Frequency-specific gaze modulation of emotional face processing in the human amygdala.

Determining the social significance of emotional face expression is of major importance for adaptive behavior, and gaze direction provides critical information in this process. The amygdala is implicated in both emotion and gaze processing, but how and when it integrates expression and gaze cues remains unresolved. We tackled this question using intracranial electroencephalography in epileptic patients to assess both amygdala (n = 12) and orbitofrontal cortex (OFC; n = 11) time-frequency evoked responses to faces with different emotional expressions and different gaze directions.

Amygdala function in emotion, cognition, and behavior.

The amygdala is a core structure in the anterior medial temporal lobe, with an important role in several brain functions involving memory, emotion, perception, social cognition, and even awareness. As a key brain structure for saliency detection, it triggers and controls widespread modulatory signals onto multiple areas of the brain, with a great impact on numerous aspects of adaptive behavior. Here we discuss the neural mechanisms underlying these functions, as established by animal and human research, including insights provided in both healthy and pathological conditions.

Prestimulus amygdala spectral activity is associated with visual face awareness.

Alpha cortical oscillations have been proposed to suppress sensory processing in the visual, auditory, and tactile domains, influencing conscious stimulus perception. However, it is unknown whether oscillatory neural activity in the amygdala, a subcortical structure involved in salience detection, has a similar impact on stimulus awareness. Recording intracranial electroencephalography (EEG) from 9 human amygdalae during face detection in a continuous flash suppression task, we found increased spectral prestimulus power and phase coherence, with most consistent effects in the alpha band, when faces were undetected relative to detected, similarly as previously observed in cortex with this task using scalp-EEG.

Brain reactivity to emotion persists in NREM sleep and is associated with individual dream recall.

The waking brain efficiently detects emotional signals to promote survival. However, emotion detection during sleep is poorly understood and may be influenced by individual sleep characteristics or neural reactivity. Notably, dream recall frequency has been associated with stimulus reactivity during sleep, with enhanced stimulus-driven responses in high vs.

Temporal dynamics of amygdala response to emotion- and action-relevance.

It has been proposed that the human amygdala may not only encode the emotional value of sensory events, but more generally mediate the appraisal of their relevance for the individual's goals, including relevance for action or task-based needs. However, emotional and non-emotional/action-relevance might drive amygdala activity through distinct neural signals, and the relative timing of both kinds of responses remains undetermined. Here, we recorded intracranial event-related potentials from nine amygdalae of patients undergoing epilepsy surgery, while they performed variants of a Go/NoGo task with faces and abstract shapes, where emotion- and action-relevance were orthogonally manipulated.

Human amygdala response to unisensory and multisensory emotion input: No evidence for superadditivity from intracranial recordings.

The amygdala is crucially implicated in processing emotional information from various sensory modalities. However, there is dearth of knowledge concerning the integration and relative time-course of its responses across different channels, i.e.

Neurophysiological evidence for early modulation of amygdala activity by emotional reappraisal.

How emotions unfold through time in the brain, and how fast they can be regulated by voluntary control, remain unresolved. Psychological accounts of emotion regulation posit cognitive reappraisal mechanisms may alter early emotion generative processes directly, whereas suppression impacts only later processing stages, after emotion has arisen. However, to date, there is no neurophysiological data concerning the precise latency of emotion regulation effects on the amygdala, a major emotion processing relay in the brain.

Fear Spreading Across Senses: Visual Emotional Events Alter Cortical Responses to Touch, Audition, and Vision.

Attention and perception are potentiated for emotionally significant stimuli, promoting efficient reactivity and survival. But does such enhancement extend to stimuli simultaneously presented across different sensory modalities? We used functional magnetic resonance imaging in humans to examine the effects of visual emotional signals on concomitant sensory inputs in auditory, somatosensory, and visual modalities. First, we identified sensory areas responsive to task-irrelevant tones, touches, or flickers, presented bilaterally while participants attended to either a neutral or a fearful face.

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.

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.

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.

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.

Phase re-setting of gamma neural oscillations during novelty processing in an appetitive context.

Based on the previous study where phase-synchronization (PS) of gamma-band responses (GBRs) proved a reliable cerebral correlate of involuntary attention and its enhancement under threat, we measured gamma-PS elicited by novel sounds from human electroencephalogram (EEG) scalp-recordings when participants responded to visual stimuli displaying either highly motivational or neutral sceneries. We then tested the modulatory effect of the emotional conditions on auditory responses. Novel distractor sounds did not affect behavioural accuracy on subjects' visual task performance in neutral context but markedly decreased hit rate in the appetitive one.

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 Parkinson's 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.

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.

Emotional context enhances auditory novelty processing in superior temporal gyrus.

Visualizing emotionally loaded pictures intensifies peripheral reflexes toward sudden auditory stimuli, suggesting that the emotional context may potentiate responses elicited by novel events in the acoustic environment. However, psychophysiological results have reported that attentional resources available to sounds become depleted, as attention allocation to emotional pictures increases. These findings have raised the challenging question of whether an emotional context actually enhances or attenuates auditory novelty processing at a central level in the brain.

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.

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.

Negative emotional context enhances auditory novelty processing.

We used an auditory-visual distraction task to investigate the functional relationship between distraction elicited by auditory novel events and a context of negative emotional processing, both at behavioural and electrophysiological (event-related brain potentials) levels in humans. Participants performed a decision task on pictures disclosing sceneries with a task-irrelevant emotional load or neutral, whereas ignoring sounds presented concomitantly. Our data showed that novel sounds yielded stronger behavioural disruption on participants' visual task performance in negative context compared to the neutral one.