N400 during recognition of voice identity and vocal affect

The effect of anxiety on emotional recognition: evidence from an ERP study

Anxiety-related bias in the recognition memory based on trait anxiety has induced some studies. Their results, however, were conflicting. In fact, anxious differences not only differed from personality traits but also from different anxiety mood levels. We explored the emotional memory bias in both trait and state anxiety individuals, the high trait and high state anxiety group, the high trait and low state anxiety group, the low trait and high state anxiety group, and the low trait and low state anxiety group, on classic recognition paradigm using event-related potentials (ERPs). The behavioral results showed high state anxiety levels increased the d' of negative words, regardless of the trait anxiety of participant is high or low, and a lower d' of recognition memory for negative words than for neutral and positive words in all participants. Moreover, Electrophysiological results supported the findings of behavior, showing an earlier N400 (250-500 ms) latency elicited for new-negative words in high state level than in low state levels in right parietal region. These results suggested that the memory bias to negative events resides in state anxiety, but not in trait anxiety.

Conscious and Non-conscious Representations of Emotional Faces in Asperger's Syndrome

Several neuroimaging studies have suggested that the low spatial frequency content in an emotional face mainly activates the amygdala, pulvinar, and superior colliculus especially with fearful faces(1-3). These regions constitute the limbic structure in non-conscious perception of emotions and modulate cortical activity either directly or indirectly(2). In contrast, the conscious representation of emotions is more pronounced in the anterior cingulate, prefrontal cortex, and somatosensory cortex for directing voluntary attention to details in faces(3,4). Asperger's syndrome (AS)(5,6) represents an atypical mental disturbance that affects sensory, affective and communicative abilities, without interfering with normal linguistic skills and intellectual ability. Several studies have found that functional deficits in the neural circuitry important for facial emotion recognition can partly explain social communication failure in patients with AS(7-9). In order to clarify the interplay between conscious and non-conscious representations of emotional faces in AS, an EEG experimental protocol is designed with two tasks involving emotionality evaluation of either photograph or line-drawing faces. A pilot study is introduced for selecting face stimuli that minimize the differences in reaction times and scores assigned to facial emotions between the pretested patients with AS and IQ/gender-matched healthy controls. Information from the pretested patients was used to develop the scoring system used for the emotionality evaluation. Research into facial emotions and visual stimuli with different spatial frequency contents has reached discrepant findings depending on the demographic characteristics of participants and task demands(2). The experimental protocol is intended to clarify deficits in patients with AS in processing emotional faces when compared with healthy controls by controlling for factors unrelated to recognition of facial emotions, such as task difficulty, IQ and gender.

Neural responses towards a speaker's feeling of (un)knowing

During interpersonal communication, listeners must rapidly evaluate verbal and vocal cues to arrive at an integrated meaning about the utterance and about the speaker, including a representation of the speaker's 'feeling of knowing' (i.e., how confident they are in relation to the utterance). In this study, we investigated the time course and neural responses underlying a listener's ability to evaluate speaker confidence from combined verbal and vocal cues. We recorded real-time brain responses as listeners judged statements conveying three levels of confidence with the speaker's voice (confident, close-to-confident, unconfident), which were preceded by meaning-congruent lexical phrases (e.g. I am positive, Most likely, Perhaps). Event-related potentials to utterances with combined lexical and vocal cues about speaker confidence were compared to responses elicited by utterances without the verbal phrase in a previous study (Jiang and Pell, 2015). Utterances with combined cues about speaker confidence elicited reduced, N1, P2 and N400 responses when compared to corresponding utterances without the phrase. When compared to confident statements, close-to-confident and unconfident expressions elicited reduced N1 and P2 responses and a late positivity from 900 to 1250 ms; unconfident and close-to-confident expressions were differentiated later in the 1250-1600 ms time window. The effect of lexical phrases on confidence processing differed for male and female participants, with evidence that female listeners incorporated information from the verbal and vocal channels in a distinct manner. Individual differences in trait empathy and trait anxiety also moderated neural responses during confidence processing. Our findings showcase the cognitive processing mechanisms and individual factors governing how we infer a speaker's mental (knowledge) state from the speech signal.

Atypical neural responses to vocal anger in attention-deficit/hyperactivity disorder

BACKGROUND

Deficits in facial emotion processing, reported in attention-deficit/hyperactivity disorder (ADHD), have been linked to both early perceptual and later attentional components of event-related potentials (ERPs). However, the neural underpinnings of vocal emotion processing deficits in ADHD have yet to be characterised. Here, we report the first ERP study of vocal affective prosody processing in ADHD.

METHODS

Event-related potentials of 6-11-year-old children with ADHD (n = 25) and typically developing controls (n = 25) were recorded as they completed a task measuring recognition of vocal prosodic stimuli (angry, happy and neutral). Audiometric assessments were conducted to screen for hearing impairments.

RESULTS

Children with ADHD were less accurate than controls at recognising vocal anger. Relative to controls, they displayed enhanced N100 and attenuated P300 components to vocal anger. The P300 effect was reduced, but remained significant, after controlling for N100 effects by rebaselining. Only the N100 effect was significant when children with ADHD and comorbid conduct disorder (n = 10) were excluded.

CONCLUSION

This study provides the first evidence linking ADHD to atypical neural activity during the early perceptual stages of vocal anger processing. These effects may reflect preattentive hyper-vigilance to vocal anger in ADHD.

Isolating N400 as neural marker of vocal anger processing in 6-11-year old children

Introduction

Vocal anger is a salient social signal serving adaptive functions in typical child development. Despite recent advances in the developmental neuroscience of emotion processing with regard to visual stimuli, little remains known about the neural correlates of vocal anger processing in childhood. This study represents the first attempt to isolate a neural marker of vocal anger processing in children using electrophysiological methods.

Methods

We compared ERP wave forms during the processing of non-word emotional vocal stimuli in a population sample of 55 6–11-year-old typically developing children. Children listened to three types of stimuli expressing angry, happy, and neutral prosody and completed an emotion identification task with three response options (angry, happy and neutral/‘ok’).

Results

A distinctive N400 component which was modulated by emotional content of vocal stimulus was observed in children over parietal and occipital scalp regions—amplitudes were significantly attenuated to angry compared to happy and neutral voices.

Discussion

Findings of the present study regarding the N400 are compatible with adult studies showing reduced N400 amplitudes to negative compared to neutral emotional stimuli. Implications for studies of the neural basis of vocal anger processing in children are discussed.