritized in the earliest stages of processing; yet, it remains unclear how implicit attention to affect influences subsequent cognitive control functions. The present study evaluated the influence of affective valence on early perceptual processes and subsequent response inhibition in a context where affective properties of the stimuli (facial expressions) were not critical for performing the task. Participants (N = 32) completed an affective stop-signal task (SST) while their scalp EEGs were recorded. The SST assessed response inhibition while participants implicitly attended to happy and afraid facial expressions that were matched for level of arousal. Behavioral performance was measured via response time and accuracy while physiological response was measured via the P100, N170, and N200/P300 ERP components. Decreased gender discrimination accuracy, delayed P100 latency, and more negative N170 amplitude were observed for afraid faces compared to happy faces, suggesting a shift in processing with respect to face valence. However, differences in stopping accuracy or N200/P300 ERP components during response inhibition were not observed, pointing to top-down cognitive processes likely being recruited to override the early automatic response to prioritize threat-related stimuli. Findings highlight that, in this implicit affective attention task, threat-related stimuli are prioritized early during processing, but implicitly attending to differentially valenced stimuli did not modulate subsequent cognitive control functions.     

Functional Differences Between Members of the P300 Complex: P3e and P3b

The main findings of this study bear upon differences in the functional roles of P3b and a shorter latency, more centrally distributed endogenous positive component denoted as P3e. At the present writing, we have observed P3e only in conjunction with P3b. As in the case of P3b, P3e is fully endogenous in that it can be- elicited by omission of a stimulus if stimulus omission conveys relevant information to the subject. It was found that P3e and P3b relate differently to information delivery. Information delivery was manipulated by varying event probabilities and the discriminability of the events. The well known properties of P3b, namely that its amplitude is large when elicited by low probability (high information content) events and is reduced by perceptual difficulty (information loss-equivocation), were replicated in the current study. In contrast to P3b, variation of event probability had no effect upon P3e amplitude, but increased perceptual difficulty markedly reduced P3e amplitude. In addition, two CNV-type negativities were observed in the epochs prior to presentation of the informative signal event: 1) A negativity that was maximal over central scalp related to the subject's prediction that a rare or frequent event would be presented; 2) A negativity that was maximal over occipital scalp related to a stimulus that informed the subject whether the subsequent discrimination of the signal would be easy or difficult. Finally, there was a serendipitous Hading of an apparently new short duration component, tentatively labeled Px, which is elicited by presentation of the signal that informs the subject whether the subsequent discrimination will be easy or difficult.     

Goal relevance influences performance monitoring at the level of the FRN and P3 components

The feedback‐related negativity (FRN) provides a reliable ERP marker of performance monitoring (PM). It is usually larger for negative compared to positive feedback, and for unexpected relative to expected feedback. In two experiments, we assessed whether these effects could be modulated by goal relevance, defined as feedback informativeness (reliability) and/or impact on a person's goals. EEG (64‐channel) was recorded while 30 participants (in each experiment) performed a speeded go/no‐go task across blocks in which the feedback on task performance was deemed either relevant or not. At the ERP level, the FRN component was larger for (frequent) negative compared to (deviant) positive feedback exclusively when the feedback was relevant (Experiment 1). When the probability of positive and negative feedback was balanced (Experiment 2), this valence‐driven FRN effect was absent. However, across these two experiments, the FRN was always larger for irrelevant than relevant feedback. Moreover, the subsequent P300 component was larger for feedback in the relevant than the irrelevant blocks. This effect was valence unspecific in Experiment 1, while in Experiment 2 larger P3 amplitudes were recorded for negative than positive (relevant) feedback. Across the two experiments, a larger correct‐related negativity in the irrelevant than relevant context was also observed, suggesting that PM is flexible. These ERP findings indicate that goal relevance influences feedback (and response) processing during PM, with two nonoverlapping neurophysiological effects: It gates reward prediction error brain mechanisms (FRN effect), before enhancing subsequent motivational processes (P300 effect).     

Signatures of emotional face processing measured by event-related potentials in 7-month-old infants

The ability to distinguish facial emotions emerges in infancy. Although this ability has been shown to emerge between 5 and 7 months of age, the literature is less clear regarding the extent to which neural correlates of perception and attention play a role in processing of specific emotions. This study's main goal was to examine this question among infants. To this end, we presented angry, fearful, and happy faces to 7-month-old infants (N = 107, 51% female) while recording event-related brain potentials. The perceptual N290 component showed a heightened response for fearful and happy relative to angry faces. Attentional processing, indexed by the P400, showed some evidence of a heightened response for fearful relative to happy and angry faces. We did not observe robust differences by emotion in the negative central (Nc) component, although trends were consistent with previous work suggesting a heightened response to negatively valenced expressions. Results suggest that perceptual (N290) and attentional (P400) processing is sensitive to emotions in faces, but these processes do not provide evidence for a fear-specific bias across components.     

Early interaction between perceptual load and involuntary attention: An event-related potential study

Whether selective attention affects C1, the first (earliest) visual cortical component of the event-related potential (ERP), remains controversial. We used a cued, involuntary attention task requiring discrimination of targets under low and high levels of perceptual load to examine early attentional modulation in visual cortex. Potential confounds due to physical stimulus differences between load conditions and cue–target sensory interaction were minimized. An interaction between perceptual load and involuntary attention was observed for the P1m component (peak latency between 100 and 140 ms). Furthermore, the parieto-central C1 component (peak latency 80 ms) was modulated by attention, but only under the high-load condition. Thus, whereas attention typically modulates the later P1 component, attentional modulation of C1 is possible under optimal conditions. Specifically, a high perceptual load is necessary for eliciting this earliest attentional effect on cortical processing.     

Toward a Functional Categorization of Slow Waves

This study is concerned with slowly varying, long-duration brain event-related potential (ERP) components, referred to as Slow Wave activity. Slow Wave activity can be observed in the epoch following P3b, suggesting that it reflects further processing invoked by increased task demands, beyond the processing that underlies P3b. The present experiment was designed to distinguish Slow Wave activity related to specific types of task demands which arise during difficult perceptual (pattern recognition) and conceptual (arithmetic) mental operations. Three late ERP components that respond differentially in amplitude to manipulation of perceptual and conceptual difficulty were identified: 1) A P3b, with a topography focused about P_z, evidently related to the subjective categorization of easy and difficult conceptual operations, that increased when the subjective low-probability operation was performed; 2) A longer latency, centroparietal positive Slow Wave that increased directly with perceptual difficulty but was not affected by conceptual difficulty; 3) A very long latency negative Slow Wave, broadly distributed over centroposterior scalp, that increased directly with conceptual difficulty while its onset was delayed when perceptual difficulty increased.     

The neural signature of spatial frequency-based information integration in scene perception

Spatial frequency-based information plays an important role in visual perception. By combining behavioral and electroencephalogram (EEG) measurements, we investigated the mechanisms of the interaction and information integration between different spatial frequency bands. The observers performed a scene categorization task on hybrid images that were generated by combining the low spatial frequency (LSF) component of one image with the high spatial frequency (HSF) component of another image. The results showed that the recognition of the HSF component was interfered by the non-attended LSF component at semantic level. The strength of the semantic interference was modulated by the physical similarity between the LSF and HSF components. Analyses of the EEG data revealed an early anterior N1 component (122 ms from stimulus onset) that was related to the observed interaction of the semantic and physical information between the LSF and HSF components. These findings demonstrate that the semantic information from different spatial frequency bands can be integrated at early stage of the perceptual processing. This early integration is likely to occur at frontal areas in order to initiate top-down facilitation.     

Does processing of emotional facial expressions depend on intention? Time-resolved evidence from event-related brain potentials

We assessed the automaticity of emotional face processing with respect to the intentionality criterion, holding that automatic processes are triggered independently of intention. For this purpose, we observed emotion processing in event-related brain potential (ERP) components under five different task conditions. ERP components included the P1, N170, the early posterior negativity (EPN), and the late positive complex (LPC). Enhanced processing at perceptual stages as indicated by P1, N170, and EPN effects occurred independently of intention in angry expressions. In contrast, the emotion-related LPC, a putative manifestation of higher-level, more elaborative processing stages, depended on the intentional state of the participants. This suggests an automatic threat-related processing bias at perceptual stages, while higher cognitive emotion encoding is subject to voluntary control. Moreover, an independent component analyses (ICA) showed that EPN and LPC activity occurred simultaneously, indicating perceptual and higher cognitive emotion encoding to occur in parallel.     

The electrophysiological signature of deliberate rule violations

Humans follow rules by default, and violating even simple rules induces cognitive conflict for the rule breaker. Previous studies revealed this conflict in various behavioral measures, including response times and movement trajectories. Based on these experiments, we investigated the electrophysiological signature of deliberately violating a simple stimulus‐response mapping rule. Such rule violations were characterized by a delayed and attenuated P300 component when evaluating a rule‐relevant stimulus, most likely reflecting increased response complexity. This parietal attenuation was followed by a frontal positivity for rule violations relative to correct response trials. Together, these results reinforce previous findings on the need to inhibit automatic S‐R translation when committing a rule violation, and they point toward additional factors involved in rule violation. Candidate processes such as negative emotional responses and increased monitoring should be targeted by future investigations.     

Event-Related Potentials During Controlled and Automatic Target Detection

The present study investigated the role of attentional resources in the performance of controlled and automatic detection tasks. The amplitude of the P300 component of the event-related potential has been shown to be a sensitive index of the attentional resources allocated to the perceptual processing of sensory stimuli. We found that P300s elicited in both automatic and controlled detection were large and of comparable amplitude, suggesting the involvement of a limited-capacity mechanism in both tasks. This result is in agreement with previous behavioral studies showing equivalent dual-task trade-offs with both search tasks (Hoffman & Nelson, Note 1). In contrast, P300 latency was considerably reduced in the automatic task, suggesting that the main effect of practice in the detection task is to improve the discriminability of targets and distractors.     

Decision‐ and feedback‐related brain potentials reveal risk processing mechanisms in patients with alcohol use disorder

Individuals with alcohol use disorder (AUD) are aware of the risks of alcohol abuse yet continue risky drinking. Research indicates that dysfunctional decision processes and trait variables such as impulsivity contribute to this awareness‐behavior discrepancy. The present study focused on decision‐related versus feedback‐related processes as potential contributors to decision making in AUD by examining the relationship between decision choices and decision‐ and feedback‐related ERP phenomena in the balloon analogue risk task (BART). N = 39 AUD and n = 35 healthy comparison participants (HC) performed the BART modified for EEG assessment. In each of 100 runs, participants made a series of choices about whether to pump up a virtual balloon, which popped pseudorandomly, ending the run. Alternatively, participants ended the run by pressing a “cash‐out” button. Each pump not producing a pop provided .05 €; popping resulted in loss of the run’s accumulated gain. Groups made similar choices, though AUD responded more slowly. The decision P3 200?400 ms after decision prompt (balloon) was larger in AUD than in HC, and decision P3 enhancement on high‐risk trials predicted choices to pump. Feedback‐related negativity (FRN) after loss (relative to cash out) feedback was smaller in AUD than in HC, suggesting indifference to negative feedback. In AUD, high impulsivity was associated with risk‐modulated decision P3 but not FRN. Results indicate atypical decision‐ and feedback‐related processes that could contribute to difficulties in engaging with daily challenges effectively.     

Rapid target selection of object categories based on verbs: Implications for language‐categorization interactions

Although much is known about how nouns facilitate object categorization, very little is known about how verbs (e.g., posture verbs such as stand or lie) facilitate object categorization. Native Dutch speakers are a unique population to investigate this issue with because the configurational categories distinguished by staan (to stand) and liggen (to lie) are inherent in everyday Dutch language. Using an ERP component (N2pc), four experiments demonstrate that selection of posture verb categories is rapid (between 220–320 ms). The effect was attenuated, though present, when removing the perceptual distinction between categories. A similar attenuated effect was obtained in native English speakers, where the category distinction is less familiar, and when category labels were implicit for native Dutch speakers. Our results are among the first to demonstrate that category search based on verbs can be rapid, although extensive linguistic experience and explicit labels may not be necessary to facilitate categorization in this case.     

Dissociating retrieval interference and reanalysis in the P600 during sentence comprehension

We investigated the relative independence of two key processes in language comprehension, as reflected in the P600 ERP component. Numerous studies have linked the P600 to sentence‐ or message‐level reanalysis; however, much research has shown that skilled, cue‐based memory retrieval operations are also important to successful language processing. Our goal was to identify whether these cue‐based retrieval operations are part of the reanalysis processes indexed by the P600. To this end, participants read sentences that were either grammatical or ungrammatical via subject‐verb agreement violations, and in which there was either no possibility for retrieval interference or there was an attractor noun interfering with the computation of subject‐verb agreement (e.g., “The slogan on the political poster(s) was/were …”). A stimulus onset asynchrony manipulation (fast, medium, or slow presentation rate) was designed to modulate participants' ability to engage in reanalysis processes. Results showed a reliable attraction interference effect, indexed by reduced behavioral sensitivity to ungrammaticalities and P600 amplitudes when there was an opportunity for retrieval interference, as well as an effect of presentation rate, with reduced behavioral sensitivity and smaller P600 effects at faster presentation rates. Importantly, there was no interaction between the two, suggesting that retrieval interference and sentence‐level reanalysis processes indexed by the P600 can be neurocognitively distinct processes.     

An ERP study of visual spatial attention and letter target detection for isoluminant and nonisoluminant stimuli

The event-related potential (ERP) effects of visual spatial attention and letter target detection for stimuli presented against a (nonisoluminant) dark background or against an isoluminant grey background were investigated. The goal was to study how the perceptual variable of luminance would influence early ERP reflections of selective attention. Such effects could further substantiate the claim that selective attention operates at the level of early perceptual processing and could provide evidence regarding the role of different visual routes in selective attention. Isoluminance increased the peak latency of the early ERP deflections (NP80, PI, and NI) by 40–50 ms. The ERP effects of spatial attention. consisting of PI and NI amplitude enhancements, were similarly delayed by isoluminance. supporting the idea that early selective processing is strongly dependent on bottom-up perceptual processing. P300 latency and reaction time were delayed by 70–75 ms, the additional delay probably reflecting that isoluminance affected decision processes in addition to perceptual processes. Isoluminance left the scalp topographies of the early ERP deflections largely unaffected, although a slight shift of the NI topography in the isoluminant condition toward more inferior lateral posterior regions of the scalp could have reflected an increased contribution from ventral (occipitotemporal) brain areas. Relative to nontarget letters, targels presented at both attended and unattended spatial positions elicited an early contralaterally dominant lateral occipitotemporal negativity (N2pc). This ERP component is proposed to reflect an early, partly automatic process of template matching, consistent with indications from spatiotemporal dipole modelling that the N2pc was generated in inferior occipitotemporal brain regions.     

Response dependence of reversal-related ERP components in perception of ambiguous figures

Perceptual multi-stability is characterized by alternating interpretations of an unchanging stimulus input. The reversal negativity (RN) and reversal positivity (RP) ERP components show differences in electrophysiological responses between trials on which participants experience a perceptual reversal of a multi-stable stimulus versus trials without a reversal (i.e., stable). However, it is unclear to what extent these two ERP components reflect reversal-related perceptual processing rather than task and response processes. To address this, we varied task and response requirements while measuring the RN and RP. In the standard reversal task, participants indicated whether they saw a perceptual reversal on each trial. In contrast, in the identity task participants reported perceived identity of the stimulus (e.g., face or vase) without any reference to reversals. In some blocks, reversal trials required a response whereas in other blocks stable trials required a response. We found that the RN appeared independently of task and response style. However, the early latency RP component was only present when participants responded manually. For non-response trials, a component was found during the same latency as the RP but with inverted polarity. Our results suggest that the early RP component is dependent on response-related processes rather than being a pure neural signature of perceptual processes related to endogenous perceptual reversals.     

Following the time course of face gender and expression processing: A task-dependent ERP study

The effects of task demands and the interaction between gender and expression in face perception were studied using event-related potentials (ERPs). Participants performed three different tasks with male and female faces that were emotionally inexpressive or that showed happy or angry expressions. In two of the tasks (gender and expression categorization) facial properties were task-relevant while in a third task (symbol discrimination) facial information was irrelevant. Effects of expression were observed on the visual P100 component under all task conditions, suggesting the operation of an automatic process that is not influenced by task demands. The earliest interaction between expression and gender was observed later in the face-sensitive N170 component. This component showed differential modulations by specific combinations of gender and expression (e.g., angry male vs. angry female faces). Main effects of expression and task were observed in a later occipito-temporal component peaking around 230 ms post-stimulus onset (EPN or early posterior negativity). Less positive amplitudes in the presence of angry faces and during performance of the gender and expression tasks were observed. Finally, task demands also modulated a positive component peaking around 400 ms (LPC, or late positive complex) that showed enhanced amplitude for the gender task. The pattern of results obtained here adds new evidence about the sequence of operations involved in face processing and the interaction of facial properties (gender and expression) in response to different task demands.