Judith Domínguez-Borràs

Electrophysiological and behavioral evidence of gender differences in the modulation of distraction by the emotional context.

Gender differences in brain activity while processing emotional stimuli have been demonstrated by neuroimaging and electrophysiological studies. However, the possible differential effects of emotion on attentional mechanisms between women and men are less understood. The present study aims to elucidate any gender differences in the modulation of unexpected auditory stimulus processing using an emotional context elicited by aversive images. Fourteen men and fourteen women performed a well-established auditory-visual distraction paradigm in which distraction was elicited by novel stimuli within a neutral or negative emotional context induced by images from the IAPS. Response time increased after unexpected novel sounds as a behavioral effect of distraction, and this increase was larger for women, but not for men, within the negative emotional context. Novelty-P3 was also modulated by the emotional context for women but not for men. These results reveal stronger novelty processing in women than in men during a threatening situation.

Emotional context enhances auditory novelty processing: behavioural and electrophysiological evidence

Viewing emotionally negative pictures has been proposed to attenuate brain responses towards sudden auditory events, as more attentional resources are allocated to the affective visual stimuli. However, peripheral reflexes have been shown intensified. These observations have raised the question of whether an emotional context actually facilitates or attenuates processing in the auditory novelty system. Using scalp event‐related potentials we measured brain responses induced by novel sounds when participants responded to visual stimuli displaying either threatening or neutral sceneries. We then tested the modulatory effect of the emotional task conditions on auditory responses. Novel sounds yielded a stronger behavioural disruption on subjects’ visual task performance when responding to negative pictures compared with when responding to the neutral ones. Accordingly, very early novelty‐P3 responses to novel sounds were enhanced in negative context. These results provide strong evidence that the emotional context enhances the activation of neural networks in the auditory novelty system, gating acoustic novelty processing under potentially threatening conditions.

The perception of dynamic and static facial expressions of happiness and disgust investigated by ERPs and fMRI constrained source analysis

A recent functional magnetic resonance imaging (fMRI) study by our group demonstrated that dynamic emotional faces are more accurately recognized and evoked more widespread patterns of hemodynamic brain responses than static emotional faces. Based on this experimental design, the present study aimed at investigating the spatio-temporal processing of static and dynamic emotional facial expressions in 19 healthy women by means of multi-channel electroencephalography (EEG), event-related potentials (ERP) and fMRI-constrained regional source analyses. ERP analysis showed an increased amplitude of the LPP (late posterior positivity) over centro-parietal regions for static facial expressions of disgust compared to neutral faces. In addition, the LPP was more widespread and temporally prolonged for dynamic compared to static faces of disgust and happiness. fMRI constrained source analysis on static emotional face stimuli indicated the spatio-temporal modulation of predominantly posterior regional brain activation related to the visual processing stream for both emotional valences when compared to the neutral condition in the fusiform gyrus. The spatio-temporal processing of dynamic stimuli yielded enhanced source activity for emotional compared to neutral conditions in temporal (e.g., fusiform gyrus), and frontal regions (e.g., ventromedial prefrontal cortex, medial and inferior frontal cortex) in early and again in later time windows. The present data support the view that dynamic facial displays trigger more information reflected in complex neural networks, in particular because of their changing features potentially triggering sustained activation related to a continuing evaluation of those faces. A combined fMRI and EEG approach thus provides an advanced insight to the spatio-temporal characteristics of emotional face processing, by also revealing additional neural generators, not identifiable by the only use of an fMRI approach.

Dopamine transporter regulates the enhancement of novelty processing by a negative emotional context

The dopaminergic (DA) system has been recently related the emotional modulation of cognitive processes. Moreover, patients with midbrain DA depletion, such as Parkinsons Disease (PD), have shown diminished reactivity during unpleasant events. Here, we examined the role of DA in the enhancement of novelty processing during negative emotion. Forty healthy volunteers were genotyped for the dopamine transporter (DAT) gene SLC6A3 or DAT1 and performed an auditory-visual distraction paradigm in negative and neutral emotional context conditions. 9R- individuals, associated to a lesser striatal DA display, failed to show increased distraction during negative emotion, but experienced an enhancement of the early phase of the novelty-P3 brain response, associated to the evaluation of novel events, in the negative relative to the neutral context. However, 9R+ individuals (associated to larger striatal DA display) showed larger distraction during negative emotion and larger amplitudes of the novelty-P3, irrespective of the condition. These results suggest a blunted reactivity to novelty during negative emotion in 9R- individuals due to a lesser DA display and stronger activation of the representation of novel events in the 9R+ group, due to a larger DA availability, thus reaching a ceiling effect in the neutral context condition with no further enhancement during negative emotion. The present results might help to understand the functional implications of dopamine in some neuropsychiatric disorders.

Tuning the brain for novelty detection under emotional threat: the role of increasing gamma phase-synchronization

Effective orienting of attention towards novel events is crucial for survival, particularly if they occur in a dangerous situation. This is why stimuli with emotional value are more efficient in capturing attention than neutral stimuli, and why the processing of unexpected novel stimuli is enhanced under a negative emotional context. Here we measured the phase-synchronization (PS) of gamma-band responses (GBR) from human EEG scalp-recordings during performance of a visual discrimination task in which task-irrelevant standard and novel sounds were presented in either a neutral or a negative emotional context, in order to elucidate the brain mechanisms by which emotion tunes the processing of novel events. Visual task performance was distracted by novel sounds, and this distraction was enhanced by the negative emotional context. Similarly, gamma PS was enhanced after novel as compared to standard sounds and it was also larger to auditory stimuli in the negative than in the neutral emotional context, reflecting the synchronization of neural networks for increasing of attentional processing. Remarkably, the larger PS increase of GBR after novel sounds in the negative as compared to the neutral emotional context over midline and right frontal regions reveals that a negative emotional context tunes novelty processing by means of the PS of brain activity in the gamma frequency band around 40 Hz in specific neural networks.

Emotional processing and its impact on unilateral neglect and extinction.

Unilateral spatial neglect is a neurological disorder characterized by impaired orienting of attention to stimuli located in the contralesional space, typically following right-hemisphere damage. Neuropsychological investigations in the past two decades have demonstrated that neglect is caused by deficits affecting a widespread cortico-subcortical fronto-parietal network controlling spatial attention, but usually sparing early sensory pathways. As a consequence, certain residual abilities in sensory processing remain intact and still take place for stimuli in the neglected space, such as the extraction and organization of coherent or meaningful object features. Moreover, these residual abilities can alleviate inattention symptoms when contralesional stimuli are perceptually or biologically salient. Here we review recent studies suggesting that the emotional content of stimuli may also be processed despite impaired attention towards contralesional space, and that such processing may act to enhance attention and partly reduce neglect for these stimuli, relative to similar but emotionally neutral stimuli. For example, faces with emotional expressions, voices with emotional prosody, as well as pictures of scenes or even spiders have been found to be less severely extinguished from awareness in conditions of bilateral stimulations, and/or lead to fewer omissions in search tasks with multiple distracters. Gaze cues and reward learning might also produce similar effects. Altogether, these findings suggest that emotionally significant information is not only extracted from stimuli at neglected locations through spared pathways, but can also induce emotional biases in attention that partly counteract the abnormal spatial biases caused by fronto-parietal damage. We discuss results from neuropsychology and neuroimaging research suggesting that specific mechanisms for emotional attention might exist, centered on the amygdala and other limbic regions, and that these mechanisms can operate partly independent from other circuits controlling spatial and object-based attention. Although we are only beginning to understand these interactive effects of emotion and attention and to identify their neuroanatomical substrates, we believe that a deeper knowledge of such mechanisms and their conditions of optimal operation will help develop or improve therapeutic strategies in neglect patients.

Partial recovery of visual extinction by pavlovian conditioning in a patient with hemispatial neglect

Patients with parietal lesions and unilateral spatial neglect (USN) are unable to detect or respond to information in the contralesional side of space. However, some residual sensory processing may still occur and overcome inattention symptoms when contralesional stimuli are perceptually or biologically salient, as shown for emotional faces or voices. These effects have been attributed to enhanced neural responses of sensory regions to emotional stimuli, presumably driven by feedback signals from limbic regions such as the amygdala. However, because emotional faces and voices also differ from neutral stimuli in terms of physical features, the affective nature of these effects still remains to be confirmed. Here we report data from a right parietal patient in whom left visual extinction was reduced for contralesional visual stimuli following pavlovian aversive conditioning, relative to the same stimulus before conditioning, and relative to similar but non-conditioned stimuli. This reduction of visual extinction was thus mediated by the emotional meaning of stimuli acquired through implicit learning. Functional magnetic resonance imaging also showed that conditioned visual stimuli elicited greater activation in right visual cortex, relative to the non-conditioned stimuli, together with differential activations in amygdala. These results support the hypothesis that emotional appraisal, not only the processing of perceptual features, may partly restore attention to salient information in contralesional space. These findings open new perspectives to improve rehabilitation strategies in neglect, based on affective and motivational signals.

Phasic boosting of auditory perception by visual emotion

Emotionally negative stimuli boost perceptual processes. There is little known, however, about the timing of this modulation. The present study aims at elucidating the phasic effects of, emotional processing on auditory processing within subsequent time-windows of visual emotional, processing in humans. We recorded the electroencephalogram (EEG) while participants responded to a, discrimination task of faces with neutral or fearful expressions. A brief complex tone, which subjects, were instructed to ignore, was displayed concomitantly, but with different asynchronies respective to, the image onset. Analyses of the N1 auditory event-related potential (ERP) revealed enhanced brain, responses in presence of fearful faces. Importantly, this effect occurred at picture-tone asynchronies of, 100 and 150ms, but not when these were displayed simultaneously, or at 50ms or 200ms asynchrony. These results confirm the existence of a fast-operating crossmodal effect of visual emotion on auditory, processing, suggesting a phasic variation according to the time-course of emotional processing.